src/lib/istream-limit.c

	istream-limit.c revision a0eb3ee018793937018672a75afe320375abe3b4
/* Copyright (C) 2003 Timo Sirainen */

#include "lib.h"
#include "istream-internal.h"

struct limit_istream {
    struct istream_private istream;

    struct istream *input;
    uoff_t v_start_offset, v_size;
};

static void _destroy(struct iostream_private *stream)
{
    struct limit_istream *lstream = (struct limit_istream *) stream;

    /* get to same position in parent stream */
    i_stream_seek(lstream->input, lstream->v_start_offset +
              lstream->istream.istream.v_offset);
    i_stream_unref(&lstream->input);
}

static void
_set_max_buffer_size(struct iostream_private *stream, size_t max_size)
{
    struct limit_istream *lstream = (struct limit_istream *) stream;

    i_stream_set_max_buffer_size(lstream->input, max_size);
}

static ssize_t _read(struct istream_private *stream)
{
    struct limit_istream *lstream = (struct limit_istream *) stream;
    uoff_t left;
    ssize_t ret;
    size_t pos;

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

    if (lstream->input->v_offset !=
        lstream->v_start_offset + stream->istream.v_offset) {
        i_stream_seek(lstream->input,
                  lstream->v_start_offset +
                  stream->istream.v_offset);
    }

    stream->buffer = i_stream_get_data(lstream->input, &pos);
    if (pos <= stream->pos) {
        if ((ret = i_stream_read(lstream->input)) == -2) {
            if (stream->skip == 0)
                return -2;
        }
        stream->istream.stream_errno = lstream->input->stream_errno;
        stream->istream.eof = lstream->input->eof;
        stream->buffer = i_stream_get_data(lstream->input, &pos);
    } else {
        ret = 0;
    }

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

    if (lstream->v_size != (uoff_t)-1) {
        left = lstream->v_size - stream->istream.v_offset;
        if (pos >= left) {
            pos = left;
            stream->istream.eof = TRUE;
        }
    }

    ret = pos > stream->pos ? (ssize_t)(pos - stream->pos) :
        (ret == 0 ? 0 : -1);
    stream->pos = pos;
    return ret;
}

static void _seek(struct istream_private *stream, uoff_t v_offset,
          bool mark ATTR_UNUSED)
{
    struct limit_istream *lstream = (struct limit_istream *) stream;

    i_assert(v_offset <= lstream->v_size);

    stream->istream.stream_errno = 0;
    stream->istream.v_offset = v_offset;
    stream->skip = stream->pos = 0;
}

static const struct stat *_stat(struct istream_private *stream, bool exact)
{
    struct limit_istream *lstream = (struct limit_istream *) stream;
    const struct stat *st;

    st = i_stream_stat(lstream->input, exact);
    if (st == NULL)
        return NULL;

    stream->statbuf = *st;
    if (lstream->v_size != (uoff_t)-1)
        stream->statbuf.st_size = lstream->v_size;
    return &stream->statbuf;
}

struct istream *i_stream_create_limit(struct istream *input,
                      uoff_t v_start_offset, uoff_t v_size)
{
    struct limit_istream *lstream;

    i_stream_ref(input);

    lstream = i_new(struct limit_istream, 1);
    lstream->input = input;
    lstream->v_start_offset = v_start_offset;
    lstream->v_size = v_size;

    lstream->istream.istream.v_offset =
        input->v_offset < v_start_offset ? 0 :
        input->v_offset - v_start_offset > v_size ? v_size :
        input->v_offset - v_start_offset;

    lstream->istream.iostream.destroy = _destroy;
    lstream->istream.iostream.set_max_buffer_size = _set_max_buffer_size;

    lstream->istream.read = _read;
    lstream->istream.seek = _seek;
    lstream->istream.stat = _stat;

    lstream->istream.istream.blocking = input->blocking;
    lstream->istream.istream.seekable = input->seekable;
    return i_stream_create(&lstream->istream, i_stream_get_fd(input),
                   input->real_stream->abs_start_offset +
                   v_start_offset);
}