diff options
Diffstat (limited to 'absl/hash/internal')
| -rw-r--r-- | absl/hash/internal/city.cc | 346 | ||||
| -rw-r--r-- | absl/hash/internal/city.h | 94 | ||||
| -rw-r--r-- | absl/hash/internal/city_test.cc | 595 | ||||
| -rw-r--r-- | absl/hash/internal/hash.cc | 25 | ||||
| -rw-r--r-- | absl/hash/internal/hash.h | 898 | ||||
| -rw-r--r-- | absl/hash/internal/print_hash_of.cc | 23 | ||||
| -rw-r--r-- | absl/hash/internal/spy_hash_state.h | 220 |
7 files changed, 2201 insertions, 0 deletions
diff --git a/absl/hash/internal/city.cc b/absl/hash/internal/city.cc new file mode 100644 index 00000000..5c076fb5 --- /dev/null +++ b/absl/hash/internal/city.cc @@ -0,0 +1,346 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// This file provides CityHash64() and related functions. +// +// It's probably possible to create even faster hash functions by +// writing a program that systematically explores some of the space of +// possible hash functions, by using SIMD instructions, or by +// compromising on hash quality. + +#include "absl/hash/internal/city.h" + +#include <string.h> // for memcpy and memset +#include <algorithm> + +#include "absl/base/config.h" +#include "absl/base/internal/endian.h" +#include "absl/base/internal/unaligned_access.h" +#include "absl/base/optimization.h" + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +#ifdef ABSL_IS_BIG_ENDIAN +#define uint32_in_expected_order(x) (absl::gbswap_32(x)) +#define uint64_in_expected_order(x) (absl::gbswap_64(x)) +#else +#define uint32_in_expected_order(x) (x) +#define uint64_in_expected_order(x) (x) +#endif + +static uint64_t Fetch64(const char *p) { + return uint64_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD64(p)); +} + +static uint32_t Fetch32(const char *p) { + return uint32_in_expected_order(ABSL_INTERNAL_UNALIGNED_LOAD32(p)); +} + +// Some primes between 2^63 and 2^64 for various uses. +static const uint64_t k0 = 0xc3a5c85c97cb3127ULL; +static const uint64_t k1 = 0xb492b66fbe98f273ULL; +static const uint64_t k2 = 0x9ae16a3b2f90404fULL; + +// Magic numbers for 32-bit hashing. Copied from Murmur3. +static const uint32_t c1 = 0xcc9e2d51; +static const uint32_t c2 = 0x1b873593; + +// A 32-bit to 32-bit integer hash copied from Murmur3. +static uint32_t fmix(uint32_t h) { + h ^= h >> 16; + h *= 0x85ebca6b; + h ^= h >> 13; + h *= 0xc2b2ae35; + h ^= h >> 16; + return h; +} + +static uint32_t Rotate32(uint32_t val, int shift) { + // Avoid shifting by 32: doing so yields an undefined result. + return shift == 0 ? val : ((val >> shift) | (val << (32 - shift))); +} + +#undef PERMUTE3 +#define PERMUTE3(a, b, c) \ + do { \ + std::swap(a, b); \ + std::swap(a, c); \ + } while (0) + +static uint32_t Mur(uint32_t a, uint32_t h) { + // Helper from Murmur3 for combining two 32-bit values. + a *= c1; + a = Rotate32(a, 17); + a *= c2; + h ^= a; + h = Rotate32(h, 19); + return h * 5 + 0xe6546b64; +} + +static uint32_t Hash32Len13to24(const char *s, size_t len) { + uint32_t a = Fetch32(s - 4 + (len >> 1)); + uint32_t b = Fetch32(s + 4); + uint32_t c = Fetch32(s + len - 8); + uint32_t d = Fetch32(s + (len >> 1)); + uint32_t e = Fetch32(s); + uint32_t f = Fetch32(s + len - 4); + uint32_t h = len; + + return fmix(Mur(f, Mur(e, Mur(d, Mur(c, Mur(b, Mur(a, h))))))); +} + +static uint32_t Hash32Len0to4(const char *s, size_t len) { + uint32_t b = 0; + uint32_t c = 9; + for (size_t i = 0; i < len; i++) { + signed char v = s[i]; + b = b * c1 + v; + c ^= b; + } + return fmix(Mur(b, Mur(len, c))); +} + +static uint32_t Hash32Len5to12(const char *s, size_t len) { + uint32_t a = len, b = len * 5, c = 9, d = b; + a += Fetch32(s); + b += Fetch32(s + len - 4); + c += Fetch32(s + ((len >> 1) & 4)); + return fmix(Mur(c, Mur(b, Mur(a, d)))); +} + +uint32_t CityHash32(const char *s, size_t len) { + if (len <= 24) { + return len <= 12 + ? (len <= 4 ? Hash32Len0to4(s, len) : Hash32Len5to12(s, len)) + : Hash32Len13to24(s, len); + } + + // len > 24 + uint32_t h = len, g = c1 * len, f = g; + + uint32_t a0 = Rotate32(Fetch32(s + len - 4) * c1, 17) * c2; + uint32_t a1 = Rotate32(Fetch32(s + len - 8) * c1, 17) * c2; + uint32_t a2 = Rotate32(Fetch32(s + len - 16) * c1, 17) * c2; + uint32_t a3 = Rotate32(Fetch32(s + len - 12) * c1, 17) * c2; + uint32_t a4 = Rotate32(Fetch32(s + len - 20) * c1, 17) * c2; + h ^= a0; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + h ^= a2; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + g ^= a1; + g = Rotate32(g, 19); + g = g * 5 + 0xe6546b64; + g ^= a3; + g = Rotate32(g, 19); + g = g * 5 + 0xe6546b64; + f += a4; + f = Rotate32(f, 19); + f = f * 5 + 0xe6546b64; + size_t iters = (len - 1) / 20; + do { + uint32_t b0 = Rotate32(Fetch32(s) * c1, 17) * c2; + uint32_t b1 = Fetch32(s + 4); + uint32_t b2 = Rotate32(Fetch32(s + 8) * c1, 17) * c2; + uint32_t b3 = Rotate32(Fetch32(s + 12) * c1, 17) * c2; + uint32_t b4 = Fetch32(s + 16); + h ^= b0; + h = Rotate32(h, 18); + h = h * 5 + 0xe6546b64; + f += b1; + f = Rotate32(f, 19); + f = f * c1; + g += b2; + g = Rotate32(g, 18); + g = g * 5 + 0xe6546b64; + h ^= b3 + b1; + h = Rotate32(h, 19); + h = h * 5 + 0xe6546b64; + g ^= b4; + g = absl::gbswap_32(g) * 5; + h += b4 * 5; + h = absl::gbswap_32(h); + f += b0; + PERMUTE3(f, h, g); + s += 20; + } while (--iters != 0); + g = Rotate32(g, 11) * c1; + g = Rotate32(g, 17) * c1; + f = Rotate32(f, 11) * c1; + f = Rotate32(f, 17) * c1; + h = Rotate32(h + g, 19); + h = h * 5 + 0xe6546b64; + h = Rotate32(h, 17) * c1; + h = Rotate32(h + f, 19); + h = h * 5 + 0xe6546b64; + h = Rotate32(h, 17) * c1; + return h; +} + +// Bitwise right rotate. Normally this will compile to a single +// instruction, especially if the shift is a manifest constant. +static uint64_t Rotate(uint64_t val, int shift) { + // Avoid shifting by 64: doing so yields an undefined result. + return shift == 0 ? val : ((val >> shift) | (val << (64 - shift))); +} + +static uint64_t ShiftMix(uint64_t val) { return val ^ (val >> 47); } + +static uint64_t HashLen16(uint64_t u, uint64_t v) { + return Hash128to64(uint128(u, v)); +} + +static uint64_t HashLen16(uint64_t u, uint64_t v, uint64_t mul) { + // Murmur-inspired hashing. + uint64_t a = (u ^ v) * mul; + a ^= (a >> 47); + uint64_t b = (v ^ a) * mul; + b ^= (b >> 47); + b *= mul; + return b; +} + +static uint64_t HashLen0to16(const char *s, size_t len) { + if (len >= 8) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) + k2; + uint64_t b = Fetch64(s + len - 8); + uint64_t c = Rotate(b, 37) * mul + a; + uint64_t d = (Rotate(a, 25) + b) * mul; + return HashLen16(c, d, mul); + } + if (len >= 4) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch32(s); + return HashLen16(len + (a << 3), Fetch32(s + len - 4), mul); + } + if (len > 0) { + uint8_t a = s[0]; + uint8_t b = s[len >> 1]; + uint8_t c = s[len - 1]; + uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8); + uint32_t z = len + (static_cast<uint32_t>(c) << 2); + return ShiftMix(y * k2 ^ z * k0) * k2; + } + return k2; +} + +// This probably works well for 16-byte strings as well, but it may be overkill +// in that case. +static uint64_t HashLen17to32(const char *s, size_t len) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) * k1; + uint64_t b = Fetch64(s + 8); + uint64_t c = Fetch64(s + len - 8) * mul; + uint64_t d = Fetch64(s + len - 16) * k2; + return HashLen16(Rotate(a + b, 43) + Rotate(c, 30) + d, + a + Rotate(b + k2, 18) + c, mul); +} + +// Return a 16-byte hash for 