lib/dns/name.c

	name.c revision fcedc0b54b76f53a9f23bc4b9120e3e8c51328e0
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence/*
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence * Copyright (C) 1998  Internet Software Consortium.
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence *
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence * Permission to use, copy, modify, and distribute this software for any
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence * purpose with or without fee is hereby granted, provided that the above
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence * copyright notice and this permission notice appear in all copies.
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence *
15a44745412679c30a6d022733925af70a38b715David Lawrence * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
15a44745412679c30a6d022733925af70a38b715David Lawrence * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
15a44745412679c30a6d022733925af70a38b715David Lawrence * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
15a44745412679c30a6d022733925af70a38b715David Lawrence * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
15a44745412679c30a6d022733925af70a38b715David Lawrence * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
15a44745412679c30a6d022733925af70a38b715David Lawrence * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
15a44745412679c30a6d022733925af70a38b715David Lawrence * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
15a44745412679c30a6d022733925af70a38b715David Lawrence * SOFTWARE.
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence */
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
40f53fa8d9c6a4fc38c0014495e7a42b08f52481David Lawrence#include <config.h>
cb4a97bb1c84fcab089136f0a4686ab5fea6a07cDavid Lawrence
cb4a97bb1c84fcab089136f0a4686ab5fea6a07cDavid Lawrence#include <ctype.h>
cb4a97bb1c84fcab089136f0a4686ab5fea6a07cDavid Lawrence#include <stdio.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <stdlib.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <string.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <isc/assertions.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <dns/types.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <dns/result.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#include <dns/name.h>
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence#define VALID_NAME(n)           ((n) != NULL && (n)->length > 0)
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrencetypedef enum {
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_init = 0,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_start,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_ordinary,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_initialescape,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_escape,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_escdecimal,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_bitstring,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_binary,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_octal,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_hex,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_dottedquad,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_dqdecimal,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_maybeslash,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_finishbitstring,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_bitlength,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    tw_eatdot
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence} tw_state;
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrencestatic char digitvalue[256] = {
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*16*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*32*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*48*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, /*64*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*80*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*96*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*112*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*128*/
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
0c73b546ecfa49b9d1c8fdb9a48d4cd62176124aDavid Lawrence    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*256*/
};

static char hexdigits[16] = {
    '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
};

static unsigned char maptolower[] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
    0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
    0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
    0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
    0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
    0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
    0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
    0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
    0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
    0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
    0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
    0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
};

#define CONVERTTOASCII(c)
#define CONVERTFROMASCII(c)

static struct dns_name root = { "", 1, 1 };

dns_name_t *dns_rootname = &root;

static void set_offsets(dns_name_t *, dns_boolean_t);
static void compact(dns_name_t *);

/*
 * Yes, get_bit and set_bit are lame.  We define them here so they can
 * be inlined by smart compilers.
 */

static unsigned int
get_bit(unsigned char *array, unsigned int index) {
    unsigned int byte, shift;

    byte = array[index / 8];
    shift = 7 - (index % 8);

    return ((byte >> shift) & 0x01);
}

static void
set_bit(unsigned char *array, unsigned int index, unsigned int bit) {
    unsigned int byte, shift, mask;

    byte = array[index / 8];
    shift = 7 - (index % 8);
    mask = 1 << shift;

    if (bit)
        array[index / 8] |= mask;
    else
        array[index / 8] &= (~mask & 0xFF);
}

dns_labeltype_t
dns_label_type(dns_label_t *label) {
    /*
     * Get the type of 'label'.
     */

    REQUIRE(label != NULL);
    REQUIRE(label->length > 0);
    REQUIRE(label->base[0] <= 63 ||
        label->base[0] == DNS_LABELTYPE_BITSTRING);

    if (label->base[0] <= 63)
        return (dns_labeltype_ordinary);
    else
        return (dns_labeltype_bitstring);
}

unsigned int
dns_label_countbits(dns_label_t *label) {
    unsigned int count;

    /*
     * The number of bits in a bitstring label.
     */

    REQUIRE(label != NULL);
    REQUIRE(label->length > 2);
    REQUIRE(label->base[0] == DNS_LABELTYPE_BITSTRING);

    count = label->base[1];
    if (count == 0)
        count = 256;

    return (count);
}

dns_bitlabel_t
dns_label_getbit(dns_label_t *label, unsigned int n) {
    unsigned int count, bit;

