diff --git a/archive-zip.c b/archive-zip.c
index cf285044e3..72d55a58ac 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -90,14 +90,14 @@ static void copy_le32(unsigned char *dest, unsigned int n)
 static void *zlib_deflate(void *data, unsigned long size,
 		int compression_level, unsigned long *compressed_size)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned long maxsize;
 	void *buffer;
 	int result;
 
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, compression_level);
-	maxsize = deflateBound(&stream, size);
+	git_deflate_init(&stream, compression_level);
+	maxsize = git_deflate_bound(&stream, size);
 	buffer = xmalloc(maxsize);
 
 	stream.next_in = data;
@@ -106,7 +106,7 @@ static void *zlib_deflate(void *data, unsigned long size,
 	stream.avail_out = maxsize;
 
 	do {
-		result = deflate(&stream, Z_FINISH);
+		result = git_deflate(&stream, Z_FINISH);
 	} while (result == Z_OK);
 
 	if (result != Z_STREAM_END) {
@@ -114,7 +114,7 @@ static void *zlib_deflate(void *data, unsigned long size,
 		return NULL;
 	}
 
-	deflateEnd(&stream);
+	git_deflate_end(&stream);
 	*compressed_size = stream.total_out;
 
 	return buffer;
diff --git a/builtin/apply.c b/builtin/apply.c
index 530d4bb7e7..f2edc52818 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -1634,7 +1634,7 @@ static inline int metadata_changes(struct patch *patch)
 static char *inflate_it(const void *data, unsigned long size,
 			unsigned long inflated_size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *out;
 	int st;
 
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index e40451ffb4..81cdc28b30 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -265,7 +265,7 @@ static void unlink_base_data(struct base_data *c)
 static void *unpack_entry_data(unsigned long offset, unsigned long size)
 {
 	int status;
-	z_stream stream;
+	git_zstream stream;
 	void *buf = xmalloc(size);
 
 	memset(&stream, 0, sizeof(stream));
@@ -355,7 +355,7 @@ static void *get_data_from_pack(struct object_entry *obj)
 	off_t from = obj[0].idx.offset + obj[0].hdr_size;
 	unsigned long len = obj[1].idx.offset - from;
 	unsigned char *data, *inbuf;
-	z_stream stream;
+	git_zstream stream;
 	int status;
 
 	data = xmalloc(obj->size);
@@ -666,26 +666,26 @@ static void parse_pack_objects(unsigned char *sha1)
 
 static int write_compressed(struct sha1file *f, void *in, unsigned int size)
 {
-	z_stream stream;
+	git_zstream stream;
 	int status;
 	unsigned char outbuf[4096];
 
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, zlib_compression_level);
+	git_deflate_init(&stream, zlib_compression_level);
 	stream.next_in = in;
 	stream.avail_in = size;
 
 	do {
 		stream.next_out = outbuf;
 		stream.avail_out = sizeof(outbuf);
-		status = deflate(&stream, Z_FINISH);
+		status = git_deflate(&stream, Z_FINISH);
 		sha1write(f, outbuf, sizeof(outbuf) - stream.avail_out);
 	} while (status == Z_OK);
 
 	if (status != Z_STREAM_END)
 		die("unable to deflate appended object (%d)", status);
 	size = stream.total_out;
-	deflateEnd(&stream);
+	git_deflate_end(&stream);
 	return size;
 }
 
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index f402a843bb..c6e2d8766b 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -126,13 +126,13 @@ static void *get_delta(struct object_entry *entry)
 
 static unsigned long do_compress(void **pptr, unsigned long size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *in, *out;
 	unsigned long maxsize;
 
