Merge branch 'ps/zlib-ng' into seen

* ps/zlib-ng:
  compat/zlib: allow use of zlib-ng as backend
  git-zlib: cast away potential constness of `next_in` pointer
  compat/zlib: provide stubs for `deflateSetHeader()`
  compat/zlib: provide `deflateBound()` shim centrally
  git-compat-util: move include of "compat/zlib.h" into "git-zlib.h"
  compat: introduce new "zlib.h" header
  git-compat-util: drop `z_const` define
  compat: drop `uncompress2()` compatibility shim

Author: gitster

Makefile

@@ -993,7 +993,6 @@ LIB_OBJS += common-init.o
 LIB_OBJS += compat/nonblock.o
 LIB_OBJS += compat/obstack.o
 LIB_OBJS += compat/terminal.o
-LIB_OBJS += compat/zlib-uncompress2.o
 LIB_OBJS += config.o
 LIB_OBJS += connect.o
 LIB_OBJS += connected.o

archive-tar.c

@@ -473,9 +473,7 @@ static const char internal_gzip_command[] = "git archive gzip";
 static int write_tar_filter_archive(const struct archiver *ar,
 				    struct archiver_args *args)
 {
-#if ZLIB_VERNUM >= 0x1221
 	struct gz_header_s gzhead = { .os = 3 }; /* Unix, for reproducibility */
-#endif
 	struct strbuf cmd = STRBUF_INIT;
 	struct child_process filter = CHILD_PROCESS_INIT;
 	int r;
@@ -486,10 +484,8 @@ static int write_tar_filter_archive(const struct archiver *ar,
 	if (!strcmp(ar->filter_command, internal_gzip_command)) {
 		write_block = tgz_write_block;
 		git_deflate_init_gzip(&gzstream, args->compression_level);
-#if ZLIB_VERNUM >= 0x1221
 		if (deflateSetHeader(&gzstream.z, &gzhead) != Z_OK)
 			BUG("deflateSetHeader() called too late");
-#endif
 		gzstream.next_out = outbuf;
 		gzstream.avail_out = sizeof(outbuf);
 

archive.c

@@ -7,6 +7,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "hex.h"
 #include "object-name.h"
 #include "path.h"

compat/zlib-compat.h

@@ -0,0 +1,47 @@
+#ifndef COMPAT_ZLIB_H
+#define COMPAT_ZLIB_H
+
+#ifdef HAVE_ZLIB_NG
+# include <zlib-ng.h>
+
+# define z_stream zng_stream
+#define gz_header_s zng_gz_header_s
+
+# define crc32(crc, buf, len) zng_crc32(crc, buf, len)
+
+# define inflate(strm, bits) zng_inflate(strm, bits)
+# define inflateEnd(strm) zng_inflateEnd(strm)
+# define inflateInit(strm) zng_inflateInit(strm)
+# define inflateInit2(strm, bits) zng_inflateInit2(strm, bits)
+# define inflateReset(strm) zng_inflateReset(strm)
+
+# define deflate(strm, flush) zng_deflate(strm, flush)
+# define deflateBound(strm, source_len) zng_deflateBound(strm, source_len)
+# define deflateEnd(strm) zng_deflateEnd(strm)
+# define deflateInit(strm, level) zng_deflateInit(strm, level)
+# define deflateInit2(stream, level, method, window_bits, mem_level, strategy) zng_deflateInit2(stream, level, method, window_bits, mem_level, strategy)
+# define deflateReset(strm) zng_deflateReset(strm)
+# define deflateSetHeader(strm, head) zng_deflateSetHeader(strm, head)
+
+#else
+# include <zlib.h>
+
+# if defined(NO_DEFLATE_BOUND) || ZLIB_VERNUM < 0x1200
+#  define deflateBound(c,s)  ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
+# endif
+
+# if ZLIB_VERNUM < 0x1221
+struct gz_header_s {
+	int os;
+};
+
+static int deflateSetHeader(z_streamp strm, struct gz_header_s *head)
+{
+	(void)(strm);
+	(void)(head);
+	return Z_OK;
+}
+# endif
+#endif /* HAVE_ZLIB_NG */
+
+#endif /* COMPAT_ZLIB_H */

compat/zlib-uncompress2.c

@@ -19,6 +19,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "ident.h"
 #include "repository.h"
 #include "lockfile.h"

config.c

@@ -11,9 +11,10 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
-#include "progress.h"
 #include "csum-file.h"
+#include "git-zlib.h"
 #include "hash.h"
+#include "progress.h"
 
 static void verify_buffer_or_die(struct hashfile *f,
 				 const void *buf,

csum-file.c

@@ -16,6 +16,7 @@
 #include "convert.h"
 #include "environment.h"
 #include "gettext.h"
+#include "git-zlib.h"
 #include "repository.h"
 #include "config.h"
 #include "refs.h"

environment.c

@@ -1555,18 +1555,6 @@ int cmd_main(int, const char **);
 int common_exit(const char *file, int line, int code);
 #define exit(code) exit(common_exit(__FILE__, __LINE__, (code)))
 