    /*
     * The 'n'th most significant bit of 'label'.
     *
     * Notes:
     *  Numbering starts at 0.
     */

    REQUIRE(label != NULL);
    REQUIRE(label->length > 2);
    REQUIRE(label->base[0] == DNS_LABELTYPE_BITSTRING);

    count = label->base[1];
    if (count == 0)
        count = 256;

    REQUIRE(n < count);

    bit = get_bit(&label->base[2], n);
    if (bit == 0)
        return (dns_bitlabel_0);
    return (dns_bitlabel_1);
}

void
dns_name_init(dns_name_t *name) {
    /*
     * Make 'name' empty.
     */

    name->ndata = NULL;
    name->length = 0;
    name->labels = 0;
}

dns_boolean_t
dns_name_isabsolute(dns_name_t *name) {
    /*
     * Does 'name' end in the root label?
     */

    REQUIRE(VALID_NAME(name));

    if (name->ndata[name->offsets[name->labels - 1]] == 0)
        return (DNS_TRUE);
    return (DNS_FALSE);
}

int
dns_name_compare(dns_name_t *name1, dns_name_t *name2) {
    unsigned int l1, l2, l, count1, count2, count;
    unsigned int b1, b2, n;
    unsigned char c1, c2;
    int cdiff, ldiff;
    unsigned char *label1, *label2;

    /*
     * Determine the relative ordering under the DNSSEC order relation of
     * 'name1' and 'name2'.
     */

    REQUIRE(VALID_NAME(name1));
    REQUIRE(VALID_NAME(name2));

    l1 = name1->labels;
    l2 = name2->labels;
    if (l1 < l2) {
        l = l1;
        ldiff = -1;
    } else {
        l = l2;
        if (l1 > l2)
            ldiff = 1;
        else
            ldiff = 0;
    }

    while (l > 0) {
        l--;
        l1--;
        l2--;
        label1 = &name1->ndata[name1->offsets[l1]];
        label2 = &name2->ndata[name2->offsets[l2]];
        count1 = *label1++;
        count2 = *label2++;
        if (count1 <= 63 && count2 <= 63) {
            if (count1 < count2) {
                cdiff = -1;
                count = count1;
            } else {
                count = count2;
                if (count1 > count2)
                    cdiff = 1;
                else
                    cdiff = 0;
            }

            while (count > 0) {
                count--;
                c1 = maptolower[*label1++];
                c2 = maptolower[*label2++];
                if (c1 < c2)
                    return (-1);
                else if (c1 > c2)
                    return (1);
            }
            if (cdiff != 0)
                return (cdiff);
        } else if (count1 == DNS_LABELTYPE_BITSTRING && count2 <= 63) {
            if (count2 == 0)
                return (1);
            return (-1);
        } else if (count2 == DNS_LABELTYPE_BITSTRING && count1 <= 63) {
            if (count1 == 0)
                return (-1);
            return (1);
        } else {
            INSIST(count1 == DNS_LABELTYPE_BITSTRING &&
                   count2 == DNS_LABELTYPE_BITSTRING);
            count1 = *label1++;
            if (count1 == 0)
                count1 = 256;
            count2 = *label2++;
            if (count2 == 0)
                count2 = 256;
            if (count1 < count2) {
                cdiff = -1;
                count = count1;
            } else {
                count = count2;
                if (count1 > count2)
                    cdiff = 1;
                else
                    cdiff = 0;
            }
            /* Yes, this loop is really slow! */
            for (n = 0; n < count; n++) {
                b1 = get_bit(label1, n);
                b2 = get_bit(label2, n);
                if (b1 < b2)
                    return (-1);
                else if (b1 > b2)
                    return (1);
            }
            if (cdiff != 0)
                return (cdiff);
        }
    }

    return (ldiff);
}

dns_boolean_t
dns_name_issubdomain(dns_name_t *name1, dns_name_t *name2) {
    dns_boolean_t a1, a2;
    unsigned int l1, l2, count1, count2;
    unsigned int b1, b2, n;
    unsigned char c1, c2;
    unsigned char *label1, *label2;