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, pack_compression_level);
-	maxsize = deflateBound(&stream, size);
+	git_deflate_init(&stream, pack_compression_level);
+	maxsize = git_deflate_bound(&stream, size);
 
 	in = *pptr;
 	out = xmalloc(maxsize);
@@ -142,9 +142,9 @@ static unsigned long do_compress(void **pptr, unsigned long size)
 	stream.avail_in = size;
 	stream.next_out = out;
 	stream.avail_out = maxsize;
-	while (deflate(&stream, Z_FINISH) == Z_OK)
+	while (git_deflate(&stream, Z_FINISH) == Z_OK)
 		; /* nothing */
-	deflateEnd(&stream);
+	git_deflate_end(&stream);
 
 	free(in);
 	return stream.total_out;
@@ -160,7 +160,7 @@ static int check_pack_inflate(struct packed_git *p,
 		off_t len,
 		unsigned long expect)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned char fakebuf[4096], *in;
 	int st;
 
@@ -187,12 +187,12 @@ static void copy_pack_data(struct sha1file *f,
 		off_t len)
 {
 	unsigned char *in;
-	unsigned int avail;
+	unsigned long avail;
 
 	while (len) {
 		in = use_pack(p, w_curs, offset, &avail);
 		if (avail > len)
-			avail = (unsigned int)len;
+			avail = (unsigned long)len;
 		sha1write(f, in, avail);
 		offset += avail;
 		len -= avail;
@@ -994,7 +994,7 @@ static void check_object(struct object_entry *entry)
 		const unsigned char *base_ref = NULL;
 		struct object_entry *base_entry;
 		unsigned long used, used_0;
-		unsigned int avail;
+		unsigned long avail;
 		off_t ofs;
 		unsigned char *buf, c;
 
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index f63973c914..14e04e6795 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -90,7 +90,7 @@ static void use(int bytes)
 
 static void *get_data(unsigned long size)
 {
-	z_stream stream;
+	git_zstream stream;
 	void *buf = xmalloc(size);
 
 	memset(&stream, 0, sizeof(stream));
diff --git a/cache.h b/cache.h
index e11cf6ab1c..be506187f8 100644
--- a/cache.h
+++ b/cache.h
@@ -16,13 +16,27 @@
 #endif
 
 #include <zlib.h>
-#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
-#define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
-#endif
+typedef struct git_zstream {
+	z_stream z;
+	unsigned long avail_in;
+	unsigned long avail_out;
+	unsigned long total_in;
+	unsigned long total_out;
+	unsigned char *next_in;
+	unsigned char *next_out;
+} git_zstream;
 
-void git_inflate_init(z_streamp strm);
-void git_inflate_end(z_streamp strm);
-int git_inflate(z_streamp strm, int flush);
+void git_inflate_init(git_zstream *);
+void git_inflate_init_gzip_only(git_zstream *);
+void git_inflate_end(git_zstream *);
+int git_inflate(git_zstream *, int flush);
+
+void git_deflate_init(git_zstream *, int level);
+void git_deflate_init_gzip(git_zstream *, int level);
+void git_deflate_end(git_zstream *);
+int git_deflate_end_gently(git_zstream *);
+int git_deflate(git_zstream *, int flush);
+unsigned long git_deflate_bound(git_zstream *, unsigned long);
 
 #if defined(DT_UNKNOWN) && !defined(NO_D_TYPE_IN_DIRENT)
 #define DTYPE(de)	((de)->d_type)
@@ -1009,7 +1023,7 @@ extern struct packed_git *find_sha1_pack(const unsigned char *sha1,
 extern void pack_report(void);
 extern int open_pack_index(struct packed_git *);
 extern void close_pack_index(struct packed_git *);
-extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned int *);
+extern unsigned char *use_pack(struct packed_git *, struct pack_window **, off_t, unsigned long *);
 extern void close_pack_windows(struct packed_git *);
 extern void unuse_pack(struct pack_window **);
 extern void free_pack_by_name(const char *);
diff --git a/diff.c b/diff.c
index 5dd9049c7d..9038f190ec 100644
--- a/diff.c
+++ b/diff.c
@@ -1839,20 +1839,20 @@ static unsigned char *deflate_it(char *data,
 {
 	int bound;
 	unsigned char *deflated;
-	z_stream stream;
+	git_zstream stream;
 