-#define z_const
-#include <zlib.h>
-
-#if ZLIB_VERNUM < 0x1290
-/*
- * This is uncompress2, which is only available in zlib >= 1.2.9
- * (released as of early 2017). See compat/zlib-uncompress2.c.
- */
-int uncompress2(Bytef *dest, uLongf *destLen, const Bytef *source,
-		uLong *sourceLen);
-#endif
-
 /*
  * This include must come after system headers, since it introduces macros that
  * replace system names.

git-compat-util.h

@@ -59,7 +59,7 @@ static void zlib_post_call(git_zstream *s)
 
 	s->total_out = s->z.total_out;
 	s->total_in = s->z.total_in;
-	s->next_in = s->z.next_in;
+	s->next_in = (unsigned char *) s->z.next_in;
 	s->next_out = s->z.next_out;
 	s->avail_in -= bytes_consumed;
 	s->avail_out -= bytes_produced;
@@ -147,10 +147,6 @@ int git_inflate(git_zstream *strm, int flush)
 	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);

git-zlib.c

@@ -1,6 +1,8 @@
 #ifndef GIT_ZLIB_H
 #define GIT_ZLIB_H
 
+#include "compat/zlib-compat.h"
+
 typedef struct git_zstream {
 	z_stream z;
 	unsigned long avail_in;

git-zlib.h

@@ -250,7 +250,6 @@ libgit_sources = [
   'compat/nonblock.c',
   'compat/obstack.c',
   'compat/terminal.c',
-  'compat/zlib-uncompress2.c',
   'config.c',
   'connect.c',
   'connected.c',
@@ -789,11 +788,23 @@ else
   build_options_config.set('NO_PERL_CPAN_FALLBACKS', '')
 endif
 
-zlib = dependency('zlib', default_options: ['default_library=static', 'tests=disabled'])
-if zlib.version().version_compare('<1.2.0')
-  libgit_c_args += '-DNO_DEFLATE_BOUND'
+zlib_backend = get_option('zlib_backend')
+if zlib_backend in ['auto', 'zlib-ng']
+  zlib_ng = dependency('zlib-ng', required: zlib_backend == 'zlib-ng')
+  if zlib_ng.found()
+    zlib_backend = 'zlib-ng'
+    libgit_c_args += '-DHAVE_ZLIB_NG'
+    libgit_dependencies += zlib_ng
+  endif
+endif
+if zlib_backend in ['auto', 'zlib']
+  zlib = dependency('zlib', default_options: ['default_library=static', 'tests=disabled'])
+  if zlib.version().version_compare('<1.2.0')
+    libgit_c_args += '-DNO_DEFLATE_BOUND'
+  endif
+  zlib_backend = 'zlib'
+  libgit_dependencies += zlib
 endif
-libgit_dependencies += zlib
 
 threads = dependency('threads', required: false)
 if threads.found()
@@ -1960,4 +1971,5 @@ summary({
   'sha1': sha1_backend,
   'sha1_unsafe': sha1_unsafe_backend,
   'sha256': sha256_backend,
+  'zlib': zlib_backend,
 }, section: 'Backends')

meson.build

@@ -55,6 +55,8 @@ option('sha1_unsafe_backend', type: 'combo', choices: ['openssl', 'block', 'Comm
   description: 'The backend used for hashing data with the SHA1 object format in case no cryptographic security is needed.')
 option('sha256_backend', type: 'combo', choices: ['openssl', 'nettle', 'gcrypt', 'block'], value: 'block',
   description: 'The backend used for hashing objects with the SHA256 object format.')
+option('zlib_backend', type: 'combo', choices: ['auto', 'zlib', 'zlib-ng'], value: 'auto',
+  description: 'The backend used for compressing objects and other data.')
 
 # Build tweaks.
 option('breaking_changes', type: 'boolean', value: false,

meson_options.txt

@@ -13,7 +13,6 @@ license that can be found in the LICENSE file or at
 #include "record.h"
 #include "reftable-error.h"
 #include "system.h"
-#include <zlib.h>
 
 int header_size(int version)
 {

reftable/block.c

@@ -14,6 +14,7 @@ license that can be found in the LICENSE file or at
 #define DISABLE_SIGN_COMPARE_WARNINGS
 
 #include "git-compat-util.h"
+#include "compat/zlib-compat.h"
 
 /*
  * An implementation-specific temporary file. By making this specific to the