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| /*
| * 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 "SkChecksum.h"
| #include "SkOpts.h"
| #include "SkRandom.h"
| #include "SkTypes.h"
| #include "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)));
| }
| }
|
|