    /*
     * Is 'name1' a subdomain of 'name2'?
     *
     * Note: It makes no sense for one of the names to be relative and the
     * other absolute.  If both names are relative, then to be meaningfully
     * compared the caller must ensure that they are both relative to the
     * same domain.
     */

    REQUIRE(VALID_NAME(name1));
    REQUIRE(VALID_NAME(name2));

    /* We're not going for maximal speed yet... */
    a1 = dns_name_isabsolute(name1);
    a2 = dns_name_isabsolute(name2);

    REQUIRE((a1 && a2) || (!a1 && !a2));

    l1 = name1->labels;
    l2 = name2->labels;
    if (l1 < l2)
        return (DNS_FALSE);

    while (l2 > 0) {
        l1--;
        l2--;
        label1 = &name1->ndata[name1->offsets[l1]];
        label2 = &name2->ndata[name2->offsets[l2]];
        count1 = *label1++;
        count2 = *label2++;
        if (count1 <= 63 && count2 <= 63) {
            if (count1 != count2)
                return (DNS_FALSE);
            while (count2 > 0) {
                count2--;
                c1 = maptolower[*label1++];
                c2 = maptolower[*label2++];
                if (c1 != c2)
                    return (DNS_FALSE);
            }
        } else {
            if (count1 != count2)
                return (DNS_FALSE);
            INSIST(count1 == DNS_LABELTYPE_BITSTRING &&
                   count2 == DNS_LABELTYPE_BITSTRING);
            count1 = *label1++;
            if (count1 == 0)
                count1 = 256;
            count2 = *label2++;
            if (count2 == 0)
                count2 = 256;
            if (count1 < count2)
                return (DNS_FALSE);
            /* Yes, this loop is really slow! */
            for (n = 0; n < count2; n++) {
                b1 = get_bit(label1, n);
                b2 = get_bit(label2, n);
                if (b1 != b2)
                    return (DNS_FALSE);
            }
            if (count1 != count2 && l2 != 0)
                return (DNS_FALSE);
        }
    }

    return (DNS_TRUE);
}

unsigned int
dns_name_countlabels(dns_name_t *name) {
    /*
     * How many labels does 'name' have?
     */

    REQUIRE(VALID_NAME(name));

    ENSURE(name->labels <= 128);

    return (name->labels);
}

void
dns_name_getlabel(dns_name_t *name, unsigned int n, dns_label_t *label) {
    /*
     * Make 'label' refer to the 'n'th least significant label of 'name'.
     */

    REQUIRE(VALID_NAME(name));
    REQUIRE(n < name->labels);
    REQUIRE(label != NULL);

    label->base = &name->ndata[name->offsets[n]];
    if (n == name->labels - 1)
        label->length = name->length - name->offsets[n];
    else
        label->length = name->offsets[n + 1] - name->offsets[n];
}

void
dns_name_getlabelsequence(dns_name_t *source,
              unsigned int first, unsigned int n,
              dns_name_t *target)
{
    /*
     * Make 'target' refer to the 'n' labels including and following
     * 'first' in 'source'.
     */

    REQUIRE(VALID_NAME(source));
    REQUIRE(n > 0);
    REQUIRE(first < source->labels);
    REQUIRE(first + n <= source->labels);

    target->ndata = &source->ndata[source->offsets[first]];
    if (first + n == source->labels)
        target->length = source->length - source->offsets[first];
    else
        target->length = source->offsets[first + n] -
            source->offsets[first];
    target->labels = n;

    set_offsets(target, DNS_FALSE);
}

void
dns_name_fromregion(dns_name_t *name, dns_region_t *r) {
    /*
     * Make 'name' refer to region 'r'.
     */

    REQUIRE(name != NULL);
    REQUIRE(r != NULL);
    REQUIRE(r->length <= 255);

    name->ndata = r->base;
    name->length = r->length;

    if (r->length > 0)
        set_offsets(name, DNS_TRUE);
    else
        name->labels = 0;
}

void
dns_name_toregion(dns_name_t *name, dns_region_t *r) {
    /*
     * Make 'r' refer to 'name'.
     */

