lib/dns/journal.c

	journal.c revision 0c27b3fe77ac1d5094ba3521e8142d9e7973133f
/*
 * Copyright (C) 1999-2002, 2004, 2005, 2007-2011, 2013-2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/* $Id: journal.c,v 1.120 2011/12/22 07:32:41 each Exp $ */

#include <config.h>

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#include <isc/file.h>
#include <isc/mem.h>
#include <isc/print.h>
#include <isc/stdio.h>
#include <isc/string.h>
#include <isc/util.h>

#include <dns/compress.h>
#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/diff.h>
#include <dns/fixedname.h>
#include <dns/journal.h>
#include <dns/log.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/result.h>
#include <dns/soa.h>

/*! \file
 * \brief Journaling.
 *
 * A journal file consists of
 *
 *   \li A fixed-size header of type journal_rawheader_t.
 *
 *   \li The index.  This is an unordered array of index entries
 *     of type journal_rawpos_t giving the locations
 *     of some arbitrary subset of the journal's addressable
 *     transactions.  The index entries are used as hints to
 *     speed up the process of locating a transaction with a given
 *     serial number.  Unused index entries have an "offset"
 *     field of zero.  The size of the index can vary between
 *     journal files, but does not change during the lifetime
 *     of a file.  The size can be zero.
 *
 *   \li The journal data.  This  consists of one or more transactions.
 *     Each transaction begins with a transaction header of type
 *     journal_rawxhdr_t.  The transaction header is followed by a
 *     sequence of RRs, similar in structure to an IXFR difference
 *     sequence (RFC1995).  That is, the pre-transaction SOA,
 *     zero or more other deleted RRs, the post-transaction SOA,
 *     and zero or more other added RRs.  Unlike in IXFR, each RR
 *     is prefixed with a 32-bit length.
 *
 *     The journal data part grows as new transactions are
 *     appended to the file.  Only those transactions
 *     whose serial number is current-(2^31-1) to current
 *     are considered "addressable" and may be pointed
 *     to from the header or index.  They may be preceded
 *     by old transactions that are no longer addressable,
 *     and they may be followed by transactions that were
 *     appended to the journal but never committed by updating
 *     the "end" position in the header.  The latter will
 *     be overwritten when new transactions are added.
 */
/*%
 * When true, accept IXFR difference sequences where the
 * SOA serial number does not change (BIND 8 sends such
 * sequences).
 */
static isc_boolean_t bind8_compat = ISC_TRUE; /* XXX config */

/**************************************************************************/
/*
 * Miscellaneous utilities.
 */

#define JOURNAL_COMMON_LOGARGS \
    dns_lctx, DNS_LOGCATEGORY_GENERAL, DNS_LOGMODULE_JOURNAL

#define JOURNAL_DEBUG_LOGARGS(n) \
    JOURNAL_COMMON_LOGARGS, ISC_LOG_DEBUG(n)

/*%
 * It would be non-sensical (or at least obtuse) to use FAIL() with an
 * ISC_R_SUCCESS code, but the test is there to keep the Solaris compiler
 * from complaining about "end-of-loop code not reached".
 */
#define FAIL(code) \
    do { result = (code);                   \
        if (result != ISC_R_SUCCESS) goto failure;  \
    } while (0)

#define CHECK(op) \
    do { result = (op);                     \
        if (result != ISC_R_SUCCESS) goto failure;  \
    } while (0)

#define JOURNAL_SERIALSET   0x01U

static isc_result_t index_to_disk(dns_journal_t *);

static inline isc_uint32_t
decode_uint32(unsigned char *p) {
    return ((p[0] << 24) +
        (p[1] << 16) +
        (p[2] <<  8) +
        (p[3] <<  0));
}

static inline void
encode_uint32(isc_uint32_t val, unsigned char *p) {
    p[0] = (isc_uint8_t)(val >> 24);
    p[1] = (isc_uint8_t)(val >> 16);
    p[2] = (isc_uint8_t)(val >>  8);
    p[3] = (isc_uint8_t)(val >>  0);
}

isc_result_t
dns_db_createsoatuple(dns_db_t *db, dns_dbversion_t *ver, isc_mem_t *mctx,
              dns_diffop_t op, dns_difftuple_t **tp)
{
    isc_result_t result;
    dns_dbnode_t *node;
    dns_rdataset_t rdataset;
    dns_rdata_t rdata = DNS_RDATA_INIT;
    dns_fixedname_t fixed;
    dns_name_t *zonename;

    dns_fixedname_init(&fixed);
    zonename = dns_fixedname_name(&fixed);
    dns_name_copy(dns_db_origin(db), zonename, NULL);

    node = NULL;
    result = dns_db_findnode(db, zonename, ISC_FALSE, &node);
    if (result != ISC_R_SUCCESS)
        goto nonode;

    dns_rdataset_init(&rdataset);
    result = dns_db_findrdataset(db, node, ver, dns_rdatatype_soa, 0,
                     (isc_stdtime_t)0, &rdataset, NULL);
    if (result != ISC_R_SUCCESS)
        goto freenode;

    result = dns_rdataset_first(&rdataset);
    if (result != ISC_R_SUCCESS)
        goto freenode;

    dns_rdataset_current(&rdataset, &rdata);
    dns_rdataset_getownercase(&rdataset, zonename);

    result = dns_difftuple_create(mctx, op, zonename, rdataset.ttl,
                      &rdata, tp);

    dns_rdataset_disassociate(&rdataset);
    dns_db_detachnode(db, &node);
    return (result);

 freenode:
    dns_db_detachnode(db, &node);
 nonode:
    UNEXPECTED_ERROR(__FILE__, __LINE__, "missing SOA");
    return (result);
}

/* Journaling */

/*%
 * On-disk representation of a "pointer" to a journal entry.
 * These are used in the journal header to locate the beginning
 * and end of the journal, and in the journal index to locate
 * other transactions.
 */
typedef struct {
    unsigned char   serial[4];  /*%< SOA serial before update. */
    /*
     * XXXRTH  Should offset be 8 bytes?
     * XXXDCL ... probably, since isc_offset_t is 8 bytes on many OSs.
     * XXXAG  ... but we will not be able to seek >2G anyway on many
     *            platforms as long as we are using fseek() rather
     *            than lseek().
     */
    unsigned char   offset[4];  /*%< Offset from beginning of file. */
} journal_rawpos_t;


/*%
 * The header is of a fixed size, with some spare room for future
 * extensions.
 */
#define JOURNAL_HEADER_SIZE 64 /* Bytes. */

/*%
 * The on-disk representation of the journal header.
 * All numbers are stored in big-endian order.
 */
typedef union {
    struct {
        /*% File format version ID. */
        unsigned char       format[16];
        /*% Position of the first addressable transaction */
        journal_rawpos_t    begin;
        /*% Position of the next (yet nonexistent) transaction. */
        journal_rawpos_t    end;
        /*% Number of index entries following the header. */
        unsigned char       index_size[4];
        /*% Source serial number. */
        unsigned char           sourceserial[4];
        unsigned char           flags;
    } h;
    /* Pad the header to a fixed size. */
    unsigned char pad[JOURNAL_HEADER_SIZE];
} journal_rawheader_t;

/*%
 * The on-disk representation of the transaction header.
 * There is one of these at the beginning of each transaction.
 */
typedef struct {
    unsigned char   size[4];    /*%< In bytes, excluding header. */
    unsigned char   serial0[4]; /*%< SOA serial before update. */
    unsigned char   serial1[4]; /*%< SOA serial after update. */
} journal_rawxhdr_t;

/*%
 * The on-disk representation of the RR header.
 * There is one of these at the beginning of each RR.
 */
typedef struct {
    unsigned char   size[4];    /*%< In bytes, excluding header. */
} journal_rawrrhdr_t;

/*%
 * The in-core representation of the journal header.
 */
typedef struct {
    isc_uint32_t    serial;
    isc_offset_t    offset;
} journal_pos_t;

#define POS_VALID(pos)      ((pos).offset != 0)
#define POS_INVALIDATE(pos)     ((pos).offset = 0, (pos).serial = 0)

typedef struct {
    unsigned char   format[16];
    journal_pos_t   begin;
    journal_pos_t   end;
    isc_uint32_t    index_size;
    isc_uint32_t    sourceserial;
    isc_boolean_t   serialset;
} journal_header_t;

/*%
 * The in-core representation of the transaction header.
 */

typedef struct {
    isc_uint32_t    size;
    isc_uint32_t    serial0;
    isc_uint32_t    serial1;
} journal_xhdr_t;

/*%
 * The in-core representation of the RR header.
 */
typedef struct {
    isc_uint32_t    size;
} journal_rrhdr_t;


/*%
 * Initial contents to store in the header of a newly created
 * journal file.
 *
 * The header starts with the magic string ";BIND LOG V9\n"
 * to identify the file as a BIND 9 journal file.  An ASCII
 * identification string is used rather than a binary magic
 * number to be consistent with BIND 8 (BIND 8 journal files
 * are ASCII text files).
 */

static journal_header_t
initial_journal_header = { ";BIND LOG V9\n", { 0, 0 }, { 0, 0 }, 0, 0, 0 };

