skia2/tests/ChecksumTest.cpp
mtklein 02f46cf878 Some usability ideas around SkTHash.
- By default, use new SkGoodHash to hash keys, which is:
    * for 4 byte values, use SkChecksum::Mix,
    * for SkStrings, use SkChecksum::Murmur3 on the data,
    * for other structs, shallow hash the struct with Murmur3.
  - Expand SkChecksum::Murmur3 to support non-4-byte-aligned data.
  - Add const foreach() methods.
  - Have foreach() take a functor, which allows lambdas.

BUG=skia:

Review URL: https://codereview.chromium.org/1021033002
2015-03-20 13:48:42 -07:00

66 lines
2.3 KiB
C++

/*
* 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 "SkRandom.h"
#include "Test.h"
// Murmur3 has an optional third seed argument, so we wrap it to fit a uniform type.
static uint32_t murmur_noseed(const uint32_t* d, size_t l) { return SkChecksum::Murmur3(d, l); }
#define ASSERT(x) REPORTER_ASSERT(r, x)
DEF_TEST(Checksum, r) {
// Algorithms to test. They're currently all uint32_t(const uint32_t*, size_t).
typedef uint32_t(*algorithmProc)(const uint32_t*, size_t);
const algorithmProc kAlgorithms[] = { &SkChecksum::Compute, &murmur_noseed };
// 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();
}
// Test each algorithm.
for (size_t i = 0; i < SK_ARRAY_COUNT(kAlgorithms); ++i) {
const algorithmProc algorithm = kAlgorithms[i];
// Hash of NULL is always 0.
ASSERT(algorithm(NULL, 0) == 0);
const uint32_t hash = algorithm(data, kBytes);
// Should be deterministic.
ASSERT(hash == algorithm(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 = algorithm(tweaked, kBytes);
ASSERT(tweakedHash != hash);
ASSERT(tweakedHash == algorithm(tweaked, kBytes));
tweaked[j] = saved;
}
}
}
DEF_TEST(GoodHash, r) {
ASSERT(SkGoodHash(( int32_t)4) == 614249093); // 4 bytes. Hits SkChecksum::Mix fast path.
ASSERT(SkGoodHash((uint32_t)4) == 614249093); // (Ditto)
// None of these are 4 byte sized, so they use SkChecksum::Murmur3, not SkChecksum::Mix.
ASSERT(SkGoodHash((uint64_t)4) == 3491892518);
ASSERT(SkGoodHash((uint16_t)4) == 899251846);
ASSERT(SkGoodHash( (uint8_t)4) == 962700458);
// Tests SkString is correctly specialized.
ASSERT(SkGoodHash(SkString("Hi")) == 55667557);
}