From b7bf7afc7c0ce730a430ef6e47ca359c97fef2ff Mon Sep 17 00:00:00 2001
From: Stefan Sperling <stsp@stsp.name>
Date: Fri, 11 Feb 2022 22:45:00 +0000
Subject: [PATCH] use murmurhash instead of sha1 for deltification blocks;
 suggested by ori

---
 lib/deltify.c            | 18 ++++++------------
 regress/deltify/Makefile |  2 +-
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/lib/deltify.c b/lib/deltify.c
index a2405479..f12135df 100644
--- a/lib/deltify.c
+++ b/lib/deltify.c
@@ -28,6 +28,7 @@
 #include "got_error.h"
 
 #include "got_lib_deltify.h"
+#include "murmurhash2.h"
 
 #ifndef MIN
 #define	MIN(_a,_b) ((_a) < (_b) ? (_a) : (_b))
@@ -84,17 +85,10 @@ static uint32_t geartab[256] = {
     0xf1f6e72c, 0x5551128a, 0x83af87e2, 0x6f0342ba,
 };
 
-static uint64_t
+static uint32_t
 hashblk(const unsigned char *p, off_t n)
 {
-	unsigned char buf[SHA1_DIGEST_LENGTH];
-	uint64_t h;
-	SHA1_CTX ctx;
-	SHA1Init(&ctx);
-	SHA1Update(&ctx, p, n);
-	SHA1Final(buf, &ctx);
-	memcpy(&h, buf, sizeof(h));
-	return be64toh(h);
+	return murmurhash2(p, n, 0x1d7c5ac3);
 }
 
 static const struct got_error *
@@ -244,7 +238,7 @@ lookupblk(struct got_delta_block **block, struct got_delta_table *dt,
     unsigned char *p, off_t len, FILE *basefile, off_t basefile_offset0)
 {
 	int i;
-	uint64_t h;
+	uint32_t h;
 	uint8_t buf[GOT_DELTIFY_MAXCHUNK];
 	size_t r;
 
@@ -275,7 +269,7 @@ lookupblk_mem(struct got_delta_block **block, struct got_delta_table *dt,
     unsigned char *p, off_t len, uint8_t *basedata, off_t basefile_offset0)
 {
 	int i;
-	uint64_t h;
+	uint32_t h;
 	uint8_t *b;
 
 	*block = NULL;
@@ -357,7 +351,7 @@ got_deltify_init(struct got_delta_table **dt, FILE *f, off_t fileoffset,
     off_t filesize)
 {
 	const struct got_error *err = NULL;
-	uint64_t h;
+	uint32_t h;
 	const off_t offset0 = fileoffset;
 
 	*dt = calloc(1, sizeof(**dt));
diff --git a/regress/deltify/Makefile b/regress/deltify/Makefile
index b903bbec..3685d581 100644
--- a/regress/deltify/Makefile
+++ b/regress/deltify/Makefile
@@ -1,7 +1,7 @@
 .PATH:${.CURDIR}/../../lib
 
 PROG = deltify_test
-SRCS = deltify.c error.c opentemp.c sha1.c deltify_test.c
+SRCS = deltify.c error.c opentemp.c sha1.c deltify_test.c murmurhash2.c
 
 CPPFLAGS = -I${.CURDIR}/../../include -I${.CURDIR}/../../lib
 LDADD = -lz
-- 
2.11.4.GIT