#define JOURNAL_EMPTY(h) ((h)->begin.offset == (h)->end.offset)

typedef enum {
    JOURNAL_STATE_INVALID,
    JOURNAL_STATE_READ,
    JOURNAL_STATE_WRITE,
    JOURNAL_STATE_TRANSACTION,
    JOURNAL_STATE_INLINE
} journal_state_t;

struct dns_journal {
    unsigned int        magic;      /*%< JOUR */
    isc_mem_t       *mctx;      /*%< Memory context */
    journal_state_t     state;
    char            *filename;  /*%< Journal file name */
    FILE *          fp;     /*%< File handle */
    isc_offset_t        offset;     /*%< Current file offset */
    journal_header_t    header;     /*%< In-core journal header */
    unsigned char       *rawindex;  /*%< In-core buffer for journal index in on-disk format */
    journal_pos_t       *index;     /*%< In-core journal index */

    /*% Current transaction state (when writing). */
    struct {
        unsigned int    n_soa;      /*%< Number of SOAs seen */
        journal_pos_t   pos[2];     /*%< Begin/end position */
    } x;

    /*% Iteration state (when reading). */
    struct {
        /* These define the part of the journal we iterate over. */
        journal_pos_t bpos;     /*%< Position before first, */
        journal_pos_t epos;     /*%< and after last transaction */
        /* The rest is iterator state. */
        isc_uint32_t current_serial;    /*%< Current SOA serial */
        isc_buffer_t source;        /*%< Data from disk */
        isc_buffer_t target;        /*%< Data from _fromwire check */
        dns_decompress_t dctx;      /*%< Dummy decompression ctx */
        dns_name_t name;        /*%< Current domain name */
        dns_rdata_t rdata;      /*%< Current rdata */
        isc_uint32_t ttl;       /*%< Current TTL */
        unsigned int xsize;     /*%< Size of transaction data */
        unsigned int xpos;      /*%< Current position in it */
        isc_result_t result;        /*%< Result of last call */
    } it;
};

#define DNS_JOURNAL_MAGIC   ISC_MAGIC('J', 'O', 'U', 'R')
#define DNS_JOURNAL_VALID(t)    ISC_MAGIC_VALID(t, DNS_JOURNAL_MAGIC)

static void
journal_pos_decode(journal_rawpos_t *raw, journal_pos_t *cooked) {
    cooked->serial = decode_uint32(raw->serial);
    cooked->offset = decode_uint32(raw->offset);
}

static void
journal_pos_encode(journal_rawpos_t *raw, journal_pos_t *cooked) {
    encode_uint32(cooked->serial, raw->serial);
    encode_uint32(cooked->offset, raw->offset);
}

static void
journal_header_decode(journal_rawheader_t *raw, journal_header_t *cooked) {
    INSIST(sizeof(cooked->format) == sizeof(raw->h.format));
    memmove(cooked->format, raw->h.format, sizeof(cooked->format));
    journal_pos_decode(&raw->h.begin, &cooked->begin);
    journal_pos_decode(&raw->h.end, &cooked->end);
    cooked->index_size = decode_uint32(raw->h.index_size);
    cooked->sourceserial = decode_uint32(raw->h.sourceserial);
    cooked->serialset = ISC_TF(raw->h.flags & JOURNAL_SERIALSET);
}

static void
journal_header_encode(journal_header_t *cooked, journal_rawheader_t *raw) {
    unsigned char flags = 0;

    INSIST(sizeof(cooked->format) == sizeof(raw->h.format));
    memset(raw->pad, 0, sizeof(raw->pad));
    memmove(raw->h.format, cooked->format, sizeof(raw->h.format));
    journal_pos_encode(&raw->h.begin, &cooked->begin);
    journal_pos_encode(&raw->h.end, &cooked->end);
    encode_uint32(cooked->index_size, raw->h.index_size);
    encode_uint32(cooked->sourceserial, raw->h.sourceserial);
    if (cooked->serialset)
        flags |= JOURNAL_SERIALSET;
    raw->h.flags = flags;
}

/*
 * Journal file I/O subroutines, with error checking and reporting.
 */
static isc_result_t
journal_seek(dns_journal_t *j, isc_uint32_t offset) {
    isc_result_t result;

    result = isc_stdio_seek(j->fp, (off_t)offset, SEEK_SET);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: seek: %s", j->filename,
                  isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }
    j->offset = offset;
    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_read(dns_journal_t *j, void *mem, size_t nbytes) {
    isc_result_t result;

    result = isc_stdio_read(mem, 1, nbytes, j->fp, NULL);
    if (result != ISC_R_SUCCESS) {
        if (result == ISC_R_EOF)
            return (ISC_R_NOMORE);
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: read: %s",
                  j->filename, isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }
    j->offset += (isc_offset_t)nbytes;
    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_write(dns_journal_t *j, void *mem, size_t nbytes) {
    isc_result_t result;

    result = isc_stdio_write(mem, 1, nbytes, j->fp, NULL);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: write: %s",
                  j->filename, isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }
    j->offset += (isc_offset_t)nbytes;
    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_fsync(dns_journal_t *j) {
    isc_result_t result;
    result = isc_stdio_flush(j->fp);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: flush: %s",
                  j->filename, isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }
    result = isc_stdio_sync(j->fp);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: fsync: %s",
                  j->filename, isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }
    return (ISC_R_SUCCESS);
}

/*
 * Read/write a transaction header at the current file position.
 */

static isc_result_t
journal_read_xhdr(dns_journal_t *j, journal_xhdr_t *xhdr) {
    journal_rawxhdr_t raw;
    isc_result_t result;
    result = journal_read(j, &raw, sizeof(raw));
    if (result != ISC_R_SUCCESS)
        return (result);
    xhdr->size = decode_uint32(raw.size);
    xhdr->serial0 = decode_uint32(raw.serial0);
    xhdr->serial1 = decode_uint32(raw.serial1);
    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_write_xhdr(dns_journal_t *j, isc_uint32_t size,
           isc_uint32_t serial0, isc_uint32_t serial1)
{
    journal_rawxhdr_t raw;
    encode_uint32(size, raw.size);
    encode_uint32(serial0, raw.serial0);
    encode_uint32(serial1, raw.serial1);
    return (journal_write(j, &raw, sizeof(raw)));
}


/*
 * Read an RR header at the current file position.
 */

static isc_result_t
journal_read_rrhdr(dns_journal_t *j, journal_rrhdr_t *rrhdr) {
    journal_rawrrhdr_t raw;
    isc_result_t result;
    result = journal_read(j, &raw, sizeof(raw));
    if (result != ISC_R_SUCCESS)
        return (result);
    rrhdr->size = decode_uint32(raw.size);
    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_file_create(isc_mem_t *mctx, const char *filename) {
    FILE *fp = NULL;
    isc_result_t result;
    journal_header_t header;
    journal_rawheader_t rawheader;
    int index_size = 56; /* XXX configurable */
    int size;
    void *mem; /* Memory for temporary index image. */

    INSIST(sizeof(journal_rawheader_t) == JOURNAL_HEADER_SIZE);

    result = isc_stdio_open(filename, "wb", &fp);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: create: %s",
                  filename, isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }

    header = initial_journal_header;
    header.index_size = index_size;
    journal_header_encode(&header, &rawheader);

    size = sizeof(journal_rawheader_t) +
        index_size * sizeof(journal_rawpos_t);

    mem = isc_mem_get(mctx, size);
    if (mem == NULL) {
        (void)isc_stdio_close(fp);
        (void)isc_file_remove(filename);
        return (ISC_R_NOMEMORY);
    }
    memset(mem, 0, size);
    memmove(mem, &rawheader, sizeof(rawheader));

    result = isc_stdio_write(mem, 1, (size_t) size, fp, NULL);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                 "%s: write: %s",
                 filename, isc_result_totext(result));
        (void)isc_stdio_close(fp);
        (void)isc_file_remove(filename);
        isc_mem_put(mctx, mem, size);
        return (ISC_R_UNEXPECTED);
    }
    isc_mem_put(mctx, mem, size);

    result = isc_stdio_close(fp);
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                 "%s: close: %s",
                 filename, isc_result_totext(result));
        (void)isc_file_remove(filename);
        return (ISC_R_UNEXPECTED);
    }

    return (ISC_R_SUCCESS);
}

static isc_result_t
journal_open(isc_mem_t *mctx, const char *filename, isc_boolean_t writable,
         isc_boolean_t create, dns_journal_t **journalp)
{
    FILE *fp = NULL;
    isc_result_t result;
    journal_rawheader_t rawheader;
    dns_journal_t *j;

    INSIST(journalp != NULL && *journalp == NULL);
    j = isc_mem_get(mctx, sizeof(*j));
    if (j == NULL)
        return (ISC_R_NOMEMORY);

    j->mctx = NULL;
    isc_mem_attach(mctx, &j->mctx);
    j->state = JOURNAL_STATE_INVALID;
    j->fp = NULL;
    j->filename = isc_mem_strdup(mctx, filename);
    j->index = NULL;
    j->rawindex = NULL;

    if (j->filename == NULL)
        FAIL(ISC_R_NOMEMORY);

    result = isc_stdio_open(j->filename, writable ? "rb+" : "rb", &fp);

    if (result == ISC_R_FILENOTFOUND) {
        if (create) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_DEBUG(1),
                      "journal file %s does not exist, "
                      "creating it", j->filename);
            CHECK(journal_file_create(mctx, filename));
            /*
             * Retry.
             */
            result = isc_stdio_open(j->filename, "rb+", &fp);
        } else {
            FAIL(ISC_R_NOTFOUND);
        }
    }
    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: open: %s",
                  j->filename, isc_result_totext(result));
        FAIL(ISC_R_UNEXPECTED);
    }

    j->fp = fp;

