/* * Copyright 2012 Google Inc. * * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ #include "include/core/SkTypes.h" #include "include/private/SkChecksum.h" #include "include/utils/SkRandom.h" #include "src/core/SkOpts.h" #include "tests/Test.h" DEF_TEST(Checksum, r) { // Put 128 random bytes into two identical buffers. Any multiple of 4 will do. const size_t kBytes = SkAlign4(128); SkRandom rand; uint32_t data[kBytes/4], tweaked[kBytes/4]; for (size_t i = 0; i < SK_ARRAY_COUNT(tweaked); ++i) { data[i] = tweaked[i] = rand.nextU(); } // Hash of nullptr is always 0. REPORTER_ASSERT(r, SkOpts::hash(nullptr, 0) == 0); const uint32_t hash = SkOpts::hash(data, kBytes); // Should be deterministic. REPORTER_ASSERT(r, hash == SkOpts::hash(data, kBytes)); // Changing any single element should change the hash. for (size_t j = 0; j < SK_ARRAY_COUNT(tweaked); ++j) { const uint32_t saved = tweaked[j]; tweaked[j] = rand.nextU(); const uint32_t tweakedHash = SkOpts::hash(tweaked, kBytes); REPORTER_ASSERT(r, tweakedHash != hash); REPORTER_ASSERT(r, tweakedHash == SkOpts::hash(tweaked, kBytes)); tweaked[j] = saved; } } DEF_TEST(GoodHash, r) { // 4 bytes --> hits SkChecksum::Mix fast path. REPORTER_ASSERT(r, SkGoodHash()(( int32_t)4) == 614249093); REPORTER_ASSERT(r, SkGoodHash()((uint32_t)4) == 614249093); } DEF_TEST(ChecksumCollisions, r) { // We noticed a few workloads that would cause hash collisions due to the way // our optimized hashes split into three concurrent hashes and merge those hashes together. // // One of these two workloads ought to cause an unintentional hash collision on very similar // data in those old algorithms, the float version on 32-bit x86 and double elsewhere. { float a[9] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, }; float b[9] = { 1, 2, 0, 4, 5, 3, 7, 8, 6, }; REPORTER_ASSERT(r, SkOpts::hash(a, sizeof(a)) != SkOpts::hash(b, sizeof(b))); } { double a[9] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, }; double b[9] = { 1, 2, 0, 4, 5, 3, 7, 8, 6, }; REPORTER_ASSERT(r, SkOpts::hash(a, sizeof(a)) != SkOpts::hash(b, sizeof(b))); } }