ostream-zlib.c

/* Copyright (c) 2010-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"

#ifdef HAVE_ZLIB

#include "crc32.h"
#include "ostream-private.h"
#include "ostream-zlib.h"
#include <zlib.h>

#define CHUNK_SIZE (1024*32)
#define ZLIB_OS_CODE 0x03  /* Unix */

struct zlib_ostream {
	struct ostream_private ostream;
	z_stream zs;

	unsigned char gz_header[10];
	unsigned char outbuf[CHUNK_SIZE];
	unsigned int outbuf_offset, outbuf_used;

	uint32_t crc, bytes32;

	bool gz:1;
	bool header_sent:1;
	bool flushed:1;
};

static void o_stream_zlib_close(struct iostream_private *stream,
				bool close_parent)
{
	struct zlib_ostream *zstream = (struct zlib_ostream *)stream;

	i_assert(zstream->ostream.finished ||
		 zstream->ostream.ostream.stream_errno != 0 ||
		 zstream->ostream.error_handling_disabled);
	(void)deflateEnd(&zstream->zs);
	if (close_parent)
		o_stream_close(zstream->ostream.parent);
}

static int o_stream_zlib_send_gz_header(struct zlib_ostream *zstream)
{
	ssize_t ret;

	ret = o_stream_send(zstream->ostream.parent, zstream->gz_header,
			    sizeof(zstream->gz_header));
	if ((size_t)ret != sizeof(zstream->gz_header)) {
		o_stream_copy_error_from_parent(&zstream->ostream);
		return -1;
	}
	zstream->header_sent = TRUE;
	return 0;
}

static int o_stream_zlib_lsb_uint32(struct ostream *output, uint32_t num)
{
	unsigned char buf[sizeof(uint32_t)];
	unsigned int i;

	for (i = 0; i < sizeof(buf); i++) {
		buf[i] = num & 0xff;
		num >>= 8;
	}
	if (o_stream_send(output, buf, sizeof(buf)) != sizeof(buf))
		return -1;
	return 0;
}

static int o_stream_zlib_send_gz_trailer(struct zlib_ostream *zstream)
{
	struct ostream *output = zstream->ostream.parent;

	if (!zstream->gz)
		return 0;

	if (o_stream_zlib_lsb_uint32(output, zstream->crc) < 0 ||
	    o_stream_zlib_lsb_uint32(output, zstream->bytes32) < 0) {
		o_stream_copy_error_from_parent(&zstream->ostream);
		return -1;
	}
	return 0;
}

static int o_stream_zlib_send_outbuf(struct zlib_ostream *zstream)
{
	ssize_t ret;
	size_t size;

	if (zstream->outbuf_used == 0)
		return 1;

	size = zstream->outbuf_used - zstream->outbuf_offset;
	i_assert(size > 0);
	ret = o_stream_send(zstream->ostream.parent,
			    zstream->outbuf + zstream->outbuf_offset, size);
	if (ret < 0) {
		o_stream_copy_error_from_parent(&zstream->ostream);
		return -1;
	}
	if ((size_t)ret != size) {
		zstream->outbuf_offset += ret;
		return 0;
	}
	zstream->outbuf_offset = 0;
	zstream->outbuf_used = 0;
	return 1;
}

static ssize_t
o_stream_zlib_send_chunk(struct zlib_ostream *zstream,
			 const void *data, size_t size)
{
	z_stream *zs = &zstream->zs;
	int ret, flush;

	i_assert(zstream->outbuf_used == 0);

	flush = zstream->ostream.corked || zstream->gz ?
		Z_NO_FLUSH : Z_SYNC_FLUSH;

	if (!zstream->header_sent) {
		if (o_stream_zlib_send_gz_header(zstream) < 0)
			return -1;
	}