    /*
     * Set magic early so that seek/read can succeed.
     */
    j->magic = DNS_JOURNAL_MAGIC;

    CHECK(journal_seek(j, 0));
    CHECK(journal_read(j, &rawheader, sizeof(rawheader)));

    if (memcmp(rawheader.h.format, initial_journal_header.format,
           sizeof(initial_journal_header.format)) != 0) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                 "%s: journal format not recognized",
                 j->filename);
        FAIL(ISC_R_UNEXPECTED);
    }
    journal_header_decode(&rawheader, &j->header);

    /*
     * If there is an index, read the raw index into a dynamically
     * allocated buffer and then convert it into a cooked index.
     */
    if (j->header.index_size != 0) {
        unsigned int i;
        unsigned int rawbytes;
        unsigned char *p;

        rawbytes = j->header.index_size * sizeof(journal_rawpos_t);
        j->rawindex = isc_mem_get(mctx, rawbytes);
        if (j->rawindex == NULL)
            FAIL(ISC_R_NOMEMORY);

        CHECK(journal_read(j, j->rawindex, rawbytes));

        j->index = isc_mem_get(mctx, j->header.index_size *
                       sizeof(journal_pos_t));
        if (j->index == NULL)
            FAIL(ISC_R_NOMEMORY);

        p = j->rawindex;
        for (i = 0; i < j->header.index_size; i++) {
            j->index[i].serial = decode_uint32(p);
            p += 4;
            j->index[i].offset = decode_uint32(p);
            p += 4;
        }
        INSIST(p == j->rawindex + rawbytes);
    }
    j->offset = -1; /* Invalid, must seek explicitly. */

    /*
     * Initialize the iterator.
     */
    dns_name_init(&j->it.name, NULL);
    dns_rdata_init(&j->it.rdata);

    /*
     * Set up empty initial buffers for unchecked and checked
     * wire format RR data.  They will be reallocated
     * later.
     */
    isc_buffer_init(&j->it.source, NULL, 0);
    isc_buffer_init(&j->it.target, NULL, 0);
    dns_decompress_init(&j->it.dctx, -1, DNS_DECOMPRESS_NONE);

    j->state =
        writable ? JOURNAL_STATE_WRITE : JOURNAL_STATE_READ;

    *journalp = j;
    return (ISC_R_SUCCESS);

 failure:
    j->magic = 0;
    if (j->rawindex != NULL)
        isc_mem_put(j->mctx, j->rawindex, j->header.index_size *
                sizeof(journal_rawpos_t));
    if (j->index != NULL)
        isc_mem_put(j->mctx, j->index, j->header.index_size *
                sizeof(journal_pos_t));
    if (j->filename != NULL)
        isc_mem_free(j->mctx, j->filename);
    if (j->fp != NULL)
        (void)isc_stdio_close(j->fp);
    isc_mem_putanddetach(&j->mctx, j, sizeof(*j));
    return (result);
}

isc_result_t
dns_journal_open(isc_mem_t *mctx, const char *filename, unsigned int mode,
         dns_journal_t **journalp)
{
    isc_result_t result;
    size_t namelen;
    char backup[1024];
    isc_boolean_t writable, create;

    create = ISC_TF(mode & DNS_JOURNAL_CREATE);
    writable = ISC_TF(mode & (DNS_JOURNAL_WRITE|DNS_JOURNAL_CREATE));

    result = journal_open(mctx, filename, writable, create, journalp);
    if (result == ISC_R_NOTFOUND) {
        namelen = strlen(filename);
        if (namelen > 4U && strcmp(filename + namelen - 4, ".jnl") == 0)
            namelen -= 4;

        result = isc_string_printf(backup, sizeof(backup), "%.*s.jbk",
                       (int)namelen, filename);
        if (result != ISC_R_SUCCESS)
            return (result);
        result = journal_open(mctx, backup, writable, writable,
                      journalp);
    }
    return (result);
}

/*
 * A comparison function defining the sorting order for
 * entries in the IXFR-style journal file.
 *
 * The IXFR format requires that deletions are sorted before
 * additions, and within either one, SOA records are sorted
 * before others.
 *
 * Also sort the non-SOA records by type as a courtesy to the
 * server receiving the IXFR - it may help reduce the amount of
 * rdataset merging it has to do.
 */
static int
ixfr_order(const void *av, const void *bv) {
    dns_difftuple_t const * const *ap = av;
    dns_difftuple_t const * const *bp = bv;
    dns_difftuple_t const *a = *ap;
    dns_difftuple_t const *b = *bp;
    int r;
    int bop = 0, aop = 0;

    switch (a->op) {
    case DNS_DIFFOP_DEL:
    case DNS_DIFFOP_DELRESIGN:
        aop = 1;
        break;
    case DNS_DIFFOP_ADD:
    case DNS_DIFFOP_ADDRESIGN:
        aop = 0;
        break;
    default:
        INSIST(0);
    }

    switch (b->op) {
    case DNS_DIFFOP_DEL:
    case DNS_DIFFOP_DELRESIGN:
        bop = 1;
        break;
    case DNS_DIFFOP_ADD:
    case DNS_DIFFOP_ADDRESIGN:
        bop = 0;
        break;
    default:
        INSIST(0);
    }

    r = bop - aop;
    if (r != 0)
        return (r);

    r = (b->rdata.type == dns_rdatatype_soa) -
        (a->rdata.type == dns_rdatatype_soa);
    if (r != 0)
        return (r);

    r = (a->rdata.type - b->rdata.type);
    return (r);
}

/*
 * Advance '*pos' to the next journal transaction.
 *
 * Requires:
 *  *pos refers to a valid journal transaction.
 *
 * Ensures:
 *  When ISC_R_SUCCESS is returned,
 *  *pos refers to the next journal transaction.
 *
 * Returns one of:
 *
 *    ISC_R_SUCCESS
 *    ISC_R_NOMORE  *pos pointed at the last transaction
 *    Other results due to file errors are possible.
 */
static isc_result_t
journal_next(dns_journal_t *j, journal_pos_t *pos) {
    isc_result_t result;
    journal_xhdr_t xhdr;
    REQUIRE(DNS_JOURNAL_VALID(j));

    result = journal_seek(j, pos->offset);
    if (result != ISC_R_SUCCESS)
        return (result);

    if (pos->serial == j->header.end.serial)
        return (ISC_R_NOMORE);
    /*
     * Read the header of the current transaction.
     * This will return ISC_R_NOMORE if we are at EOF.
     */
    result = journal_read_xhdr(j, &xhdr);
    if (result != ISC_R_SUCCESS)
        return (result);

    /*
     * Check serial number consistency.
     */
    if (xhdr.serial0 != pos->serial) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: journal file corrupt: "
                  "expected serial %u, got %u",
                  j->filename, pos->serial, xhdr.serial0);
        return (ISC_R_UNEXPECTED);
    }

    /*
     * Check for offset wraparound.
     */
    if ((isc_offset_t)(pos->offset + sizeof(journal_rawxhdr_t) + xhdr.size)
        < pos->offset) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: offset too large", j->filename);
        return (ISC_R_UNEXPECTED);
    }

    pos->offset += sizeof(journal_rawxhdr_t) + xhdr.size;
    pos->serial = xhdr.serial1;
    return (ISC_R_SUCCESS);
}

/*
 * If the index of the journal 'j' contains an entry "better"
 * than '*best_guess', replace '*best_guess' with it.
 *
 * "Better" means having a serial number closer to 'serial'
 * but not greater than 'serial'.
 */
static void
index_find(dns_journal_t *j, isc_uint32_t serial, journal_pos_t *best_guess) {
    unsigned int i;
    if (j->index == NULL)
        return;
    for (i = 0; i < j->header.index_size; i++) {
        if (POS_VALID(j->index[i]) &&
            DNS_SERIAL_GE(serial, j->index[i].serial) &&
            DNS_SERIAL_GT(j->index[i].serial, best_guess->serial))
            *best_guess = j->index[i];
    }
}

/*
 * Add a new index entry.  If there is no room, make room by removing
 * the odd-numbered entries and compacting the others into the first
 * half of the index.  This decimates old index entries exponentially
 * over time, so that the index always contains a much larger fraction
 * of recent serial numbers than of old ones.  This is deliberate -
 * most index searches are for outgoing IXFR, and IXFR tends to request
 * recent versions more often than old ones.
 */
static void
index_add(dns_journal_t *j, journal_pos_t *pos) {
    unsigned int i;
    if (j->index == NULL)
        return;
    /*
     * Search for a vacant position.
     */
    for (i = 0; i < j->header.index_size; i++) {
        if (! POS_VALID(j->index[i]))
            break;
    }
    if (i == j->header.index_size) {
        unsigned int k = 0;
        /*
         * Found no vacant position.  Make some room.
         */
        for (i = 0; i < j->header.index_size; i += 2) {
            j->index[k++] = j->index[i];
        }
        i = k; /* 'i' identifies the first vacant position. */
        while (k < j->header.index_size) {
            POS_INVALIDATE(j->index[k]);
            k++;
        }
    }
    INSIST(i < j->header.index_size);
    INSIST(! POS_VALID(j->index[i]));

