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Subject[PATCH 1/5] crypto/sha1.c: avoid useless memcpy()

The current code unconditionally copy the first block for every call to
sha1_update(). This can be avoided if there is no pending partial block.
This is always the case on the first call to sha1_update() (if the length
is >= 64 of course0.

In the case where sha1_update() is called successively with len=64,
a 8.5% performance increase can be observed on i386, and 8.2% on ARm.

Signed-off-by: Nicolas Pitre <nico@cam.org>

Index: linux-2.6/crypto/sha1.c
===================================================================
--- linux-2.6.orig/crypto/sha1.c
+++ linux-2.6/crypto/sha1.c
@@ -48,23 +48,26 @@
static void sha1_update(void *ctx, const u8 *data, unsigned int len)
{
struct sha1_ctx *sctx = ctx;
- unsigned int i, j;
+ unsigned int partial, done;
u32 temp[SHA_WORKSPACE_WORDS];

- j = (sctx->count >> 3) & 0x3f;
+ partial = (sctx->count >> 3) & 0x3f;
sctx->count += len << 3;
+ done = 0;

- if ((j + len) > 63) {
- memcpy(&sctx->buffer[j], data, (i = 64-j));
- sha_transform(sctx->state, sctx->buffer, temp);
- for ( ; i + 63 < len; i += 64) {
- sha_transform(sctx->state, &data[i], temp);
+ if ((partial + len) > 63) {
+ if (partial) {
+ done = 64 - partial;
+ memcpy(sctx->buffer + partial, data, done);
+ sha_transform(sctx->state, sctx->buffer, temp);
+ partial = 0;
}
- j = 0;
+ for ( ; done + 63 < len; done += 64)
+ sha_transform(sctx->state, data + done, temp);
}
- else i = 0;
+ if (len - done)
+ memcpy(sctx->buffer + partial, data + done, len - done);
memset(temp, 0, sizeof(temp));
- memcpy(&sctx->buffer[j], &data[i], len - i);
}


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