block-sha1: get rid of redundant 'lenW' context

.. and simplify the ctx->size logic.

We now count the size in bytes, which means that 'lenW' was always just
the low 6 bits of the total size, so we don't carry it around separately
any more.  And we do the 'size in bits' shift at the end.

Suggested by Nicolas Pitre and linux@horizon.com.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

block-sha1/sha1.c

@@ -14,7 +14,6 @@ static void blk_SHA1Block(blk_SHA_CTX *ctx, const unsigned int *data);
 
 void blk_SHA1_Init(blk_SHA_CTX *ctx)
 {
-	ctx->lenW = 0;
 	ctx->size = 0;
 
 	/* Initialize H with the magic constants (see FIPS180 for constants)
@@ -29,9 +28,9 @@ void blk_SHA1_Init(blk_SHA_CTX *ctx)
 
 void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
 {
-	int lenW = ctx->lenW;
+	int lenW = ctx->size & 63;
 
-	ctx->size += (unsigned long long) len << 3;
+	ctx->size += len;
 
 	/* Read the data into W and process blocks as they get full
 	 */
@@ -43,7 +42,6 @@ void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
 		lenW = (lenW + left) & 63;
 		len -= left;
 		data += left;
-		ctx->lenW = lenW;
 		if (lenW)
 			return;
 		blk_SHA1Block(ctx, ctx->W);
@@ -53,10 +51,8 @@ void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
 		data += 64;
 		len -= 64;
 	}
-	if (len) {
+	if (len)
 		memcpy(ctx->W, data, len);
-		ctx->lenW = len;
-	}
 }
 
 
@@ -68,10 +64,11 @@ void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
 
 	/* Pad with a binary 1 (ie 0x80), then zeroes, then length
 	 */
-	padlen[0] = htonl(ctx->size >> 32);
-	padlen[1] = htonl(ctx->size);
+	padlen[0] = htonl(ctx->size >> 29);
+	padlen[1] = htonl(ctx->size << 3);
 
-	blk_SHA1_Update(ctx, pad, 1+ (63 & (55 - ctx->lenW)));
+	i = ctx->size & 63;
+	blk_SHA1_Update(ctx, pad, 1+ (63 & (55 - i)));
 	blk_SHA1_Update(ctx, padlen, 8);
 
 	/* Output hash

block-sha1/sha1.h

@@ -7,7 +7,6 @@
 typedef struct {
 	unsigned int H[5];
 	unsigned int W[16];
-	int lenW;
 	unsigned long long size;
 } blk_SHA_CTX;