    /*
     * Store the new index entry.
     */
    j->index[i] = *pos;
}

/*
 * Invalidate any existing index entries that could become
 * ambiguous when a new transaction with number 'serial' is added.
 */
static void
index_invalidate(dns_journal_t *j, isc_uint32_t serial) {
    unsigned int i;
    if (j->index == NULL)
        return;
    for (i = 0; i < j->header.index_size; i++) {
        if (! DNS_SERIAL_GT(serial, j->index[i].serial))
            POS_INVALIDATE(j->index[i]);
    }
}

/*
 * Try to find a transaction with initial serial number 'serial'
 * in the journal 'j'.
 *
 * If found, store its position at '*pos' and return ISC_R_SUCCESS.
 *
 * If 'serial' is current (= the ending serial number of the
 * last transaction in the journal), set '*pos' to
 * the position immediately following the last transaction and
 * return ISC_R_SUCCESS.
 *
 * If 'serial' is within the range of addressable serial numbers
 * covered by the journal but that particular serial number is missing
 * (from the journal, not just from the index), return ISC_R_NOTFOUND.
 *
 * If 'serial' is outside the range of addressable serial numbers
 * covered by the journal, return ISC_R_RANGE.
 *
 */
static isc_result_t
journal_find(dns_journal_t *j, isc_uint32_t serial, journal_pos_t *pos) {
    isc_result_t result;
    journal_pos_t current_pos;
    REQUIRE(DNS_JOURNAL_VALID(j));

    if (DNS_SERIAL_GT(j->header.begin.serial, serial))
        return (ISC_R_RANGE);
    if (DNS_SERIAL_GT(serial, j->header.end.serial))
        return (ISC_R_RANGE);
    if (serial == j->header.end.serial) {
        *pos = j->header.end;
        return (ISC_R_SUCCESS);
    }

    current_pos = j->header.begin;
    index_find(j, serial, &current_pos);

    while (current_pos.serial != serial) {
        if (DNS_SERIAL_GT(current_pos.serial, serial))
            return (ISC_R_NOTFOUND);
        result = journal_next(j, &current_pos);
        if (result != ISC_R_SUCCESS)
            return (result);
    }
    *pos = current_pos;
    return (ISC_R_SUCCESS);
}

isc_result_t
dns_journal_begin_transaction(dns_journal_t *j) {
    isc_uint32_t offset;
    isc_result_t result;
    journal_rawxhdr_t hdr;

    REQUIRE(DNS_JOURNAL_VALID(j));
    REQUIRE(j->state == JOURNAL_STATE_WRITE ||
        j->state == JOURNAL_STATE_INLINE);

    /*
     * Find the file offset where the new transaction should
     * be written, and seek there.
     */
    if (JOURNAL_EMPTY(&j->header)) {
        offset = sizeof(journal_rawheader_t) +
            j->header.index_size * sizeof(journal_rawpos_t);
    } else {
        offset = j->header.end.offset;
    }
    j->x.pos[0].offset = offset;
    j->x.pos[1].offset = offset; /* Initial value, will be incremented. */
    j->x.n_soa = 0;

    CHECK(journal_seek(j, offset));

    /*
     * Write a dummy transaction header of all zeroes to reserve
     * space.  It will be filled in when the transaction is
     * finished.
     */
    memset(&hdr, 0, sizeof(hdr));
    CHECK(journal_write(j, &hdr, sizeof(hdr)));
    j->x.pos[1].offset = j->offset;

    j->state = JOURNAL_STATE_TRANSACTION;
    result = ISC_R_SUCCESS;
 failure:
    return (result);
}

isc_result_t
dns_journal_writediff(dns_journal_t *j, dns_diff_t *diff) {
    dns_difftuple_t *t;
    isc_buffer_t buffer;
    void *mem = NULL;
    unsigned int size;
    isc_result_t result;
    isc_region_t used;

    REQUIRE(DNS_DIFF_VALID(diff));
    REQUIRE(j->state == JOURNAL_STATE_TRANSACTION);

    isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "writing to journal");
    (void)dns_diff_print(diff, NULL);

    /*
     * Pass 1: determine the buffer size needed, and
     * keep track of SOA serial numbers.
     */
    size = 0;
    for (t = ISC_LIST_HEAD(diff->tuples); t != NULL;
         t = ISC_LIST_NEXT(t, link))
    {
        if (t->rdata.type == dns_rdatatype_soa) {
            if (j->x.n_soa < 2)
                j->x.pos[j->x.n_soa].serial =
                    dns_soa_getserial(&t->rdata);
            j->x.n_soa++;
        }
        size += sizeof(journal_rawrrhdr_t);
        size += t->name.length; /* XXX should have access macro? */
        size += 10;
        size += t->rdata.length;
    }

    mem = isc_mem_get(j->mctx, size);
    if (mem == NULL)
        return (ISC_R_NOMEMORY);

    isc_buffer_init(&buffer, mem, size);

    /*
     * Pass 2.  Write RRs to buffer.
     */
    for (t = ISC_LIST_HEAD(diff->tuples); t != NULL;
         t = ISC_LIST_NEXT(t, link))
    {
        /*
         * Write the RR header.
         */
        isc_buffer_putuint32(&buffer, t->name.length + 10 +
                     t->rdata.length);
        /*
         * Write the owner name, RR header, and RR data.
         */
        isc_buffer_putmem(&buffer, t->name.ndata, t->name.length);
        isc_buffer_putuint16(&buffer, t->rdata.type);
        isc_buffer_putuint16(&buffer, t->rdata.rdclass);
        isc_buffer_putuint32(&buffer, t->ttl);
        INSIST(t->rdata.length < 65536);
        isc_buffer_putuint16(&buffer, (isc_uint16_t)t->rdata.length);
        INSIST(isc_buffer_availablelength(&buffer) >= t->rdata.length);
        isc_buffer_putmem(&buffer, t->rdata.data, t->rdata.length);
    }

    isc_buffer_usedregion(&buffer, &used);
    INSIST(used.length == size);

    j->x.pos[1].offset += used.length;

    /*
     * Write the buffer contents to the journal file.
     */
    CHECK(journal_write(j, used.base, used.length));

    result = ISC_R_SUCCESS;

 failure:
    if (mem != NULL)
        isc_mem_put(j->mctx, mem, size);
    return (result);

}

isc_result_t
dns_journal_commit(dns_journal_t *j) {
    isc_result_t result;
    journal_rawheader_t rawheader;

    REQUIRE(DNS_JOURNAL_VALID(j));
    REQUIRE(j->state == JOURNAL_STATE_TRANSACTION ||
        j->state == JOURNAL_STATE_INLINE);

    /*
     * Just write out a updated header.
     */
    if (j->state == JOURNAL_STATE_INLINE) {
        CHECK(journal_fsync(j));
        journal_header_encode(&j->header, &rawheader);
        CHECK(journal_seek(j, 0));
        CHECK(journal_write(j, &rawheader, sizeof(rawheader)));
        CHECK(journal_fsync(j));
        j->state = JOURNAL_STATE_WRITE;
        return (ISC_R_SUCCESS);
    }

    /*
     * Perform some basic consistency checks.
     */
    if (j->x.n_soa != 2) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: malformed transaction: %d SOAs",
                  j->filename, j->x.n_soa);
        return (ISC_R_UNEXPECTED);
    }
    if (! (DNS_SERIAL_GT(j->x.pos[1].serial, j->x.pos[0].serial) ||
           (bind8_compat &&
        j->x.pos[1].serial == j->x.pos[0].serial)))
    {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "%s: malformed transaction: serial number "
                  "would decrease", j->filename);
        return (ISC_R_UNEXPECTED);
    }
    if (! JOURNAL_EMPTY(&j->header)) {
        if (j->x.pos[0].serial != j->header.end.serial) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                     "malformed transaction: "
                     "%s last serial %u != "
                     "transaction first serial %u",
                     j->filename,
                     j->header.end.serial,
                     j->x.pos[0].serial);
            return (ISC_R_UNEXPECTED);
        }
    }

    /*
     * Some old journal entries may become non-addressable
     * when we increment the current serial number.  Purge them
     * by stepping header.begin forward to the first addressable
     * transaction.  Also purge them from the index.
     */
    if (! JOURNAL_EMPTY(&j->header)) {
        while (! DNS_SERIAL_GT(j->x.pos[1].serial,
                       j->header.begin.serial)) {
            CHECK(journal_next(j, &j->header.begin));
        }
        index_invalidate(j, j->x.pos[1].serial);
    }
#ifdef notyet
    if (DNS_SERIAL_GT(last_dumped_serial, j->x.pos[1].serial)) {
        force_dump(...);
    }
#endif

    /*
     * Commit the transaction data to stable storage.
     */
    CHECK(journal_fsync(j));

    if (j->state == JOURNAL_STATE_TRANSACTION) {
        isc_offset_t offset;
        offset = (j->x.pos[1].offset - j->x.pos[0].offset) -
                 sizeof(journal_rawxhdr_t);
        /*
         * Update the transaction header.
         */
        CHECK(journal_seek(j, j->x.pos[0].offset));
        CHECK(journal_write_xhdr(j, offset, j->x.pos[0].serial,
                     j->x.pos[1].serial));
    }