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, zlib_compression_level);
-	bound = deflateBound(&stream, size);
+	git_deflate_init(&stream, zlib_compression_level);
+	bound = git_deflate_bound(&stream, size);
 	deflated = xmalloc(bound);
 	stream.next_out = deflated;
 	stream.avail_out = bound;
 
 	stream.next_in = (unsigned char *)data;
 	stream.avail_in = size;
-	while (deflate(&stream, Z_FINISH) == Z_OK)
+	while (git_deflate(&stream, Z_FINISH) == Z_OK)
 		; /* nothing */
-	deflateEnd(&stream);
+	git_deflate_end(&stream);
 	*result_size = stream.total_out;
 	return deflated;
 }
diff --git a/fast-import.c b/fast-import.c
index 78d978684d..1d5e3336a5 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1017,7 +1017,7 @@ static int store_object(
 	unsigned char sha1[20];
 	unsigned long hdrlen, deltalen;
 	git_SHA_CTX c;
-	z_stream s;
+	git_zstream s;
 
 	hdrlen = sprintf((char *)hdr,"%s %lu", typename(type),
 		(unsigned long)dat->len) + 1;
@@ -1050,7 +1050,7 @@ static int store_object(
 		delta = NULL;
 
 	memset(&s, 0, sizeof(s));
-	deflateInit(&s, pack_compression_level);
+	git_deflate_init(&s, pack_compression_level);
 	if (delta) {
 		s.next_in = delta;
 		s.avail_in = deltalen;
@@ -1058,11 +1058,11 @@ static int store_object(
 		s.next_in = (void *)dat->buf;
 		s.avail_in = dat->len;
 	}
-	s.avail_out = deflateBound(&s, s.avail_in);
+	s.avail_out = git_deflate_bound(&s, s.avail_in);
 	s.next_out = out = xmalloc(s.avail_out);
-	while (deflate(&s, Z_FINISH) == Z_OK)
-		/* nothing */;
-	deflateEnd(&s);
+	while (git_deflate(&s, Z_FINISH) == Z_OK)
+		; /* nothing */
+	git_deflate_end(&s);
 
 	/* Determine if we should auto-checkpoint. */
 	if ((max_packsize && (pack_size + 60 + s.total_out) > max_packsize)
@@ -1078,14 +1078,14 @@ static int store_object(
 			delta = NULL;
 
 			memset(&s, 0, sizeof(s));
-			deflateInit(&s, pack_compression_level);
+			git_deflate_init(&s, pack_compression_level);
 			s.next_in = (void *)dat->buf;
 			s.avail_in = dat->len;
-			s.avail_out = deflateBound(&s, s.avail_in);
+			s.avail_out = git_deflate_bound(&s, s.avail_in);
 			s.next_out = out = xrealloc(out, s.avail_out);
-			while (deflate(&s, Z_FINISH) == Z_OK)
-				/* nothing */;
-			deflateEnd(&s);
+			while (git_deflate(&s, Z_FINISH) == Z_OK)
+				; /* nothing */
+			git_deflate_end(&s);
 		}
 	}
 
@@ -1163,7 +1163,7 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
 	off_t offset;
 	git_SHA_CTX c;
 	git_SHA_CTX pack_file_ctx;
-	z_stream s;
+	git_zstream s;
 	int status = Z_OK;
 
 	/* Determine if we should auto-checkpoint. */
@@ -1187,7 +1187,7 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
 	crc32_begin(pack_file);
 
 	memset(&s, 0, sizeof(s));
-	deflateInit(&s, pack_compression_level);
+	git_deflate_init(&s, pack_compression_level);
 
 	hdrlen = encode_in_pack_object_header(OBJ_BLOB, len, out_buf);
 	if (out_sz <= hdrlen)
@@ -1209,7 +1209,7 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
 			len -= n;
 		}
 
