Replace SkConsistentChecksum with SkCityHash (now including CityHash via DEPS)

Alternative to https://codereview.appspot.com/6847087/ ('Change SkConsistentChecksum to use SuperFastHash')
Review URL: https://codereview.appspot.com/6867060

git-svn-id: http://skia.googlecode.com/svn/trunk@6701 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 53 insertions, 49 deletions

diff --git a/tests/ChecksumTest.cpp b/tests/ChecksumTest.cpp
index 5d5d83bc93..dea0eef856 100644
--- a/tests/ChecksumTest.cpp
+++ b/tests/ChecksumTest.cpp
@@ -7,7 +7,10 @@
  */
 #include "Test.h"
 #include "SkChecksum.h"
-#include "SkConsistentChecksum.h"
+#include "SkCityHash.h"
+
+// Word size that is large enough to hold results of any checksum type.
+typedef uint64_t checksum_result;
 
 namespace skiatest {
     class ChecksumTestClass : public Test {
@@ -22,26 +25,25 @@ namespace skiatest {
     private:
         enum Algorithm {
             kSkChecksum,
-            kSkConsistentChecksum
+            kSkCityHash32,
+            kSkCityHash64
         };
 
         // Call Compute(data, size) on the appropriate checksum algorithm,
         // depending on this->fWhichAlgorithm.
-        uint32_t ComputeChecksum(uint32_t* data, size_t size) {
-            // Our checksum algorithms require 32-bit aligned data.
-            // If either of these tests fail, then the algorithm
-            // doesn't have a chance.
-            REPORTER_ASSERT_MESSAGE(fReporter,
-                                    reinterpret_cast<uintptr_t>(data) % 4 == 0,
-                                    "test data pointer is not 32-bit aligned");
-            REPORTER_ASSERT_MESSAGE(fReporter, SkIsAlign4(size),
-                                    "test data size is not 32-bit aligned");
-
+        checksum_result ComputeChecksum(const char *data, size_t size) {
             switch(fWhichAlgorithm) {
             case kSkChecksum:
-                return SkChecksum::Compute(data, size);
-            case kSkConsistentChecksum:
-                return SkConsistentChecksum::Compute(data, size);
+                REPORTER_ASSERT_MESSAGE(fReporter,
+                                        reinterpret_cast<uintptr_t>(data) % 4 == 0,
+                                        "test data pointer is not 32-bit aligned");
+                REPORTER_ASSERT_MESSAGE(fReporter, SkIsAlign4(size),
+                                        "test data size is not 32-bit aligned");
+                return SkChecksum::Compute(reinterpret_cast<const uint32_t *>(data), size);
+            case kSkCityHash32:
+                return SkCityHash::Compute32(data, size);
+            case kSkCityHash64:
+                return SkCityHash::Compute64(data, size);
             default:
                 SkString message("fWhichAlgorithm has unknown value ");
                 message.appendf("%d", fWhichAlgorithm);
@@ -55,16 +57,22 @@ namespace skiatest {
         // generates the same results if called twice over the same data.
         void TestChecksumSelfConsistency(size_t buf_size) {
             SkAutoMalloc storage(buf_size);
-            uint32_t*    ptr = (uint32_t*)storage.get();
-            char*        cptr = (char*)ptr;
+            char* ptr = reinterpret_cast<char *>(storage.get());
+
+            REPORTER_ASSERT(fReporter,
+                            GetTestDataChecksum(8, 0) ==
+                            GetTestDataChecksum(8, 0));
+            REPORTER_ASSERT(fReporter,
+                            GetTestDataChecksum(8, 0) !=
+                            GetTestDataChecksum(8, 1));
 
             sk_bzero(ptr, buf_size);
-            uint32_t prev = 0;
+            checksum_result prev = 0;
 
             // assert that as we change values (from 0 to non-zero) in
             // our buffer, we get a different value
             for (size_t i = 0; i < buf_size; ++i) {
-                cptr[i] = (i & 0x7f) + 1; // need some non-zero value here
+                ptr[i] = (i & 0x7f) + 1; // need some non-zero value here
 
                 // Try checksums of different-sized chunks, but always
                 // 32-bit aligned and big enough to contain all the
@@ -73,9 +81,9 @@ namespace skiatest {
                 size_t checksum_size = (((i/4)+1)*4);
                 REPORTER_ASSERT(fReporter, checksum_size <= buf_size);
 