    /*
     * Update the journal header.
     */
    if (JOURNAL_EMPTY(&j->header))
        j->header.begin = j->x.pos[0];
    j->header.end = j->x.pos[1];
    journal_header_encode(&j->header, &rawheader);
    CHECK(journal_seek(j, 0));
    CHECK(journal_write(j, &rawheader, sizeof(rawheader)));

    /*
     * Update the index.
     */
    index_add(j, &j->x.pos[0]);

    /*
     * Convert the index into on-disk format and write
     * it to disk.
     */
    CHECK(index_to_disk(j));

    /*
     * Commit the header to stable storage.
     */
    CHECK(journal_fsync(j));

    /*
     * We no longer have a transaction open.
     */
    j->state = JOURNAL_STATE_WRITE;

    result = ISC_R_SUCCESS;

 failure:
    return (result);
}

isc_result_t
dns_journal_write_transaction(dns_journal_t *j, dns_diff_t *diff) {
    isc_result_t result;
    CHECK(dns_diff_sort(diff, ixfr_order));
    CHECK(dns_journal_begin_transaction(j));
    CHECK(dns_journal_writediff(j, diff));
    CHECK(dns_journal_commit(j));
    result = ISC_R_SUCCESS;
 failure:
    return (result);
}

void
dns_journal_destroy(dns_journal_t **journalp) {
    dns_journal_t *j = *journalp;
    REQUIRE(DNS_JOURNAL_VALID(j));

    j->it.result = ISC_R_FAILURE;
    dns_name_invalidate(&j->it.name);
    dns_decompress_invalidate(&j->it.dctx);
    if (j->rawindex != NULL)
        isc_mem_put(j->mctx, j->rawindex, j->header.index_size *
                sizeof(journal_rawpos_t));
    if (j->index != NULL)
        isc_mem_put(j->mctx, j->index, j->header.index_size *
                sizeof(journal_pos_t));
    if (j->it.target.base != NULL)
        isc_mem_put(j->mctx, j->it.target.base, j->it.target.length);
    if (j->it.source.base != NULL)
        isc_mem_put(j->mctx, j->it.source.base, j->it.source.length);
    if (j->filename != NULL)
        isc_mem_free(j->mctx, j->filename);
    if (j->fp != NULL)
        (void)isc_stdio_close(j->fp);
    j->magic = 0;
    isc_mem_putanddetach(&j->mctx, j, sizeof(*j));
    *journalp = NULL;
}

/*
 * Roll the open journal 'j' into the database 'db'.
 * A new database version will be created.
 */

/* XXX Share code with incoming IXFR? */

static isc_result_t
roll_forward(dns_journal_t *j, dns_db_t *db, unsigned int options) {
    isc_buffer_t source;        /* Transaction data from disk */
    isc_buffer_t target;        /* Ditto after _fromwire check */
    isc_uint32_t db_serial;     /* Database SOA serial */
    isc_uint32_t end_serial;    /* Last journal SOA serial */
    isc_result_t result;
    dns_dbversion_t *ver = NULL;
    journal_pos_t pos;
    dns_diff_t diff;
    unsigned int n_soa = 0;
    unsigned int n_put = 0;
    dns_diffop_t op;

    REQUIRE(DNS_JOURNAL_VALID(j));
    REQUIRE(DNS_DB_VALID(db));

    dns_diff_init(j->mctx, &diff);

    /*
     * Set up empty initial buffers for unchecked and checked
     * wire format transaction data.  They will be reallocated
     * later.
     */
    isc_buffer_init(&source, NULL, 0);
    isc_buffer_init(&target, NULL, 0);

    /*
     * Create the new database version.
     */
    CHECK(dns_db_newversion(db, &ver));

    /*
     * Get the current database SOA serial number.
     */
    CHECK(dns_db_getsoaserial(db, ver, &db_serial));

    /*
     * Locate a journal entry for the current database serial.
     */
    CHECK(journal_find(j, db_serial, &pos));
    /*
     * XXX do more drastic things, like marking zone stale,
     * if this fails?
     */
    /*
     * XXXRTH  The zone code should probably mark the zone as bad and
     *         scream loudly into the log if this is a dynamic update
     *     log reply that failed.
     */

    end_serial = dns_journal_last_serial(j);
    if (db_serial == end_serial)
        CHECK(DNS_R_UPTODATE);

    CHECK(dns_journal_iter_init(j, db_serial, end_serial));

    for (result = dns_journal_first_rr(j);
         result == ISC_R_SUCCESS;
         result = dns_journal_next_rr(j))
    {
        dns_name_t *name;
        isc_uint32_t ttl;
        dns_rdata_t *rdata;
        dns_difftuple_t *tuple = NULL;

        name = NULL;
        rdata = NULL;
        dns_journal_current_rr(j, &name, &ttl, &rdata);

        if (rdata->type == dns_rdatatype_soa) {
            n_soa++;
            if (n_soa == 2)
                db_serial = j->it.current_serial;
        }

        if (n_soa == 3)
            n_soa = 1;
        if (n_soa == 0) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                     "%s: journal file corrupt: missing "
                     "initial SOA", j->filename);
            FAIL(ISC_R_UNEXPECTED);
        }
        if ((options & DNS_JOURNALOPT_RESIGN) != 0)
            op = (n_soa == 1) ? DNS_DIFFOP_DELRESIGN :
                        DNS_DIFFOP_ADDRESIGN;
        else
            op = (n_soa == 1) ? DNS_DIFFOP_DEL : DNS_DIFFOP_ADD;

        CHECK(dns_difftuple_create(diff.mctx, op, name, ttl, rdata,
                       &tuple));
        dns_diff_append(&diff, &tuple);

        if (++n_put > 100)  {
            isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                      "%s: applying diff to database (%u)",
                      j->filename, db_serial);
            (void)dns_diff_print(&diff, NULL);
            CHECK(dns_diff_apply(&diff, db, ver));
            dns_diff_clear(&diff);
            n_put = 0;
        }
    }
    if (result == ISC_R_NOMORE)
        result = ISC_R_SUCCESS;
    CHECK(result);

    if (n_put != 0) {
        isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                  "%s: applying final diff to database (%u)",
                  j->filename, db_serial);
        (void)dns_diff_print(&diff, NULL);
        CHECK(dns_diff_apply(&diff, db, ver));
        dns_diff_clear(&diff);
    }

 failure:
    if (ver != NULL)
        dns_db_closeversion(db, &ver, result == ISC_R_SUCCESS ?
                    ISC_TRUE : ISC_FALSE);

    if (source.base != NULL)
        isc_mem_put(j->mctx, source.base, source.length);
    if (target.base != NULL)
        isc_mem_put(j->mctx, target.base, target.length);

    dns_diff_clear(&diff);

    INSIST(ver == NULL);

    return (result);
}

isc_result_t
dns_journal_rollforward(isc_mem_t *mctx, dns_db_t *db, unsigned int options,
            const char *filename)
{
    dns_journal_t *j;
    isc_result_t result;

    REQUIRE(DNS_DB_VALID(db));
    REQUIRE(filename != NULL);

    j = NULL;
    result = dns_journal_open(mctx, filename, DNS_JOURNAL_READ, &j);
    if (result == ISC_R_NOTFOUND) {
        isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                  "no journal file, but that's OK");
        return (DNS_R_NOJOURNAL);
    }
    if (result != ISC_R_SUCCESS)
        return (result);
    if (JOURNAL_EMPTY(&j->header))
        result = DNS_R_UPTODATE;
    else
        result = roll_forward(j, db, options);

    dns_journal_destroy(&j);

    return (result);
}

isc_result_t
dns_journal_print(isc_mem_t *mctx, const char *filename, FILE *file) {
    dns_journal_t *j;
    isc_buffer_t source;        /* Transaction data from disk */
    isc_buffer_t target;        /* Ditto after _fromwire check */
    isc_uint32_t start_serial;      /* Database SOA serial */
    isc_uint32_t end_serial;    /* Last journal SOA serial */
    isc_result_t result;
    dns_diff_t diff;
    unsigned int n_soa = 0;
    unsigned int n_put = 0;

    REQUIRE(filename != NULL);

    j = NULL;
    result = dns_journal_open(mctx, filename, DNS_JOURNAL_READ, &j);
    if (result == ISC_R_NOTFOUND) {
        isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "no journal file");
        return (DNS_R_NOJOURNAL);
    }

    if (result != ISC_R_SUCCESS) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                  "journal open failure: %s: %s",
                  isc_result_totext(result), filename);
        return (result);
    }

    if (j->header.serialset)
        fprintf(file, "Source serial = %u\n", j->header.sourceserial);
    dns_diff_init(j->mctx, &diff);

    /*
     * Set up empty initial buffers for unchecked and checked
     * wire format transaction data.  They will be reallocated
     * later.
     */
    isc_buffer_init(&source, NULL, 0);
    isc_buffer_init(&target, NULL, 0);

    start_serial = dns_journal_first_serial(j);
    end_serial = dns_journal_last_serial(j);