-		status = deflate(&s, len ? 0 : Z_FINISH);
+		status = git_deflate(&s, len ? 0 : Z_FINISH);
 
 		if (!s.avail_out || status == Z_STREAM_END) {
 			size_t n = s.next_out - out_buf;
@@ -1228,7 +1228,7 @@ static void stream_blob(uintmax_t len, unsigned char *sha1out, uintmax_t mark)
 			die("unexpected deflate failure: %d", status);
 		}
 	}
-	deflateEnd(&s);
+	git_deflate_end(&s);
 	git_SHA1_Final(sha1, &c);
 
 	if (sha1out)
diff --git a/http-backend.c b/http-backend.c
index 85015048dd..59ad7da605 100644
--- a/http-backend.c
+++ b/http-backend.c
@@ -271,16 +271,13 @@ static struct rpc_service *select_service(const char *name)
 
 static void inflate_request(const char *prog_name, int out)
 {
-	z_stream stream;
+	git_zstream stream;
 	unsigned char in_buf[8192];
 	unsigned char out_buf[8192];
 	unsigned long cnt = 0;
-	int ret;
 
 	memset(&stream, 0, sizeof(stream));
-	ret = inflateInit2(&stream, (15 + 16));
-	if (ret != Z_OK)
-		die("cannot start zlib inflater, zlib err %d", ret);
+	git_inflate_init_gzip_only(&stream);
 
 	while (1) {
 		ssize_t n = xread(0, in_buf, sizeof(in_buf));
@@ -296,7 +293,7 @@ static void inflate_request(const char *prog_name, int out)
 			stream.next_out = out_buf;
 			stream.avail_out = sizeof(out_buf);
 
-			ret = inflate(&stream, Z_NO_FLUSH);
+			ret = git_inflate(&stream, Z_NO_FLUSH);
 			if (ret != Z_OK && ret != Z_STREAM_END)
 				die("zlib error inflating request, result %d", ret);
 
@@ -311,7 +308,7 @@ static void inflate_request(const char *prog_name, int out)
 	}
 
 done:
-	inflateEnd(&stream);
+	git_inflate_end(&stream);
 	close(out);
 }
 
diff --git a/http-push.c b/http-push.c
index 28bfe768f7..6e8f6d09ab 100644
--- a/http-push.c
+++ b/http-push.c
@@ -377,15 +377,15 @@ static void start_put(struct transfer_request *request)
 	unsigned long len;
 	int hdrlen;
 	ssize_t size;
-	z_stream stream;
+	git_zstream stream;
 
 	unpacked = read_sha1_file(request->obj->sha1, &type, &len);
 	hdrlen = sprintf(hdr, "%s %lu", typename(type), len) + 1;
 
 	/* Set it up */
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, zlib_compression_level);
-	size = deflateBound(&stream, len + hdrlen);
+	git_deflate_init(&stream, zlib_compression_level);
+	size = git_deflate_bound(&stream, len + hdrlen);
 	strbuf_init(&request->buffer.buf, size);
 	request->buffer.posn = 0;
 
@@ -396,15 +396,15 @@ static void start_put(struct transfer_request *request)
 	/* First header.. */
 	stream.next_in = (void *)hdr;
 	stream.avail_in = hdrlen;
-	while (deflate(&stream, 0) == Z_OK)
-		/* nothing */;
+	while (git_deflate(&stream, 0) == Z_OK)
+		; /* nothing */
 
 	/* Then the data itself.. */
 	stream.next_in = unpacked;
 	stream.avail_in = len;
-	while (deflate(&stream, Z_FINISH) == Z_OK)
-		/* nothing */;
-	deflateEnd(&stream);
+	while (git_deflate(&stream, Z_FINISH) == Z_OK)
+		; /* nothing */
+	git_deflate_end(&stream);
 	free(unpacked);
 
