1 /* 2 * Copyright 2012 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #include "SkChecksum.h" 9 #include "SkOpts.h" 10 #include "SkRandom.h" 11 #include "SkTypes.h" 12 #include "Test.h" 13 DEF_TEST(Checksum,r)14 DEF_TEST(Checksum, r) { 15 // Put 128 random bytes into two identical buffers. Any multiple of 4 will do. 16 const size_t kBytes = SkAlign4(128); 17 SkRandom rand; 18 uint32_t data[kBytes/4], tweaked[kBytes/4]; 19 for (size_t i = 0; i < SK_ARRAY_COUNT(tweaked); ++i) { 20 data[i] = tweaked[i] = rand.nextU(); 21 } 22 23 // Hash of nullptr is always 0. 24 REPORTER_ASSERT(r, SkOpts::hash(nullptr, 0) == 0); 25 26 const uint32_t hash = SkOpts::hash(data, kBytes); 27 // Should be deterministic. 28 REPORTER_ASSERT(r, hash == SkOpts::hash(data, kBytes)); 29 30 // Changing any single element should change the hash. 31 for (size_t j = 0; j < SK_ARRAY_COUNT(tweaked); ++j) { 32 const uint32_t saved = tweaked[j]; 33 tweaked[j] = rand.nextU(); 34 const uint32_t tweakedHash = SkOpts::hash(tweaked, kBytes); 35 REPORTER_ASSERT(r, tweakedHash != hash); 36 REPORTER_ASSERT(r, tweakedHash == SkOpts::hash(tweaked, kBytes)); 37 tweaked[j] = saved; 38 } 39 } 40 DEF_TEST(GoodHash,r)41 DEF_TEST(GoodHash, r) { 42 // 4 bytes --> hits SkChecksum::Mix fast path. 43 REPORTER_ASSERT(r, SkGoodHash()(( int32_t)4) == 614249093); 44 REPORTER_ASSERT(r, SkGoodHash()((uint32_t)4) == 614249093); 45 } 46 DEF_TEST(ChecksumCollisions,r)47 DEF_TEST(ChecksumCollisions, r) { 48 // We noticed a few workloads that would cause hash collisions due to the way 49 // our optimized hashes split into three concurrent hashes and merge those hashes together. 50 // 51 // One of these two workloads ought to cause an unintentional hash collision on very similar 52 // data in those old algorithms, the float version on 32-bit x86 and double elsewhere. 53 { 54 float a[9] = { 0, 1, 2, 55 3, 4, 5, 56 6, 7, 8, }; 57 float b[9] = { 1, 2, 0, 58 4, 5, 3, 59 7, 8, 6, }; 60 61 REPORTER_ASSERT(r, SkOpts::hash(a, sizeof(a)) != SkOpts::hash(b, sizeof(b))); 62 } 63 { 64 double a[9] = { 0, 1, 2, 65 3, 4, 5, 66 6, 7, 8, }; 67 double b[9] = { 1, 2, 0, 68 4, 5, 3, 69 7, 8, 6, }; 70 71 REPORTER_ASSERT(r, SkOpts::hash(a, sizeof(a)) != SkOpts::hash(b, sizeof(b))); 72 } 73 } 74