    REQUIRE(VALID_NAME(name));
    REQUIRE(r != NULL);

    r->base = name->ndata;
    r->length = name->length;
}


dns_result_t
dns_name_fromtext(dns_name_t *name, dns_region_t *source,
          dns_name_t *origin, dns_boolean_t downcase,
          dns_region_t *target)
{
    unsigned char *ndata, *label;
    char *tdata;
    char c;
    tw_state state, kind;
    unsigned int value, count, tbcount, bitlength, maxlength;
    unsigned int n1, n2, vlen, tlen, nrem, digits, labels;
    dns_boolean_t done, saw_bitstring;
    unsigned char dqchars[4];

    /*
     * Convert the textual representation of a DNS name at source
     * into uncompressed wire form stored in target.
     *
     * Notes:
     *  Relative domain names will have 'origin' appended to them
     *  unless 'origin' is NULL, in which case relative domain names
     *  will remain relative.
     */

    REQUIRE(source != NULL);
    REQUIRE(target != NULL);

    /*
     * Initialize things to make the compiler happy; they're not required.
     */
    n1 = 0;
    n2 = 0;
    vlen = 0;
    label = NULL;
    digits = 0;
    value = 0;
    count = 0;
    tbcount = 0;
    bitlength = 0;
    maxlength = 0;
    kind = tw_init;

    /*
     * Invalidate 'name'.
     */
    name->ndata = NULL;
    name->length = 0;
    name->labels = 0;

    /*
     * Set up the state machine.
     */
    tdata = (char *)source->base;
    tlen = source->length;
    ndata = target->base;
    nrem = target->length;
    if (nrem > 255)
        nrem = 255;
    labels = 0;
    done = DNS_FALSE;
    saw_bitstring = DNS_FALSE;
    state = tw_init;

    while (nrem > 0 && tlen > 0 && !done) {
        c = *tdata++;
        tlen--;

