sha1dc: offer accelerated C and Rust backends

Cargo.toml

@@ -8,3 +8,7 @@ rust-version = "1.49.0"
 crate-type = ["staticlib"]
 
 [dependencies]
+sha1dc = { version = "0.1.5", optional = true }
+
+[features]
+sha1dc-rs = ["sha1dc"]

Documentation/config/core.adoc

@@ -382,6 +382,14 @@ core.repositoryFormatVersion::
 	Internal variable identifying the repository format and layout
 	version. See linkgit:gitrepository-layout[5].
 
+core.sha1dcBackend::
+	Select the collision-detecting SHA-1 implementation: `c` keeps the
+	original C code and is the default, `accel` selects accelerated C,
+	and `rust` selects the Rust implementation. Rust is available only
+	in builds with `DC_SHA1_RS`, and accelerated C can be omitted at build
+	time. Selecting an unavailable implementation is an error.
+	This setting has no effect with other SHA-1 backends.
+
 core.sharedRepository::
 	When 'group' (or 'true'), the repository is made shareable between
 	several users in a group (making sure all the files and objects are

Makefile

@@ -572,6 +572,13 @@ include shared.mak
 # by the git project to migrate to using sha1collisiondetection as a
 # submodule.
 #
+# Define DC_SHA1_RS to make the sha1dc Rust crate available via
+# core.sha1dcBackend=rust. This requires Rust 1.87 or newer.
+#
+# The original C implementation remains the default. Select the faster
+# sha1dc-accel code with core.sha1dcBackend=accel. Define DC_SHA1_NO_ACCEL
+# to omit that implementation.
+#
 # === SHA-256 backend ===
 #
 # ==== Security ====
@@ -1564,6 +1571,7 @@ CLAR_TEST_SUITES += u-reftable-readwrite
 CLAR_TEST_SUITES += u-reftable-stack
 CLAR_TEST_SUITES += u-reftable-table
 CLAR_TEST_SUITES += u-reftable-tree
+CLAR_TEST_SUITES += u-sha1dc
 CLAR_TEST_SUITES += u-strbuf
 CLAR_TEST_SUITES += u-strcmp-offset
 CLAR_TEST_SUITES += u-string-list
@@ -2159,6 +2167,23 @@ ifdef PPC_SHA1
 $(error the PPC_SHA1 flag has been removed along with the PowerPC-specific SHA-1 implementation.)
 endif
 
+ifdef DC_SHA1_RS
+ifdef NO_RUST
+$(error DC_SHA1_RS requires Rust support)
+endif
+ifneq ($(strip $(OPENSSL_SHA1)$(BLK_SHA1)$(APPLE_COMMON_CRYPTO_SHA1)),)
+$(error DC_SHA1_RS cannot be combined with another SHA-1 backend)
+endif
+ifdef DC_SHA1_EXTERNAL
+$(error Only set DC_SHA1_RS or DC_SHA1_EXTERNAL, not both)
+endif
+ifdef DC_SHA1_SUBMODULE
+ifneq ($(DC_SHA1_SUBMODULE),auto)
+$(error Only set DC_SHA1_RS or DC_SHA1_SUBMODULE, not both)
+endif
+endif
+endif
+
 ifdef OPENSSL_SHA1
 	EXTLIBS += $(LIB_4_CRYPTO)
 	BASIC_CFLAGS += -DSHA1_OPENSSL
@@ -2173,6 +2198,14 @@ ifdef APPLE_COMMON_CRYPTO_SHA1
 else
 	BASIC_CFLAGS += -DSHA1_DC
 	LIB_OBJS += sha1dc_git.o
+ifdef DC_SHA1_RS
+	BASIC_CFLAGS += -DDC_SHA1_RS
+	CARGO_ARGS += --features sha1dc-rs
+	RUST_SOURCES += src/sha1dc_rs.rs
+ifeq ($(uname_S),MINGW)
+	EXTLIBS += -luserenv
+endif
+endif
 ifdef DC_SHA1_EXTERNAL
         ifdef DC_SHA1_SUBMODULE
                 ifneq ($(DC_SHA1_SUBMODULE),auto)
@@ -2189,6 +2222,14 @@ ifdef DC_SHA1_SUBMODULE
 else
 	LIB_OBJS += sha1dc/sha1.o
 	LIB_OBJS += sha1dc/ubc_check.o
+endif
+ifdef DC_SHA1_NO_ACCEL
+	BASIC_CFLAGS += -DDC_SHA1_NO_ACCEL
+else
+	LIB_OBJS += sha1dc-accel/arm.o
+	LIB_OBJS += sha1dc-accel/sha1.o
+	LIB_OBJS += sha1dc-accel/ubc_check.o
+	LIB_OBJS += sha1dc-accel/x86.o
 endif
 	BASIC_CFLAGS += \
 		-DSHA1DC_NO_STANDARD_INCLUDES \
@@ -3466,6 +3507,15 @@ check-sha1:: t/helper/test-tool$X
 SP_SRC = $(filter-out $(THIRD_PARTY_SOURCES),$(patsubst %.o,%.c,$(OBJECTS)))
 SP_OBJ = $(patsubst %.c,%.sp,$(SP_SRC))
 
