src/lib/istream-seekable.c

	istream-seekable.c revision 032964c7cc6788188b63ae6270fc26cbd4a3ca26
/* Copyright (c) 2005-2012 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "read-full.h"
#include "write-full.h"
#include "istream-private.h"
#include "istream-concat.h"
#include "istream-seekable.h"

#include <unistd.h>

#define BUF_INITIAL_SIZE (1024*32)

struct seekable_istream {
    struct istream_private istream;

    char *temp_path;
    uoff_t write_peak;
    uoff_t size;

    int (*fd_callback)(const char **path_r, void *context);
    void *context;

    buffer_t *buffer;
    struct istream **input, *cur_input;
    struct istream *fd_input;
    unsigned int cur_idx;
    int fd;
};

static void i_stream_seekable_close(struct iostream_private *stream)
{
    struct seekable_istream *sstream = (struct seekable_istream *)stream;
    unsigned int i;

    sstream->fd = -1;
    if (sstream->fd_input != NULL)
        i_stream_close(sstream->fd_input);
    for (i = 0; sstream->input[i] != NULL; i++)
        i_stream_close(sstream->input[i]);
}

static void i_stream_seekable_destroy(struct iostream_private *stream)
{
    struct seekable_istream *sstream = (struct seekable_istream *)stream;
    unsigned int i;

    if (sstream->buffer != NULL)
        buffer_free(&sstream->buffer);
    if (sstream->fd_input != NULL)
        i_stream_unref(&sstream->fd_input);
    for (i = 0; sstream->input[i] != NULL; i++)
        i_stream_unref(&sstream->input[i]);

    i_free(sstream->temp_path);
    i_free(sstream->input);
}

static void
i_stream_seekable_set_max_buffer_size(struct iostream_private *stream,
                      size_t max_size)
{
    struct seekable_istream *sstream = (struct seekable_istream *)stream;
    unsigned int i;

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

static int copy_to_temp_file(struct seekable_istream *sstream)
{
    struct istream_private *stream = &sstream->istream;
    const char *path;
    const unsigned char *buffer;
    size_t size;
    int fd;

    fd = sstream->fd_callback(&path, sstream->context);
    if (fd == -1)
        return -1;

    /* copy our currently read buffer to it */
    if (write_full(fd, sstream->buffer->data, sstream->buffer->used) < 0) {
        if (!ENOSPACE(errno))
            i_error("write_full(%s) failed: %m", path);
        i_close_fd(&fd);
        return -1;
    }
    sstream->temp_path = i_strdup(path);
    sstream->write_peak = sstream->buffer->used;

    sstream->fd = fd;
    sstream->fd_input =
        i_stream_create_fd(fd, sstream->istream.max_buffer_size, TRUE);

    /* read back the data we just had in our buffer */
    i_stream_seek(sstream->fd_input, stream->istream.v_offset);
    for (;;) {
        buffer = i_stream_get_data(sstream->fd_input, &size);
        if (size >= stream->pos)
            break;

        if (i_stream_read(sstream->fd_input) <= 0) {
            i_error("istream-seekable: Couldn't read back "
                "in-memory input %s",
                i_stream_get_name(&stream->istream));
            i_stream_destroy(&sstream->fd_input);
            return -1;
        }
    }
    stream->buffer = buffer;
    stream->pos = size;
    buffer_free(&sstream->buffer);
    return 0;
}

static ssize_t read_more(struct seekable_istream *sstream)
{
    size_t size;
    ssize_t ret;

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

    while ((ret = i_stream_read(sstream->cur_input)) < 0) {
        if (!sstream->cur_input->eof) {
            /* full / error */
            sstream->istream.istream.stream_errno =
                sstream->cur_input->stream_errno;
            return -1;
        }

        /* go to next stream */
        sstream->cur_input = sstream->input[sstream->cur_idx++];
        if (sstream->cur_input == NULL) {
            /* last one, EOF */
            sstream->size = sstream->istream.istream.v_offset;
            sstream->istream.istream.eof = TRUE;
            return -1;
        }

