src/lib/iostream-temp.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "str.h"
#include "safe-mkstemp.h"
#include "write-full.h"
#include "istream-private.h"
#include "ostream-private.h"
#include "iostream-temp.h"

#include <unistd.h>

#define IOSTREAM_TEMP_MAX_BUF_SIZE_DEFAULT (1024*128)

struct temp_ostream {
    struct ostream_private ostream;

    char *temp_path_prefix;
    enum iostream_temp_flags flags;
    size_t max_mem_size;

    struct istream *dupstream;
    uoff_t dupstream_offset, dupstream_start_offset;
    char *name;

    buffer_t *buf;
    int fd;
    bool fd_tried;
    uoff_t fd_size;
};

static bool o_stream_temp_dup_cancel(struct temp_ostream *tstream,
                     enum ostream_send_istream_result *res_r);

static void
o_stream_temp_close(struct iostream_private *stream,
            bool close_parent ATTR_UNUSED)
{
    struct temp_ostream *tstream = (struct temp_ostream *)stream;

    i_close_fd(&tstream->fd);
    buffer_free(&tstream->buf);
    i_free(tstream->temp_path_prefix);
    i_free(tstream->name);
}

static int o_stream_temp_move_to_fd(struct temp_ostream *tstream)
{
    string_t *path;

    if (tstream->fd_tried)
        return -1;
    tstream->fd_tried = TRUE;

    path = t_str_new(128);
    str_append(path, tstream->temp_path_prefix);
    tstream->fd = safe_mkstemp_hostpid(path, 0600, (uid_t)-1, (gid_t)-1);
    if (tstream->fd == -1) {
        i_error("safe_mkstemp(%s) failed: %m", str_c(path));
        return -1;
    }
    if (i_unlink(str_c(path)) < 0) {
        i_close_fd(&tstream->fd);
        return -1;
    }
    if (write_full(tstream->fd, tstream->buf->data, tstream->buf->used) < 0) {
        i_error("write(%s) failed: %m", str_c(path));
        i_close_fd(&tstream->fd);
        return -1;
    }
    /* make the fd available also to o_stream_get_fd(),
       e.g. for unit tests */
    tstream->ostream.fd = tstream->fd;
    tstream->fd_size = tstream->buf->used;
    buffer_free(&tstream->buf);
    return 0;
}

int o_stream_temp_move_to_memory(struct ostream *output)
{
    struct temp_ostream *tstream =
        (struct temp_ostream *)output->real_stream;
    unsigned char buf[IO_BLOCK_SIZE];
    uoff_t offset = 0;
    ssize_t ret = 0;

    i_assert(tstream->buf == NULL);
    tstream->buf = buffer_create_dynamic(default_pool, 8192);
    while (offset < tstream->ostream.ostream.offset &&
           (ret = pread(tstream->fd, buf, sizeof(buf), offset)) > 0) {
        if ((size_t)ret > tstream->ostream.ostream.offset - offset)
            ret = tstream->ostream.ostream.offset - offset;
        buffer_append(tstream->buf, buf, ret);
        offset += ret;
    }
    if (ret < 0) {
        /* not really expecting this to happen */
        i_error("iostream-temp %s: read(%s*) failed: %m",
            o_stream_get_name(&tstream->ostream.ostream),
            tstream->temp_path_prefix);
        tstream->ostream.ostream.stream_errno = EIO;
        return -1;
    }
    i_close_fd(&tstream->fd);
    tstream->ostream.fd = -1;
    return 0;
}

static ssize_t
o_stream_temp_fd_sendv(struct temp_ostream *tstream,
               const struct const_iovec *iov, unsigned int iov_count)
{
    size_t bytes = 0;
    unsigned int i;

    for (i = 0; i < iov_count; i++) {
        if (write_full(tstream->fd, iov[i].iov_base, iov[i].iov_len) < 0) {
            i_error("iostream-temp %s: write(%s*) failed: %m - moving to memory",
                o_stream_get_name(&tstream->ostream.ostream),
                tstream->temp_path_prefix);
            if (o_stream_temp_move_to_memory(&tstream->ostream.ostream) < 0)
                return -1;
            for (; i < iov_count; i++) {
                buffer_append(tstream->buf, iov[i].iov_base, iov[i].iov_len);
                bytes += iov[i].iov_len;
                tstream->ostream.ostream.offset += iov[i].iov_len;
            }
            i_assert(tstream->fd_tried);
            return bytes;
        }
        bytes += iov[i].iov_len;
        tstream->ostream.ostream.offset += iov[i].iov_len;
    }
    tstream->fd_size += bytes;
    return bytes;
}

static ssize_t
o_stream_temp_sendv(struct ostream_private *stream,
            const struct const_iovec *iov, unsigned int iov_count)
{
    struct temp_ostream *tstream = (struct temp_ostream *)stream;
    ssize_t ret = 0;
    unsigned int i;
    enum ostream_send_istream_result res;


