util: add git__compress()

src/compress.c

+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * 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 "compress.h"
+
+#include <zlib.h>
+
+#define BUFFER_SIZE (1024 * 1024)
+
+int git__compress(git_buf *buf, const void *buff, size_t len)
+{
+	z_stream zs;
+	char *zb;
+	size_t have;
+
+	memset(&zs, 0, sizeof(zs));
+	if (deflateInit(&zs, Z_DEFAULT_COMPRESSION) != Z_OK)
+		return -1;
+
+	zb = git__malloc(BUFFER_SIZE);
+	GITERR_CHECK_ALLOC(zb);
+
+	zs.next_in = (void *)buff;
+	zs.avail_in = (uInt)len;
+
+	do {
+		zs.next_out = (unsigned char *)zb;
+		zs.avail_out = BUFFER_SIZE;
+
+		if (deflate(&zs, Z_FINISH) == Z_STREAM_ERROR) {
+			git__free(zb);
+			return -1;
+		}
+
+		have = BUFFER_SIZE - (size_t)zs.avail_out;
+
+		if (git_buf_put(buf, zb, have) < 0) {
+			git__free(zb);
+			return -1;
+		}
+
+	} while (zs.avail_out == 0);
+
+	assert(zs.avail_in == 0);
+
+	deflateEnd(&zs);
+	git__free(zb);
+	return 0;
+}

src/compress.h

+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_compress_h__
+#define INCLUDE_compress_h__
+
+#include "common.h"
+
+#include "buffer.h"
+
+int git__compress(git_buf *buf, const void *buff, size_t len);
+
+#endif /* INCLUDE_compress_h__ */