-                uint32_t curr = ComputeChecksum(ptr, checksum_size);
+                checksum_result curr = ComputeChecksum(ptr, checksum_size);
                 REPORTER_ASSERT(fReporter, prev != curr);
-                uint32_t again = ComputeChecksum(ptr, checksum_size);
+                checksum_result again = ComputeChecksum(ptr, checksum_size);
                 REPORTER_ASSERT(fReporter, again == curr);
                 prev = curr;
             }
@@ -84,48 +92,49 @@ namespace skiatest {
         // Return the checksum of a buffer of bytes 'len' long.
         // The pattern of values within the buffer will be consistent
         // for every call, based on 'seed'.
-        uint32_t GetTestDataChecksum(size_t len, char seed=0) {
+        checksum_result GetTestDataChecksum(size_t len, char seed=0) {
             SkAutoMalloc storage(len);
-            uint32_t* start = (uint32_t *)storage.get();
-            char* ptr = (char *)start;
+            char* start = reinterpret_cast<char *>(storage.get());
+            char* ptr = start;
             for (size_t i = 0; i < len; ++i) {
                 *ptr++ = ((seed+i) & 0x7f);
             }
-            uint32_t result = ComputeChecksum(start, len);
+            checksum_result result = ComputeChecksum(start, len);
             return result;
         }
 
         void RunTest() {
             // Test self-consistency of checksum algorithms.
             fWhichAlgorithm = kSkChecksum;
-            REPORTER_ASSERT(fReporter,
-                            GetTestDataChecksum(8, 0) ==
-                            GetTestDataChecksum(8, 0));
-            REPORTER_ASSERT(fReporter,
-                            GetTestDataChecksum(8, 0) !=
-                            GetTestDataChecksum(8, 1));
             TestChecksumSelfConsistency(128);
-            fWhichAlgorithm = kSkConsistentChecksum;
-            REPORTER_ASSERT(fReporter,
-                            GetTestDataChecksum(8, 0) ==
-                            GetTestDataChecksum(8, 0));
-            REPORTER_ASSERT(fReporter,
-                            GetTestDataChecksum(8, 0) !=
-                            GetTestDataChecksum(8, 1));
+            fWhichAlgorithm = kSkCityHash32;
+            TestChecksumSelfConsistency(128);
+            fWhichAlgorithm = kSkCityHash64;
             TestChecksumSelfConsistency(128);
 
             // Test checksum results that should be consistent across
             // versions and platforms.
             fWhichAlgorithm = kSkChecksum;
             REPORTER_ASSERT(fReporter, ComputeChecksum(NULL, 0) == 0);
-            fWhichAlgorithm = kSkConsistentChecksum;
-            REPORTER_ASSERT(fReporter, ComputeChecksum(NULL, 0) == 0);
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(4)  == 0x03020100);
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(8)  == 0x07860485);
+            fWhichAlgorithm = kSkCityHash32;
+            REPORTER_ASSERT(fReporter, ComputeChecksum(NULL, 0) == 0xdc56d17a);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(4)   == 0x616e1132);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(8)   == 0xeb0fd2d6);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(128) == 0x5321e430);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(132) == 0x924a10e4);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(256) == 0xd4de9dc9);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(260) == 0xecf0325d);
+            fWhichAlgorithm = kSkCityHash64;
+            REPORTER_ASSERT(fReporter, ComputeChecksum(NULL, 0) == 0x9ae16a3b2f90404f);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(4)   == 0x82bffd898958e540);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(8)   == 0xad5a13e1e8e93b98);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(128) == 0x10b153630af1f395);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(132) == 0x7db71dc4adcc6647);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(256) == 0xeee763519b91b010);
+            REPORTER_ASSERT(fReporter, GetTestDataChecksum(260) == 0x2fe19e0b2239bc23);
 
             // TODO: note the weakness exposed by these collisions...
-            // We need to improve the SkConsistentChecksum algorithm
-            // (and maybe SkChecksum too?)
+            // We need to improve the SkChecksum algorithm.
             // We would prefer that these asserts FAIL!
             // Filed as https://code.google.com/p/skia/issues/detail?id=981
             // ('SkChecksum algorithm allows for way too many collisions')
@@ -134,11 +143,6 @@ namespace skiatest {
                 GetTestDataChecksum(128) == GetTestDataChecksum(256));
             REPORTER_ASSERT(fReporter,
                 GetTestDataChecksum(132) == GetTestDataChecksum(260));
-            fWhichAlgorithm = kSkConsistentChecksum;
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(128) == 0);
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(132) == 0x03020100);
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(256) == 0);
-            REPORTER_ASSERT(fReporter, GetTestDataChecksum(260) == 0x03020100);
         }
 
         Reporter* fReporter;