 	request->buffer.buf.len = stream.total_out;
diff --git a/http.h b/http.h
index 19b7134fa5..0bf8592dc4 100644
--- a/http.h
+++ b/http.h
@@ -172,7 +172,7 @@ struct http_object_request {
 	unsigned char sha1[20];
 	unsigned char real_sha1[20];
 	git_SHA_CTX c;
-	z_stream stream;
+	git_zstream stream;
 	int zret;
 	int rename;
 	struct active_request_slot *slot;
diff --git a/pack-check.c b/pack-check.c
index a1a521648d..0c19b6e5a5 100644
--- a/pack-check.c
+++ b/pack-check.c
@@ -26,7 +26,7 @@ int check_pack_crc(struct packed_git *p, struct pack_window **w_curs,
 	uint32_t data_crc = crc32(0, NULL, 0);
 
 	do {
-		unsigned int avail;
+		unsigned long avail;
 		void *data = use_pack(p, w_curs, offset, &avail);
 		if (avail > len)
 			avail = len;
@@ -61,7 +61,7 @@ static int verify_packfile(struct packed_git *p,
 
 	git_SHA1_Init(&ctx);
 	do {
-		unsigned int remaining;
+		unsigned long remaining;
 		unsigned char *in = use_pack(p, w_curs, offset, &remaining);
 		offset += remaining;
 		if (!pack_sig_ofs)
diff --git a/remote-curl.c b/remote-curl.c
index 8ac5028343..69831e931a 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -473,16 +473,12 @@ static int post_rpc(struct rpc_state *rpc)
 		 * the transfer time.
 		 */
 		size_t size;
-		z_stream stream;
+		git_zstream stream;
 		int ret;
 
 		memset(&stream, 0, sizeof(stream));
-		ret = deflateInit2(&stream, Z_BEST_COMPRESSION,
-				Z_DEFLATED, (15 + 16),
-				8, Z_DEFAULT_STRATEGY);
-		if (ret != Z_OK)
-			die("cannot deflate request; zlib init error %d", ret);
-		size = deflateBound(&stream, rpc->len);
+		git_deflate_init_gzip(&stream, Z_BEST_COMPRESSION);
+		size = git_deflate_bound(&stream, rpc->len);
 		gzip_body = xmalloc(size);
 
 		stream.next_in = (unsigned char *)rpc->buf;
@@ -490,11 +486,11 @@ static int post_rpc(struct rpc_state *rpc)
 		stream.next_out = (unsigned char *)gzip_body;
 		stream.avail_out = size;
 
-		ret = deflate(&stream, Z_FINISH);
+		ret = git_deflate(&stream, Z_FINISH);
 		if (ret != Z_STREAM_END)
 			die("cannot deflate request; zlib deflate error %d", ret);
 
-		ret = deflateEnd(&stream);
+		ret = git_deflate_end_gently(&stream);
 		if (ret != Z_OK)
 			die("cannot deflate request; zlib end error %d", ret);
 
diff --git a/sha1_file.c b/sha1_file.c
index 697f4a43c5..92e87ee225 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -834,7 +834,7 @@ static int in_window(struct pack_window *win, off_t offset)
 unsigned char *use_pack(struct packed_git *p,
 		struct pack_window **w_cursor,
 		off_t offset,
-		unsigned int *left)
+		unsigned long *left)
 {
 	struct pack_window *win = *w_cursor;
 
@@ -1254,7 +1254,7 @@ unsigned long unpack_object_header_buffer(const unsigned char *buf,
 	return used;
 }
 
-static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
+static int unpack_sha1_header(git_zstream *stream, unsigned char *map, unsigned long mapsize, void *buffer, unsigned long bufsiz)
 {
 	unsigned long size, used;
 	static const char valid_loose_object_type[8] = {
@@ -1296,7 +1296,7 @@ static int unpack_sha1_header(z_stream *stream, unsigned char *map, unsigned lon
 	return git_inflate(stream, 0);
 }
 
-static void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
+static void *unpack_sha1_rest(git_zstream *stream, void *buffer, unsigned long size, const unsigned char *sha1)
 {
 	int bytes = strlen(buffer) + 1;
 	unsigned char *buf = xmallocz(size);
@@ -1395,7 +1395,7 @@ static int parse_sha1_header(const char *hdr, unsigned long *sizep)
 static void *unpack_sha1_file(void *map, unsigned long mapsize, enum object_type *type, unsigned long *size, const unsigned char *sha1)
 {
 	int ret;
-	z_stream stream;
+	git_zstream stream;
 	char hdr[8192];
 
