src/lib-compression/istream-lz4.c

	istream-lz4.c revision 6307d76096764e66bddc63d4a3e5a1aa19cc528f
/* Copyright (c) 2013-2017 Dovecot authors, see the included COPYING file */

#include "lib.h"

#ifdef HAVE_LZ4

#include "buffer.h"
#include "istream-private.h"
#include "istream-zlib.h"
#include "iostream-lz4.h"
#include <lz4.h>

struct lz4_istream {
    struct istream_private istream;

    uoff_t stream_size;
    struct stat last_parent_statbuf;

    buffer_t *chunk_buf;
    uint32_t chunk_size, chunk_left, max_uncompressed_chunk_size;

    bool log_errors:1;
    bool marked:1;
    bool header_read:1;
};

static void i_stream_lz4_close(struct iostream_private *stream,
                   bool close_parent)
{
    struct lz4_istream *zstream = (struct lz4_istream *)stream;

    buffer_free(&zstream->chunk_buf);
    if (close_parent)
        i_stream_close(zstream->istream.parent);
}

static void lz4_read_error(struct lz4_istream *zstream, const char *error)
{
    io_stream_set_error(&zstream->istream.iostream,
                "lz4.read(%s): %s at %"PRIuUOFF_T,
                i_stream_get_name(&zstream->istream.istream), error,
                i_stream_get_absolute_offset(&zstream->istream.istream));
    if (zstream->log_errors)
        i_error("%s", zstream->istream.iostream.error);
}

static int i_stream_lz4_read_header(struct lz4_istream *zstream)
{
    const struct iostream_lz4_header *hdr;
    const unsigned char *data;
    size_t size;
    int ret;

    ret = i_stream_read_bytes(zstream->istream.parent, &data, &size,
                  sizeof(*hdr));
    if (ret < 0) {
        zstream->istream.istream.stream_errno =
            zstream->istream.parent->stream_errno;
        return ret;
    }
    if (ret == 0 && !zstream->istream.istream.eof)
        return 0;
    hdr = (const void *)data;
    if (ret == 0 || memcmp(hdr->magic, IOSTREAM_LZ4_MAGIC,
                   IOSTREAM_LZ4_MAGIC_LEN) != 0) {
        lz4_read_error(zstream, "wrong magic in header (not lz4 file?)");
        zstream->istream.istream.stream_errno = EINVAL;
        return -1;
    }
    zstream->max_uncompressed_chunk_size =
        be32_to_cpu_unaligned(hdr->max_uncompressed_chunk_size);
    if (zstream->max_uncompressed_chunk_size > ISTREAM_LZ4_CHUNK_SIZE) {
        lz4_read_error(zstream, t_strdup_printf(
            "lz4 max chunk size too large (%u > %u)",
            zstream->max_uncompressed_chunk_size,
            ISTREAM_LZ4_CHUNK_SIZE));
        zstream->istream.istream.stream_errno = EINVAL;
        return -1;
    }
    i_stream_skip(zstream->istream.parent, sizeof(*hdr));
    return 1;
}

static ssize_t i_stream_lz4_read(struct istream_private *stream)
{
    struct lz4_istream *zstream = (struct lz4_istream *)stream;
    const unsigned char *data;
    size_t size, max_size;
    int ret;

    if (!zstream->header_read) {
        if ((ret = i_stream_lz4_read_header(zstream)) <= 0)
            return ret;
        zstream->header_read = TRUE;
    }

    if (zstream->chunk_left == 0) {
        ret = i_stream_read_bytes(stream->parent, &data, &size,
                      IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
        if (ret < 0) {
            stream->istream.stream_errno =
                stream->parent->stream_errno;
            if (stream->istream.stream_errno == 0) {
                stream->istream.eof = TRUE;
                zstream->stream_size = stream->istream.v_offset +
                    stream->pos - stream->skip;
            }
            return ret;
        }
        if (ret == 0 && !stream->istream.eof)
            return 0;
        zstream->chunk_size = zstream->chunk_left =
            be32_to_cpu_unaligned(data);
        if (zstream->chunk_size == 0 ||
            zstream->chunk_size > ISTREAM_LZ4_CHUNK_SIZE) {
            lz4_read_error(zstream, t_strdup_printf(
                "invalid lz4 chunk size: %u", zstream->chunk_size));
            stream->istream.stream_errno = EINVAL;
            return -1;
        }
        i_stream_skip(stream->parent, IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
        buffer_set_used_size(zstream->chunk_buf, 0);
    }

    /* read the whole compressed chunk into memory */
    while (zstream->chunk_left > 0 &&
           (ret = i_stream_read_more(zstream->istream.parent, &data, &size)) > 0) {
        if (size > zstream->chunk_left)
            size = zstream->chunk_left;
        buffer_append(zstream->chunk_buf, data, size);
        i_stream_skip(zstream->istream.parent, size);
        zstream->chunk_left -= size;
    }
    if (zstream->chunk_left > 0) {
        if (ret == -1 && zstream->istream.parent->stream_errno == 0) {
            lz4_read_error(zstream, "truncated lz4 chunk");
            stream->istream.stream_errno = EPIPE;
            return -1;
        }
        zstream->istream.istream.stream_errno =
            zstream->istream.parent->stream_errno;
        return ret;
    }
    /* if we already have max_buffer_size amount of data, fail here */
    i_stream_compress(stream);
    if (stream->pos >= i_stream_get_max_buffer_size(&stream->istream))
        return -2;
    /* allocate enough space for the old data and the new
       decompressed chunk. we don't know the original compressed size,
       so just allocate the max amount of memory. */
    max_size = stream->pos + zstream->max_uncompressed_chunk_size;
    if (stream->buffer_size < max_size) {
        stream->w_buffer = i_realloc(stream->w_buffer,
                         stream->buffer_size, max_size);
        stream->buffer_size = max_size;
        stream->buffer = stream->w_buffer;
    }
    ret = LZ4_decompress_safe(zstream->chunk_buf->data,
                  (void *)(stream->w_buffer + stream->pos),
                  zstream->chunk_buf->used,
                  stream->buffer_size - stream->pos);
    i_assert(ret <= (int)zstream->max_uncompressed_chunk_size);
    if (ret < 0) {
        lz4_read_error(zstream, "corrupted lz4 chunk");
        stream->istream.stream_errno = EINVAL;
        return -1;
    }
    i_assert(ret > 0);
    stream->pos += ret;
    i_assert(stream->pos <= stream->buffer_size);
    return ret;
}

