src/lib/istream-tee.c

	istream-tee.c revision 4fdf60e22b5340fe35f083b9ea5eb3fd1cf2e742
/* Copyright (C) 2006 Timo Sirainen */

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

struct tee_istream {
    pool_t pool;
    struct istream *input;
    struct tee_child_istream *children;

    uoff_t max_read_offset;
};

struct tee_child_istream {
    struct _istream istream;

    struct tee_istream *tee;
    struct tee_child_istream *next;
};

static void tee_streams_update_buffer(struct tee_istream *tee)
{
    struct tee_child_istream *tstream = tee->children;
    const unsigned char *data;
    size_t size, old_used;

    data = i_stream_get_data(tee->input, &size);
    for (; tstream != NULL; tstream = tstream->next) {
        if (tstream->istream.istream.closed) {
            tstream->istream.skip = tstream->istream.pos = 0;
            continue;
        }
        old_used = tstream->istream.pos - tstream->istream.skip;

        tstream->istream.buffer = data;
        tstream->istream.skip = tstream->istream.istream.v_offset -
            tee->input->v_offset;
        i_assert(tstream->istream.skip + old_used <= size);
        tstream->istream.pos = tstream->istream.skip + old_used;
    }
}

static void tee_streams_skip(struct tee_istream *tee)
{
    struct tee_child_istream *tstream = tee->children;
    size_t min_skip;

    min_skip = (size_t)-1;
    for (; tstream != NULL; tstream = tstream->next) {
        if (tstream->istream.skip < min_skip &&
            !tstream->istream.istream.closed)
            min_skip = tstream->istream.skip;
    }

    if (min_skip > 0 && min_skip != (size_t)-1) {
        i_stream_skip(tee->input, min_skip);
        tee_streams_update_buffer(tee);
    }
}

static void _close(struct _iostream *stream)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;

    tee_streams_skip(tstream->tee);
}

static void _destroy(struct _iostream *stream)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;
    struct tee_istream *tee = tstream->tee;
    struct tee_child_istream **p;

    if (tstream->istream.istream.v_offset > tee->max_read_offset)
        tee->max_read_offset = tstream->istream.istream.v_offset;

    for (p = &tee->children; *p != NULL; p = &(*p)->next) {
        if (*p == tstream) {
            *p = tstream->next;
            break;
        }
    }

    if (tee->children == NULL) {
        i_assert(tee->input->v_offset <= tee->max_read_offset);
        i_stream_skip(tee->input,
                  tee->max_read_offset - tee->input->v_offset);

        i_stream_unref(&tee->input);
        p_free(tee->pool, tee);
    } else {
        tee_streams_skip(tstream->tee);
    }
}

static void _set_max_buffer_size(struct _iostream *stream, size_t max_size)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;

    return i_stream_set_max_buffer_size(tstream->tee->input, max_size);
}

static ssize_t _read(struct _istream *stream)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;
    struct istream *input = tstream->tee->input;
    const unsigned char *data;
    size_t size;
    uoff_t last_high_offset;
    ssize_t ret;

    data = i_stream_get_data(input, &size);

    last_high_offset = stream->istream.v_offset +
        (tstream->istream.pos - tstream->istream.skip);
    i_assert(last_high_offset <= input->v_offset + size);
    if (last_high_offset == input->v_offset + size) {
        tee_streams_skip(tstream->tee);
        ret = i_stream_read(input);
        if (ret <= 0) {
            data = i_stream_get_data(input, &size);
            if (ret == -2 && stream->skip != 0) {
                /* someone else is holding the data,
                   wait for it */
                return 0;
            }
            stream->istream.eof = input->eof;
            return ret;
        }
        tee_streams_update_buffer(tstream->tee);
        data = i_stream_get_data(input, &size);
    } else if (stream->buffer == NULL) {
        tee_streams_update_buffer(tstream->tee);
    } else {
        stream->buffer = data;
    }

    i_assert(stream->buffer == data);
    ret = size - stream->pos;
    stream->pos = size;
    return ret;
}

static void __attr_noreturn__
_seek(struct _istream *stream __attr_unused__,
      uoff_t v_offset __attr_unused__, bool mark __attr_unused__)
{
    i_panic("tee-istream: seeking unsupported currently");
}

static const struct stat *_stat(struct _istream *stream, bool exact)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;

    return i_stream_stat(tstream->tee->input, exact);
}

static void _sync(struct _istream *stream)
{
    struct tee_child_istream *tstream = (struct tee_child_istream *)stream;
    size_t size;

    tee_streams_skip(tstream->tee);
    (void)i_stream_get_data(tstream->tee->input, &size);
    if (size != 0) {
        i_panic("tee-istream: i_stream_sync() called "
            "with data still buffered");
    }
    return i_stream_sync(tstream->tee->input);
}

struct tee_istream *tee_i_stream_create(struct istream *input, pool_t pool)
{
    struct tee_istream *tee;

    tee = p_new(pool, struct tee_istream, 1);
    tee->pool = pool;
    tee->input = input;

    i_stream_ref(input);
    return tee;
}

struct istream *
tee_i_stream_create_child(struct tee_istream *tee, pool_t pool)
{
    struct tee_child_istream *tstream;

    tstream = p_new(pool, struct tee_child_istream, 1);
    tstream->tee = tee;

    tstream->istream.iostream.close = _close;
    tstream->istream.iostream.destroy = _destroy;
    tstream->istream.iostream.set_max_buffer_size = _set_max_buffer_size;

    tstream->istream.read = _read;
    tstream->istream.seek = _seek;
    tstream->istream.stat = _stat;
    tstream->istream.sync = _sync;

    tstream->next = tee->children;
    tee->children = tstream;

    return _i_stream_create(&tstream->istream, pool,
                i_stream_get_fd(tee->input), 0);
}