48 bytes. Quick and dirty. +// Callers do best to use "random-looking" values for a and b. +static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(uint64_t w, uint64_t x, + uint64_t y, uint64_t z, + uint64_t a, uint64_t b) { + a += w; + b = Rotate(b + a + z, 21); + uint64_t c = a; + a += x; + a += y; + b += Rotate(a, 44); + return std::make_pair(a + z, b + c); +} + +// Return a 16-byte hash for s[0] ... s[31], a, and b. Quick and dirty. +static std::pair<uint64_t, uint64_t> WeakHashLen32WithSeeds(const char *s, uint64_t a, + uint64_t b) { + return WeakHashLen32WithSeeds(Fetch64(s), Fetch64(s + 8), Fetch64(s + 16), + Fetch64(s + 24), a, b); +} + +// Return an 8-byte hash for 33 to 64 bytes. +static uint64_t HashLen33to64(const char *s, size_t len) { + uint64_t mul = k2 + len * 2; + uint64_t a = Fetch64(s) * k2; + uint64_t b = Fetch64(s + 8); + uint64_t c = Fetch64(s + len - 24); + uint64_t d = Fetch64(s + len - 32); + uint64_t e = Fetch64(s + 16) * k2; + uint64_t f = Fetch64(s + 24) * 9; + uint64_t g = Fetch64(s + len - 8); + uint64_t h = Fetch64(s + len - 16) * mul; + uint64_t u = Rotate(a + g, 43) + (Rotate(b, 30) + c) * 9; + uint64_t v = ((a + g) ^ d) + f + 1; + uint64_t w = absl::gbswap_64((u + v) * mul) + h; + uint64_t x = Rotate(e + f, 42) + c; + uint64_t y = (absl::gbswap_64((v + w) * mul) + g) * mul; + uint64_t z = e + f + c; + a = absl::gbswap_64((x + z) * mul + y) + b; + b = ShiftMix((z + a) * mul + d + h) * mul; + return b + x; +} + +uint64_t CityHash64(const char *s, size_t len) { + if (len <= 32) { + if (len <= 16) { + return HashLen0to16(s, len); + } else { + return HashLen17to32(s, len); + } + } else if (len <= 64) { + return HashLen33to64(s, len); + } + + // For strings over 64 bytes we hash the end first, and then as we + // loop we keep 56 bytes of state: v, w, x, y, and z. + uint64_t x = Fetch64(s + len - 40); + uint64_t y = Fetch64(s + len - 16) + Fetch64(s + len - 56); + uint64_t z = HashLen16(Fetch64(s + len - 48) + len, Fetch64(s + len - 24)); + std::pair<uint64_t, uint64_t> v = WeakHashLen32WithSeeds(s + len - 64, len, z); + std::pair<uint64_t, uint64_t> w = WeakHashLen32WithSeeds(s + len - 32, y + k1, x); + x = x * k1 + Fetch64(s); + + // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks. + len = (len - 1) & ~static_cast<size_t>(63); + do { + x = Rotate(x + y + v.first + Fetch64(s + 8), 37) * k1; + y = Rotate(y + v.second + Fetch64(s + 48), 42) * k1; + x ^= w.second; + y += v.first + Fetch64(s + 40); + z = Rotate(z + w.first, 33) * k1; + v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first); + w = WeakHashLen32WithSeeds(s + 32, z + w.second, y + Fetch64(s + 16)); + std::swap(z, x); + s += 64; + len -= 64; + } while (len != 0); + return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z, + HashLen16(v.second, w.second) + x); +} + +uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed) { + return CityHash64WithSeeds(s, len, k2, seed); +} + +uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0, + uint64_t seed1) { + return HashLen16(CityHash64(s, len) - seed0, seed1); +} + +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl diff --git a/absl/hash/internal/city.h b/absl/hash/internal/city.h new file mode 100644 index 00000000..46c18ffa --- /dev/null +++ b/absl/hash/internal/city.h @@ -0,0 +1,94 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// http://code.google.com/p/cityhash/ +// +// This file provides a few functions for hashing strings. All of them are +// high-quality functions in the sense that they pass standard tests such +// as Austin Appleby's SMHasher. They are also fast. +// +// For 64-bit x86 code, on short strings, we don't know of anything faster than +// CityHash64 that is of comparable quality. We believe our nearest competitor +// is Murmur3. For 64-bit x86 code, CityHash64 is an excellent choice for hash +// tables and most other hashing (excluding cryptography). +// +// For 32-bit x86 code, we don't know of anything faster than CityHash32 that +// is of comparable quality. We believe our nearest competitor is Murmur3A. +// (On 64-bit CPUs, it is typically faster to use the other CityHash variants.) +// +// Functions in the CityHash family are not suitable for cryptography. +// +// Please see CityHash's README file for more details on our performance +// measurements and so on. +// +// WARNING: This code has been only lightly tested on big-endian platforms! +// It is known to work well on little-endian platforms that have a small penalty +// for unaligned reads, such as current Intel and AMD moderate-to-high-end CPUs. +// It should work on all 32-bit and 64-bit platforms that allow unaligned reads; +// bug reports are welcome. +// +// By the way, for some hash functions, given strings a and b, the hash +// of a+b is easily derived from the hashes of a and b. This property +// doesn't hold for any hash functions in this file. + +#ifndef ABSL_HASH_INTERNAL_CITY_H_ +#define ABSL_HASH_INTERNAL_CITY_H_ + +#include <stdint.h> +#include <stdlib.h> // for size_t. +#include <utility> + + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +typedef std::pair<uint64_t, uint64_t> uint128; + +inline uint64_t Uint128Low64(const uint128 &x) { return x.first; } +inline uint64_t Uint128High64(const uint128 &x) { return x.second; } + +// Hash function for a byte array. +uint64_t CityHash64(const char *s, size_t len); + +// Hash function for a byte array. For convenience, a 64-bit seed is also +// hashed into the result. +uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed); + +// Hash function for a byte array. For convenience, two seeds are also +// hashed into the result. +uint64_t CityHash64WithSeeds(const char *s, size_t len, uint64_t seed0, + uint64_t seed1); + +// Hash function for a byte array. Most useful in 32-bit binaries. +uint32_t CityHash32(const char *s, size_t len); + +// Hash 128 input bits down to 64 bits of output. +// This is intended to be a reasonably good hash function. +inline uint64_t Hash128to64(const uint128 &x) { + // Murmur-inspired hashing. + const uint64_t kMul = 0x9ddfea08eb382d69ULL; + uint64_t a = (Uint128Low64(x) ^ Uint128High64(x)) * kMul; + a ^= (a >> 47); + uint64_t b = (Uint128High64(x) ^ a) * kMul; + b ^= (b >> 47); + b *= kMul; + return b; +} + +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl + +#endif // ABSL_HASH_INTERNAL_CITY_H_ diff --git a/absl/hash/internal/city_test.cc b/absl/hash/internal/city_test.cc new file mode 100644 index 00000000..f305ed9e --- /dev/null +++ b/absl/hash/internal/city_test.cc @@ -0,0 +1,595 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/hash/internal/city.h" + +#include <string.h> +#include <cstdio> +#include <iostream> +#include "gtest/gtest.h" + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +static const uint64_t k0 = 0xc3a5c85c97cb3127ULL; +static const uint64_t kSeed0 = 1234567; +static const uint64_t kSeed1 = k0; +static const int kDataSize = 1 << 20; +static const int kTestSize = 300; + +static char data[kDataSize]; + +// Initialize data to pseudorandom values. +void setup() { + uint64_t a = 9; + uint64_t b = 777; + for (int i = 0; i < kDataSize; i++) { + a += b; + b += a; + a = (a ^ (a >> 41)) * k0; + b = (b ^ (b >> 41)) * k0 + i; + uint8_t u = b >> 37; + memcpy(data + i, &u, 1); // uint8_t -> char + } +} + +#define C(x) 0x##x##ULL +static const uint64_t