src/lib/istream-seekable.c

	istream-seekable.c revision 8255a22cccf3b0ccf38206c594941820ac1c9e00
/* Copyright (C) 2005 Timo Sirainen */

#include "lib.h"
#include "buffer.h"
#include "hex-binary.h"
#include "randgen.h"
#include "write-full.h"
#include "istream-internal.h"
#include "istream-seekable.h"

#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>

#define BUF_INITIAL_SIZE (1024*32)

struct seekable_istream {
    struct _istream istream;
    pool_t pool;

    size_t max_buffer_size;
    char *temp_prefix;
    uoff_t write_peak;

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

static void _close(struct _iostream *stream __attr_unused__)
{
    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 _destroy(struct _iostream *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]);

    p_free(sstream->pool, sstream->temp_prefix);
    pool_unref(sstream->pool);
}

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

    sstream->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)
{
    unsigned char randbuf[8];
    const char *path;
    struct stat st;
    int fd;

    /* create a temporary file */
    for (;;) {
        random_fill_weak(randbuf, sizeof(randbuf));
        path = t_strconcat(sstream->temp_prefix, ".",
                   dec2str(time(NULL)), ".",
                   dec2str(getpid()), ".",
                   binary_to_hex(randbuf, sizeof(randbuf)),
                   NULL);
        if (stat(path, &st) == 0)
            continue;

        if (errno != ENOENT) {
            i_error("stat(%s) failed: %m", path);
            return -1;
        }

        fd = open(path, O_RDWR | O_EXCL | O_CREAT, 0600);
        if (fd != -1)
            break;

        if (errno != EEXIST) {
            i_error("open(%s) failed: %m", path);
            return -1;
        }
    }

    /* we just want the fd, unlink it */
    if (unlink(path) < 0) {
        /* shouldn't happen.. */
        i_error("unlink(%s) failed: %m", path);
        (void)close(fd);
        return -1;
    }

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

    buffer_free(sstream->buffer);
    sstream->buffer = NULL;

    sstream->fd = fd;
    sstream->fd_input =
        i_stream_create_file(fd, sstream->pool,
                     sstream->max_buffer_size, TRUE);
    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) {
            /* 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->istream.istream.eof = TRUE;
            return -1;
        }

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

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

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

        /* read more to buffer */
        *ret = read_more(sstream);
        if (*ret <= 0)
            return TRUE;

        /* we should have more now. */
        data = i_stream_get_data(sstream->cur_input, &size);
        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 = pos - stream->pos;
    stream->pos = pos;
    return TRUE;
}

static ssize_t _read(struct _istream *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) {
            i_stream_close(&stream->istream);
            return -1;
        }
        i_assert(sstream->buffer == NULL);
    }

    while (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);
        if (write_full(sstream->fd, data, size) < 0) {
            i_error("write_full(%s...) failed: %m",
                sstream->temp_prefix);
            i_stream_close(&stream->istream);
            return -1;
        }
        i_stream_sync(sstream->fd_input);
        i_stream_skip(sstream->cur_input, size);
        sstream->write_peak += size;
    }

    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;
    }

    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 void _seek(struct _istream *stream, uoff_t v_offset,
          bool mark __attr_unused__)
{
    stream->istream.stream_errno = 0;
    stream->istream.v_offset = v_offset;
    stream->skip = stream->pos = 0;
}

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

    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->skip);
        } while ((ret = _read(stream)) > 0);

        if (ret == 0) {
            i_panic("i_stream_stat() used for non-blocking "
                "seekable stream");
        }
        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[], pool_t pool,
             size_t max_buffer_size, const char *temp_prefix)
{
    struct seekable_istream *sstream;
    const unsigned char *data;
    unsigned int count;
    size_t size;

    for (count = 0; input[count] != NULL; count++)
        i_stream_ref(input[count]);
    i_assert(count != 0);

    pool_ref(pool);
    sstream = p_new(pool, struct seekable_istream, 1);
    sstream->pool = pool;
    sstream->temp_prefix = p_strdup(pool, temp_prefix);
    sstream->buffer = buffer_create_dynamic(pool, BUF_INITIAL_SIZE);
        sstream->max_buffer_size = max_buffer_size;

    sstream->input = p_new(pool, 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 = _close;
    sstream->istream.iostream.destroy = _destroy;
    sstream->istream.iostream.set_max_buffer_size = _set_max_buffer_size;

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

    return _i_stream_create(&sstream->istream, pool, -1, 0);
}