/*

 * Copyright (C) the libgit2 contributors. All rights reserved.

 *

 * This file is part of libgit2, distributed under the GNU GPL v2 with

 * a Linking Exception. For full terms see the included COPYING file.

 */

#include <zlib.h>

#include "zstream.h"

#include "buffer.h"

#define ZSTREAM_BUFFER_SIZE (1024 * 1024)

#define ZSTREAM_BUFFER_MIN_EXTRA 8

static int zstream_seterr(git_zstream *zs)

{

	if (zs->zerr == Z_OK || zs->zerr == Z_STREAM_END)

		return 0;

	if (zs->zerr == Z_MEM_ERROR)

		giterr_set_oom();

	else if (zs->z.msg)

		giterr_set_str(GITERR_ZLIB, zs->z.msg);

	else

		giterr_set(GITERR_ZLIB, "unknown compression error");

	return -1;

}

int git_zstream_init(git_zstream *zstream, git_zstream_t type)

{

	zstream->type = type;

	if (zstream->type == GIT_ZSTREAM_INFLATE)

		zstream->zerr = inflateInit(&zstream->z);

	else

		zstream->zerr = deflateInit(&zstream->z, Z_DEFAULT_COMPRESSION);

	return zstream_seterr(zstream);

}

void git_zstream_free(git_zstream *zstream)

{

	if (zstream->type == GIT_ZSTREAM_INFLATE)

		inflateEnd(&zstream->z);

	else

		deflateEnd(&zstream->z);

}

void git_zstream_reset(git_zstream *zstream)

{

	if (zstream->type == GIT_ZSTREAM_INFLATE)

		inflateReset(&zstream->z);

	else

		deflateReset(&zstream->z);

	zstream->in = NULL;

	zstream->in_len = 0;

	zstream->zerr = Z_STREAM_END;

}

int git_zstream_set_input(git_zstream *zstream, const void *in, size_t in_len)

{

	zstream->in = in;

	zstream->in_len = in_len;

	zstream->zerr = Z_OK;

	return 0;

}

bool git_zstream_done(git_zstream *zstream)

{

	return (!zstream->in_len && zstream->zerr == Z_STREAM_END);

}

size_t git_zstream_suggest_output_len(git_zstream *zstream)

{

	if (zstream->in_len > ZSTREAM_BUFFER_SIZE)

		return ZSTREAM_BUFFER_SIZE;

	else if (zstream->in_len > ZSTREAM_BUFFER_MIN_EXTRA)

		return zstream->in_len;

	else

		return ZSTREAM_BUFFER_MIN_EXTRA;

}

int git_zstream_get_output(void *out, size_t *out_len, git_zstream *zstream)

{

	int zflush = Z_FINISH;

	size_t out_remain = *out_len;

	if (zstream->in_len && zstream->zerr == Z_STREAM_END) {

		giterr_set(GITERR_ZLIB, "zlib input had trailing garbage");

		return -1;

	}

	while (out_remain > 0 && zstream->zerr != Z_STREAM_END) {

		size_t out_queued, in_queued, out_used, in_used;

		/* set up in data */

		zstream->z.next_in  = (Bytef *)zstream->in;

		zstream->z.avail_in = (uInt)zstream->in_len;

		if ((size_t)zstream->z.avail_in != zstream->in_len) {

			zstream->z.avail_in = INT_MAX;

			zflush = Z_NO_FLUSH;

		} else {

			zflush = Z_FINISH;

		}

		in_queued = (size_t)zstream->z.avail_in;

		/* set up out data */

		zstream->z.next_out = out;

		zstream->z.avail_out = (uInt)out_remain;

		if ((size_t)zstream->z.avail_out != out_remain)

			zstream->z.avail_out = INT_MAX;

		out_queued = (size_t)zstream->z.avail_out;

		/* compress next chunk */

		if (zstream->type == GIT_ZSTREAM_INFLATE)

			zstream->zerr = inflate(&zstream->z, zflush);

		else

			zstream->zerr = deflate(&zstream->z, zflush);

		if (zstream->zerr == Z_STREAM_ERROR)

			return zstream_seterr(zstream);

		out_used = (out_queued - zstream->z.avail_out);

		out_remain -= out_used;

		out = ((char *)out) + out_used;

		in_used = (in_queued - zstream->z.avail_in);

		zstream->in_len -= in_used;

		zstream->in += in_used;

	}

	/* either we finished the input or we did not flush the data */

	assert(zstream->in_len > 0 || zflush == Z_FINISH);

	/* set out_size to number of bytes actually written to output */

	*out_len = *out_len - out_remain;

	return 0;

}

static int zstream_buf(git_buf *out, const void *in, size_t in_len, git_zstream_t type)

{

	git_zstream zs = GIT_ZSTREAM_INIT;

	int error = 0;

	if ((error = git_zstream_init(&zs, type)) < 0)

		return error;

	if ((error = git_zstream_set_input(&zs, in, in_len)) < 0)

		goto done;

	while (!git_zstream_done(&zs)) {

		size_t step = git_zstream_suggest_output_len(&zs), written;

		if ((error = git_buf_grow_by(out, step)) < 0)

			goto done;

		written = out->asize - out->size;

		if ((error = git_zstream_get_output(

				out->ptr + out->size, &written, &zs)) < 0)

			goto done;

		out->size += written;

	}

	/* NULL terminate for consistency if possible */

	if (out->size < out->asize)

		out->ptr[out->size] = '\0';

done:

	git_zstream_free(&zs);

	return error;

}

int git_zstream_deflatebuf(git_buf *out, const void *in, size_t in_len)

{

	return zstream_buf(out, in, in_len, GIT_ZSTREAM_DEFLATE);

}

int git_zstream_inflatebuf(git_buf *out, const void *in, size_t in_len)

{

	return zstream_buf(out, in, in_len, GIT_ZSTREAM_INFLATE);

}