/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"

#ifdef HAVE_LZ4

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

#define CHUNK_SIZE OSTREAM_LZ4_CHUNK_SIZE

struct lz4_ostream {
	struct ostream_private ostream;

	unsigned char compressbuf[CHUNK_SIZE];
	unsigned int compressbuf_offset;

	/* chunk size, followed by compressed data */
	unsigned char outbuf[IOSTREAM_LZ4_CHUNK_PREFIX_LEN +
	                     LZ4_COMPRESSBOUND(CHUNK_SIZE)];
	unsigned int outbuf_offset, outbuf_used;
};

/* There is no actual compression level in LZ4, so for legacy
   reasons we allow 1-9 to avoid breaking anyone's config. */
int compression_get_min_level_lz4(void)
{
	return 1;
}

int compression_get_default_level_lz4(void)
{
	return 1;
}

int compression_get_max_level_lz4(void)
{
	return 9;
}

static void o_stream_lz4_close(struct iostream_private *stream,
			       bool close_parent)
{
	struct lz4_ostream *zstream = (struct lz4_ostream *)stream;

	if (close_parent)
		o_stream_close(zstream->ostream.parent);
}

static int o_stream_lz4_send_outbuf(struct lz4_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 int o_stream_lz4_compress(struct lz4_ostream *zstream)
{
	uint32_t chunk_size;
	int ret;

	if (zstream->compressbuf_offset == 0)
		return 1;
	if ((ret = o_stream_lz4_send_outbuf(zstream)) <= 0)
		return ret;

	i_assert(zstream->outbuf_offset == 0);
	i_assert(zstream->outbuf_used == 0);

#if defined(HAVE_LZ4_COMPRESS_DEFAULT)
	int max_dest_size = LZ4_compressBound(zstream->compressbuf_offset);
	i_assert(max_dest_size >= 0);
	if (max_dest_size == 0) {
		io_stream_set_error(&zstream->ostream.iostream,
			"lz4-compress: input size %u too large (> %u)",
			zstream->compressbuf_offset, LZ4_MAX_INPUT_SIZE);
		zstream->ostream.ostream.stream_errno = EINVAL;
		return -1;
	}
	ret = LZ4_compress_default((void *)zstream->compressbuf,
				   (void *)(zstream->outbuf +
				            IOSTREAM_LZ4_CHUNK_PREFIX_LEN),
				   zstream->compressbuf_offset,
				   max_dest_size);
#else
	ret = LZ4_compress((void *)zstream->compressbuf,
			   (void *)(zstream->outbuf +
			            IOSTREAM_LZ4_CHUNK_PREFIX_LEN),
			   zstream->compressbuf_offset);
#endif /* defined(HAVE_LZ4_COMPRESS_DEFAULT) */
	i_assert(ret > 0 && (unsigned int)ret <= sizeof(zstream->outbuf) -
	         IOSTREAM_LZ4_CHUNK_PREFIX_LEN);
	zstream->outbuf_used = IOSTREAM_LZ4_CHUNK_PREFIX_LEN + ret;
	chunk_size = zstream->outbuf_used - IOSTREAM_LZ4_CHUNK_PREFIX_LEN;
	zstream->outbuf[0] = (chunk_size & 0xff000000) >> 24;
	zstream->outbuf[1] = (chunk_size & 0x00ff0000) >> 16;
	zstream->outbuf[2] = (chunk_size & 0x0000ff00) >> 8;
	zstream->outbuf[3] = (chunk_size & 0x000000ff);
	zstream->compressbuf_offset = 0;
	return 1;
}

static ssize_t
o_stream_lz4_send_chunk(struct lz4_ostream *zstream,
			const void *data, size_t size)
{
	size_t max_size;
	ssize_t added_bytes = 0;
	int ret;

	i_assert(zstream->outbuf_used == 0);