    CHECK(dns_journal_iter_init(j, start_serial, end_serial));

    for (result = dns_journal_first_rr(j);
         result == ISC_R_SUCCESS;
         result = dns_journal_next_rr(j))
    {
        dns_name_t *name;
        isc_uint32_t ttl;
        dns_rdata_t *rdata;
        dns_difftuple_t *tuple = NULL;

        name = NULL;
        rdata = NULL;
        dns_journal_current_rr(j, &name, &ttl, &rdata);

        if (rdata->type == dns_rdatatype_soa)
            n_soa++;

        if (n_soa == 3)
            n_soa = 1;
        if (n_soa == 0) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                      "%s: journal file corrupt: missing "
                      "initial SOA", j->filename);
            FAIL(ISC_R_UNEXPECTED);
        }
        CHECK(dns_difftuple_create(diff.mctx, n_soa == 1 ?
                       DNS_DIFFOP_DEL : DNS_DIFFOP_ADD,
                       name, ttl, rdata, &tuple));
        dns_diff_append(&diff, &tuple);

        if (++n_put > 100)  {
            result = dns_diff_print(&diff, file);
            dns_diff_clear(&diff);
            n_put = 0;
            if (result != ISC_R_SUCCESS)
                break;
        }
    }
    if (result == ISC_R_NOMORE)
        result = ISC_R_SUCCESS;
    CHECK(result);

    if (n_put != 0) {
        result = dns_diff_print(&diff, file);
        dns_diff_clear(&diff);
    }
    goto cleanup;

 failure:
    isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
              "%s: cannot print: journal file corrupt", j->filename);

 cleanup:
    if (source.base != NULL)
        isc_mem_put(j->mctx, source.base, source.length);
    if (target.base != NULL)
        isc_mem_put(j->mctx, target.base, target.length);

    dns_diff_clear(&diff);
    dns_journal_destroy(&j);

    return (result);
}

/**************************************************************************/
/*
 * Miscellaneous accessors.
 */
isc_uint32_t
dns_journal_first_serial(dns_journal_t *j) {
    return (j->header.begin.serial);
}

isc_uint32_t
dns_journal_last_serial(dns_journal_t *j) {
    return (j->header.end.serial);
}

void
dns_journal_set_sourceserial(dns_journal_t *j, isc_uint32_t sourceserial) {

    REQUIRE(j->state == JOURNAL_STATE_WRITE ||
        j->state == JOURNAL_STATE_INLINE ||
        j->state == JOURNAL_STATE_TRANSACTION);

    j->header.sourceserial = sourceserial;
    j->header.serialset = ISC_TRUE;
    if (j->state == JOURNAL_STATE_WRITE)
        j->state = JOURNAL_STATE_INLINE;
}

isc_boolean_t
dns_journal_get_sourceserial(dns_journal_t *j, isc_uint32_t *sourceserial) {
    REQUIRE(sourceserial != NULL);

    if (!j->header.serialset)
        return (ISC_FALSE);
    *sourceserial = j->header.sourceserial;
    return (ISC_TRUE);
}

/**************************************************************************/
/*
 * Iteration support.
 *
 * When serving an outgoing IXFR, we transmit a part the journal starting
 * at the serial number in the IXFR request and ending at the serial
 * number that is current when the IXFR request arrives.  The ending
 * serial number is not necessarily at the end of the journal:
 * the journal may grow while the IXFR is in progress, but we stop
 * when we reach the serial number that was current when the IXFR started.
 */

static isc_result_t read_one_rr(dns_journal_t *j);

/*
 * Make sure the buffer 'b' is has at least 'size' bytes
 * allocated, and clear it.
 *
 * Requires:
 *  Either b->base is NULL, or it points to b->length bytes of memory
 *  previously allocated by isc_mem_get().
 */

static isc_result_t
size_buffer(isc_mem_t *mctx, isc_buffer_t *b, unsigned size) {
    if (b->length < size) {
        void *mem = isc_mem_get(mctx, size);
        if (mem == NULL)
            return (ISC_R_NOMEMORY);
        if (b->base != NULL)
            isc_mem_put(mctx, b->base, b->length);
        b->base = mem;
        b->length = size;
    }
    isc_buffer_clear(b);
    return (ISC_R_SUCCESS);
}

isc_result_t
dns_journal_iter_init(dns_journal_t *j,
              isc_uint32_t begin_serial, isc_uint32_t end_serial)
{
    isc_result_t result;

    CHECK(journal_find(j, begin_serial, &j->it.bpos));
    INSIST(j->it.bpos.serial == begin_serial);

    CHECK(journal_find(j, end_serial, &j->it.epos));
    INSIST(j->it.epos.serial == end_serial);

    result = ISC_R_SUCCESS;
 failure:
    j->it.result = result;
    return (j->it.result);
}


isc_result_t
dns_journal_first_rr(dns_journal_t *j) {
    isc_result_t result;

    /*
     * Seek to the beginning of the first transaction we are
     * interested in.
     */
    CHECK(journal_seek(j, j->it.bpos.offset));
    j->it.current_serial = j->it.bpos.serial;

    j->it.xsize = 0;  /* We have no transaction data yet... */
    j->it.xpos = 0;   /* ...and haven't used any of it. */

    return (read_one_rr(j));

 failure:
    return (result);
}

static isc_result_t
read_one_rr(dns_journal_t *j) {
    isc_result_t result;

    dns_rdatatype_t rdtype;
    dns_rdataclass_t rdclass;
    unsigned int rdlen;
    isc_uint32_t ttl;
    journal_xhdr_t xhdr;
    journal_rrhdr_t rrhdr;

    INSIST(j->offset <= j->it.epos.offset);
    if (j->offset == j->it.epos.offset)
        return (ISC_R_NOMORE);
    if (j->it.xpos == j->it.xsize) {
        /*
         * We are at a transaction boundary.
         * Read another transaction header.
         */
        CHECK(journal_read_xhdr(j, &xhdr));
        if (xhdr.size == 0) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                      "%s: journal corrupt: empty transaction",
                      j->filename);
            FAIL(ISC_R_UNEXPECTED);
        }
        if (xhdr.serial0 != j->it.current_serial) {
            isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                     "%s: journal file corrupt: "
                     "expected serial %u, got %u",
                     j->filename,
                     j->it.current_serial, xhdr.serial0);
            FAIL(ISC_R_UNEXPECTED);
        }
        j->it.xsize = xhdr.size;
        j->it.xpos = 0;
    }
    /*
     * Read an RR.
     */
    CHECK(journal_read_rrhdr(j, &rrhdr));
    /*
     * Perform a sanity check on the journal RR size.
     * The smallest possible RR has a 1-byte owner name
     * and a 10-byte header.  The largest possible
     * RR has 65535 bytes of data, a header, and a maximum-
     * size owner name, well below 70 k total.
     */
    if (rrhdr.size < 1+10 || rrhdr.size > 70000) {
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                 "%s: journal corrupt: impossible RR size "
                 "(%d bytes)", j->filename, rrhdr.size);
        FAIL(ISC_R_UNEXPECTED);
    }

    CHECK(size_buffer(j->mctx, &j->it.source, rrhdr.size));
    CHECK(journal_read(j, j->it.source.base, rrhdr.size));
    isc_buffer_add(&j->it.source, rrhdr.size);

    /*
     * The target buffer is made the same size
     * as the source buffer, with the assumption that when
     * no compression in present, the output of dns_*_fromwire()
     * is no larger than the input.
     */
    CHECK(size_buffer(j->mctx, &j->it.target, rrhdr.size));

    /*
     * Parse the owner name.  We don't know where it
     * ends yet, so we make the entire "remaining"
     * part of the buffer "active".
     */
    isc_buffer_setactive(&j->it.source,
                 j->it.source.used - j->it.source.current);
    CHECK(dns_name_fromwire(&j->it.name, &j->it.source,
                &j->it.dctx, 0, &j->it.target));

    /*
     * Check that the RR header is there, and parse it.
     */
    if (isc_buffer_remaininglength(&j->it.source) < 10)
        FAIL(DNS_R_FORMERR);

    rdtype = isc_buffer_getuint16(&j->it.source);
    rdclass = isc_buffer_getuint16(&j->it.source);
    ttl = isc_buffer_getuint32(&j->it.source);
    rdlen = isc_buffer_getuint16(&j->it.source);

    /*
     * Parse the rdata.
     */
    if (isc_buffer_remaininglength(&j->it.source) != rdlen)
        FAIL(DNS_R_FORMERR);
    isc_buffer_setactive(&j->it.source, rdlen);
    dns_rdata_reset(&j->it.rdata);
    CHECK(dns_rdata_fromwire(&j->it.rdata, rdclass,
                 rdtype, &j->it.source, &j->it.dctx,
                 0, &j->it.target));
    j->it.ttl = ttl;

    j->it.xpos += sizeof(journal_rawrrhdr_t) + rrhdr.size;
    if (rdtype == dns_rdatatype_soa) {
        /* XXX could do additional consistency checks here */
        j->it.current_serial = dns_soa_getserial(&j->it.rdata);
    }

    result = ISC_R_SUCCESS;

 failure:
    j->it.result = result;
    return (result);
}

isc_result_t
dns_journal_next_rr(dns_journal_t *j) {
    j->it.result = read_one_rr(j);
    return (j->it.result);
}

void
dns_journal_current_rr(dns_journal_t *j, dns_name_t **name, isc_uint32_t *ttl,
           dns_rdata_t **rdata)
{
    REQUIRE(j->it.result == ISC_R_SUCCESS);
    *name = &j->it.name;
    *ttl = j->it.ttl;
    *rdata = &j->it.rdata;
}