    no_read:
        switch (state) {
        case tw_init:
            /*
             * Is this the root name?
             */
            if (c == '.') {
                if (tlen != 0)
                    return (DNS_R_EMPTYLABEL);
                labels++;
                *ndata++ = 0;
                nrem--;
                done = DNS_TRUE;
                break;
            }
            /* FALLTHROUGH */
        case tw_start:
            label = ndata;
            ndata++;
            nrem--;
            count = 0;
            if (c == '\\') {
                state = tw_initialescape;
                break;
            }
            kind = tw_ordinary;
            state = tw_ordinary;
            /* FALLTHROUGH */
        case tw_ordinary:
            if (c == '.') {
                if (count == 0)
                    return (DNS_R_EMPTYLABEL);
                *label = count;
                labels++;
                if (tlen == 0) {
                    labels++;
                    *ndata++ = 0;
                    nrem--;
                    done = DNS_TRUE;
                }
                state = tw_start;
            } else if (c == '\\') {
                state = tw_escape;
            } else {
                if (count >= 63)
                    return (DNS_R_LABELTOOLONG);
                count++;
                CONVERTTOASCII(c);
                if (downcase)
                    c = maptolower[(int)c];
                *ndata++ = c;
                nrem--;
            }
            break;
        case tw_initialescape:
            if (c == '[') {
                saw_bitstring = DNS_TRUE;
                kind = tw_bitstring;
                state = tw_bitstring;
                *label = DNS_LABELTYPE_BITSTRING;
                label = ndata;
                ndata++;
                nrem--;
                break;
            }
            kind = tw_ordinary;
            state = tw_escape;
            /* FALLTHROUGH */
        case tw_escape:
            if (!isdigit(c)) {
                if (count >= 63)
                    return (DNS_R_LABELTOOLONG);
                count++;
                CONVERTTOASCII(c);
                if (downcase)
                    c = maptolower[(int)c];
                *ndata++ = c;
                nrem--;
                state = tw_ordinary;
                break;
            }
            digits = 0;
            value = 0;
            state = tw_escdecimal;
            /* FALLTHROUGH */
        case tw_escdecimal:
            if (!isdigit(c))
                return (DNS_R_BADESCAPE);
            value *= 10;
            value += digitvalue[(int)c];
            digits++;
            if (digits == 3) {
                if (value > 255)
                    return (DNS_R_BADESCAPE);
                if (count >= 63)
                    return (DNS_R_LABELTOOLONG);
                count++;
                if (downcase)
                    value = maptolower[value];
                *ndata++ = value;
                nrem--;
                state = tw_ordinary;
            }
            break;
        case tw_bitstring:
            /* count is zero */
            tbcount = 0;
            value = 0;
            if (c == 'b') {
                vlen = 8;
                maxlength = 256;
                kind = tw_binary;
                state = tw_binary;
            } else if (c == 'o') {
                vlen = 8;
                maxlength = 256;
                kind = tw_octal;
                state = tw_octal;
            } else if (c == 'x') {
                vlen = 8;
                maxlength = 256;
                kind = tw_hex;
                state = tw_hex;
            } else if (isdigit(c)) {
                vlen = 32;
                maxlength = 32;
                n1 = 0;
                n2 = 0;
                digits = 0;
                kind = tw_dottedquad;
                state = tw_dqdecimal;
                goto no_read;
            } else
                return (DNS_R_BADBITSTRING);
            break;
        case tw_binary:
            if (c != '0' && c != '1') {
                state = tw_maybeslash;
                goto no_read;
            }
            value <<= 1;
            if (c == '1')
                value |= 1;
            count++;
            tbcount++;
            if (tbcount > 256)
                return (DNS_R_BITSTRINGTOOLONG);
            if (count == 8) {
                *ndata++ = value;
                nrem--;
                count = 0;
            }
            break;
        case tw_octal:
            if (!isdigit(c) || c == '9') {
                state = tw_maybeslash;
                goto no_read;
            }
            value <<= 3;
            value += digitvalue[(int)c];
            count += 3;
            tbcount += 3;
            if (tbcount > 256)
                return (DNS_R_BITSTRINGTOOLONG);
            if (count == 8) {
                *ndata++ = value;
                nrem--;
                count = 0;
            } else if (count == 9) {
                *ndata++ = (value >> 1);
                nrem--;
                value &= 1;
                count = 1;
            } else if (count == 10) {
                *ndata++ = (value >> 2);
                nrem--;
                value &= 3;
                count = 2;
            }
            break;
        case tw_hex:
            if (!isxdigit(c)) {
                state = tw_maybeslash;
                goto no_read;
            }
            value <<= 4;
            value += digitvalue[(int)c];
            count += 4;
            tbcount += 4;
            if (tbcount > 256)
                return (DNS_R_BITSTRINGTOOLONG);
            if (count == 8) {
                *ndata++ = value;
                nrem--;
                count = 0;
            }
            break;