 	ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
@@ -1411,7 +1411,7 @@ unsigned long get_size_from_delta(struct packed_git *p,
 {
 	const unsigned char *data;
 	unsigned char delta_head[20], *in;
-	z_stream stream;
+	git_zstream stream;
 	int st;
 
 	memset(&stream, 0, sizeof(stream));
@@ -1533,7 +1533,7 @@ static int unpack_object_header(struct packed_git *p,
 				unsigned long *sizep)
 {
 	unsigned char *base;
-	unsigned int left;
+	unsigned long left;
 	unsigned long used;
 	enum object_type type;
 
@@ -1646,7 +1646,7 @@ static void *unpack_compressed_entry(struct packed_git *p,
 				    unsigned long size)
 {
 	int st;
-	z_stream stream;
+	git_zstream stream;
 	unsigned char *buffer, *in;
 
 	buffer = xmallocz(size);
@@ -2079,7 +2079,7 @@ static int sha1_loose_object_info(const unsigned char *sha1, unsigned long *size
 	int status;
 	unsigned long mapsize, size;
 	void *map;
-	z_stream stream;
+	git_zstream stream;
 	char hdr[32];
 
 	map = map_sha1_file(sha1, &mapsize);
@@ -2428,7 +2428,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 {
 	int fd, ret;
 	unsigned char compressed[4096];
-	z_stream stream;
+	git_zstream stream;
 	git_SHA_CTX c;
 	unsigned char parano_sha1[20];
 	char *filename;
@@ -2445,7 +2445,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 
 	/* Set it up */
 	memset(&stream, 0, sizeof(stream));
-	deflateInit(&stream, zlib_compression_level);
+	git_deflate_init(&stream, zlib_compression_level);
 	stream.next_out = compressed;
 	stream.avail_out = sizeof(compressed);
 	git_SHA1_Init(&c);
@@ -2453,8 +2453,8 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 	/* First header.. */
 	stream.next_in = (unsigned char *)hdr;
 	stream.avail_in = hdrlen;
-	while (deflate(&stream, 0) == Z_OK)
-		/* nothing */;
+	while (git_deflate(&stream, 0) == Z_OK)
+		; /* nothing */
 	git_SHA1_Update(&c, hdr, hdrlen);
 
 	/* Then the data itself.. */
@@ -2462,7 +2462,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 	stream.avail_in = len;
 	do {
 		unsigned char *in0 = stream.next_in;
-		ret = deflate(&stream, Z_FINISH);
+		ret = git_deflate(&stream, Z_FINISH);
 		git_SHA1_Update(&c, in0, stream.next_in - in0);
 		if (write_buffer(fd, compressed, stream.next_out - compressed) < 0)
 			die("unable to write sha1 file");
@@ -2472,7 +2472,7 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen,
 
 	if (ret != Z_STREAM_END)
 		die("unable to deflate new object %s (%d)", sha1_to_hex(sha1), ret);
-	ret = deflateEnd(&stream);
+	ret = git_deflate_end_gently(&stream);
 	if (ret != Z_OK)
 		die("deflateEnd on object %s failed (%d)", sha1_to_hex(sha1), ret);
 	git_SHA1_Final(parano_sha1, &c);
diff --git a/zlib.c b/zlib.c
index c4d58da4e9..3c63d480c7 100644
--- a/zlib.c
+++ b/zlib.c
@@ -4,58 +4,248 @@
  */
 #include "cache.h"
 
