src/lib/istream-sized.c

	istream-sized.c revision 032964c7cc6788188b63ae6270fc26cbd4a3ca26
/* Copyright (c) 2003-2012 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "istream-private.h"
#include "istream-sized.h"

struct sized_istream {
    struct istream_private istream;

    uoff_t size;
};

static ssize_t i_stream_sized_read(struct istream_private *stream)
{
    struct sized_istream *sstream =
        (struct sized_istream *)stream;
    uoff_t left;
    ssize_t ret;
    size_t pos;

    if (stream->istream.v_offset +
        (stream->pos - stream->skip) >= sstream->size) {
        stream->istream.eof = TRUE;
        return -1;
    }

    i_stream_seek(stream->parent, sstream->istream.parent_start_offset +
              stream->istream.v_offset);

    stream->pos -= stream->skip;
    stream->skip = 0;

    stream->buffer = i_stream_get_data(stream->parent, &pos);
    if (pos > stream->pos)
        ret = 0;
    else do {
        if ((ret = i_stream_read(stream->parent)) == -2)
            return -2;

        stream->istream.stream_errno = stream->parent->stream_errno;
        stream->istream.eof = stream->parent->eof;
        stream->buffer = i_stream_get_data(stream->parent, &pos);
    } while (pos <= stream->pos && ret > 0);

    left = sstream->size - stream->istream.v_offset;
    if (pos == left)
        stream->istream.eof = TRUE;
    else if (pos > left) {
        i_error("%s is larger than expected (%"PRIuUOFF_T")",
            i_stream_get_name(stream->parent), sstream->size);
        pos = left;
        stream->istream.eof = TRUE;
    } else if (!stream->istream.eof) {
        /* still more to read */
    } else if (stream->istream.stream_errno == ENOENT) {
        /* lost the file */
    } else {
        i_error("%s smaller than expected "
            "(%"PRIuUOFF_T" < %"PRIuUOFF_T")",
            i_stream_get_name(stream->parent),
            stream->istream.v_offset, sstream->size);
        stream->istream.stream_errno = EIO;
    }

    ret = pos > stream->pos ? (ssize_t)(pos - stream->pos) :
        (ret == 0 ? 0 : -1);
    stream->pos = pos;
    i_assert(ret != -1 || stream->istream.eof ||
         stream->istream.stream_errno != 0);
    return ret;
}

static const struct stat *
i_stream_sized_stat(struct istream_private *stream, bool sized ATTR_UNUSED)
{
    struct sized_istream *sstream = (struct sized_istream *)stream;
    const struct stat *st;

    /* parent stream may be base64-decoder. don't waste time decoding the
       entire stream, since we already know what the size is supposed
       to be. */
    st = i_stream_stat(stream->parent, FALSE);
    if (st == NULL)
        return NULL;

    stream->statbuf = *st;
    stream->statbuf.st_size = sstream->size;
    return &stream->statbuf;
}

struct istream *i_stream_create_sized(struct istream *input, uoff_t size)
{
    struct sized_istream *sstream;

    sstream = i_new(struct sized_istream, 1);
    sstream->size = size;
    sstream->istream.max_buffer_size = input->real_stream->max_buffer_size;

    sstream->istream.parent = input;
    sstream->istream.read = i_stream_sized_read;
    sstream->istream.stat = i_stream_sized_stat;

    sstream->istream.istream.readable_fd = input->readable_fd;
    sstream->istream.istream.blocking = input->blocking;
    sstream->istream.istream.seekable = input->seekable;
    return i_stream_create(&sstream->istream, input,
                   i_stream_get_fd(input));
}