        case tw_dottedquad:
            if (c != '.' && n1 < 3)
                return (DNS_R_BADDOTTEDQUAD);
            dqchars[n1] = value;
            n2 *= 256;
            n2 += value;
            n1++;
            if (n1 == 4) {
                tbcount = 32;
                value = n2;
                state = tw_maybeslash;
                goto no_read;
            }
            value = 0;
            digits = 0;
            state = tw_dqdecimal;
            break;
        case tw_dqdecimal:
            if (!isdigit(c)) {
                if (digits == 0 || value > 255)
                    return (DNS_R_BADDOTTEDQUAD);
                state = tw_dottedquad;
                goto no_read;
            }
            digits++;
            if (digits > 3)
                return (DNS_R_BADDOTTEDQUAD);
            value *= 10;
            value += digitvalue[(int)c];
            break;
        case tw_maybeslash:
            bitlength = 0;
            if (c == '/') {
                state = tw_bitlength;
                break;
            }
            /* FALLTHROUGH */
        case tw_finishbitstring:
            if (c == ']') {
                if (tbcount == 0)
                    return (DNS_R_BADBITSTRING);
                if (count > 0) {
                    n1 = count % 8;
                    if (n1 != 0)
                        value <<= (8 - n1);
                    *ndata++ = value;
                    nrem--;
                }
                if (bitlength != 0) {
                    if (bitlength > tbcount)
                        return (DNS_R_BADBITSTRING);
                    if (kind == tw_binary &&
                        bitlength != tbcount) {
                        return (DNS_R_BADBITSTRING);
                    } else if (kind == tw_octal) {
                        /*
                         * Figure out correct number
                         * of octal digits for the
                         * bitlength, and compare to
                         * what was given.
                         */
                        n1 = bitlength / 3;
                        if (bitlength % 3 != 0)
                            n1++;
                        n2 = tbcount / 3;
                        /* tbcount % 3 == 0 */
                        if (n1 != n2)
                          return (DNS_R_BADBITSTRING);
                    } else if (kind == tw_hex) {
                        /*
                         * Figure out correct number
                         * of hex digits for the
                         * bitlength, and compare to
                         * what was given.
                         */
                        n1 = bitlength / 4;
                        if (bitlength % 4 != 0)
                            n1++;
                        n2 = tbcount / 4;
                        /* tbcount % 4 == 0 */
                        if (n1 != n2)
                          return (DNS_R_BADBITSTRING);
                    }
                    n1 = bitlength % vlen;
                    if (n1 != 0) {
                        /*
                         * Are the pad bits in the
                         * last 'vlen' bits zero?
                         */
                        if ((value &
                            ~((~0) << (vlen-n1))) != 0)
                          return (DNS_R_BADBITSTRING);
                    }
                } else if (kind == tw_dottedquad)
                    bitlength = 32;
                else
                    bitlength = tbcount;
                if (kind == tw_dottedquad) {
                    n1 = bitlength / 8;
                    if (bitlength % 8 != 0)
                        n1++;
                    if (nrem < n1)
                        return (DNS_R_NOSPACE);
                    for (n2 = 0; n2 < n1; n2++) {
                        *ndata++ = dqchars[n2];
                        nrem--;
                    }
                }
                if (bitlength == 256)
                    *label = 0;
                else
                    *label = bitlength;
                labels++;
            } else
                return (DNS_R_BADBITSTRING);
            state = tw_eatdot;
            break;
        case tw_bitlength:
            if (!isdigit(c)) {
                if (bitlength == 0)
                    return (DNS_R_BADBITSTRING);
                state = tw_finishbitstring;
                goto no_read;
            }
            bitlength *= 10;
            bitlength += digitvalue[(int)c];
            if (bitlength > maxlength)
                return (DNS_R_BADBITSTRING);
            break;
        case tw_eatdot:
            if (c != '.')
                return (DNS_R_BADBITSTRING);
            if (tlen == 0) {
                labels++;
                *ndata++ = 0;
                nrem--;
                done = DNS_TRUE;
            }
            state = tw_start;
            break;
        default:
            INSIST(0);
        }
    }
    if (!done) {
        if (nrem == 0)
            return (DNS_R_NOSPACE);
        if (state != tw_ordinary && state != tw_eatdot)
            return (DNS_R_UNEXPECTEDEND);
        if (state == tw_ordinary) {
            INSIST(tlen == 0 && count != 0);
            *label = count;
            labels++;
        }
        if (tlen == 0 && origin != NULL) {
            if (nrem < origin->length)
                return (DNS_R_NOSPACE);
            label = origin->ndata;
            n1 = origin->length;
            nrem -= n1;
            labels += origin->labels;
            while (n1 > 0) {
                c = *label++;
                /* 'origin' is already ASCII. */
                if (downcase)
                    c = maptolower[(int)c];
                *ndata++ = c;
                n1--;
            }
        }
    }

