src/lib/istream-concat.c

	istream-concat.c revision 9511a40d933181045343110c8101b75887062aae
/* Copyright (c) 2007 Dovecot authors, see the included COPYING file */

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

struct concat_istream {
    struct istream_private istream;

    struct istream **input, *cur_input;
    uoff_t *input_size;

    unsigned int cur_idx, unknown_size_idx;
    size_t prev_size;
};

static void i_stream_concat_close(struct iostream_private *stream)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;
    unsigned int i;

    for (i = 0; cstream->input[i] != NULL; i++)
        i_stream_close(cstream->input[i]);
}

static void i_stream_concat_destroy(struct iostream_private *stream)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;
    unsigned int i;

    for (i = 0; cstream->input[i] != NULL; i++)
        i_stream_unref(&cstream->input[i]);
}

static void
i_stream_concat_set_max_buffer_size(struct iostream_private *stream,
                    size_t max_size)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;
    unsigned int i;

    cstream->istream.max_buffer_size = max_size;
    for (i = 0; cstream->input[i] != NULL; i++)
        i_stream_set_max_buffer_size(cstream->input[i], max_size);
}

static void i_stream_concat_read_next(struct concat_istream *cstream)
{
    const unsigned char *data;
    size_t data_size, size;

    i_assert(cstream->cur_input->eof);

    cstream->cur_idx++;
    cstream->cur_input = cstream->input[cstream->cur_idx];
    i_stream_seek(cstream->cur_input, 0);

    if (cstream->istream.pos == cstream->istream.skip) {
        i_assert(cstream->prev_size == 0);
        cstream->istream.skip = 0;
        cstream->istream.pos = 0;
        return;
    }

    /* we need to keep the current data */
    data = cstream->istream.buffer + cstream->istream.skip;
    data_size = cstream->istream.pos - cstream->istream.skip;

    cstream->istream.skip = cstream->istream.pos = 0;

    /* we already verified that the data size is less than the
       maximum buffer size */
    if (!i_stream_get_buffer_space(&cstream->istream, data_size, &size))
        i_unreached();
    i_assert(size >= data_size);

    cstream->prev_size = data_size;
    memcpy(cstream->istream.w_buffer, data, data_size);
    cstream->istream.pos = data_size;
}

static ssize_t i_stream_concat_read(struct istream_private *stream)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;
    const unsigned char *data;
    size_t size, pos, skip;
    ssize_t ret;
    bool last_stream;

    if (cstream->cur_input == NULL) {
        stream->istream.eof = TRUE;
        return -1;
    }

    skip = stream->skip;
    if (cstream->prev_size > 0) {
        if (stream->skip < cstream->prev_size) {
            cstream->prev_size -= stream->skip;
            skip = 0;
        } else {
            /* we don't need the buffer anymore */
            skip -= cstream->prev_size;
            stream->skip -= cstream->prev_size;
            cstream->prev_size = 0;

            i_free_and_null(stream->w_buffer);
            stream->buffer = NULL;
            stream->buffer_size = 0;
        }
    }
    i_stream_skip(cstream->cur_input, skip);

    data = i_stream_get_data(cstream->cur_input, &pos);
    if (pos > stream->pos)
        ret = 0;
    else {
        /* need to read more */
        ret = i_stream_read(cstream->cur_input);
        if (ret == -2 || ret == 0)
            return ret;

        if (ret == -1 && stream->istream.stream_errno != 0) {
            stream->istream.stream_errno =
                cstream->cur_input->stream_errno;
            return -1;
        }

        /* we either read something or we're at EOF */
        last_stream = cstream->input[cstream->cur_idx+1] == NULL;
        if (ret == -1 && !last_stream) {
            if (stream->pos - stream->skip >=
                stream->max_buffer_size)
                return -2;

            i_stream_concat_read_next(cstream);
            return i_stream_concat_read(stream);
        }

        stream->istream.eof = cstream->cur_input->eof && last_stream;
        data = i_stream_get_data(cstream->cur_input, &pos);
    }

    if (stream->w_buffer == NULL) {
        stream->buffer = data;
        stream->pos -= stream->skip;
        stream->skip = 0;
    } else {
        if (!i_stream_get_buffer_space(stream, pos, &size))
            return -2;

        if (pos > size)
            pos = size;
        memcpy(stream->w_buffer + stream->pos, data, pos);
    }