-void git_inflate_init(z_streamp strm)
+static const char *zerr_to_string(int status)
 {
-	const char *err;
-
-	switch (inflateInit(strm)) {
-	case Z_OK:
-		return;
-
+	switch (status) {
 	case Z_MEM_ERROR:
-		err = "out of memory";
-		break;
+		return "out of memory";
 	case Z_VERSION_ERROR:
-		err = "wrong version";
-		break;
-	default:
-		err = "error";
-	}
-	die("inflateInit: %s (%s)", err, strm->msg ? strm->msg : "no message");
-}
-
-void git_inflate_end(z_streamp strm)
-{
-	if (inflateEnd(strm) != Z_OK)
-		error("inflateEnd: %s", strm->msg ? strm->msg : "failed");
-}
-
-int git_inflate(z_streamp strm, int flush)
-{
-	int ret = inflate(strm, flush);
-	const char *err;
-
-	switch (ret) {
-	/* Out of memory is fatal. */
-	case Z_MEM_ERROR:
-		die("inflate: out of memory");
-
-	/* Data corruption errors: we may want to recover from them (fsck) */
+		return "wrong version";
 	case Z_NEED_DICT:
-		err = "needs dictionary"; break;
+		return "needs dictionary";
 	case Z_DATA_ERROR:
-		err = "data stream error"; break;
+		return "data stream error";
 	case Z_STREAM_ERROR:
-		err = "stream consistency error"; break;
+		return "stream consistency error";
 	default:
-		err = "unknown error"; break;
+		return "unknown error";
+	}
+}
 