    name->ndata = target->base;
    name->labels = labels;
    name->length = target->length - nrem;

    /*
     * We should build the offsets table directly.
     */
    set_offsets(name, DNS_FALSE);

    if (saw_bitstring)
        compact(name);

    return (DNS_R_SUCCESS);
}

dns_result_t
dns_name_totext(dns_name_t *name, dns_boolean_t omit_final_dot,
        dns_region_t *target, unsigned int *bytesp)
{
    unsigned char *ndata;
    char *tdata;
    unsigned int nlen, tlen;
    unsigned char c;
    unsigned int trem, count;
    unsigned int bytes, nibbles;
    size_t i, len;
    unsigned int labels;
    dns_boolean_t saw_root = DNS_FALSE;
    char num[4];

    /*
     * This function assumes the name is in proper uncompressed
     * wire format.
     */
    REQUIRE(name->labels > 0);

    ndata = name->ndata;
    nlen = name->length;
    labels = name->labels;
    tdata = target->base;
    tlen = target->length;

    trem = tlen;

    /* Special handling for root label. */
    if (nlen == 1 && labels == 1 && *ndata == 0) {
        saw_root = DNS_TRUE;
        labels = 0;
        nlen = 0;
        if (trem == 0)
            return (DNS_R_NOSPACE);
        *tdata++ = '.';
        trem--;
    }

    while (labels > 0 && nlen > 0 && trem > 0) {
        labels--;
        count = *ndata++;
        nlen--;
        if (count == 0) {
            saw_root = DNS_TRUE;
            break;
        }
        if (count < 64) {
            INSIST(nlen >= count);
            while (count > 0) {
                c = *ndata;
                switch (c) {
                case 0x22: /* '"' */
                case 0x2E: /* '.' */
                case 0x3B: /* ';' */
                case 0x5C: /* '\\' */
                /* Special modifiers in zone files. */
                case 0x40: /* '@' */
                case 0x24: /* '$' */
                    if (trem < 2)
                        return (DNS_R_NOSPACE);
                    *tdata++ = '\\';
                    *tdata++ = c;
                    ndata++;
                    trem -= 2;
                    nlen--;
                    break;
                default:
                    if (c > 0x20 && c < 0x7f) {
                        if (trem == 0)
                            return (DNS_R_NOSPACE);
                        *tdata++ = c;
                        ndata++;
                        trem--;
                        nlen--;
                    } else {
                        if (trem < 4)
                            return (DNS_R_NOSPACE);
                        sprintf(tdata, "\\%03u",
                            c);
                        tdata += 4;
                        trem -= 4;
                        ndata++;
                        nlen--;
                    }
                }
                count--;
            }
        } else if (count == DNS_LABELTYPE_BITSTRING) {
            if (trem < 3)
                return (DNS_R_NOSPACE);
            *tdata++ = '\\';
            *tdata++ = '[';
            *tdata++ = 'x';
            trem -= 3;
            INSIST(nlen > 0);
            count = *ndata++;
            if (count == 0)
                count = 256;
            nlen--;
            len = sprintf(num, "%u", count);    /* XXX */
            INSIST(len <= 4);
            bytes = count / 8;
            if (count % 8 != 0)
                bytes++;
            INSIST(nlen >= bytes);
            nibbles = count / 4;
            if (count % 4 != 0)
                nibbles++;
            if (trem < nibbles)
                return (DNS_R_NOSPACE);
            trem -= nibbles;
            nlen -= bytes;
            while (nibbles > 0) {
                c = *ndata++;
                *tdata++ = hexdigits[(c >> 4)];
                nibbles--;
                if (nibbles != 0) {
                    *tdata++ = hexdigits[c & 0xf];
                    i++;
                    nibbles--;
                }
            }
            if (trem < 2 + len)
                return (DNS_R_NOSPACE);
            *tdata++ = '/';
            for (i = 0; i < len; i++)
                *tdata++ = num[i];
            *tdata++ = ']';
            trem -= 2 + len;
        } else
            INSIST(0);
        /*
         * The following assumes names are absolute.  If not, we
         * fix things up later.  Note that this means that in some
         * cases one more byte of text buffer is required than is
         * needed in the final output.
         */
        if (trem == 0)
            return (DNS_R_NOSPACE);
        *tdata++ = '.';
        trem--;
    }

    if (nlen != 0 && trem == 0)
        return (DNS_R_NOSPACE);
    INSIST(nlen == 0);
    if (!saw_root || omit_final_dot)
        trem++;

