reset: disallow using --keep when there are unmerged entries

[git.git] / block-sha1 / sha1.c

diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index c3f1ae59b9252e499fc8d79dfd0f8fac49bacf2e..d8934757a5e5e259f26c4a09f7ea5d10615df0c1 100644 (file)
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -1,20 +1,28 @@
 /*
- * Based on the Mozilla SHA1 (see mozilla-sha1/sha1.c),
- * optimized to do word accesses rather than byte accesses,
+ * SHA1 routine optimized to do word accesses rather than byte accesses,
  * and to avoid unnecessary copies into the context array.
+ *
+ * This was initially based on the Mozilla SHA1 implementation, although
+ * none of the original Mozilla code remains.
  */
 
-#include <string.h>
-#include <arpa/inet.h>
+/* this is only to get definitions for memcpy(), ntohl() and htonl() */
+#include "../git-compat-util.h"
 
 #include "sha1.h"
 
-#if defined(__i386__) || defined(__x86_64__)
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
+
+/*
+ * Force usage of rol or ror by selecting the one with the smaller constant.
+ * It _can_ generate slightly smaller code (a constant of 1 is special), but
+ * perhaps more importantly it's possibly faster on any uarch that does a
+ * rotate with a loop.
+ */
 
 #define SHA_ASM(op, x, n) ({ unsigned int __res; __asm__(op " %1,%0":"=r" (__res):"i" (n), "0" (x)); __res; })
 #define SHA_ROL(x,n)   SHA_ASM("rol", x, n)
 #define SHA_ROR(x,n)   SHA_ASM("ror", x, n)
-#define SMALL_REGISTER_SET
 
 #else
 
@@ -24,9 +32,6 @@
 
 #endif
 
-/* This "rolls" over the 512-bit array */
-#define W(x) (array[(x)&15])
-
 /*
  * If you have 32 registers or more, the compiler can (and should)
  * try to change the array[] accesses into registers. However, on
@@ -43,18 +48,59 @@
  * Ben Herrenschmidt reports that on PPC, the C version comes close
  * to the optimized asm with this (ie on PPC you don't want that
  * 'volatile', since there are lots of registers).
+ *
+ * On ARM we get the best code generation by forcing a full memory barrier
+ * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
+ * the stack frame size simply explode and performance goes down the drain.
  */
-#ifdef SMALL_REGISTER_SET
+
+#if defined(__i386__) || defined(__x86_64__)
   #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))
+#elif defined(__GNUC__) && defined(__arm__)
+  #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
 #else
   #define setW(x, val) (W(x) = (val))
 #endif
 
+/*
+ * Performance might be improved if the CPU architecture is OK with
+ * unaligned 32-bit loads and a fast ntohl() is available.
+ * Otherwise fall back to byte loads and shifts which is portable,
+ * and is faster on architectures with memory alignment issues.
+ */
+
+#if defined(__i386__) || defined(__x86_64__) || \
+    defined(__ppc__) || defined(__ppc64__) || \
+    defined(__powerpc__) || defined(__powerpc64__) || \
+    defined(__s390__) || defined(__s390x__)
+
+#define get_be32(p)    ntohl(*(unsigned int *)(p))
+#define put_be32(p, v) do { *(unsigned int *)(p) = htonl(v); } while (0)
+
+#else
+
+#define get_be32(p)    ( \
+       (*((unsigned char *)(p) + 0) << 24) | \
+       (*((unsigned char *)(p) + 1) << 16) | \
+       (*((unsigned char *)(p) + 2) <<  8) | \
+       (*((unsigned char *)(p) + 3) <<  0) )
+#define put_be32(p, v) do { \
+       unsigned int __v = (v); \
+       *((unsigned char *)(p) + 0) = __v >> 24; \
+       *((unsigned char *)(p) + 1) = __v >> 16; \
+       *((unsigned char *)(p) + 2) = __v >>  8; \
+       *((unsigned char *)(p) + 3) = __v >>  0; } while (0)
+
+#endif
+
+/* This "rolls" over the 512-bit array */
+#define W(x) (array[(x)&15])
+
 /*
  * Where do we get the source from? The first 16 iterations get it from
  * the input data, the next mix it from the 512-bit array.
  */
-#define SHA_SRC(t) htonl(data[t])
+#define SHA_SRC(t) get_be32(data + t)
 #define SHA_MIX(t) SHA_ROL(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)
 
 #define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \
@@ -202,14 +248,14 @@ void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
                memcpy(lenW + (char *)ctx->W, data, left);
                lenW = (lenW + left) & 63;
                len -= left;
-               data += left;
+               data = ((const char *)data + left);
                if (lenW)
                        return;
                blk_SHA1_Block(ctx, ctx->W);
        }
        while (len >= 64) {
                blk_SHA1_Block(ctx, data);
-               data += 64;
+               data = ((const char *)data + 64);
                len -= 64;
        }
        if (len)
@@ -232,5 +278,5 @@ void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
 
        /* Output hash */
        for (i = 0; i < 5; i++)
-               ((unsigned int *)hashout)[i] = htonl(ctx->H[i]);
+               put_be32(hashout + i*4, ctx->H[i]);
 }