testdata[kTestSize][4] = { + {C(9ae16a3b2f90404f), C(75106db890237a4a), C(3feac5f636039766), + C(dc56d17a)}, + {C(541150e87f415e96), C(1aef0d24b3148a1a), C(bacc300e1e82345a), + C(99929334)}, + {C(f3786a4b25827c1), C(34ee1a2bf767bd1c), C(2f15ca2ebfb631f2), C(4252edb7)}, + {C(ef923a7a1af78eab), C(79163b1e1e9a9b18), C(df3b2aca6e1e4a30), + C(ebc34f3c)}, + {C(11df592596f41d88), C(843ec0bce9042f9c), C(cce2ea1e08b1eb30), + C(26f2b463)}, + {C(831f448bdc5600b3), C(62a24be3120a6919), C(1b44098a41e010da), + C(b042c047)}, + {C(3eca803e70304894), C(d80de767e4a920a), C(a51cfbb292efd53d), C(e73bb0a8)}, + {C(1b5a063fb4c7f9f1), C(318dbc24af66dee9), C(10ef7b32d5c719af), + C(91dfdd75)}, + {C(a0f10149a0e538d6), C(69d008c20f87419f), C(41b36376185b3e9e), + C(c87f95de)}, + {C(fb8d9c70660b910b), C(a45b0cc3476bff1b), C(b28d1996144f0207), + C(3f5538ef)}, + {C(236827beae282a46), C(e43970221139c946), C(4f3ac6faa837a3aa), + C(70eb1a1f)}, + {C(c385e435136ecf7c), C(d9d17368ff6c4a08), C(1b31eed4e5251a67), + C(cfd63b83)}, + {C(e3f6828b6017086d), C(21b4d1900554b3b0), C(bef38be1809e24f1), + C(894a52ef)}, + {C(851fff285561dca0), C(4d1277d73cdf416f), C(28ccffa61010ebe2), + C(9cde6a54)}, + {C(61152a63595a96d9), C(d1a3a91ef3a7ba45), C(443b6bb4a493ad0c), + C(6c4898d5)}, + {C(44473e03be306c88), C(30097761f872472a), C(9fd1b669bfad82d7), + C(13e1978e)}, + {C(3ead5f21d344056), C(fb6420393cfb05c3), C(407932394cbbd303), C(51b4ba8)}, + {C(6abbfde37ee03b5b), C(83febf188d2cc113), C(cda7b62d94d5b8ee), + C(b6b06e40)}, + {C(943e7ed63b3c080), C(1ef207e9444ef7f8), C(ef4a9f9f8c6f9b4a), C(240a2f2)}, + {C(d72ce05171ef8a1a), C(c6bd6bd869203894), C(c760e6396455d23a), + C(5dcefc30)}, + {C(4182832b52d63735), C(337097e123eea414), C(b5a72ca0456df910), + C(7a48b105)}, + {C(d6cdae892584a2cb), C(58de0fa4eca17dcd), C(43df30b8f5f1cb00), + C(fd55007b)}, + {C(5c8e90bc267c5ee4), C(e9ae044075d992d9), C(f234cbfd1f0a1e59), + C(6b95894c)}, + {C(bbd7f30ac310a6f3), C(b23b570d2666685f), C(fb13fb08c9814fe7), + C(3360e827)}, + {C(36a097aa49519d97), C(8204380a73c4065), C(77c2004bdd9e276a), C(45177e0b)}, + {C(dc78cb032c49217), C(112464083f83e03a), C(96ae53e28170c0f5), C(7c6fffe4)}, + {C(441593e0da922dfe), C(936ef46061469b32), C(204a1921197ddd87), + C(bbc78da4)}, + {C(2ba3883d71cc2133), C(72f2bbb32bed1a3c), C(27e1bd96d4843251), + C(c5c25d39)}, + {C(f2b6d2adf8423600), C(7514e2f016a48722), C(43045743a50396ba), + C(b6e5d06e)}, + {C(38fffe7f3680d63c), C(d513325255a7a6d1), C(31ed47790f6ca62f), + C(6178504e)}, + {C(b7477bf0b9ce37c6), C(63b1c580a7fd02a4), C(f6433b9f10a5dac), C(bd4c3637)}, + {C(55bdb0e71e3edebd), C(c7ab562bcf0568bc), C(43166332f9ee684f), + C(6e7ac474)}, + {C(782fa1b08b475e7), C(fb7138951c61b23b), C(9829105e234fb11e), C(1fb4b518)}, + {C(c5dc19b876d37a80), C(15ffcff666cfd710), C(e8c30c72003103e2), + 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C(74e2179d)}, + {C(b371f768cdf4edb9), C(bdef2ace6d2de0f0), C(e05b4100f7f1baec), + C(ee9bae25)}, + {C(7a1d2e96934f61f), C(eb1760ae6af7d961), C(887eb0da063005df), C(b66edf10)}, + {C(8be53d466d4728f2), C(86a5ac8e0d416640), C(984aa464cdb5c8bb), + C(d6209737)}, + {C(829677eb03abf042), C(43cad004b6bc2c0), C(f2f224756803971a), C(b994a88)}, + {C(754435bae3496fc), C(5707fc006f094dcf), C(8951c86ab19d8e40), C(a05d43c0)}, + {C(fda9877ea8e3805f), C(31e868b6ffd521b7), C(b08c90681fb6a0fd), + C(c79f73a8)}, + {C(2e36f523ca8f5eb5), C(8b22932f89b27513), C(331cd6ecbfadc1bb), + C(a490aff5)}, + {C(21a378ef76828208), C(a5c13037fa841da2), C(506d22a53fbe9812), + C(dfad65b4)}, + {C(ccdd5600054b16ca), C(f78846e84204cb7b), C(1f9faec82c24eac9), C(1d07dfb)}, + {C(7854468f4e0cabd0), C(3a3f6b4f098d0692), C(ae2423ec7799d30d), + C(416df9a0)}, + {C(7f88db5346d8f997), C(88eac9aacc653798), C(68a4d0295f8eefa1), + C(1f8fb9cc)}, + {C(bb3fb5fb01d60fcf), C(1b7cc0847a215eb6), C(1246c994437990a1), + C(7abf48e3)}, + {C(2e783e1761acd84d), C(39158042bac975a0), C(1cd21c5a8071188d), + C(dea4e3dd)}, + {C(392058251cf22acc), C(944ec4475ead4620), C(b330a10b5cb94166), + C(c6064f22)}, + {C(adf5c1e5d6419947), C(2a9747bc659d28aa), C(95c5b8cb1f5d62c), C(743bed9c)}, + {C(6bc1db2c2bee5aba), C(e63b0ed635307398), C(7b2eca111f30dbbc), + C(fce254d5)}, + {C(b00f898229efa508), C(83b7590ad7f6985c), C(2780e70a0592e41d), + C(e47ec9d1)}, + {C(b56eb769ce0d9a8c), C(ce196117bfbcaf04), C(b26c3c3797d66165), + C(334a145c)}, + {C(70c0637675b94150), C(259e1669305b0a15), C(46e1dd9fd387a58d), + C(adec1e3c)}, + {C(74c0b8a6821faafe), C(abac39d7491370e7), C(faf0b2a48a4e6aed), + C(f6a9fbf8)}, + {C(5fb5e48ac7b7fa4f), C(a96170f08f5acbc7), C(bbf5c63d4f52a1e5), + C(5398210c)}, +}; + +void TestUnchanging(const uint64_t* expected, int offset, int len) { + EXPECT_EQ(expected[0], CityHash64(data + offset, len)); + EXPECT_EQ(expected[3], CityHash32(data + offset, len)); + EXPECT_EQ(expected[1], CityHash64WithSeed(data + offset, len, kSeed0)); + EXPECT_EQ(expected[2], + CityHash64WithSeeds(data + offset, len, kSeed0, kSeed1)); +} + +TEST(CityHashTest, Unchanging) { + setup(); + int i = 0; + for (; i < kTestSize - 1; i++) { + TestUnchanging(testdata[i], i * i, i); + } + TestUnchanging(testdata[i], 0, kDataSize); +} + +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl diff --git a/absl/hash/internal/hash.cc b/absl/hash/internal/hash.cc new file mode 100644 index 00000000..3e553625 --- /dev/null +++ b/absl/hash/internal/hash.cc @@ -0,0 +1,25 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/hash/internal/hash.h" + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +ABSL_CONST_INIT const void* const CityHashState::kSeed = &kSeed; + +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h new file mode 100644 index 00000000..a51ca954 --- /dev/null +++ b/absl/hash/internal/hash.h @@ -0,0 +1,898 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// ----------------------------------------------------------------------------- +// File: hash.h +// ----------------------------------------------------------------------------- +// +#ifndef ABSL_HASH_INTERNAL_HASH_H_ +#define ABSL_HASH_INTERNAL_HASH_H_ + +#include <algorithm> +#include <array> +#include <cmath> +#include <cstring> +#include <deque> +#include <forward_list> +#include <functional> +#include <iterator> +#include <limits> +#include <list> +#include <map> +#include <memory> +#include <set> +#include <string> +#include <tuple> +#include <type_traits> +#include <utility> +#include <vector> + +#include "absl/base/internal/endian.h" +#include "absl/base/port.h" +#include "absl/container/fixed_array.h" +#include "absl/meta/type_traits.h" +#include "absl/numeric/int128.h" +#include "absl/strings/string_view.h" +#include "absl/types/optional.h" +#include "absl/types/variant.h" +#include "absl/utility/utility.h" +#include "absl/hash/internal/city.h" + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +// HashStateBase +// +// A hash state object represents an intermediate state in the computation +// of an unspecified hash algorithm. `HashStateBase` provides a CRTP style +// base class for hash state implementations. Developers adding type support +// for `absl::Hash` should not rely on any parts of the state object other than +// the following member functions: +// +// * HashStateBase::combine() +// * HashStateBase::combine_contiguous() +// +// A derived hash state class of type `H` must provide a static member function +// with a signature similar to the following: +// +// `static H combine_contiguous(H state, const unsigned char*, size_t)`. +// +// `HashStateBase` will provide a complete implementations for a hash state +// object