src/lib/istream-concat.c

	istream-concat.c revision 948b838c8e9896132e3a2d802fb5dad37e8dc716
/* Copyright (c) 2007-2016 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "istream-private.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_stream_left, prev_stream_skip, prev_skip;
};

static void i_stream_concat_skip(struct concat_istream *cstream);

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

    if (cstream->istream.istream.stream_errno == 0) {
        /* get the parent streams to the wanted offset */
        (void)i_stream_concat_skip(cstream);
    }

    if (close_parent) {
        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]);
    i_free(cstream->input);
    i_free(cstream->input_size);
    i_free(cstream->istream.w_buffer);
}

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)
{
    struct istream *prev_input = cstream->cur_input;
    const unsigned char *data;
    size_t data_size, size;

    i_assert(cstream->cur_input->eof);

    if (cstream->prev_stream_skip != 0) {
        i_stream_skip(cstream->input[cstream->cur_idx-1], cstream->prev_stream_skip);
        cstream->prev_stream_skip = 0;
    }

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

    if (cstream->prev_stream_left > 0 || cstream->istream.pos == 0) {
        /* all the pending data is already in w_buffer */
        cstream->prev_stream_skip = data_size;
        cstream->prev_stream_left += data_size;
        i_assert(cstream->prev_stream_left ==
             cstream->istream.pos - cstream->istream.skip);
        return;
    }
    i_assert(cstream->prev_stream_skip == 0);

    /* we already verified that the data size is less than the
       maximum buffer size */
    cstream->istream.pos = 0;
    if (data_size > 0) {
        if (!i_stream_try_alloc(&cstream->istream, data_size, &size))
            i_unreached();
        i_assert(size >= data_size);
    }

    cstream->prev_stream_left = data_size;
    memcpy(cstream->istream.w_buffer, data, data_size);
    i_stream_skip(prev_input, data_size);
    cstream->istream.skip = 0;
    cstream->istream.pos = data_size;
}

static void i_stream_concat_skip(struct concat_istream *cstream)
{
    struct istream_private *stream = &cstream->istream;
    size_t bytes_skipped;

    i_assert(stream->skip >= cstream->prev_skip);
    bytes_skipped = stream->skip - cstream->prev_skip;

    if (cstream->prev_stream_left == 0) {
        /* no need to worry about buffers, skip everything */
    } else if (bytes_skipped < cstream->prev_stream_left) {
        /* we're still skipping inside buffer */
        cstream->prev_stream_left -= bytes_skipped;
        bytes_skipped = 0;
    } else {
        /* done with the buffer */
        i_stream_skip(cstream->input[cstream->cur_idx-1], cstream->prev_stream_skip);
        cstream->prev_stream_skip = 0;

        bytes_skipped -= cstream->prev_stream_left;
        cstream->prev_stream_left = 0;
    }
    stream->pos -= bytes_skipped;
    stream->skip -= bytes_skipped;
    stream->buffer += bytes_skipped;
    cstream->prev_skip = stream->skip;
    i_stream_skip(cstream->cur_input, bytes_skipped);
}

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, data_size, cur_data_pos, new_pos;
    size_t new_bytes_count;
    ssize_t ret;
    bool last_stream;

    i_assert(cstream->cur_input != NULL);
    i_stream_concat_skip(cstream);

    i_assert(stream->pos >= stream->skip + cstream->prev_stream_left);
    cur_data_pos = stream->pos - (stream->skip + cstream->prev_stream_left);

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

        if (ret == -1 && cstream->cur_input->stream_errno != 0) {
            io_stream_set_error(&cstream->istream.iostream,
                "read(%s) failed: %s",
                i_stream_get_name(cstream->cur_input),
                i_stream_get_error(cstream->cur_input));
            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);
            cstream->prev_skip = stream->skip;
            return i_stream_concat_read(stream);
        }

        stream->istream.eof = cstream->cur_input->eof && last_stream;
        i_assert(ret != -1 || stream->istream.eof);
        data = i_stream_get_data(cstream->cur_input, &data_size);
    }

    if (cstream->prev_stream_left == 0) {
        /* we can point directly to the current stream's buffers */
        stream->buffer = data;
        stream->pos -= stream->skip;
        stream->skip = 0;
        new_pos = data_size;
    } else if (data_size == cur_data_pos) {
        /* nothing new read */
        i_assert(ret == 0 || ret == -1);
        stream->buffer = stream->w_buffer;
        new_pos = stream->pos;
    } else {
        /* we still have some of the previous stream left. merge the
           new data with it. */
        i_assert(data_size > cur_data_pos);
        new_bytes_count = data_size - cur_data_pos;
        if (!i_stream_try_alloc(stream, new_bytes_count, &size)) {
            stream->buffer = stream->w_buffer;
            return -2;
        }
        stream->buffer = stream->w_buffer;

        /* we'll copy all the new input to w_buffer. if we skip over
           prev_stream_left bytes, the next read will switch to
           pointing to cur_input's data directly. */
        if (new_bytes_count > size)
            new_bytes_count = size;
        memcpy(stream->w_buffer + stream->pos,
               data + cur_data_pos, new_bytes_count);
        new_pos = stream->pos + new_bytes_count;
    }

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

static int
find_v_offset(struct concat_istream *cstream, uoff_t *v_offset,
          unsigned int *idx_r)
{
    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 */
            if (i_stream_stat(cstream->input[i], TRUE, &st) < 0) {
                io_stream_set_error(&cstream->istream.iostream,
                    "stat(%s) failed: %s",
                    i_stream_get_name(cstream->input[i]),
                    i_stream_get_error(cstream->input[i]));
                i_error("istream-concat: stat(%s) failed: %s",
                    i_stream_get_name(cstream->input[i]),
                    i_stream_get_error(cstream->input[i]));
                cstream->istream.istream.stream_errno =
                    cstream->input[i]->stream_errno;
                return -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];
    }

    *idx_r = i;
    return 0;
}

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.v_offset = v_offset;
    stream->skip = stream->pos = 0;
    cstream->prev_stream_left = 0;
    cstream->prev_stream_skip = 0;
    cstream->prev_skip = 0;

    if (find_v_offset(cstream, &v_offset, &cstream->cur_idx) < 0) {
        /* failed */
        stream->istream.stream_errno = EINVAL;
        return;
    }
    cstream->cur_input = cstream->input[cstream->cur_idx];
    if (cstream->cur_input == NULL) {
        /* we allow seeking to EOF, but not past it. */
        if (v_offset != 0) {
            io_stream_set_error(&cstream->istream.iostream,
                "Seeking past EOF by %"PRIuUOFF_T" bytes", v_offset);
            cstream->istream.istream.stream_errno = EINVAL;
            return;
        }
        i_assert(cstream->cur_idx > 0);
        cstream->cur_input = cstream->input[cstream->cur_idx-1];
        v_offset = cstream->input_size[cstream->cur_idx-1];
    }
    i_stream_seek(cstream->cur_input, v_offset);
}

static int
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, cur_idx;

    /* make sure we have all sizes */
    if (find_v_offset(cstream, &v_offset, &cur_idx) < 0)
        return -1;

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

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