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

static unsigned int
find_v_offset(struct concat_istream *cstream, uoff_t *v_offset)
{
    const struct stat *st;
    unsigned int i;

    for (i = 0; cstream->input[i] != NULL; i++) {
        if (*v_offset == 0) {
            /* seek to beginning of this stream */
            break;
        }
        if (i == cstream->unknown_size_idx) {
            /* we'll need to figure out this stream's size */
            st = i_stream_stat(cstream->input[i], TRUE);
            if (st == NULL) {
                cstream->istream.istream.stream_errno =
                    cstream->input[i]->stream_errno;
                return (unsigned int)-1;
            }

            /* @UNSAFE */
            cstream->input_size[i] = st->st_size;
            cstream->unknown_size_idx = i + 1;
        }
        if (*v_offset < cstream->input_size[i])
            break;
        *v_offset -= cstream->input_size[i];
    }

    return i;
}

static void i_stream_concat_seek(struct istream_private *stream,
                 uoff_t v_offset, bool mark ATTR_UNUSED)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;

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

    cstream->cur_idx = find_v_offset(cstream, &v_offset);
    if (cstream->cur_idx == (unsigned int)-1) {
        cstream->cur_input = NULL;
        return;
    }
    cstream->cur_input = cstream->input[cstream->cur_idx];
    if (cstream->cur_input != NULL)
        i_stream_seek(cstream->cur_input, v_offset);
}

static const struct stat *
i_stream_concat_stat(struct istream_private *stream, bool exact ATTR_UNUSED)
{
    struct concat_istream *cstream = (struct concat_istream *)stream;
    uoff_t v_offset = (uoff_t)-1;
    unsigned int i;

    /* make sure we have all sizes */
    (void)find_v_offset(cstream, &v_offset);

    stream->statbuf.st_size = 0;
    for (i = 0; i < cstream->unknown_size_idx; i++)
        stream->statbuf.st_size += cstream->input_size[i];
    return &stream->statbuf;
}

struct istream *i_stream_create_concat(struct istream *input[])
{
    struct concat_istream *cstream;
    unsigned int count;
    size_t max_buffer_size = I_STREAM_MIN_SIZE;
    bool blocking = TRUE, seekable = TRUE;

    /* if any of the streams isn't blocking or seekable, set ourself also
       nonblocking/nonseekable */
    for (count = 0; input[count] != NULL; count++) {
        size_t cur_max = input[count]->real_stream->max_buffer_size;

        if (cur_max > max_buffer_size)
            max_buffer_size = cur_max;
        if (!input[count]->blocking)
            blocking = FALSE;
        if (!input[count]->seekable)
            seekable = FALSE;
        i_stream_ref(input[count]);
    }
    i_assert(count != 0);

    cstream = i_new(struct concat_istream, 1);
    cstream->input = i_new(struct istream *, count + 1);
    cstream->input_size = i_new(uoff_t, count + 1);

    memcpy(cstream->input, input, sizeof(*input) * count);
    cstream->cur_input = cstream->input[0];
    i_stream_seek(cstream->cur_input, 0);

    cstream->istream.iostream.close = i_stream_concat_close;
    cstream->istream.iostream.destroy = i_stream_concat_destroy;
    cstream->istream.iostream.set_max_buffer_size =
        i_stream_concat_set_max_buffer_size;

    cstream->istream.max_buffer_size = max_buffer_size;
    cstream->istream.read = i_stream_concat_read;
    cstream->istream.seek = i_stream_concat_seek;
    cstream->istream.stat = i_stream_concat_stat;

    cstream->istream.istream.blocking = blocking;
    cstream->istream.istream.seekable = seekable;
    return i_stream_create(&cstream->istream, NULL, -1);
}