        /* see if stream has pending data */
        size = i_stream_get_data_size(sstream->cur_input);
        if (size != 0)
            return size;
    }
    return ret;
}

static bool read_from_buffer(struct seekable_istream *sstream, ssize_t *ret_r)
{
    struct istream_private *stream = &sstream->istream;
    const unsigned char *data;
    size_t size, pos, offset;

    i_assert(stream->skip == 0);

    if (stream->istream.v_offset + stream->pos >= sstream->buffer->used) {
        /* need to read more */
        if (sstream->buffer->used >= stream->max_buffer_size)
            return FALSE;

        size = sstream->cur_input == NULL ? 0 :
            i_stream_get_data_size(sstream->cur_input);
        if (size == 0) {
            /* read more to buffer */
            *ret_r = read_more(sstream);
            if (*ret_r <= 0)
                return TRUE;
        }

        /* we should have more now. */
        data = i_stream_get_data(sstream->cur_input, &size);
        i_assert(size > 0);
        buffer_append(sstream->buffer, data, size);
        i_stream_skip(sstream->cur_input, size);
    }

    offset = stream->istream.v_offset;
    stream->buffer = CONST_PTR_OFFSET(sstream->buffer->data, offset);
    pos = sstream->buffer->used - offset;

    *ret_r = pos - stream->pos;
    i_assert(*ret_r > 0);
    stream->pos = pos;
    return TRUE;
}

static int i_stream_seekable_write_failed(struct seekable_istream *sstream)
{
    struct istream_private *stream = &sstream->istream;
    void *data;

    i_assert(sstream->buffer == NULL);

    sstream->buffer =
        buffer_create_dynamic(default_pool, sstream->write_peak);
    data = buffer_append_space_unsafe(sstream->buffer, sstream->write_peak);

    if (pread_full(sstream->fd, data, sstream->write_peak, 0) < 0) {
        i_error("read(%s) failed: %m", sstream->temp_path);
        buffer_free(&sstream->buffer);
        return -1;
    }
    i_stream_destroy(&sstream->fd_input);
    i_close_fd(&sstream->fd);

    stream->max_buffer_size = (size_t)-1;
    i_free_and_null(sstream->temp_path);
    return 0;
}

static ssize_t i_stream_seekable_read(struct istream_private *stream)
{
    struct seekable_istream *sstream = (struct seekable_istream *)stream;
    const unsigned char *data;
    size_t size, pos;
    ssize_t ret;

    stream->buffer = CONST_PTR_OFFSET(stream->buffer, stream->skip);
    stream->pos -= stream->skip;
    stream->skip = 0;

    if (sstream->buffer != NULL) {
        if (read_from_buffer(sstream, &ret))
            return ret;

        /* copy everything to temp file and use it as the stream */
        if (copy_to_temp_file(sstream) < 0) {
            stream->max_buffer_size = (size_t)-1;
            if (!read_from_buffer(sstream, &ret))
                i_unreached();
            return ret;
        }
        i_assert(sstream->buffer == NULL);
    }

    i_assert(stream->istream.v_offset + stream->pos <= sstream->write_peak);
    if (stream->istream.v_offset + stream->pos == sstream->write_peak) {
        /* need to read more */
        ret = read_more(sstream);
        if (ret <= 0)
            return ret;

        /* save to our file */
        data = i_stream_get_data(sstream->cur_input, &size);
        ret = write(sstream->fd, data, size);
        if (ret <= 0) {
            if (ret < 0 && !ENOSPACE(errno)) {
                i_error("write_full(%s) failed: %m",
                    sstream->temp_path);
            }
            if (i_stream_seekable_write_failed(sstream) < 0)
                return -1;
            if (!read_from_buffer(sstream, &ret))
                i_unreached();
            return ret;
        }
        i_stream_sync(sstream->fd_input);
        i_stream_skip(sstream->cur_input, ret);
        sstream->write_peak += ret;
    }

    i_stream_seek(sstream->fd_input, stream->istream.v_offset);
    ret = i_stream_read(sstream->fd_input);
    if (ret <= 0) {
        stream->istream.eof = sstream->fd_input->eof;
        stream->istream.stream_errno =
            sstream->fd_input->stream_errno;
    } else {
        ret = -2;
    }

    stream->buffer = i_stream_get_data(sstream->fd_input, &pos);
    stream->pos -= stream->skip;
    stream->skip = 0;