in terms of this method. +// +// Example: +// +// // Use CRTP to define your derived class. +// struct MyHashState : HashStateBase<MyHashState> { +// static H combine_contiguous(H state, const unsigned char*, size_t); +// using MyHashState::HashStateBase::combine; +// using MyHashState::HashStateBase::combine_contiguous; +// }; +template <typename H> +class HashStateBase { + public: + // HashStateBase::combine() + // + // Combines an arbitrary number of values into a hash state, returning the + // updated state. + // + // Each of the value types `T` must be separately hashable by the Abseil + // hashing framework. + // + // NOTE: + // + // state = H::combine(std::move(state), value1, value2, value3); + // + // is guaranteed to produce the same hash expansion as: + // + // state = H::combine(std::move(state), value1); + // state = H::combine(std::move(state), value2); + // state = H::combine(std::move(state), value3); + template <typename T, typename... Ts> + static H combine(H state, const T& value, const Ts&... values); + static H combine(H state) { return state; } + + // HashStateBase::combine_contiguous() + // + // Combines a contiguous array of `size` elements into a hash state, returning + // the updated state. + // + // NOTE: + // + // state = H::combine_contiguous(std::move(state), data, size); + // + // is NOT guaranteed to produce the same hash expansion as a for-loop (it may + // perform internal optimizations). If you need this guarantee, use the + // for-loop instead. + template <typename T> + static H combine_contiguous(H state, const T* data, size_t size); +}; + +// is_uniquely_represented +// +// `is_uniquely_represented<T>` is a trait class that indicates whether `T` +// is uniquely represented. +// +// A type is "uniquely represented" if two equal values of that type are +// guaranteed to have the same bytes in their underlying storage. In other +// words, if `a == b`, then `memcmp(&a, &b, sizeof(T))` is guaranteed to be +// zero. This property cannot be detected automatically, so this trait is false +// by default, but can be specialized by types that wish to assert that they are +// uniquely represented. This makes them eligible for certain optimizations. +// +// If you have any doubt whatsoever, do not specialize this template. +// The default is completely safe, and merely disables some optimizations +// that will not matter for most types. Specializing this template, +// on the other hand, can be very hazardous. +// +// To be uniquely represented, a type must not have multiple ways of +// representing the same value; for example, float and double are not +// uniquely represented, because they have distinct representations for +// +0 and -0. Furthermore, the type's byte representation must consist +// solely of user-controlled data, with no padding bits and no compiler- +// controlled data such as vptrs or sanitizer metadata. This is usually +// very difficult to guarantee, because in most cases the compiler can +// insert data and padding bits at its own discretion. +// +// If you specialize this template for a type `T`, you must do so in the file +// that defines that type (or in this file). If you define that specialization +// anywhere else, `is_uniquely_represented<T>` could have different meanings +// in different places. +// +// The Enable parameter is meaningless; it is provided as a convenience, +// to support certain SFINAE techniques when defining specializations. +template <typename T, typename Enable = void> +struct is_uniquely_represented : std::false_type {}; + +// is_uniquely_represented<unsigned char> +// +// unsigned char is a synonym for "byte", so it is guaranteed to be +// uniquely represented. +template <> +struct is_uniquely_represented<unsigned char> : std::true_type {}; + +// is_uniquely_represented for non-standard integral types +// +// Integral types other than bool should be uniquely represented on any +// platform that this will plausibly be ported to. +template <typename Integral> +struct is_uniquely_represented< + Integral, typename std::enable_if<std::is_integral<Integral>::value>::type> + : std::true_type {}; + +// is_uniquely_represented<bool> +// +// +template <> +struct is_uniquely_represented<bool> : std::false_type {}; + +// hash_bytes() +// +// Convenience function that combines `hash_state` with the byte representation +// of `value`. +template <typename H, typename T> +H hash_bytes(H hash_state, const T& value) { + const unsigned char* start = reinterpret_cast<const unsigned char*>(&value); + return H::combine_contiguous(std::move(hash_state), start, sizeof(value)); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Basic Types +// ----------------------------------------------------------------------------- + +// Note: Default `AbslHashValue` implementations live in `hash_internal`. This +// allows us to block lexical scope lookup when doing an unqualified call to +// `AbslHashValue` below. User-defined implementations of `AbslHashValue` can +// only be found via ADL. + +// AbslHashValue() for hashing bool values +// +// We use SFINAE to ensure that this overload only accepts bool, not types that +// are convertible to bool. +template <typename H, typename B> +typename std::enable_if<std::is_same<B, bool>::value, H>::type AbslHashValue( + H hash_state, B value) { + return H::combine(std::move(hash_state), + static_cast<unsigned char>(value ? 1 : 0)); +} + +// AbslHashValue() for hashing enum values +template <typename H, typename Enum> +typename std::enable_if<std::is_enum<Enum>::value, H>::type AbslHashValue( + H hash_state, Enum e) { + // In practice, we could almost certainly just invoke hash_bytes directly, + // but it's possible that a sanitizer might one day want to + // store data in the unused bits of an enum. To avoid that risk, we + // convert to the underlying type before hashing. Hopefully this will get + // optimized away; if not, we can reopen discussion with c-toolchain-team. + return H::combine(std::move(hash_state), + static_cast<typename std::underlying_type<Enum>::type>(e)); +} +// AbslHashValue() for hashing floating-point values +template <typename H, typename Float> +typename std::enable_if<std::is_floating_point<Float>::value, H>::type +AbslHashValue(H hash_state, Float value) { + return hash_internal::hash_bytes(std::move(hash_state), + value == 0 ? 