	zs->next_in = (void *)data;
	zs->avail_in = size;
	while (zs->avail_in > 0) {
		if (zs->avail_out == 0) {
			/* previous block was compressed. send it and start
			   compression for a new block. */
			zs->next_out = zstream->outbuf;
			zs->avail_out = sizeof(zstream->outbuf);

			zstream->outbuf_used = sizeof(zstream->outbuf);
			if ((ret = o_stream_zlib_send_outbuf(zstream)) < 0)
				return -1;
			if (ret == 0) {
				/* parent stream's buffer full */
				break;
			}
		}

		ret = deflate(zs, flush);
		switch (ret) {
		case Z_OK:
		case Z_BUF_ERROR:
			break;
		case Z_STREAM_ERROR:
			i_assert(zstream->gz);
			i_panic("zlib.write(%s) failed: Can't write more data to .gz after flushing",
				o_stream_get_name(&zstream->ostream.ostream));
		default:
			i_panic("zlib.write(%s) failed with unexpected code %d",
				o_stream_get_name(&zstream->ostream.ostream), ret);
		}
	}
	size -= zs->avail_in;

	zstream->crc = crc32_data_more(zstream->crc, data, size);
	zstream->bytes32 += size;
	zstream->flushed = flush == Z_SYNC_FLUSH && zs->avail_in == 0 &&
		zs->avail_out == sizeof(zstream->outbuf);
	return size;
}

static int
o_stream_zlib_send_flush(struct zlib_ostream *zstream, bool final)
{
	z_stream *zs = &zstream->zs;
	size_t len;
	bool done = FALSE;
	int ret, flush;

	i_assert(zs->avail_in == 0);

	if (zstream->flushed)
		return 0;

	if ((ret = o_stream_flush_parent_if_needed(&zstream->ostream)) <= 0)
		return ret;
	if (!zstream->header_sent) {
		if (o_stream_zlib_send_gz_header(zstream) < 0)
			return -1;
	}

	if ((ret = o_stream_zlib_send_outbuf(zstream)) <= 0)
		return ret;

	flush = !zstream->gz ? Z_SYNC_FLUSH :
		(final ? Z_FINISH : Z_NO_FLUSH);

	i_assert(zstream->outbuf_used == 0);
	do {
		len = sizeof(zstream->outbuf) - zs->avail_out;
		if (len != 0) {
			zs->next_out = zstream->outbuf;
			zs->avail_out = sizeof(zstream->outbuf);

			zstream->outbuf_used = len;
			if ((ret = o_stream_zlib_send_outbuf(zstream)) <= 0)
				return ret;
			if (done)
				break;
		}

		switch (deflate(zs, flush)) {
		case Z_OK:
		case Z_BUF_ERROR:
			break;
		case Z_STREAM_END:
			done = TRUE;
			break;
		default:
			i_unreached();
		}
	} while (zs->avail_out != sizeof(zstream->outbuf));

	if (final) {
		if (o_stream_zlib_send_gz_trailer(zstream) < 0)
			return -1;
	}
	if (final || flush != Z_NO_FLUSH)
		zstream->flushed = TRUE;
	return 0;
}

static int o_stream_zlib_flush(struct ostream_private *stream)
{
	struct zlib_ostream *zstream = (struct zlib_ostream *)stream;

	if (o_stream_zlib_send_flush(zstream, stream->finished) < 0)
		return -1;

	return o_stream_flush_parent(stream);
}

static size_t
o_stream_zlib_get_buffer_used_size(const struct ostream_private *stream)
{
	const struct zlib_ostream *zstream =
		(const struct zlib_ostream *)stream;

