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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/hash/hash.h"
#include <cstdint>
#include <string>
#include <string_view>
#include <vector>
#include "base/containers/span.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace base {
TEST(HashTest, DeprecatedHashFromString) {
std::string str;
// Empty string (should hash to 0).
str = "";
EXPECT_EQ(0u, Hash(str));
// Simple test.
str = "hello world";
EXPECT_EQ(2794219650u, Hash(str));
// Change one bit.
str = "helmo world";
EXPECT_EQ(1006697176u, Hash(str));
// Insert a null byte.
str = "hello world";
str[5] = '\0';
EXPECT_EQ(2319902537u, Hash(str));
// Test that the bytes after the null contribute to the hash.
str = "hello worle";
str[5] = '\0';
EXPECT_EQ(553904462u, Hash(str));
// Extremely long string.
// Also tests strings with high bit set, and null byte.
std::vector<char> long_string_buffer;
for (int i = 0; i < 4096; ++i) {
long_string_buffer.push_back((i % 256) - 128);
}
str.assign(&long_string_buffer.front(), long_string_buffer.size());
EXPECT_EQ(2797962408u, Hash(str));
// All possible lengths (mod 4). Tests separate code paths. Also test with
// final byte high bit set (regression test for http://crbug.com/90659).
// Note that the 1 and 3 cases have a weird bug where the final byte is
// treated as a signed char. It was decided on the above bug discussion to
// enshrine that behaviour as "correct" to avoid invalidating existing hashes.
// Length mod 4 == 0.
str = "hello w\xab";
EXPECT_EQ(615571198u, Hash(str));
// Length mod 4 == 1.
str = "hello wo\xab";
EXPECT_EQ(623474296u, Hash(str));
// Length mod 4 == 2.
str = "hello wor\xab";
EXPECT_EQ(4278562408u, Hash(str));
// Length mod 4 == 3.
str = "hello worl\xab";
EXPECT_EQ(3224633008u, Hash(str));
}
TEST(HashTest, DeprecatedHashFromCString) {
const char* str;
// Empty string (should hash to 0).
str = "";
EXPECT_EQ(0u, Hash(str));
// Simple test.
str = "hello world";
EXPECT_EQ(2794219650u, Hash(str));
}
TEST(HashTest, PersistentHashFromSpan) {
// Empty span (should hash to 0).
EXPECT_EQ(0u, PersistentHash(base::span<const uint8_t>()));
// The hash loads four bytes at a time, and is sensitive to the high bit of
// the last few bytes. Test hashes of various lengths, and with and without
// the high bit set, to confirm the persistent hash remains persistent.
const std::string_view str1 = "hello world";
const std::array<uint32_t, 12> kHashesByLength1 = {
0u, 1213478405u, 2371107848u, 2412215855u,
2296013106u, 2963130491u, 342812795u, 1345887711u,
2394271580u, 2806845956u, 2484860346u, 2794219650u};
for (size_t i = 0; i <= str1.size(); i++) {
SCOPED_TRACE(i);
EXPECT_EQ(kHashesByLength1[i],
PersistentHash(as_byte_span(str1.substr(0, i))));
}
const std::string_view str2 = "\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa";
const std::array<uint32_t, 12> kHashesByLength2 = {
0u, 2524495555u, 901867827u, 52332316u,
1053305007u, 4170027104u, 1891345481u, 2246421829u,
1241531838u, 4191939542u, 4100345281u, 896950651u};
for (size_t i = 0; i <= str2.size(); i++) {
SCOPED_TRACE(i);
EXPECT_EQ(kHashesByLength2[i],
PersistentHash(as_byte_span(str2.substr(0, i))));
}
}
TEST(HashTest, FastHash) {
std::string s;
constexpr char kEmptyString[] = "";
EXPECT_EQ(FastHash(s), FastHash(kEmptyString));
}
} // namespace base
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