/**************************************************************************/
/*
 * Generating diffs from databases
 */

/*
 * Construct a diff containing all the RRs at the current name of the
 * database iterator 'dbit' in database 'db', version 'ver'.
 * Set '*name' to the current name, and append the diff to 'diff'.
 * All new tuples will have the operation 'op'.
 *
 * Requires: 'name' must have buffer large enough to hold the name.
 * Typically, a dns_fixedname_t would be used.
 */
static isc_result_t
get_name_diff(dns_db_t *db, dns_dbversion_t *ver, isc_stdtime_t now,
          dns_dbiterator_t *dbit, dns_name_t *name, dns_diffop_t op,
          dns_diff_t *diff)
{
    isc_result_t result;
    dns_dbnode_t *node = NULL;
    dns_rdatasetiter_t *rdsiter = NULL;
    dns_difftuple_t *tuple = NULL;

    result = dns_dbiterator_current(dbit, &node, name);
    if (result != ISC_R_SUCCESS)
        return (result);

    result = dns_db_allrdatasets(db, node, ver, now, &rdsiter);
    if (result != ISC_R_SUCCESS)
        goto cleanup_node;

    for (result = dns_rdatasetiter_first(rdsiter);
         result == ISC_R_SUCCESS;
         result = dns_rdatasetiter_next(rdsiter))
    {
        dns_rdataset_t rdataset;

        dns_rdataset_init(&rdataset);
        dns_rdatasetiter_current(rdsiter, &rdataset);

        for (result = dns_rdataset_first(&rdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(&rdataset))
        {
            dns_rdata_t rdata = DNS_RDATA_INIT;
            dns_rdataset_current(&rdataset, &rdata);
            result = dns_difftuple_create(diff->mctx, op, name,
                              rdataset.ttl, &rdata,
                              &tuple);
            if (result != ISC_R_SUCCESS) {
                dns_rdataset_disassociate(&rdataset);
                goto cleanup_iterator;
            }
            dns_diff_append(diff, &tuple);
        }
        dns_rdataset_disassociate(&rdataset);
        if (result != ISC_R_NOMORE)
            goto cleanup_iterator;
    }
    if (result != ISC_R_NOMORE)
        goto cleanup_iterator;

    result = ISC_R_SUCCESS;

 cleanup_iterator:
    dns_rdatasetiter_destroy(&rdsiter);

 cleanup_node:
    dns_db_detachnode(db, &node);

    return (result);
}

/*
 * Comparison function for use by dns_diff_subtract when sorting
 * the diffs to be subtracted.  The sort keys are the rdata type
 * and the rdata itself.  The owner name is ignored, because
 * it is known to be the same for all tuples.
 */
static int
rdata_order(const void *av, const void *bv) {
    dns_difftuple_t const * const *ap = av;
    dns_difftuple_t const * const *bp = bv;
    dns_difftuple_t const *a = *ap;
    dns_difftuple_t const *b = *bp;
    int r;
    r = (b->rdata.type - a->rdata.type);
    if (r != 0)
        return (r);
    r = dns_rdata_compare(&a->rdata, &b->rdata);
    return (r);
}

static isc_result_t
dns_diff_subtract(dns_diff_t diff[2], dns_diff_t *r) {
    isc_result_t result;
    dns_difftuple_t *p[2];
    int i, t;
    isc_boolean_t append;

    CHECK(dns_diff_sort(&diff[0], rdata_order));
    CHECK(dns_diff_sort(&diff[1], rdata_order));

    for (;;) {
        p[0] = ISC_LIST_HEAD(diff[0].tuples);
        p[1] = ISC_LIST_HEAD(diff[1].tuples);
        if (p[0] == NULL && p[1] == NULL)
            break;

        for (i = 0; i < 2; i++)
            if (p[!i] == NULL) {
                ISC_LIST_UNLINK(diff[i].tuples, p[i], link);
                ISC_LIST_APPEND(r->tuples, p[i], link);
                goto next;
            }
        t = rdata_order(&p[0], &p[1]);
        if (t < 0) {
            ISC_LIST_UNLINK(diff[0].tuples, p[0], link);
            ISC_LIST_APPEND(r->tuples, p[0], link);
            goto next;
        }
        if (t > 0) {
            ISC_LIST_UNLINK(diff[1].tuples, p[1], link);
            ISC_LIST_APPEND(r->tuples, p[1], link);
            goto next;
        }
        INSIST(t == 0);
        /*
         * Identical RRs in both databases; skip them both
         * if the ttl differs.
         */
        append = ISC_TF(p[0]->ttl != p[1]->ttl);
        for (i = 0; i < 2; i++) {
            ISC_LIST_UNLINK(diff[i].tuples, p[i], link);
            if (append) {
                ISC_LIST_APPEND(r->tuples, p[i], link);
            } else {
                dns_difftuple_free(&p[i]);
            }
        }
    next: ;
    }
    result = ISC_R_SUCCESS;
 failure:
    return (result);
}

static isc_result_t
diff_namespace(dns_db_t *dba, dns_dbversion_t *dbvera,
           dns_db_t *dbb, dns_dbversion_t *dbverb,
           unsigned int options, dns_diff_t *resultdiff)
{
    dns_db_t *db[2];
    dns_dbversion_t *ver[2];
    dns_dbiterator_t *dbit[2] = { NULL, NULL };
    isc_boolean_t have[2] = { ISC_FALSE, ISC_FALSE };
    dns_fixedname_t fixname[2];
    isc_result_t result, itresult[2];
    dns_diff_t diff[2];
    int i, t;

    db[0] = dba, db[1] = dbb;
    ver[0] = dbvera, ver[1] = dbverb;

    dns_diff_init(resultdiff->mctx, &diff[0]);
    dns_diff_init(resultdiff->mctx, &diff[1]);

    dns_fixedname_init(&fixname[0]);
    dns_fixedname_init(&fixname[1]);

    result = dns_db_createiterator(db[0], options, &dbit[0]);
    if (result != ISC_R_SUCCESS)
        return (result);
    result = dns_db_createiterator(db[1], options, &dbit[1]);
    if (result != ISC_R_SUCCESS)
        goto cleanup_iterator;

    itresult[0] = dns_dbiterator_first(dbit[0]);
    itresult[1] = dns_dbiterator_first(dbit[1]);

    for (;;) {
        for (i = 0; i < 2; i++) {
            if (! have[i] && itresult[i] == ISC_R_SUCCESS) {
                CHECK(get_name_diff(db[i], ver[i], 0, dbit[i],
                        dns_fixedname_name(&fixname[i]),
                        i == 0 ?
                        DNS_DIFFOP_ADD :
                        DNS_DIFFOP_DEL,
                        &diff[i]));
                itresult[i] = dns_dbiterator_next(dbit[i]);
                have[i] = ISC_TRUE;
            }
        }

        if (! have[0] && ! have[1]) {
            INSIST(ISC_LIST_EMPTY(diff[0].tuples));
            INSIST(ISC_LIST_EMPTY(diff[1].tuples));
            break;
        }

        for (i = 0; i < 2; i++) {
            if (! have[!i]) {
                ISC_LIST_APPENDLIST(resultdiff->tuples,
                            diff[i].tuples, link);
                INSIST(ISC_LIST_EMPTY(diff[i].tuples));
                have[i] = ISC_FALSE;
                goto next;
            }
        }

        t = dns_name_compare(dns_fixedname_name(&fixname[0]),
                     dns_fixedname_name(&fixname[1]));
        if (t < 0) {
            ISC_LIST_APPENDLIST(resultdiff->tuples,
                        diff[0].tuples, link);
            INSIST(ISC_LIST_EMPTY(diff[0].tuples));
            have[0] = ISC_FALSE;
            continue;
        }
        if (t > 0) {
            ISC_LIST_APPENDLIST(resultdiff->tuples,
                        diff[1].tuples, link);
            INSIST(ISC_LIST_EMPTY(diff[1].tuples));
            have[1] = ISC_FALSE;
            continue;
        }
        INSIST(t == 0);
        CHECK(dns_diff_subtract(diff, resultdiff));
        INSIST(ISC_LIST_EMPTY(diff[0].tuples));
        INSIST(ISC_LIST_EMPTY(diff[1].tuples));
        have[0] = have[1] = ISC_FALSE;
    next: ;
    }
    if (itresult[0] != ISC_R_NOMORE)
        FAIL(itresult[0]);
    if (itresult[1] != ISC_R_NOMORE)
        FAIL(itresult[1]);

    INSIST(ISC_LIST_EMPTY(diff[0].tuples));
    INSIST(ISC_LIST_EMPTY(diff[1].tuples));

 failure:
    dns_dbiterator_destroy(&dbit[1]);

 cleanup_iterator:
    dns_dbiterator_destroy(&dbit[0]);
    dns_diff_clear(&diff[0]);
    dns_diff_clear(&diff[1]);
    return (result);
}