    tstream->flags &= ~IOSTREAM_TEMP_FLAG_TRY_FD_DUP;
    if (tstream->dupstream != NULL) {
        if (o_stream_temp_dup_cancel(tstream, &res))
            return -1;
    }

    if (tstream->fd != -1)
        return o_stream_temp_fd_sendv(tstream, iov, iov_count);

    for (i = 0; i < iov_count; i++) {
        if (tstream->buf->used + iov[i].iov_len > tstream->max_mem_size) {
            if (o_stream_temp_move_to_fd(tstream) == 0) {
                i_assert(tstream->fd != -1);
                return o_stream_temp_fd_sendv(tstream, iov+i,
                                  iov_count-i);
            }
            /* failed to move to temp fd, just keep it in memory */
        }
        buffer_append(tstream->buf, iov[i].iov_base, iov[i].iov_len);
        ret += iov[i].iov_len;
        stream->ostream.offset += iov[i].iov_len;
    }
    return ret;
}

static bool o_stream_temp_dup_cancel(struct temp_ostream *tstream,
                     enum ostream_send_istream_result *res_r)
{
    struct istream *input;
    uoff_t size = tstream->dupstream_offset -
        tstream->dupstream_start_offset;
    bool ret = TRUE; /* use res_r to return error */

    i_stream_seek(tstream->dupstream, tstream->dupstream_start_offset);
    tstream->ostream.ostream.offset = 0;

    input = i_stream_create_limit(tstream->dupstream, size);
    i_stream_unref(&tstream->dupstream);

    *res_r = io_stream_copy(&tstream->ostream.ostream, input);
    switch (*res_r) {
    case OSTREAM_SEND_ISTREAM_RESULT_FINISHED:
        /* everything copied */
        ret = FALSE;
        break;
    case OSTREAM_SEND_ISTREAM_RESULT_WAIT_INPUT:
    case OSTREAM_SEND_ISTREAM_RESULT_WAIT_OUTPUT:
        i_unreached();
    case OSTREAM_SEND_ISTREAM_RESULT_ERROR_INPUT:
        tstream->ostream.ostream.stream_errno = input->stream_errno;
        io_stream_set_error(&tstream->ostream.iostream,
            "iostream-temp: read(%s) failed: %s",
            i_stream_get_name(input),
            i_stream_get_error(input));
        break;
    case OSTREAM_SEND_ISTREAM_RESULT_ERROR_OUTPUT:
        break;
    }
    i_stream_destroy(&input);
    return ret;
}

static bool
o_stream_temp_dup_istream(struct temp_ostream *outstream,
              struct istream *instream,
              enum ostream_send_istream_result *res_r)
{
    uoff_t in_size;

    if (!instream->readable_fd || i_stream_get_fd(instream) == -1)
        return FALSE;

    if (i_stream_get_size(instream, TRUE, &in_size) <= 0) {
        if (outstream->dupstream != NULL)
            return o_stream_temp_dup_cancel(outstream, res_r);
        return FALSE;
    }
    i_assert(instream->v_offset <= in_size);

    if (outstream->dupstream == NULL) {
        outstream->dupstream = instream;
        outstream->dupstream_start_offset = instream->v_offset;
        i_stream_ref(outstream->dupstream);
    } else {
        if (outstream->dupstream != instream ||
            outstream->dupstream_offset != instream->v_offset ||
            outstream->dupstream_offset > in_size)
            return o_stream_temp_dup_cancel(outstream, res_r);
    }
    i_stream_seek(instream, in_size);
    /* we should be at EOF now. o_stream_send_istream() asserts if
       eof isn't set. */
    instream->eof = TRUE;
    outstream->dupstream_offset = instream->v_offset;
    outstream->ostream.ostream.offset =
        outstream->dupstream_offset - outstream->dupstream_start_offset;
    *res_r = OSTREAM_SEND_ISTREAM_RESULT_FINISHED;
    return TRUE;
}

static enum ostream_send_istream_result
o_stream_temp_send_istream(struct ostream_private *_outstream,
               struct istream *instream)
{
    struct temp_ostream *outstream = (struct temp_ostream *)_outstream;
    enum ostream_send_istream_result res;

    if ((outstream->flags & IOSTREAM_TEMP_FLAG_TRY_FD_DUP) != 0) {
        if (o_stream_temp_dup_istream(outstream, instream, &res))
            return res;
        outstream->flags &= ~IOSTREAM_TEMP_FLAG_TRY_FD_DUP;
    }
    return io_stream_copy(&outstream->ostream.ostream, instream);
}

static int
o_stream_temp_write_at(struct ostream_private *stream,
               const void *data, size_t size, uoff_t offset)
{
    struct temp_ostream *tstream = (struct temp_ostream *)stream;