	/* outbuf has already compressed data that we're trying to send to the
	   parent stream. We're not including zlib's internal compression
	   buffer size. */
	return (zstream->outbuf_used - zstream->outbuf_offset) +
		o_stream_get_buffer_used_size(stream->parent);
}

static size_t
o_stream_zlib_get_buffer_avail_size(const struct ostream_private *stream)
{
	/* FIXME: not correct - this is counting compressed size, which may be
	   too larger than uncompressed size in some situations. Fixing would
	   require some kind of additional buffering. */
	return o_stream_get_buffer_avail_size(stream->parent);
}

static ssize_t
o_stream_zlib_sendv(struct ostream_private *stream,
		    const struct const_iovec *iov, unsigned int iov_count)
{
	struct zlib_ostream *zstream = (struct zlib_ostream *)stream;
	ssize_t ret, bytes = 0;
	unsigned int i;

	if ((ret = o_stream_zlib_send_outbuf(zstream)) <= 0) {
		/* error / we still couldn't flush existing data to
		   parent stream. */
		return ret;
	}

	for (i = 0; i < iov_count; i++) {
		ret = o_stream_zlib_send_chunk(zstream, iov[i].iov_base,
					       iov[i].iov_len);
		if (ret < 0)
			return -1;
		bytes += ret;
		if ((size_t)ret != iov[i].iov_len)
			break;
	}
	stream->ostream.offset += bytes;

	if (!zstream->ostream.corked && i == iov_count) {
		if (o_stream_zlib_send_flush(zstream, FALSE) < 0)
			return -1;
	}
	/* avail_in!=0 check is used to detect errors. if it's non-zero here
	   it simply means we didn't send all the data */
	zstream->zs.avail_in = 0;
	return bytes;
}

static void o_stream_zlib_init_gz_header(struct zlib_ostream *zstream,
					 int level, int strategy)
{
	unsigned char *hdr = zstream->gz_header;

	hdr[0] = 0x1f;
	hdr[1] = 0x8b;
	hdr[2] = Z_DEFLATED;
	hdr[8] = level == 9 ? 2 :
		(strategy >= Z_HUFFMAN_ONLY ||
		 (level != Z_DEFAULT_COMPRESSION && level < 2) ? 4 : 0);
	hdr[9] = ZLIB_OS_CODE;
	i_assert(sizeof(zstream->gz_header) == 10);
}

static struct ostream *
o_stream_create_zlib(struct ostream *output, int level, bool gz)
{
	const int strategy = Z_DEFAULT_STRATEGY;
	struct zlib_ostream *zstream;
	int ret;

	i_assert(level >= 1 && level <= 9);

	zstream = i_new(struct zlib_ostream, 1);
	zstream->ostream.sendv = o_stream_zlib_sendv;
	zstream->ostream.flush = o_stream_zlib_flush;
	zstream->ostream.get_buffer_used_size =
		o_stream_zlib_get_buffer_used_size;
	zstream->ostream.get_buffer_avail_size =
		o_stream_zlib_get_buffer_avail_size;
	zstream->ostream.iostream.close = o_stream_zlib_close;
	zstream->crc = 0;
	zstream->gz = gz;
	if (!gz)
		zstream->header_sent = TRUE;

	o_stream_zlib_init_gz_header(zstream, level, strategy);
	ret = deflateInit2(&zstream->zs, level, Z_DEFLATED, -15, 8, strategy);
	switch (ret) {
	case Z_OK:
		break;
	case Z_MEM_ERROR:
		i_fatal_status(FATAL_OUTOFMEM, "deflateInit(): Out of memory");
	case Z_VERSION_ERROR:
		i_fatal("Wrong zlib library version (broken compilation)");
	case Z_STREAM_ERROR:
		i_fatal("Invalid compression level %d", level);
	default:
		i_fatal("deflateInit() failed with %d", ret);
	}

	zstream->zs.next_out = zstream->outbuf;
	zstream->zs.avail_out = sizeof(zstream->outbuf);
	return o_stream_create(&zstream->ostream, output,
			       o_stream_get_fd(output));
}

struct ostream *o_stream_create_gz(struct ostream *output, int level)
{
	return o_stream_create_zlib(output, level, TRUE);
}

struct ostream *o_stream_create_deflate(struct ostream *output, int level)
{
	return o_stream_create_zlib(output, level, FALSE);
}
#endif