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 "SkRandom.h"
10#include "Test.h"
11
12
13// Murmur3 has an optional third seed argument, so we wrap it to fit a uniform type.
14static uint32_t murmur_noseed(const uint32_t* d, size_t l) { return SkChecksum::Murmur3(d, l); }
15
16#define ASSERT(x) REPORTER_ASSERT(r, x)
17
18DEF_TEST(Checksum, r) {
19    // Algorithms to test.  They're currently all uint32_t(const uint32_t*, size_t).
20    typedef uint32_t(*algorithmProc)(const uint32_t*, size_t);
21    const algorithmProc kAlgorithms[] = { &SkChecksum::Compute, &murmur_noseed };
22
23    // Put 128 random bytes into two identical buffers.  Any multiple of 4 will do.
24    const size_t kBytes = SkAlign4(128);
25    SkRandom rand;
26    uint32_t data[kBytes/4], tweaked[kBytes/4];
27    for (size_t i = 0; i < SK_ARRAY_COUNT(tweaked); ++i) {
28        data[i] = tweaked[i] = rand.nextU();
29    }
30
31    // Test each algorithm.
32    for (size_t i = 0; i < SK_ARRAY_COUNT(kAlgorithms); ++i) {
33        const algorithmProc algorithm = kAlgorithms[i];
34
35        // Hash of NULL is always 0.
36        ASSERT(algorithm(NULL, 0) == 0);
37
38        const uint32_t hash = algorithm(data, kBytes);
39        // Should be deterministic.
40        ASSERT(hash == algorithm(data, kBytes));
41
42        // Changing any single element should change the hash.
43        for (size_t j = 0; j < SK_ARRAY_COUNT(tweaked); ++j) {
44            const uint32_t saved = tweaked[j];
45            tweaked[j] = rand.nextU();
46            const uint32_t tweakedHash = algorithm(tweaked, kBytes);
47            ASSERT(tweakedHash != hash);
48            ASSERT(tweakedHash == algorithm(tweaked, kBytes));
49            tweaked[j] = saved;
50        }
51    }
52}
53