    if (tstream->fd == -1) {
        i_assert(stream->ostream.offset == tstream->buf->used);
        buffer_write(tstream->buf, offset, data, size);
        stream->ostream.offset = tstream->buf->used;
    } else {
        if (pwrite_full(tstream->fd, data, size, offset) < 0) {
            stream->ostream.stream_errno = errno;
            i_close_fd(&tstream->fd);
            return -1;
        }
        if (tstream->fd_size < offset + size)
            tstream->fd_size = offset + size;
    }
    return 0;
}

static int o_stream_temp_seek(struct ostream_private *_stream, uoff_t offset)
{
    _stream->ostream.offset = offset;
    return 0;
}

struct ostream *iostream_temp_create(const char *temp_path_prefix,
                     enum iostream_temp_flags flags)
{
    return iostream_temp_create_named(temp_path_prefix, flags, "");
}

struct ostream *iostream_temp_create_named(const char *temp_path_prefix,
                       enum iostream_temp_flags flags,
                       const char *name)
{
    return iostream_temp_create_sized(temp_path_prefix, flags, name,
                      IOSTREAM_TEMP_MAX_BUF_SIZE_DEFAULT);
}

struct ostream *iostream_temp_create_sized(const char *temp_path_prefix,
                       enum iostream_temp_flags flags,
                       const char *name,
                       size_t max_mem_size)
{
    struct temp_ostream *tstream;
    struct ostream *output;

    tstream = i_new(struct temp_ostream, 1);
    tstream->ostream.ostream.blocking = TRUE;
    tstream->ostream.sendv = o_stream_temp_sendv;
    tstream->ostream.send_istream = o_stream_temp_send_istream;
    tstream->ostream.write_at = o_stream_temp_write_at;
    tstream->ostream.seek = o_stream_temp_seek;
    tstream->ostream.iostream.close = o_stream_temp_close;
    tstream->temp_path_prefix = i_strdup(temp_path_prefix);
    tstream->flags = flags;
    tstream->max_mem_size = max_mem_size;
    tstream->buf = buffer_create_dynamic(default_pool, 8192);
    tstream->fd = -1;

    output = o_stream_create(&tstream->ostream, NULL, -1);
    tstream->name = i_strdup(name);
    if (name[0] == '\0') {
        o_stream_set_name(output, t_strdup_printf(
            "(temp iostream in %s)", temp_path_prefix));
    } else {
        o_stream_set_name(output, t_strdup_printf(
            "(temp iostream in %s for %s)", temp_path_prefix, name));
    }
    return output;
}

static void iostream_temp_buf_destroyed(buffer_t *buf)
{
    buffer_free(&buf);
}

struct istream *iostream_temp_finish(struct ostream **output,
                     size_t max_buffer_size)
{
    struct temp_ostream *tstream =
        (struct temp_ostream *)(*output)->real_stream;
    struct istream *input, *input2;
    uoff_t abs_offset, size;
    const char *for_path;
    int fd;

    if (tstream->name[0] == '\0')
        for_path = "";
    else
        for_path = t_strdup_printf(" for %s", tstream->name);

    if (tstream->dupstream != NULL && !tstream->dupstream->closed) {
        abs_offset = i_stream_get_absolute_offset(tstream->dupstream) -
            tstream->dupstream->v_offset +
            tstream->dupstream_start_offset;
        size = tstream->dupstream_offset -
            tstream->dupstream_start_offset;
        fd = dup(i_stream_get_fd(tstream->dupstream));
        if (fd == -1)
            input = i_stream_create_error_str(errno, "dup() failed: %m");
        else {
            input2 = i_stream_create_fd_autoclose(&fd, max_buffer_size);
            i_stream_seek(input2, abs_offset);
            input = i_stream_create_limit(input2, size);
            i_stream_unref(&input2);
        }
        i_stream_set_name(input, t_strdup_printf(
            "(Temp file in %s%s, from %s)", tstream->temp_path_prefix,
            for_path, i_stream_get_name(tstream->dupstream)));
        i_stream_unref(&tstream->dupstream);
    } else if (tstream->dupstream != NULL) {
        /* return the original failed stream. */
        input = tstream->dupstream;
    } else if (tstream->fd != -1) {
        int fd = tstream->fd;
        input = i_stream_create_fd_autoclose(&tstream->fd, max_buffer_size);
        i_stream_set_name(input, t_strdup_printf(
            "(Temp file fd %d in %s%s, %"PRIuUOFF_T" bytes)",
            fd, tstream->temp_path_prefix, for_path, tstream->fd_size));
    } else {
        input = i_stream_create_from_data(tstream->buf->data,
                          tstream->buf->used);
        i_stream_set_name(input, t_strdup_printf(
            "(Temp buffer in %s%s, %"PRIuSIZE_T" bytes)",
            tstream->temp_path_prefix, for_path, tstream->buf->used));
        i_stream_add_destroy_callback(input, iostream_temp_buf_destroyed,
                          tstream->buf);
        tstream->buf = NULL;
    }
    o_stream_destroy(output);
    return input;
}