/*
 * Compare the databases 'dba' and 'dbb' and generate a journal
 * entry containing the changes to make 'dba' from 'dbb' (note
 * the order).  This journal entry will consist of a single,
 * possibly very large transaction.
 */
isc_result_t
dns_db_diff(isc_mem_t *mctx, dns_db_t *dba, dns_dbversion_t *dbvera,
        dns_db_t *dbb, dns_dbversion_t *dbverb, const char *filename)
{
    isc_result_t result;
    dns_diff_t diff;

    dns_diff_init(mctx, &diff);

    result = dns_db_diffx(&diff, dba, dbvera, dbb, dbverb, filename);

    dns_diff_clear(&diff);

    return (result);
}

isc_result_t
dns_db_diffx(dns_diff_t *diff, dns_db_t *dba, dns_dbversion_t *dbvera,
         dns_db_t *dbb, dns_dbversion_t *dbverb, const char *filename)
{
    isc_result_t result;
    dns_journal_t *journal = NULL;

    if (filename != NULL) {
        result = dns_journal_open(diff->mctx, filename,
                      DNS_JOURNAL_CREATE, &journal);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    CHECK(diff_namespace(dba, dbvera, dbb, dbverb, DNS_DB_NONSEC3, diff));
    CHECK(diff_namespace(dba, dbvera, dbb, dbverb, DNS_DB_NSEC3ONLY, diff));

    if (journal != NULL) {
        if (ISC_LIST_EMPTY(diff->tuples))
            isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "no changes");
        else
            CHECK(dns_journal_write_transaction(journal, diff));
    }

 failure:
    if (journal != NULL)
        dns_journal_destroy(&journal);
    return (result);
}

isc_result_t
dns_journal_compact(isc_mem_t *mctx, char *filename, isc_uint32_t serial,
            isc_uint32_t target_size)
{
    unsigned int i;
    journal_pos_t best_guess;
    journal_pos_t current_pos;
    dns_journal_t *j = NULL;
    dns_journal_t *new = NULL;
    journal_rawheader_t rawheader;
    unsigned int copy_length;
    size_t namelen;
    char *buf = NULL;
    unsigned int size = 0;
    isc_result_t result;
    unsigned int indexend;
    char newname[1024];
    char backup[1024];
    isc_boolean_t is_backup = ISC_FALSE;

    REQUIRE(filename != NULL);

    namelen = strlen(filename);
    if (namelen > 4U && strcmp(filename + namelen - 4, ".jnl") == 0)
        namelen -= 4;

    result = isc_string_printf(newname, sizeof(newname), "%.*s.jnw",
                   (int)namelen, filename);
    if (result != ISC_R_SUCCESS)
        return (result);

    result = isc_string_printf(backup, sizeof(backup), "%.*s.jbk",
                   (int)namelen, filename);
    if (result != ISC_R_SUCCESS)
        return (result);

    result = journal_open(mctx, filename, ISC_FALSE, ISC_FALSE, &j);
    if (result == ISC_R_NOTFOUND) {
        is_backup = ISC_TRUE;
        result = journal_open(mctx, backup, ISC_FALSE, ISC_FALSE, &j);
    }
    if (result != ISC_R_SUCCESS)
        return (result);

    if (JOURNAL_EMPTY(&j->header)) {
        dns_journal_destroy(&j);
        return (ISC_R_SUCCESS);
    }

    if (DNS_SERIAL_GT(j->header.begin.serial, serial) ||
        DNS_SERIAL_GT(serial, j->header.end.serial)) {
        dns_journal_destroy(&j);
        return (ISC_R_RANGE);
    }

    /*
     * Cope with very small target sizes.
     */
    indexend = sizeof(journal_rawheader_t) +
           j->header.index_size * sizeof(journal_rawpos_t);
    if (target_size < indexend * 2)
        target_size = target_size/2 + indexend;

    /*
     * See if there is any work to do.
     */
    if ((isc_uint32_t) j->header.end.offset < target_size) {
        dns_journal_destroy(&j);
        return (ISC_R_SUCCESS);
    }

    CHECK(journal_open(mctx, newname, ISC_TRUE, ISC_TRUE, &new));

    /*
     * Remove overhead so space test below can succeed.
     */
    if (target_size >= indexend)
        target_size -= indexend;

    /*
     * Find if we can create enough free space.
     */
    best_guess = j->header.begin;
    for (i = 0; i < j->header.index_size; i++) {
        if (POS_VALID(j->index[i]) &&
            DNS_SERIAL_GE(serial, j->index[i].serial) &&
            ((isc_uint32_t)(j->header.end.offset - j->index[i].offset)
             >= target_size / 2) &&
            j->index[i].offset > best_guess.offset)
            best_guess = j->index[i];
    }

    current_pos = best_guess;
    while (current_pos.serial != serial) {
        CHECK(journal_next(j, &current_pos));
        if (current_pos.serial == j->header.end.serial)
            break;

        if (DNS_SERIAL_GE(serial, current_pos.serial) &&
           ((isc_uint32_t)(j->header.end.offset - current_pos.offset)
             >= (target_size / 2)) &&
            current_pos.offset > best_guess.offset)
            best_guess = current_pos;
        else
            break;
    }

    INSIST(best_guess.serial != j->header.end.serial);
    if (best_guess.serial != serial)
        CHECK(journal_next(j, &best_guess));

    /*
     * We should now be roughly half target_size provided
     * we did not reach 'serial'.  If not we will just copy
     * all uncommitted deltas regardless of the size.
     */
    copy_length = j->header.end.offset - best_guess.offset;

    if (copy_length != 0) {
        /*
         * Copy best_guess to end into space just freed.
         */
        size = 64*1024;
        if (copy_length < size)
            size = copy_length;
        buf = isc_mem_get(mctx, size);
        if (buf == NULL) {
            result = ISC_R_NOMEMORY;
            goto failure;
        }

        CHECK(journal_seek(j, best_guess.offset));
        CHECK(journal_seek(new, indexend));
        for (i = 0; i < copy_length; i += size) {
            unsigned int len = (copy_length - i) > size ? size :
                             (copy_length - i);
            CHECK(journal_read(j, buf, len));
            CHECK(journal_write(new, buf, len));
        }

        CHECK(journal_fsync(new));

        /*
         * Compute new header.
         */
        new->header.begin.serial = best_guess.serial;
        new->header.begin.offset = indexend;
        new->header.end.serial = j->header.end.serial;
        new->header.end.offset = indexend + copy_length;
        new->header.sourceserial = j->header.sourceserial;
        new->header.serialset = j->header.serialset;

        /*
         * Update the journal header.
         */
        journal_header_encode(&new->header, &rawheader);
        CHECK(journal_seek(new, 0));
        CHECK(journal_write(new, &rawheader, sizeof(rawheader)));
        CHECK(journal_fsync(new));

        /*
         * Build new index.
         */
        current_pos = new->header.begin;
        while (current_pos.serial != new->header.end.serial) {
            index_add(new, &current_pos);
            CHECK(journal_next(new, &current_pos));
        }

        /*
         * Write index.
         */
        CHECK(index_to_disk(new));
        CHECK(journal_fsync(new));

        indexend = new->header.end.offset;
        POST(indexend);
    }

    /*
     * Close both journals before trying to rename files (this is
     * necessary on WIN32).
     */
    dns_journal_destroy(&j);
    dns_journal_destroy(&new);

    /*
     * With a UFS file system this should just succeed and be atomic.
     * Any IXFR outs will just continue and the old journal will be
     * removed on final close.
     *
     * With MSDOS / NTFS we need to do a two stage rename, triggered
     * by EEXIST.  (If any IXFR's are running in other threads, however,
     * this will fail, and the journal will not be compacted.  But
     * if so, hopefully they'll be finished by the next time we
     * compact.)
     */
    if (rename(newname, filename) == -1) {
        if (errno == EEXIST && !is_backup) {
            result = isc_file_remove(backup);
            if (result != ISC_R_SUCCESS &&
                result != ISC_R_FILENOTFOUND)
                goto failure;
            if (rename(filename, backup) == -1)
                goto maperrno;
            if (rename(newname, filename) == -1)
                goto maperrno;
            (void)isc_file_remove(backup);
        } else {
 maperrno:
            result = ISC_R_FAILURE;
            goto failure;
        }
    }

    result = ISC_R_SUCCESS;

 failure:
    (void)isc_file_remove(newname);
    if (buf != NULL)
        isc_mem_put(mctx, buf, size);
    if (j != NULL)
        dns_journal_destroy(&j);
    if (new != NULL)
        dns_journal_destroy(&new);
    return (result);
}

static isc_result_t
index_to_disk(dns_journal_t *j) {
    isc_result_t result = ISC_R_SUCCESS;

    if (j->header.index_size != 0) {
        unsigned int i;
        unsigned char *p;
        unsigned int rawbytes;

        rawbytes = j->header.index_size * sizeof(journal_rawpos_t);

        p = j->rawindex;
        for (i = 0; i < j->header.index_size; i++) {
            encode_uint32(j->index[i].serial, p);
            p += 4;
            encode_uint32(j->index[i].offset, p);
            p += 4;
        }
        INSIST(p == j->rawindex + rawbytes);

        CHECK(journal_seek(j, sizeof(journal_rawheader_t)));
        CHECK(journal_write(j, j->rawindex, rawbytes));
    }
failure:
    return (result);
}