+/*
+ * avail_in and avail_out in zlib are counted in uInt, which typically
+ * limits the size of the buffer we can use to 4GB when interacting
+ * with zlib in a single call to inflate/deflate.
+ */
+/* #define ZLIB_BUF_MAX ((uInt)-1) */
+#define ZLIB_BUF_MAX ((uInt) 1024 * 1024 * 1024) /* 1GB */
+static inline uInt zlib_buf_cap(unsigned long len)
+{
+	return (ZLIB_BUF_MAX < len) ? ZLIB_BUF_MAX : len;
+}
+
+static void zlib_pre_call(git_zstream *s)
+{
+	s->z.next_in = s->next_in;
+	s->z.next_out = s->next_out;
+	s->z.total_in = s->total_in;
+	s->z.total_out = s->total_out;
+	s->z.avail_in = zlib_buf_cap(s->avail_in);
+	s->z.avail_out = zlib_buf_cap(s->avail_out);
+}
+
+static void zlib_post_call(git_zstream *s)
+{
+	unsigned long bytes_consumed;
+	unsigned long bytes_produced;
+
+	bytes_consumed = s->z.next_in - s->next_in;
+	bytes_produced = s->z.next_out - s->next_out;
+	if (s->z.total_out != s->total_out + bytes_produced)
+		die("BUG: total_out mismatch");
+	if (s->z.total_in != s->total_in + bytes_consumed)
+		die("BUG: total_in mismatch");
+
+	s->total_out = s->z.total_out;
+	s->total_in = s->z.total_in;
+	s->next_in = s->z.next_in;
+	s->next_out = s->z.next_out;
+	s->avail_in -= bytes_consumed;
+	s->avail_out -= bytes_produced;
+}
+
+void git_inflate_init(git_zstream *strm)
+{
+	int status;
+
+	zlib_pre_call(strm);
+	status = inflateInit(&strm->z);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	die("inflateInit: %s (%s)", zerr_to_string(status),
+	    strm->z.msg ? strm->z.msg : "no message");
+}
+
+void git_inflate_init_gzip_only(git_zstream *strm)
+{
+	/*
+	 * Use default 15 bits, +16 is to accept only gzip and to
+	 * yield Z_DATA_ERROR when fed zlib format.
+	 */
+	const int windowBits = 15 + 16;
+	int status;
+
+	zlib_pre_call(strm);
+	status = inflateInit2(&strm->z, windowBits);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	die("inflateInit2: %s (%s)", zerr_to_string(status),
+	    strm->z.msg ? strm->z.msg : "no message");
+}
+
+void git_inflate_end(git_zstream *strm)
+{
+	int status;
+
+	zlib_pre_call(strm);
+	status = inflateEnd(&strm->z);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	error("inflateEnd: %s (%s)", zerr_to_string(status),
+	      strm->z.msg ? strm->z.msg : "no message");
+}
+
+int git_inflate(git_zstream *strm, int flush)
+{
+	int status;
+
+	for (;;) {
+		zlib_pre_call(strm);
+		/* Never say Z_FINISH unless we are feeding everything */
+		status = inflate(&strm->z,
+				 (strm->z.avail_in != strm->avail_in)
+				 ? 0 : flush);
+		if (status == Z_MEM_ERROR)
+			die("inflate: out of memory");
+		zlib_post_call(strm);
+
+		/*
+		 * Let zlib work another round, while we can still
+		 * make progress.
+		 */
+		if ((strm->avail_out && !strm->z.avail_out) &&
+		    (status == Z_OK || status == Z_BUF_ERROR))
+			continue;
+		break;
+	}
+
+	switch (status) {
 	/* Z_BUF_ERROR: normal, needs more space in the output buffer */
 	case Z_BUF_ERROR:
 	case Z_OK:
 	case Z_STREAM_END:
-		return ret;
+		return status;
+	default:
+		break;
 	}
-	error("inflate: %s (%s)", err, strm->msg ? strm->msg : "no message");
-	return ret;
+	error("inflate: %s (%s)", zerr_to_string(status),
+	      strm->z.msg ? strm->z.msg : "no message");
+	return status;
+}
+
+#if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
+#define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
+#endif
+
+unsigned long git_deflate_bound(git_zstream *strm, unsigned long size)
+{
+	return deflateBound(&strm->z, size);
+}
+
+void git_deflate_init(git_zstream *strm, int level)
+{
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateInit(&strm->z, level);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	die("deflateInit: %s (%s)", zerr_to_string(status),
+	    strm->z.msg ? strm->z.msg : "no message");
+}
+
+void git_deflate_init_gzip(git_zstream *strm, int level)
+{
+	/*
+	 * Use default 15 bits, +16 is to generate gzip header/trailer
+	 * instead of the zlib wrapper.
+	 */
+	const int windowBits = 15 + 16;
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateInit2(&strm->z, level,
+				  Z_DEFLATED, windowBits,
+				  8, Z_DEFAULT_STRATEGY);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	die("deflateInit2: %s (%s)", zerr_to_string(status),
+	    strm->z.msg ? strm->z.msg : "no message");
+}
+
+void git_deflate_end(git_zstream *strm)
+{
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateEnd(&strm->z);
+	zlib_post_call(strm);
+	if (status == Z_OK)
+		return;
+	error("deflateEnd: %s (%s)", zerr_to_string(status),
+	      strm->z.msg ? strm->z.msg : "no message");
+}
+
+int git_deflate_end_gently(git_zstream *strm)
+{
+	int status;
+
+	zlib_pre_call(strm);
+	status = deflateEnd(&strm->z);
+	zlib_post_call(strm);
+	return status;
+}
+
+int git_deflate(git_zstream *strm, int flush)
+{
+	int status;
+
+	for (;;) {
+		zlib_pre_call(strm);
+
+		/* Never say Z_FINISH unless we are feeding everything */
+		status = deflate(&strm->z,
+				 (strm->z.avail_in != strm->avail_in)
+				 ? 0 : flush);
+		if (status == Z_MEM_ERROR)
+			die("deflate: out of memory");
+		zlib_post_call(strm);
+
+		/*
+		 * Let zlib work another round, while we can still
+		 * make progress.
+		 */
+		if ((strm->avail_out && !strm->z.avail_out) &&
+		    (status == Z_OK || status == Z_BUF_ERROR))
+			continue;
+		break;
+	}
+
+	switch (status) {
+	/* Z_BUF_ERROR: normal, needs more space in the output buffer */
+	case Z_BUF_ERROR:
+	case Z_OK:
+	case Z_STREAM_END:
+		return status;
+	default:
+		break;
+	}
+	error("deflate: %s (%s)", zerr_to_string(status),
+	      strm->z.msg ? strm->z.msg : "no message");
+	return status;
 }