    *bytesp = tlen - trem;

    return (DNS_R_SUCCESS);
}

static void
set_offsets(dns_name_t *name, dns_boolean_t set_labels) {
    unsigned int offset, count, nlabels, nrem, n;
    unsigned char *ndata;

    ndata = name->ndata;
    nrem = name->length;
    offset = 0;
    nlabels = 0;
    while (nrem > 0) {
        INSIST(nlabels < 128);
        name->offsets[nlabels++] = offset;
        count = *ndata++;
        nrem--;
        offset++;
        if (count > 63) {
            INSIST(count == DNS_LABELTYPE_BITSTRING);
            INSIST(nrem != 0);
            count = *ndata++;
            nrem--;
            offset++;
            if (count == 0)
                count = 256;
            n = count / 8;
            if (count % 8 != 0)
                n++;
            count = n;
        }
        INSIST(nrem >= count);
        nrem -= count;
        offset += count;
        ndata += count;
    }
    if (set_labels)
        name->labels = nlabels;
    INSIST(nlabels == name->labels);
}

static void
compact(dns_name_t *name) {
    unsigned char *head, *curr, *last;
    unsigned int count, n, bit;
    unsigned int headbits, currbits, tailbits, newbits;
    unsigned int headrem, newrem;
    unsigned int headindex, currindex, tailindex, newindex;
    unsigned char tail[32];

    /*
     * The caller MUST ensure that all bitstrings are correctly formatted
     * and that the offsets table is valid.
     */

 again:
    memset(tail, 0, sizeof tail);
    INSIST(name->labels != 0);
    n = name->labels - 1;

    while (n > 0) {
        head = &name->ndata[name->offsets[n]];
        if (head[0] == DNS_LABELTYPE_BITSTRING && head[1] != 0) {
            if (n != 0) {
                n--;
                curr = &name->ndata[name->offsets[n]];
                if (curr[0] != DNS_LABELTYPE_BITSTRING)
                    break;
                /*
                 * We have consecutive bitstrings labels, and
                 * the more significant label ('head') has
                 * space.
                 */
                currbits = curr[1];
                if (currbits == 0)
                    currbits = 256;
                currindex = 0;
                headbits = head[1];
                if (headbits == 0)
                    headbits = 256;
                headindex = headbits;
                count = 256 - headbits;
                if (count > currbits)
                    count = currbits;
                headrem = headbits % 8;
                if (headrem != 0)
                    headrem = 8 - headrem;
                if (headrem != 0) {
                    if (headrem > count)
                        headrem = count;
                    do {
                        bit = get_bit(&curr[2],
                                  currindex);
                        set_bit(&head[2], headindex,
                            bit);
                        currindex++;
                        headindex++;
                        headbits++;
                        count--;
                        headrem--;
                    } while (headrem != 0);
                }
                tailindex = 0;
                tailbits = 0;
                while (count > 0) {
                    bit = get_bit(&curr[2], currindex);
                    set_bit(tail, tailindex, bit);
                    currindex++;
                    tailindex++;
                    tailbits++;
                    count--;
                }
                newbits = 0;
                newindex = 0;
                if (currindex < currbits) {
                    while (currindex < currbits) {
                        bit = get_bit(&curr[2],
                                  currindex);
                        set_bit(&curr[2], newindex,
                            bit);
                        currindex++;
                        newindex++;
                        newbits++;
                    }
                    INSIST(newbits < 256);
                    curr[1] = newbits;
                    count = newbits / 8;
                    newrem = newbits % 8;
                    /* Zero remaining pad bits, if any. */
                    if (newrem != 0) {
                        count++;
                        newrem = 8 - newrem;
                        while (newrem > 0) {
                            set_bit(&curr[2],
                                newindex,
                                0);
                            newrem--;
                            newindex++;
                        }
                    }
                    curr += count + 2;
                } else {
                    /* We got rid of curr. */
                    name->labels--;
                }
                /* copy head, then tail, then rest to curr. */
                count = headbits + tailbits;
                INSIST(count <= 256);
                curr[0] = DNS_LABELTYPE_BITSTRING;
                if (count == 256)
                    curr[1] = 0;
                else
                    curr[1] = count;
                curr += 2;
                head += 2;
                count = headbits / 8;
                if (headbits % 8 != 0)
                    count++;
                while (count > 0) {
                    *curr++ = *head++;
                    count--;
                }
                count = tailbits / 8;
                if (tailbits % 8 != 0)
                    count++;
                last = tail;
                while (count > 0) {
                    *curr++ = *last++;
                    count--;
                }
                last = name->ndata + name->length;
                while (head != last)
                    *curr++ = *head++;
                name->length = (curr - name->ndata);
                goto again;
            }
        }
        n--;
    };
}