From 9d00435b42ef7173099397f7a4bd1f4ded1a96e1 Mon Sep 17 00:00:00 2001
From: Andrea Mazzoleni <amadvance@gmail.com>
Date: Mon, 19 Aug 2013 12:45:12 +0200
Subject: [PATCH] Uses the CRC_IV directly in the crc32c() function.

---
 selftest.c |  2 +-
 state.c    |  2 +-
 util.c     | 24 +++++++++++++++++++-----
 util.h     |  6 ------
 4 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/selftest.c b/selftest.c
index 61552686..a5a01c4e 100644
--- a/selftest.c
+++ b/selftest.c
@@ -262,7 +262,7 @@ static void crc32ctest(void)
 
 	for(i=0;TEST_CRC32C[i].data;++i) {
 		uint32_t digest;
-		digest = CRC_IV ^ crc32c(CRC_IV, (const unsigned char*)TEST_CRC32C[i].data, TEST_CRC32C[i].len);
+		digest = crc32c(0, (const unsigned char*)TEST_CRC32C[i].data, TEST_CRC32C[i].len);
 		if (digest != TEST_CRC32C[i].digest) {
 			fprintf(stderr, "Failed CRC32C test vector %u\n", i);
 			exit(EXIT_FAILURE);
diff --git a/state.c b/state.c
index 3ad30ebc..afec0cd1 100644
--- a/state.c
+++ b/state.c
@@ -2103,7 +2103,7 @@ static void decoding_error(const char* path, STREAM* f)
 	crc_computed = scrc(f);
 
 	/* adjust the stored crc to include itself */
-	crc_stored = crc32c(crc_stored ^ CRC_IV, buf, 4) ^ CRC_IV;
+	crc_stored = crc32c(crc_stored, buf, 4);
 
 	if (crc_computed != crc_stored) {
 		fprintf(stderr, "Mismatching CRC in '%s'\n", path);
diff --git a/util.c b/util.c
index 4d343c9c..3523004c 100644
--- a/util.c
+++ b/util.c
@@ -84,8 +84,8 @@ STREAM* sopen_read(const char* file)
 	s->state_index = 0;
 	s->offset = 0;
 	s->offset_uncached = 0;
-	s->crc = CRC_IV;
-	s->crc_uncached = CRC_IV;
+	s->crc = 0;
+	s->crc_uncached = 0;
 
 	return s;
 }
@@ -109,8 +109,8 @@ STREAM* sopen_multi_write(unsigned count)
 	s->state_index = 0;
 	s->offset = 0;
 	s->offset_uncached = 0;
-	s->crc = CRC_IV;
-	s->crc_uncached = CRC_IV;
+	s->crc = 0;
+	s->crc_uncached = 0;
 
 	return s;
 }
@@ -251,7 +251,7 @@ int64_t stell(STREAM* s)
 
 uint32_t scrc(STREAM*s)
 {
-	return crc32c(s->crc_uncached, s->buffer, s->pos - s->buffer) ^ CRC_IV;
+	return crc32c(s->crc_uncached, s->buffer, s->pos - s->buffer);
 }
 
 int sgettok(STREAM* f, char* str, int size)
@@ -1061,8 +1061,16 @@ static uint32_t CRC32C_3[256] = {
 	0x4a21617b, 0x9764cbc3, 0xf54642fa, 0x2803e842
 };
 
+/**
+ * CRC initial value.
+ * Using a not zero value allows to detect a leading run of zeros.
+ */
+#define CRC_IV 0xffffffffU
+
 static uint32_t crc32c_gen(uint32_t crc, const unsigned char* ptr, unsigned size)
 {
+	crc ^= CRC_IV;
+
 	while (size >= 4) {
 		crc ^= ptr[0] | (uint32_t)ptr[1] << 8 | (uint32_t)ptr[2] << 16 | (uint32_t)ptr[3] << 24;
 		crc = CRC32C_3[crc & 0xff] ^ CRC32C_2[(crc >> 8) & 0xff] ^ CRC32C_1[(crc >> 16) & 0xff] ^ CRC32C_0[crc >> 24];
@@ -1076,6 +1084,8 @@ static uint32_t crc32c_gen(uint32_t crc, const unsigned char* ptr, unsigned size
 		--size;
 	}
 
+	crc ^= CRC_IV;
+
 	return crc;
 }
 
@@ -1083,6 +1093,8 @@ static uint32_t crc32c_gen(uint32_t crc, const unsigned char* ptr, unsigned size
 
 static uint32_t crc32c_x86(uint32_t crc, const unsigned char* ptr, unsigned size)
 {
+	crc ^= CRC_IV;
+
 	while (size >= 4) {
 		asm volatile ("crc32l %1, %0\n" : "+r" (crc) : "rm" (*(uint32_t*)ptr));
 		ptr += 4;
@@ -1095,6 +1107,8 @@ static uint32_t crc32c_x86(uint32_t crc, const unsigned char* ptr, unsigned size
 		--size;
 	}
 
+	crc ^= CRC_IV;
+
 	return crc;
 }
 
diff --git a/util.h b/util.h
index 7938e653..9821a793 100644
--- a/util.h
+++ b/util.h
@@ -496,12 +496,6 @@ void randomize(void* ptr, unsigned size);
 /****************************************************************************/
 /* crc */
 
-/**
- * CRC initial value.
- * Using a not zero value allows to detect trailing zeros at the end.
- */
-#define CRC_IV 0xffffffffU
-
 /**
  * Computes the CRC-32 (Castagnoli)
  */