1 files changed, 281 insertions, 0 deletions
diff --git a/src/lib-compression/istream-lz4.c b/src/lib-compression/istream-lz4.c
new file mode 100644
index 0000000..24d539a
--- /dev/null
+++ b/src/lib-compression/istream-lz4.c
@@ -0,0 +1,281 @@
+/* Copyright (c) 2013-2018 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;
+
+	struct stat last_parent_statbuf;
+
+	buffer_t *chunk_buf;
+	uint32_t chunk_size, chunk_left, max_uncompressed_chunk_size;
+
+	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));
+}
+
+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));
+	size = I_MIN(size, sizeof(*hdr));
+	buffer_append(zstream->chunk_buf, data, size);
+	i_stream_skip(zstream->istream.parent, size);
+	if (ret < 0 || (ret == 0 && zstream->istream.istream.eof)) {
+		i_assert(ret != -2);
+		if (zstream->istream.istream.stream_errno == 0) {
+			lz4_read_error(zstream, "missing header (not lz4 file?)");
+			zstream->istream.istream.stream_errno = EINVAL;
+		} else
+			zstream->istream.istream.stream_errno =
+				zstream->istream.parent->stream_errno;
+		return ret;
+	}
+	if (zstream->chunk_buf->used < sizeof(*hdr)) {
+		i_assert(!zstream->istream.istream.blocking);
+		return 0;
+	}
+
+	hdr = zstream->chunk_buf->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);
+	buffer_set_used_size(zstream->chunk_buf, 0);
+	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;
+	}
+	return 1;
+}
+
+static int i_stream_lz4_read_chunk_header(struct lz4_istream *zstream)
+{
+	int ret;
+	size_t size;
+	const unsigned char *data;
+	struct istream_private *stream = &zstream->istream;
+
+	i_assert(zstream->chunk_buf->used <= IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
+	ret = i_stream_read_more(stream->parent, &data, &size);
+	size = I_MIN(size, IOSTREAM_LZ4_CHUNK_PREFIX_LEN - zstream->chunk_buf->used);
+	buffer_append(zstream->chunk_buf, data, size);
+	i_stream_skip(stream->parent, size);
+	if (ret < 0) {
+		i_assert(ret != -2);
+		stream->istream.stream_errno = stream->parent->stream_errno;
+		if (stream->istream.stream_errno == 0) {
+			stream->istream.eof = TRUE;
+			stream->cached_stream_size =
+				stream->istream.v_offset +
+				stream->pos - stream->skip;
+		}
+		return ret;
+	}
+	i_assert(ret != 0 || !stream->istream.blocking);
+	if (ret == 0)
+		return ret;
+	if (zstream->chunk_buf->used < IOSTREAM_LZ4_CHUNK_PREFIX_LEN)
+		return 0;
+	zstream->chunk_size = zstream->chunk_left =
+		be32_to_cpu_unaligned(zstream->chunk_buf->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;
+	}
+	buffer_set_used_size(zstream->chunk_buf, 0);
+	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;
+	int ret;
+
+	/* if we already have max_buffer_size amount of data, fail here */
+	if (stream->pos - stream->skip >= i_stream_get_max_buffer_size(&stream->istream))
+		return -2;
+
+	if (!zstream->header_read) {
+		if ((ret = i_stream_lz4_read_header(zstream)) <= 0) {
+			stream->istream.eof = TRUE;
+			return ret;
+		}
+		zstream->header_read = TRUE;
+	}
+
+	if (zstream->chunk_left == 0) {
+		while ((ret = i_stream_lz4_read_chunk_header(zstream)) == 0) {
+			if (!stream->istream.blocking)
+				return 0;
+		}
+		if (ret < 0)
+			return ret;
+	}
+
+	/* 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;
+		i_assert(ret != 0 || !stream->istream.blocking);
+		return ret;
+	}
+	/* if we already have max_buffer_size amount of data, fail here */
+	if (stream->pos - stream->skip >= i_stream_get_max_buffer_size(&stream->istream))
+		return -2;
+	if (i_stream_get_data_size(zstream->istream.parent) > 0) {
+		/* Parent stream was only partially consumed. Set the stream's
+		   IO as pending to avoid hangs. */
+		i_stream_set_input_pending(&zstream->istream.istream, TRUE);
+	}
+	/* 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. */
+	void *dest = i_stream_alloc(stream, zstream->max_uncompressed_chunk_size);
+	ret = LZ4_decompress_safe(zstream->chunk_buf->data, dest,
+				  zstream->chunk_buf->used,
+				  zstream->max_uncompressed_chunk_size);
+	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);
+
+	/* we are going to get next chunk after this, so reset here
+	   so we can reuse the chunk buf for reading next buffer prefix */
+	if (zstream->chunk_left == 0)
+		buffer_set_used_size(zstream->chunk_buf, 0);
+
+	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;
+	buffer_set_used_size(zstream->chunk_buf, 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;
+
+	if (i_stream_nonseekable_try_seek(stream, v_offset))
+		return;
+
+	/* have to seek backwards - reset state and retry */
+	i_stream_lz4_reset(zstream);
+	if (!i_stream_nonseekable_try_seek(stream, v_offset))
+		i_unreached();
+
+	if (mark)
+		zstream->marked = TRUE;
+}
+
+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)
+{
+	struct lz4_istream *zstream;
+
+	zstream = i_new(struct lz4_istream, 1);
+
+	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.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), 0);
+}
+#endif