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

static const struct stat *
i_stream_seekable_stat(struct istream_private *stream, bool exact)
{
    struct seekable_istream *sstream = (struct seekable_istream *)stream;
    uoff_t old_offset;
    ssize_t ret;

    if (sstream->size != (uoff_t)-1) {
        /* we've already reached EOF and know the size */
        stream->statbuf.st_size = sstream->size;
        return &stream->statbuf;
    }

    if (sstream->buffer != NULL) {
        /* we want to know the full size of the file, so read until
           we're finished */
        old_offset = stream->istream.v_offset;
        do {
            i_stream_skip(&stream->istream,
                      stream->pos - stream->skip);
        } while ((ret = i_stream_seekable_read(stream)) > 0);

        if (ret == 0) {
            i_panic("i_stream_stat() used for non-blocking "
                "seekable stream %s offset %"PRIuUOFF_T,
                i_stream_get_name(sstream->cur_input),
                sstream->cur_input->v_offset);
        }
        i_stream_skip(&stream->istream, stream->pos - stream->skip);
        i_stream_seek(&stream->istream, old_offset);
    }

    if (sstream->fd_input != NULL) {
        /* using a file backed buffer, we can use real fstat() */
        return i_stream_stat(sstream->fd_input, exact);
    } else {
        /* buffer is completely in memory */
        i_assert(sstream->buffer != NULL);

        stream->statbuf.st_size = sstream->buffer->used;
        return &stream->statbuf;
    }
}

struct istream *
i_stream_create_seekable(struct istream *input[],
             size_t max_buffer_size,
             int (*fd_callback)(const char **path_r, void *context),
             void *context)
{
    struct seekable_istream *sstream;
    const unsigned char *data;
    unsigned int count;
    size_t size;
    bool blocking = TRUE;

    /* If all input streams are seekable, use concat istream instead */
    for (count = 0; input[count] != NULL; count++) {
        if (!input[count]->seekable)
            break;
    }
    if (input[count] == NULL)
        return i_stream_create_concat(input);

    /* if any of the streams isn't blocking, set ourself also nonblocking */
    for (count = 0; input[count] != NULL; count++) {
        if (!input[count]->blocking)
            blocking = FALSE;
        i_stream_ref(input[count]);
    }
    i_assert(count != 0);

    sstream = i_new(struct seekable_istream, 1);
    sstream->fd_callback = fd_callback;
    sstream->context = context;
    sstream->buffer = buffer_create_dynamic(default_pool, BUF_INITIAL_SIZE);
        sstream->istream.max_buffer_size = max_buffer_size;
    sstream->fd = -1;
    sstream->size = (uoff_t)-1;

    sstream->input = i_new(struct istream *, count + 1);
    memcpy(sstream->input, input, sizeof(*input) * count);
    sstream->cur_input = sstream->input[0];

    /* initialize our buffer from first stream's pending data */
    data = i_stream_get_data(sstream->cur_input, &size);
    buffer_append(sstream->buffer, data, size);
    i_stream_skip(sstream->cur_input, size);

    sstream->istream.iostream.close = i_stream_seekable_close;
    sstream->istream.iostream.destroy = i_stream_seekable_destroy;
    sstream->istream.iostream.set_max_buffer_size =
        i_stream_seekable_set_max_buffer_size;

    sstream->istream.read = i_stream_seekable_read;
    sstream->istream.stat = i_stream_seekable_stat;

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