Use libcrypto's SHA-1 implementation when linking to it

libcryto's SHA-1 implementation is measurably better than the one that
ships with the library. If we link to it for HTTPS support already,
use that implementation instead.

Testing on a ~600MB of the linux repository, this reduces indexing
time by 40% and removes the hashing from the top spot in the perf
output.

CMakeLists.txt

@@ -40,8 +40,10 @@ ENDIF()
 IF (SHA1_TYPE STREQUAL "ppc")
 	ADD_DEFINITIONS(-DPPC_SHA1)
 	FILE(GLOB SRC_SHA1 src/ppc/*.c src/ppc/*.S)
+ELSEIF (OPENSSL_FOUND) # libcrypto's implementation is faster than ours
+	ADD_DEFINITIONS(-DOPENSSL_SHA)
 ELSE ()
-	SET (SRC_SHA1)
+	FILE(GLOB SRC_SHA1 src/sha1/*.c)
 ENDIF()
 
 IF (NOT WIN32)
@@ -198,7 +200,7 @@ IF (BUILD_CLAR)
 		DEPENDS ${CLAR_PATH}/clar ${SRC_TEST}
 		WORKING_DIRECTORY ${CLAR_PATH}
 	)
-	ADD_EXECUTABLE(libgit2_clar ${SRC} ${CLAR_PATH}/clar_main.c ${SRC_TEST} ${SRC_ZLIB} ${SRC_HTTP} ${SRC_REGEX})
+	ADD_EXECUTABLE(libgit2_clar ${SRC} ${CLAR_PATH}/clar_main.c ${SRC_TEST} ${SRC_ZLIB} ${SRC_HTTP} ${SRC_REGEX} ${SRC_SHA1})
 	TARGET_LINK_LIBRARIES(libgit2_clar ${CMAKE_THREAD_LIBS_INIT} ${SSL_LIBRARIES})
 
         IF (MSVC)

src/sha1.h

@@ -8,12 +8,17 @@
 #ifndef INCLUDE_sha1_h__
 #define INCLUDE_sha1_h__
 
+#ifdef OPENSSL_SHA
+# include <openssl/sha.h>
+
+#else
 typedef struct {
 	unsigned long long size;
 	unsigned int H[5];
 	unsigned int W[16];
 } blk_SHA_CTX;
 
+
 void git__blk_SHA1_Init(blk_SHA_CTX *ctx);
 void git__blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, size_t len);
 void git__blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
@@ -23,4 +28,6 @@ void git__blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
 #define SHA1_Update	git__blk_SHA1_Update
 #define SHA1_Final	git__blk_SHA1_Final
 
+#endif // OPENSSL_SHA
+
 #endif