	do {
		max_size = I_MIN(size, sizeof(zstream->compressbuf) -
				 zstream->compressbuf_offset);
		memcpy(zstream->compressbuf + zstream->compressbuf_offset,
		       data, max_size);
		zstream->compressbuf_offset += max_size;

		data = CONST_PTR_OFFSET(data, max_size);
		size -= max_size;
		added_bytes += max_size;

		if (zstream->compressbuf_offset == sizeof(zstream->compressbuf)) {
			ret = o_stream_lz4_compress(zstream);
			if (ret <= 0)
				return added_bytes != 0 ? added_bytes : ret;
		}
	} while (size > 0);

	return added_bytes;
}

static int o_stream_lz4_flush(struct ostream_private *stream)
{
	struct lz4_ostream *zstream = (struct lz4_ostream *)stream;

	if (o_stream_lz4_compress(zstream) < 0)
		return -1;
	if (o_stream_lz4_send_outbuf(zstream) < 0)
		return -1;

	return o_stream_flush_parent(stream);
}

static size_t
o_stream_lz4_get_buffer_used_size(const struct ostream_private *stream)
{
	const struct lz4_ostream *zstream =
		(const struct lz4_ostream *)stream;

	/* outbuf has already compressed data that we're trying to send to the
	   parent stream. compressbuf isn't included in the return value,
	   because it needs to be filled up or flushed. */
	return (zstream->outbuf_used - zstream->outbuf_offset) +
		o_stream_get_buffer_used_size(stream->parent);
}

static size_t
o_stream_lz4_get_buffer_avail_size(const struct ostream_private *stream)
{
	const struct lz4_ostream *zstream =
		(const struct lz4_ostream *)stream;

	/* We're only guaranteed to accept data to compressbuf. The parent
	   stream might have space, but since compressed data gets written
	   there it's not really known how much we can actually write there. */
	return sizeof(zstream->compressbuf) - zstream->compressbuf_offset;
}

static ssize_t
o_stream_lz4_sendv(struct ostream_private *stream,
		    const struct const_iovec *iov, unsigned int iov_count)
{
	struct lz4_ostream *zstream = (struct lz4_ostream *)stream;
	ssize_t ret, bytes = 0;
	unsigned int i;

	if ((ret = o_stream_lz4_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_lz4_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;
	return bytes;
}

struct ostream *o_stream_create_lz4(struct ostream *output, int level)
{
	struct iostream_lz4_header *hdr;
	struct lz4_ostream *zstream;

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

	zstream = i_new(struct lz4_ostream, 1);
	zstream->ostream.sendv = o_stream_lz4_sendv;
	zstream->ostream.flush = o_stream_lz4_flush;
	zstream->ostream.get_buffer_used_size =
		o_stream_lz4_get_buffer_used_size;
	zstream->ostream.get_buffer_avail_size =
		o_stream_lz4_get_buffer_avail_size;
	zstream->ostream.iostream.close = o_stream_lz4_close;

	i_assert(sizeof(zstream->outbuf) >= sizeof(*hdr));
	hdr = (void *)zstream->outbuf;
	memcpy(hdr->magic, IOSTREAM_LZ4_MAGIC, sizeof(hdr->magic));
	hdr->max_uncompressed_chunk_size[0] =
		(OSTREAM_LZ4_CHUNK_SIZE & 0xff000000) >> 24;
	hdr->max_uncompressed_chunk_size[1] =
		(OSTREAM_LZ4_CHUNK_SIZE & 0x00ff0000) >> 16;
	hdr->max_uncompressed_chunk_size[2] =
		(OSTREAM_LZ4_CHUNK_SIZE & 0x0000ff00) >> 8;
	hdr->max_uncompressed_chunk_size[3] =
		(OSTREAM_LZ4_CHUNK_SIZE & 0x000000ff);
	zstream->outbuf_used = sizeof(*hdr);
	return o_stream_create(&zstream->ostream, output,
			       o_stream_get_fd(output));
}
#endif