From 4b7c09e0379485bcaaa6070c8d58274048881588 Mon Sep 17 00:00:00 2001
From: sebpop <sebpop@gmail.com>
Date: Wed, 14 Nov 2018 16:00:16 -0600
Subject: [PATCH] [zlib] add test for fast crc32 (#1954)

Add a check for the recently added routines to combine crc32 checksums.  This
change adds more code coverage, however the checksum_fuzzer still does not pass
the complexity check: (the threshold is at 100)

oss-fuzz$ build/out/zlib/checksum_fuzzer -runs=10 2>&1 | grep -Po "INFO: Loaded [[:digit:]]+ module.*\(.*(counters|guards)\):[[:space:]]+\K[[:digit:]]+"
92
---
 projects/zlib/checksum_fuzzer.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/projects/zlib/checksum_fuzzer.c b/projects/zlib/checksum_fuzzer.c
index 4664e05e7..b14ba6fc3 100644
--- a/projects/zlib/checksum_fuzzer.c
+++ b/projects/zlib/checksum_fuzzer.c
@@ -8,13 +8,16 @@
 #include "zlib.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t dataLen) {
-  uint32_t crc1 = crc32(0L, NULL, 0);
-  uint32_t crc2 = crc32(0L, NULL, 0);
-  uint32_t adler1 = adler32(0L, NULL, 0);
-  uint32_t adler2 = adler32(0L, NULL, 0);;
+  uint32_t crc0 = crc32(0L, NULL, 0);
+  uint32_t crc1 = crc0;
+  uint32_t crc2 = crc0;
+  uint32_t adler0 = adler32(0L, NULL, 0);
+  uint32_t adler1 = adler0;
+  uint32_t adler2 = adler0;
   /* Checksum with a buffer of size equal to the first byte in the input. */
   uint32_t buffSize = data[0];
   uint32_t offset = 0;
+  z_crc_t op[32];
 
   /* Discard inputs larger than 1Mb. */
   static size_t kMaxSize = 1024 * 1024;
@@ -26,22 +29,34 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t dataLen) {
     ++buffSize;
 
   /* CRC32 */
-  for (offset = 0; offset + buffSize <= dataLen; offset += buffSize)
+  crc32_combine_gen(op, buffSize);
+  for (offset = 0; offset + buffSize <= dataLen; offset += buffSize) {
+    uint32_t crc3 = crc32_z(crc0, data + offset, buffSize);
+    uint32_t crc4 = crc32_combine_op(crc1, crc3, op);
     crc1 = crc32_z(crc1, data + offset, buffSize);
+    assert(crc1 == crc4);
+  }
   crc1 = crc32_z(crc1, data + offset, dataLen % buffSize);
 
-  crc2 = crc32_z(crc2, data, dataLen);
+  crc2 = crc32(crc2, data, (uint32_t) dataLen);
 
   assert(crc1 == crc2);
   assert(crc32_combine(crc1, crc2, dataLen) ==
          crc32_combine(crc1, crc1, dataLen));
 
+  /* Fast CRC32 combine. */
+  crc32_combine_gen(op, dataLen);
+  assert(crc32_combine_op(crc1, crc2, op) ==
+         crc32_combine_op(crc2, crc1, op));
+  assert(crc32_combine(crc1, crc2, dataLen) ==
+         crc32_combine_op(crc2, crc1, op));
+
   /* Adler32 */
   for (offset = 0; offset + buffSize <= dataLen; offset += buffSize)
     adler1 = adler32_z(adler1, data + offset, buffSize);
   adler1 = adler32_z(adler1, data + offset, dataLen % buffSize);
 
-  adler2 = adler32_z(adler2, data, dataLen);
+  adler2 = adler32(adler2, data, (uint32_t) dataLen);
 
   assert(adler1 == adler2);
   assert(adler32_combine(adler1, adler2, dataLen) ==