0 : value); +} + +// Long double has the property that it might have extra unused bytes in it. +// For example, in x86 sizeof(long double)==16 but it only really uses 80-bits +// of it. This means we can't use hash_bytes on a long double and have to +// convert it to something else first. +template <typename H> +H AbslHashValue(H hash_state, long double value) { + const int category = std::fpclassify(value); + switch (category) { + case FP_INFINITE: + // Add the sign bit to differentiate between +Inf and -Inf + hash_state = H::combine(std::move(hash_state), std::signbit(value)); + break; + + case FP_NAN: + case FP_ZERO: + default: + // Category is enough for these. + break; + + case FP_NORMAL: + case FP_SUBNORMAL: + // We can't convert `value` directly to double because this would have + // undefined behavior if the value is out of range. + // std::frexp gives us a value in the range (-1, -.5] or [.5, 1) that is + // guaranteed to be in range for `double`. The truncation is + // implementation defined, but that works as long as it is deterministic. + int exp; + auto mantissa = static_cast<double>(std::frexp(value, &exp)); + hash_state = H::combine(std::move(hash_state), mantissa, exp); + } + + return H::combine(std::move(hash_state), category); +} + +// AbslHashValue() for hashing pointers +template <typename H, typename T> +H AbslHashValue(H hash_state, T* ptr) { + return hash_internal::hash_bytes(std::move(hash_state), ptr); +} + +// AbslHashValue() for hashing nullptr_t +template <typename H> +H AbslHashValue(H hash_state, std::nullptr_t) { + return H::combine(std::move(hash_state), static_cast<void*>(nullptr)); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Composite Types +// ----------------------------------------------------------------------------- + +// is_hashable() +// +// Trait class which returns true if T is hashable by the absl::Hash framework. +// Used for the AbslHashValue implementations for composite types below. +template <typename T> +struct is_hashable; + +// AbslHashValue() for hashing pairs +template <typename H, typename T1, typename T2> +typename std::enable_if<is_hashable<T1>::value && is_hashable<T2>::value, + H>::type +AbslHashValue(H hash_state, const std::pair<T1, T2>& p) { + return H::combine(std::move(hash_state), p.first, p.second); +} + +// hash_tuple() +// +// Helper function for hashing a tuple. The third argument should +// be an index_sequence running from 0 to tuple_size<Tuple> - 1. +template <typename H, typename Tuple, size_t... Is> +H hash_tuple(H hash_state, const Tuple& t, absl::index_sequence<Is...>) { + return H::combine(std::move(hash_state), std::get<Is>(t)...); +} + +// AbslHashValue for hashing tuples +template <typename H, typename... Ts> +#if defined(_MSC_VER) +// This SFINAE gets MSVC confused under some conditions. Let's just disable it +// for now. +H +#else // _MSC_VER +typename std::enable_if<absl::conjunction<is_hashable<Ts>...>::value, H>::type +#endif // _MSC_VER +AbslHashValue(H hash_state, const std::tuple<Ts...>& t) { + return hash_internal::hash_tuple(std::move(hash_state), t, + absl::make_index_sequence<sizeof...(Ts)>()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Pointers +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing unique_ptr +template <typename H, typename T, typename D> +H AbslHashValue(H hash_state, const std::unique_ptr<T, D>& ptr) { + return H::combine(std::move(hash_state), ptr.get()); +} + +// AbslHashValue for hashing shared_ptr +template <typename H, typename T> +H AbslHashValue(H hash_state, const std::shared_ptr<T>& ptr) { + return H::combine(std::move(hash_state), ptr.get()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for String-Like Types +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing strings +// +// All the string-like types supported here provide the same hash expansion for +// the same character sequence. These types are: +// +// - `std::string` (and std::basic_string<char, std::char_traits<char>, A> for +// any allocator A) +// - `absl::string_view` and `std::string_view` +// +// For simplicity, we currently support only `char` strings. This support may +// be broadened, if necessary, but with some caution - this overload would +// misbehave in cases where the traits' `eq()` member isn't equivalent to `==` +// on the underlying character type. +template <typename H> +H AbslHashValue(H hash_state, absl::string_view str) { + return H::combine( + H::combine_contiguous(std::move(hash_state), str.data(), str.size()), + str.size()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Sequence Containers +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing std::array +template <typename H, typename T, size_t N> +typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( + H hash_state, const std::array<T, N>& array) { + return H::combine_contiguous(std::move(hash_state), array.data(), + array.size()); +} + +// AbslHashValue for hashing std::deque +template <typename H, typename T, typename Allocator> +typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( + H hash_state, const std::deque<T, Allocator>& deque) { + // TODO(gromer): investigate a more efficient implementation taking + // advantage of the chunk structure. + for (const auto& t : deque) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), deque.size()); +} + +// AbslHashValue for hashing std::forward_list +template <typename H, typename T, typename Allocator> +typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( + H hash_state, const std::forward_list<T, Allocator>& list) { + size_t size = 0; + for (const T& t : list) { + hash_state = H::combine(std::move(hash_state), t); + ++size; + } + return H::combine(std::move(hash_state), size); +} + +// AbslHashValue for hashing std::list +template <typename H, typename T, typename Allocator> +typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( + H hash_state, const std::list<T, Allocator>& list) { + for (const auto& t : list) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), list.size()); +} + +// AbslHashValue for hashing std::vector +// +// Do not use this for vector<bool>. It does not have a .data(), and a fallback +// for std::hash<> is most likely faster. +template <typename H, typename T, typename Allocator> +typename std::enable_if<is_hashable<T>::value && !std::is_same<T, bool>::value, + H>::type +AbslHashValue(H hash_state, const std::vector<T, Allocator>& vector) { + return H::combine(H::combine_contiguous(std::move(hash_state), vector.data(), + vector.size()), + vector.size()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Ordered Associative Containers +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing std::map +template <typename H, typename Key, typename T, typename Compare, + typename Allocator> +typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value, + H>::type +AbslHashValue(H hash_state, const std::map<Key, T, Compare, Allocator>& map) { + for (const auto& t : map) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), map.size()); +} + +// AbslHashValue for hashing std::multimap +template <typename H, typename Key, typename T, typename Compare, + typename Allocator> +typename std::enable_if<is_hashable<Key>::value && is_hashable<T>::value, + H>::type +AbslHashValue(H hash_state, + const std::multimap<Key, T, Compare, Allocator>& map) { + for (const auto& t : map) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), map.size()); +} + +// AbslHashValue for hashing std::set +template <typename H, typename Key, typename Compare, typename Allocator> +typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue( + H hash_state, const std::set<Key, Compare, Allocator>& set) { + for (const auto& t : set) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), set.size()); +} + +// AbslHashValue for hashing std::multiset +template <typename H, typename Key, typename Compare, typename Allocator> +typename std::enable_if<is_hashable<Key>::value, H>::type AbslHashValue( + H hash_state, const std::multiset<Key, Compare, Allocator>& set) { + for (const auto& t : set) { + hash_state = H::combine(std::move(hash_state), t); + } + return H::combine(std::move(hash_state), set.size()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Wrapper Types +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing absl::optional +template <typename H, typename T> +typename std::enable_if<is_hashable<T>::value, H>::type AbslHashValue( + H hash_state, const absl::optional<T>& opt) { + if (opt) hash_state = H::combine(std::move(hash_state), *opt); + return H::combine(std::move(hash_state), opt.has_value()); +} + +// VariantVisitor +template <typename H> +struct VariantVisitor { + H&& hash_state; + template <typename T> + H operator()(const T& t) const { + return H::combine(std::move(hash_state), t); + } +}; + +// AbslHashValue for hashing absl::variant +template <typename H, typename... T> +typename std::enable_if<conjunction<is_hashable<T>...