+# Sparse cannot suppress this warning only in the intrinsic headers.
+sha1dc-accel/arm.sp sha1dc-accel/sha1.sp \
+sha1dc-accel/ubc_check.sp sha1dc-accel/x86.sp \
+$(UNIT_TEST_DIR)/u-sha1dc.sp: SP_EXTRA_FLAGS += -Wno-declaration-after-statement
+
+# Sparse 0.6.4 cannot evaluate GCC's SIMD builtins.
+sha1dc-accel/ubc_check.sp sha1dc-accel/x86.sp: \
+	SP_EXTRA_FLAGS += -DSHA1DC_ACCEL_PORTABLE_ONLY
+
 $(SP_OBJ): %.sp: %.c %.o $(GENERATED_H)
 	$(QUIET_SP)cgcc -no-compile $(ALL_CFLAGS) $(EXTRA_CPPFLAGS) \
 		-Wsparse-error \

compat/win32/pthread.c

@@ -60,6 +60,22 @@ pthread_t pthread_self(void)
 	return t;
 }
 
+static BOOL CALLBACK win32_pthread_once(PINIT_ONCE once UNUSED,
+					PVOID parameter,
+					PVOID *context UNUSED)
+{
+	(*(void (**)(void))parameter)();
+	return TRUE;
+}
+
+int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+	if (!InitOnceExecuteOnce(once_control, win32_pthread_once,
+				 &init_routine, NULL))
+		return err_win_to_posix(GetLastError());
+	return 0;
+}
+
 int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 {
 	if (SleepConditionVariableCS(cond, mutex, INFINITE) == 0)

compat/win32/pthread.h

@@ -26,6 +26,11 @@ static inline int return_0(int i UNUSED) {
 #define pthread_mutex_lock EnterCriticalSection
 #define pthread_mutex_unlock LeaveCriticalSection
 
+typedef INIT_ONCE pthread_once_t;
+#define PTHREAD_ONCE_INIT INIT_ONCE_STATIC_INIT
+
+int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));
+
 typedef int pthread_mutexattr_t;
 #define pthread_mutexattr_init(a) (*(a) = 0)
 #define pthread_mutexattr_destroy(a) do {} while (0)

contrib/buildsystems/CMakeLists.txt

@@ -244,7 +244,7 @@ add_compile_definitions(NO_OPENSSL SHA1_DC SHA1DC_NO_STANDARD_INCLUDES
 			SHA1DC_INIT_SAFE_HASH_DEFAULT=0
 			SHA1DC_CUSTOM_INCLUDE_SHA1_C="git-compat-util.h"
 			SHA1DC_CUSTOM_INCLUDE_UBC_CHECK_C="git-compat-util.h" )
-list(APPEND compat_SOURCES sha1dc_git.c sha1dc/sha1.c sha1dc/ubc_check.c block-sha1/sha1.c sha256/block/sha256.c compat/qsort_s.c)
+list(APPEND compat_SOURCES sha1dc_git.c sha1dc/sha1.c sha1dc/ubc_check.c sha1dc-accel/arm.c sha1dc-accel/sha1.c sha1dc-accel/ubc_check.c sha1dc-accel/x86.c block-sha1/sha1.c sha256/block/sha256.c compat/qsort_s.c)
 
 
 add_compile_definitions(PAGER_ENV="LESS=FRX LV=-c"

hash.h

@@ -12,8 +12,13 @@
 #    include "sha1/openssl.h"
 #  endif
 #elif defined(SHA1_DC)
+#ifdef DC_SHA1_RS
+#define SHA1_BACKEND "SHA1_DC-rs"
+#include "sha1dc_rs.h"
+#else
 #define SHA1_BACKEND "SHA1_DC"
 #include "sha1dc_git.h"
+#endif
 #else /* SHA1_BLK */
 #define SHA1_BACKEND "SHA1_BLK (No collision detection)"
 #include "block-sha1/sha1.h"

meson.build

@@ -1634,6 +1634,10 @@ if sha1_backend == 'sha1dc'
     'sha1dc_git.c',
     'sha1dc/sha1.c',
     'sha1dc/ubc_check.c',
+    'sha1dc-accel/arm.c',
+    'sha1dc-accel/sha1.c',
+    'sha1dc-accel/ubc_check.c',
+    'sha1dc-accel/x86.c',
   ]
 endif
 if sha1_backend == 'CommonCrypto' or sha1_unsafe_backend == 'CommonCrypto'