1 files changed, 156 insertions, 0 deletions
diff --git a/src/zstream.c b/src/zstream.c
new file mode 100644
index 000000000..e75fb265e
--- /dev/null
+++ b/src/zstream.c
@@ -0,0 +1,156 @@
+/*
+ * 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(GITERR_ZLIB, zs->z.msg);
+	else
+		giterr_set(GITERR_ZLIB, "Unknown compression error");
+
+	return -1;
+}
+
+int git_zstream_init(git_zstream *zstream)
+{
+	zstream->zerr = deflateInit(&zstream->z, Z_DEFAULT_COMPRESSION);
+	return zstream_seterr(zstream);
+}
+
+void git_zstream_free(git_zstream *zstream)
+{
+	deflateEnd(&zstream->z);
+}
+
+void git_zstream_reset(git_zstream *zstream)
+{
+	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;
+
+	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 */
+		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;
+}
+
+int git_zstream_deflatebuf(git_buf *out, const void *in, size_t in_len)
+{
+	git_zstream zs = GIT_ZSTREAM_INIT;
+	int error = 0;
+
+	if ((error = git_zstream_init(&zs)) < 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(out, out->size + 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;
+}