>::value, H>::type +AbslHashValue(H hash_state, const absl::variant<T...>& v) { + if (!v.valueless_by_exception()) { + hash_state = absl::visit(VariantVisitor<H>{std::move(hash_state)}, v); + } + return H::combine(std::move(hash_state), v.index()); +} + +// ----------------------------------------------------------------------------- +// AbslHashValue for Other Types +// ----------------------------------------------------------------------------- + +// AbslHashValue for hashing std::bitset is not defined, for the same reason as +// for vector<bool> (see std::vector above): It does not expose the raw bytes, +// and a fallback to std::hash<> is most likely faster. + +// ----------------------------------------------------------------------------- + +// hash_range_or_bytes() +// +// Mixes all values in the range [data, data+size) into the hash state. +// This overload accepts only uniquely-represented types, and hashes them by +// hashing the entire range of bytes. +template <typename H, typename T> +typename std::enable_if<is_uniquely_represented<T>::value, H>::type +hash_range_or_bytes(H hash_state, const T* data, size_t size) { + const auto* bytes = reinterpret_cast<const unsigned char*>(data); + return H::combine_contiguous(std::move(hash_state), bytes, sizeof(T) * size); +} + +// hash_range_or_bytes() +template <typename H, typename T> +typename std::enable_if<!is_uniquely_represented<T>::value, H>::type +hash_range_or_bytes(H hash_state, const T* data, size_t size) { + for (const auto end = data + size; data < end; ++data) { + hash_state = H::combine(std::move(hash_state), *data); + } + return hash_state; +} + +// InvokeHashTag +// +// InvokeHash(H, const T&) invokes the appropriate hash implementation for a +// hasher of type `H` and a value of type `T`. If `T` is not hashable, there +// will be no matching overload of InvokeHash(). +// Note: Some platforms (eg MSVC) do not support the detect idiom on +// std::hash. In those platforms the last fallback will be std::hash and +// InvokeHash() will always have a valid overload even if std::hash<T> is not +// valid. +// +// We try the following options in order: +// * If is_uniquely_represented, hash bytes directly. +// * ADL AbslHashValue(H, const T&) call. +// * std::hash<T> + +// In MSVC we can't probe std::hash or stdext::hash because it triggers a +// static_assert instead of failing substitution. +#if defined(_MSC_VER) +#define ABSL_HASH_INTERNAL_CAN_POISON_ 0 +#else // _MSC_VER +#define ABSL_HASH_INTERNAL_CAN_POISON_ 1 +#endif // _MSC_VER + +#if defined(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE) && \ + ABSL_HASH_INTERNAL_CAN_POISON_ +#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 1 +#else +#define ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ 0 +#endif + +enum class InvokeHashTag { + kUniquelyRepresented, + kHashValue, +#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + kLegacyHash, +#endif // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + kStdHash, + kNone +}; + +// HashSelect +// +// Type trait to select the appropriate hash implementation to use. +// HashSelect<T>::value is an instance of InvokeHashTag that indicates the best +// available hashing mechanism. +// See `Note` above about MSVC. +template <typename T> +struct HashSelect { + private: + struct State : HashStateBase<State> { + static State combine_contiguous(State hash_state, const unsigned char*, + size_t); + using State::HashStateBase::combine_contiguous; + }; + + // `Probe<V, Tag>::value` evaluates to `V<T>::value` if it is a valid + // expression, and `false` otherwise. + // `Probe<V, Tag>::tag` always evaluates to `Tag`. + template <template <typename> class V, InvokeHashTag Tag> + struct Probe { + private: + template <typename U, typename std::enable_if<V<U>::value, int>::type = 0> + static std::true_type Test(int); + template <typename U> + static std::false_type Test(char); + + public: + static constexpr InvokeHashTag kTag = Tag; + static constexpr bool value = decltype( + Test<absl::remove_const_t<absl::remove_reference_t<T>>>(0))::value; + }; + + template <typename U> + using ProbeUniquelyRepresented = is_uniquely_represented<U>; + + template <typename U> + using ProbeHashValue = + std::is_same<State, decltype(AbslHashValue(std::declval<State>(), + std::declval<const U&>()))>; + +#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + template <typename U> + using ProbeLegacyHash = + std::is_convertible<decltype(ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash< + U>()(std::declval<const U&>())), + size_t>; +#endif // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + + template <typename U> + using ProbeStdHash = +#if ABSL_HASH_INTERNAL_CAN_POISON_ + std::is_convertible<decltype(std::hash<U>()(std::declval<const U&>())), + size_t>; +#else // ABSL_HASH_INTERNAL_CAN_POISON_ + std::true_type; +#endif // ABSL_HASH_INTERNAL_CAN_POISON_ + + template <typename U> + using ProbeNone = std::true_type; + + public: + // Probe each implementation in order. + // disjunction provides short circuting wrt instantiation. + static constexpr InvokeHashTag value = absl::disjunction< + Probe<ProbeUniquelyRepresented, InvokeHashTag::kUniquelyRepresented>, + Probe<ProbeHashValue, InvokeHashTag::kHashValue>, +#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + Probe<ProbeLegacyHash, InvokeHashTag::kLegacyHash>, +#endif // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + Probe<ProbeStdHash, InvokeHashTag::kStdHash>, + Probe<ProbeNone, InvokeHashTag::kNone>>::kTag; +}; + +template <typename T> +struct is_hashable : std::integral_constant<bool, HashSelect<T>::value != + InvokeHashTag::kNone> {}; + +template <typename H, typename T> +absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kUniquelyRepresented, + H> +InvokeHash(H state, const T& value) { + return hash_internal::hash_bytes(std::move(state), value); +} + +template <typename H, typename T> +absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kHashValue, H> +InvokeHash(H state, const T& value) { + return AbslHashValue(std::move(state), value); +} + +#if ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ +template <typename H, typename T> +absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kLegacyHash, H> +InvokeHash(H state, const T& value) { + return hash_internal::hash_bytes( + std::move(state), ABSL_INTERNAL_LEGACY_HASH_NAMESPACE::hash<T>{}(value)); +} +#endif // ABSL_HASH_INTERNAL_SUPPORT_LEGACY_HASH_ + +template <typename H, typename T> +absl::enable_if_t<HashSelect<T>::value == InvokeHashTag::kStdHash, H> +InvokeHash(H state, const T& value) { + return hash_internal::hash_bytes(std::move(state), std::hash<T>{}(value)); +} + +// CityHashState +class CityHashState : public HashStateBase<CityHashState> { + // absl::uint128 is not an alias or a thin wrapper around the intrinsic. + // We use the intrinsic when available to improve performance. +#ifdef ABSL_HAVE_INTRINSIC_INT128 + using uint128 = __uint128_t; +#else // ABSL_HAVE_INTRINSIC_INT128 + using uint128 = absl::uint128; +#endif // ABSL_HAVE_INTRINSIC_INT128 + + static constexpr uint64_t kMul = + sizeof(size_t) == 4 ? uint64_t{0xcc9e2d51} : uint64_t{0x9ddfea08eb382d69}; + + template <typename T> + using IntegralFastPath = + conjunction<std::is_integral<T>, is_uniquely_represented<T>>; + + public: + // Move only + CityHashState(CityHashState&&) = default; + CityHashState& operator=(CityHashState&&) = default; + + // CityHashState::combine_contiguous() + // + // Fundamental base case for hash recursion: mixes the given range of bytes + // into the hash state. + static CityHashState combine_contiguous(CityHashState hash_state, + const unsigned char* first, + size_t size) { + return CityHashState( + CombineContiguousImpl(hash_state.state_, first, size, + std::integral_constant<int, sizeof(size_t)>{})); + } + using CityHashState::HashStateBase::combine_contiguous; + + // CityHashState::hash() + // + // For performance reasons in non-opt mode, we specialize this for + // integral types. + // Otherwise we would be instantiating and calling dozens of functions for + // something that is just one multiplication and a couple xor's. + // The result should be the same as running the whole algorithm, but faster. + template <typename T, absl::enable_if_t<IntegralFastPath<T>::value, int> = 0> + static size_t hash(T value) { + return static_cast<size_t>(Mix(Seed(), static_cast<uint64_t>(value))); + } + + // Overload of CityHashState::hash() + template <typename T, absl::enable_if_t<!IntegralFastPath<T>::value, int> = 0> + static size_t hash(const T& value) { + return static_cast<size_t>(combine(CityHashState{}, value).state_); + } + + private: + // Invoked only once for a given argument; that plus the fact that this is + // move-only ensures that there is only one non-moved-from object. + CityHashState() : state_(Seed()) {} + + // Workaround for MSVC bug. + // We make the type copyable to fix the calling convention, even though we + // never actually copy it. Keep it private to not affect the public API of the + // type. + CityHashState(const CityHashState&) = default; + + explicit CityHashState(uint64_t state) : state_(state) {} + + // Implementation of the base case for combine_contiguous where we actually + // mix the bytes into the state. + // Dispatch to different implementations of the combine_contiguous depending + // on the value of `sizeof(size_t)`. + static uint64_t CombineContiguousImpl(uint64_t state, + const unsigned char* first, size_t len, + std::integral_constant<int, 4> + /* sizeof_size_t */); + static uint64_t CombineContiguousImpl(uint64_t state, + const unsigned char* first, size_t len, + std::integral_constant<int, 8> + /* sizeof_size_t*/); + + // Reads 9 to 16 bytes from p. + // The first 8 bytes are in .first, the rest (zero padded) bytes are in + // .second. + static std::pair<uint64_t, uint64_t> Read9To16(const unsigned char* p, + size_t len) { + uint64_t high = little_endian::Load64(p + len - 8); + return {little_endian::Load64(p), high >> (128 - len * 8)}; + } + + // Reads 4 to 8 bytes from p. Zero pads to fill uint64_t. + static uint64_t Read4To8(const unsigned char* p, size_t len) { + return (static_cast<uint64_t>(little_endian::Load32(p + len - 4)) + << (len - 4) * 8) | + little_endian::Load32(p); + } + + // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t. + static uint32_t Read1To3(const unsigned char* p, size_t len) { + return static_cast<uint32_t>((p[0]) | // + (p[len / 2] << (len / 2 * 8)) | // + (p[len - 1] << ((len - 1) * 8))); + } + + ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Mix(uint64_t state, uint64_t v) { + using MultType = + absl::conditional_t<sizeof(size_t) == 4, uint64_t, uint128>; + // We do the addition in 64-bit space to make sure the 128-bit + // multiplication is fast. If we were to do it as MultType the compiler has + // to assume that the high word is non-zero and needs to perform 2 + // multiplications instead of one. + MultType m = state + v; + m *= kMul; + return static_cast<uint64_t>(m ^ (m >> (sizeof(m) * 8 / 2))); + } + + // Seed() + // + // A non-deterministic seed. + // + // The current purpose of this seed is to generate non-deterministic results + // and prevent having users depend on the particular hash values. + // It is not meant as a security feature right now, but it leaves the door + // open to upgrade it to a true per-process random seed. A true random seed + // costs more and we don't need to pay for that right now. + // + // On platforms with ASLR, we take advantage of it to make a per-process + // random value. + // See https://en.wikipedia.org/wiki/Address_space_layout_randomization + // + // On other platforms this is still going to be non-deterministic but most + // probably per-build and not per-process. + ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Seed() { + return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(kSeed)); + } + static const void* const kSeed; + + uint64_t state_; +}; + +// CityHashState::CombineContiguousImpl() +inline uint64_t CityHashState::CombineContiguousImpl( + uint64_t state, const unsigned char* first, size_t len, + std::integral_constant<int, 4> /* sizeof_size_t */) { + // For large values we use CityHash, for small ones we just use a + // multiplicative hash. + uint64_t v; + if (len > 8) { + v = absl::hash_internal::CityHash32(reinterpret_cast<const char*>(first), len); + } else if (len >= 4) { + v = Read4To8(first, len); + } else if (len > 0) { + v = Read1To3(first, len); + } else { + // Empty ranges have no effect. + return state; + } + return Mix(state, v); +} + +// Overload of CityHashState::CombineContiguousImpl() +inline uint64_t CityHashState::CombineContiguousImpl( + uint64_t state, const unsigned char* first, size_t len, + std::integral_constant<int, 8> /* sizeof_size_t */) { + // For large values we use CityHash, for small ones we just use a + // multiplicative hash. + uint64_t v; + if (len > 16) { + v = absl::hash_internal::CityHash64(reinterpret_cast<const char*>(first), len); + } else if (len > 8) { + auto p = Read9To16(first, len); + state = Mix(state, p.first); + v = p.second; + } else if (len >= 4) { + v = Read4To8(first, len); + } else if (len > 0) { + v = Read1To3(first, len); + } else { + // Empty ranges have no effect. + return state; + } + return Mix(state, v); +} + + +struct AggregateBarrier {}; + +// HashImpl + +// Add a private base class to make sure this type is not an aggregate. +// Aggregates can be aggregate initialized even if the default constructor is +// deleted. +struct PoisonedHash : private AggregateBarrier { + PoisonedHash() = delete; + PoisonedHash(const PoisonedHash&) = delete; + PoisonedHash& operator=(const PoisonedHash&) = delete; +}; + +template <typename T> +struct HashImpl { + size_t operator()(const T& value) const { return CityHashState::hash(value); } +}; + +template <typename T> +struct Hash + : absl::conditional_t<is_hashable<T>::value, HashImpl<T>, PoisonedHash> {}; + +template <typename H> +template <typename T, typename... Ts> +H HashStateBase<H>::combine(H state, const T& value, const Ts&... values) { + return H::combine(hash_internal::InvokeHash(std::move(state), value), + values...); +} + +// HashStateBase::combine_contiguous() +template <typename H> +template <typename T> +H HashStateBase<H>::combine_contiguous(H state, const T* data, size_t size) { + return