static void i_stream_lz4_reset(struct lz4_istream *zstream)
{
    struct istream_private *stream = &zstream->istream;

    i_stream_seek(stream->parent, stream->parent_start_offset);
    zstream->header_read = FALSE;
    zstream->chunk_size = zstream->chunk_left = 0;

    stream->parent_expected_offset = stream->parent_start_offset;
    stream->skip = stream->pos = 0;
    stream->istream.v_offset = 0;
}

static void
i_stream_lz4_seek(struct istream_private *stream, uoff_t v_offset, bool mark)
{
    struct lz4_istream *zstream = (struct lz4_istream *) stream;
    uoff_t start_offset = stream->istream.v_offset - stream->skip;

    if (v_offset < start_offset) {
        /* have to seek backwards */
        i_stream_lz4_reset(zstream);
        start_offset = 0;
    }

    if (v_offset <= start_offset + stream->pos) {
        /* seeking backwards within what's already cached */
        stream->skip = v_offset - start_offset;
        stream->istream.v_offset = v_offset;
        stream->pos = stream->skip;
    } else {
        /* read and cache forward */
        ssize_t ret;

        do {
            size_t avail = stream->pos - stream->skip;

            if (stream->istream.v_offset + avail >= v_offset) {
                i_stream_skip(&stream->istream,
                          v_offset -
                          stream->istream.v_offset);
                ret = -1;
                break;
            }

            i_stream_skip(&stream->istream, avail);
        } while ((ret = i_stream_read(&stream->istream)) > 0);
        i_assert(ret == -1);

        if (stream->istream.v_offset != v_offset) {
            /* some failure, we've broken it */
            if (stream->istream.stream_errno != 0) {
                i_error("lz4_istream.seek(%s) failed: %s",
                    i_stream_get_name(&stream->istream),
                    strerror(stream->istream.stream_errno));
                i_stream_close(&stream->istream);
            } else {
                /* unexpected EOF. allow it since we may just
                   want to check if there's anything.. */
                i_assert(stream->istream.eof);
            }
        }
    }

    if (mark)
        zstream->marked = TRUE;
}

static int
i_stream_lz4_stat(struct istream_private *stream, bool exact)
{
    struct lz4_istream *zstream = (struct lz4_istream *) stream;
    const struct stat *st;
    size_t size;

    if (i_stream_stat(stream->parent, exact, &st) < 0) {
        stream->istream.stream_errno = stream->parent->stream_errno;
        return -1;
    }
    stream->statbuf = *st;

    /* when exact=FALSE always return the parent stat's size, even if we
       know the exact value. this is necessary because otherwise e.g. mbox
       code can see two different values and think that a compressed mbox
       file keeps changing. */
    if (!exact)
        return 0;

    if (zstream->stream_size == (uoff_t)-1) {
        uoff_t old_offset = stream->istream.v_offset;
        ssize_t ret;

        do {
            size = i_stream_get_data_size(&stream->istream);
            i_stream_skip(&stream->istream, size);
        } while ((ret = i_stream_read(&stream->istream)) > 0);
        i_assert(ret == -1);

        i_stream_seek(&stream->istream, old_offset);
        if (zstream->stream_size == (uoff_t)-1)
            return -1;
    }
    stream->statbuf.st_size = zstream->stream_size;
    return 0;
}

static void i_stream_lz4_sync(struct istream_private *stream)
{
    struct lz4_istream *zstream = (struct lz4_istream *) stream;
    const struct stat *st;

    if (i_stream_stat(stream->parent, FALSE, &st) < 0) {
        if (memcmp(&zstream->last_parent_statbuf,
               st, sizeof(*st)) == 0) {
            /* a compressed file doesn't change unexpectedly,
               don't clear our caches unnecessarily */
            return;
        }
        zstream->last_parent_statbuf = *st;
    }
    i_stream_lz4_reset(zstream);
}

struct istream *i_stream_create_lz4(struct istream *input, bool log_errors)
{
    struct lz4_istream *zstream;

    zstream = i_new(struct lz4_istream, 1);
    zstream->stream_size = (uoff_t)-1;
    zstream->log_errors = log_errors;

    zstream->istream.iostream.close = i_stream_lz4_close;
    zstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
    zstream->istream.read = i_stream_lz4_read;
    zstream->istream.seek = i_stream_lz4_seek;
    zstream->istream.stat = i_stream_lz4_stat;
    zstream->istream.sync = i_stream_lz4_sync;

    zstream->istream.istream.readable_fd = FALSE;
    zstream->istream.istream.blocking = input->blocking;
    zstream->istream.istream.seekable = input->seekable;
    zstream->chunk_buf = buffer_create_dynamic(default_pool, 1024);

    return i_stream_create(&zstream->istream, input,
                   i_stream_get_fd(input));
}
#endif