hash_internal::hash_range_or_bytes(std::move(state), data, size); +} +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl + +#endif // ABSL_HASH_INTERNAL_HASH_H_ diff --git a/absl/hash/internal/print_hash_of.cc b/absl/hash/internal/print_hash_of.cc new file mode 100644 index 00000000..b6df31cc --- /dev/null +++ b/absl/hash/internal/print_hash_of.cc @@ -0,0 +1,23 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include <cstdlib> + +#include "absl/hash/hash.h" + +// Prints the hash of argv[1]. +int main(int argc, char** argv) { + if (argc < 2) return 1; + printf("%zu\n", absl::Hash<int>{}(std::atoi(argv[1]))); // NOLINT +} diff --git a/absl/hash/internal/spy_hash_state.h b/absl/hash/internal/spy_hash_state.h new file mode 100644 index 00000000..1886d2ef --- /dev/null +++ b/absl/hash/internal/spy_hash_state.h @@ -0,0 +1,220 @@ +// Copyright 2018 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_ +#define ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_ + +#include <ostream> +#include <string> +#include <vector> + +#include "absl/hash/hash.h" +#include "absl/strings/match.h" +#include "absl/strings/str_format.h" +#include "absl/strings/str_join.h" + +namespace absl { +inline namespace lts_2018_12_18 { +namespace hash_internal { + +// SpyHashState is an implementation of the HashState API that simply +// accumulates all input bytes in an internal buffer. This makes it useful +// for testing AbslHashValue overloads (so long as they are templated on the +// HashState parameter), since it can report the exact hash representation +// that the AbslHashValue overload produces. +// +// Sample usage: +// EXPECT_EQ(SpyHashState::combine(SpyHashState(), foo), +// SpyHashState::combine(SpyHashState(), bar)); +template <typename T> +class SpyHashStateImpl : public HashStateBase<SpyHashStateImpl<T>> { + public: + SpyHashStateImpl() + : error_(std::make_shared<absl::optional<std::string>>()) { + static_assert(std::is_void<T>::value, ""); + } + + // Move-only + SpyHashStateImpl(const SpyHashStateImpl&) = delete; + SpyHashStateImpl& operator=(const SpyHashStateImpl&) = delete; + + SpyHashStateImpl(SpyHashStateImpl&& other) noexcept { + *this = std::move(other); + } + + SpyHashStateImpl& operator=(SpyHashStateImpl&& other) noexcept { + hash_representation_ = std::move(other.hash_representation_); + error_ = other.error_; + moved_from_ = other.moved_from_; + other.moved_from_ = true; + return *this; + } + + template <typename U> + SpyHashStateImpl(SpyHashStateImpl<U>&& other) { // NOLINT + hash_representation_ = std::move(other.hash_representation_); + error_ = other.error_; + moved_from_ = other.moved_from_; + other.moved_from_ = true; + } + + template <typename A, typename... Args> + static SpyHashStateImpl combine(SpyHashStateImpl s, const A& a, + const Args&... args) { + // Pass an instance of SpyHashStateImpl<A> when trying to combine `A`. This + // allows us to test that the user only uses this instance for combine calls + // and does not call AbslHashValue directly. + // See AbslHashValue implementation at the bottom. + s = SpyHashStateImpl<A>::HashStateBase::combine(std::move(s), a); + return SpyHashStateImpl::combine(std::move(s), args...); + } + static SpyHashStateImpl combine(SpyHashStateImpl s) { + if (direct_absl_hash_value_error_) { + *s.error_ = "AbslHashValue should not be invoked directly."; + } else if (s.moved_from_) { + *s.error_ = "Used moved-from instance of the hash state object."; + } + return s; + } + + static void SetDirectAbslHashValueError() { + direct_absl_hash_value_error_ = true; + } + + // Two SpyHashStateImpl objects are equal if they hold equal hash + // representations. + friend bool operator==(const SpyHashStateImpl& lhs, + const SpyHashStateImpl& rhs) { + return lhs.hash_representation_ == rhs.hash_representation_; + } + + friend bool operator!=(const SpyHashStateImpl& lhs, + const SpyHashStateImpl& rhs) { + return !(lhs == rhs); + } + + enum class CompareResult { + kEqual, + kASuffixB, + kBSuffixA, + kUnequal, + }; + + static CompareResult Compare(const SpyHashStateImpl& a, + const SpyHashStateImpl& b) { + const std::string a_flat = absl::StrJoin(a.hash_representation_, ""); + const std::string b_flat = absl::StrJoin(b.hash_representation_, ""); + if (a_flat == b_flat) return CompareResult::kEqual; + if (absl::EndsWith(a_flat, b_flat)) return CompareResult::kBSuffixA; + if (absl::EndsWith(b_flat, a_flat)) return CompareResult::kASuffixB; + return CompareResult::kUnequal; + } + + // operator<< prints the hash representation as a hex and ASCII dump, to + // facilitate debugging. + friend std::ostream& operator<<(std::ostream& out, + const SpyHashStateImpl& hash_state) { + out << "[\n"; + for (auto& s : hash_state.hash_representation_) { + size_t offset = 0; + for (char c : s) { + if (offset % 16 == 0) { + out << absl::StreamFormat("\n0x%04x: ", offset); + } + if (offset % 2 == 0) { + out << " "; + } + out << absl::StreamFormat("%02x", c); + ++offset; + } + out << "\n"; + } + return out << "]"; + } + + // The base case of the combine recursion, which writes raw bytes into the + // internal buffer. + static SpyHashStateImpl combine_contiguous(SpyHashStateImpl hash_state, + const unsigned char* begin, + size_t size) { + hash_state.hash_representation_.emplace_back( + reinterpret_cast<const char*>(begin), size); + return hash_state; + } + + using SpyHashStateImpl::HashStateBase::combine_contiguous; + + absl::optional<std::string> error() const { + if (moved_from_) { + return "Returned a moved-from instance of the hash state object."; + } + return *error_; + } + + private: + template <typename U> + friend class SpyHashStateImpl; + + // This is true if SpyHashStateImpl<T> has been passed to a call of + // AbslHashValue with the wrong type. This detects that the user called + // AbslHashValue directly (because the hash state type does not match). + static bool direct_absl_hash_value_error_; + + + std::vector<std::string> hash_representation_; + // This is a shared_ptr because we want all instances of the particular + // SpyHashState run to share the field. This way we can set the error for + // use-after-move and all the copies will see it. + std::shared_ptr<absl::optional<std::string>> error_; + bool moved_from_ = false; +}; + +template <typename T> +bool SpyHashStateImpl<T>::direct_absl_hash_value_error_; + +template <bool& B> +struct OdrUse { + constexpr OdrUse() {} + bool& b = B; +}; + +template <void (*)()> +struct RunOnStartup { + static bool run; + static constexpr OdrUse<run> kOdrUse{}; +}; + +template <void (*f)()> +bool RunOnStartup<f>::run = (f(), true); + +template < + typename T, typename U, + // Only trigger for when (T != U), + absl::enable_if_t<!std::is_same<T, U>::value, int> = 0, + // This statement works in two ways: + // - First, it instantiates RunOnStartup and forces the initialization of + // `run`, which set the global variable. + // - Second, it triggers a SFINAE error disabling the overload to prevent + // compile time errors. If we didn't disable the overload we would get + // ambiguous overload errors, which we don't want. + int = RunOnStartup<SpyHashStateImpl<T>::SetDirectAbslHashValueError>::run> +void AbslHashValue(SpyHashStateImpl<T>, const U&); + +using SpyHashState = SpyHashStateImpl<void>; + +} // namespace hash_internal +} // inline namespace lts_2018_12_18 +} // namespace absl + +#endif // ABSL_HASH_INTERNAL_SPY_HASH_STATE_H_ |