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author | davidben <davidben@chromium.org> | 2016-01-20 17:40:42 -0800 |
---|---|---|
committer | Commit bot <commit-bot@chromium.org> | 2016-01-21 01:41:32 +0000 |
commit | 021a2b496a7eb7222c0c7f4d8cd01d697c3f2dda (patch) | |
tree | d1af96a93a7e2f4defa4c680bc50a3170f06561a /base/hash.h | |
parent | 38b5efd43f39caec997e343801e3ae712d4c67ad (diff) | |
download | chromium_src-021a2b496a7eb7222c0c7f4d8cd01d697c3f2dda.zip chromium_src-021a2b496a7eb7222c0c7f4d8cd01d697c3f2dda.tar.gz chromium_src-021a2b496a7eb7222c0c7f4d8cd01d697c3f2dda.tar.bz2 |
Revert of Allow std::unordered_*. (patchset #15 id:280001 of https://codereview.chromium.org/1502373009/ )
Reason for revert:
MSan build failure.
https://build.chromium.org/p/chromium.memory.fyi/builders/Chromium%20Linux%20ChromeOS%20MSan%20Builder/builds/12498
Original issue's description:
> Allow std::unordered_*.
>
> base::hash_* is, as a transition step, implemented in terms of
> std::unordered_*. Later commits will convert existing uses.
>
> Also fix a host of IWYU problems that arose from this CL.
>
> (NOPRESUBMIT because the wstring presubmit check is overzealous
> and complains about the reference to wstring in the comment.)
>
> NOPRESUBMIT=true
> BUG=576864
> TBR=derat@chromium.org,blundell@chromium.org,jbauman@chromium.org,dalecurtis@chromium.org
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/3f37f7f1459e7b5a452c0e433493e0a6e9649ca7
> Cr-Commit-Position: refs/heads/master@{#370553}
TBR=danakj@chromium.org,thakis@chromium.org,derat@chromium.org,blundell@chromium.org,dalecurtis@chromium.org,jbauman@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=576864
Review URL: https://codereview.chromium.org/1610023003
Cr-Commit-Position: refs/heads/master@{#370559}
Diffstat (limited to 'base/hash.h')
-rw-r--r-- | base/hash.h | 81 |
1 files changed, 0 insertions, 81 deletions
diff --git a/base/hash.h b/base/hash.h index d5dc549..ed8d9fd 100644 --- a/base/hash.h +++ b/base/hash.h @@ -10,7 +10,6 @@ #include <limits> #include <string> -#include <utility> #include "base/base_export.h" #include "base/logging.h" @@ -36,86 +35,6 @@ inline uint32_t Hash(const std::string& str) { return Hash(str.data(), str.size()); } -// Implement hashing for pairs of at-most 32 bit integer values. -// When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using -// multiply-add hashing. This algorithm, as described in -// Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in -// eingeschränkten Branchingprogrammmodellen" by Woelfel, is: -// -// h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32 -// -// Contact danakj@chromium.org for any questions. -inline size_t HashInts32(uint32_t value1, uint32_t value2) { - uint64_t value1_64 = value1; - uint64_t hash64 = (value1_64 << 32) | value2; - - if (sizeof(size_t) >= sizeof(uint64_t)) - return static_cast<size_t>(hash64); - - uint64_t odd_random = 481046412LL << 32 | 1025306955LL; - uint32_t shift_random = 10121U << 16; - - hash64 = hash64 * odd_random + shift_random; - size_t high_bits = static_cast<size_t>( - hash64 >> (8 * (sizeof(uint64_t) - sizeof(size_t)))); - return high_bits; -} - -// Implement hashing for pairs of up-to 64-bit integer values. -// We use the compound integer hash method to produce a 64-bit hash code, by -// breaking the two 64-bit inputs into 4 32-bit values: -// http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000 -// Then we reduce our result to 32 bits if required, similar to above. -inline size_t HashInts64(uint64_t value1, uint64_t value2) { - uint32_t short_random1 = 842304669U; - uint32_t short_random2 = 619063811U; - uint32_t short_random3 = 937041849U; - uint32_t short_random4 = 3309708029U; - - uint32_t value1a = static_cast<uint32_t>(value1 & 0xffffffff); - uint32_t value1b = static_cast<uint32_t>((value1 >> 32) & 0xffffffff); - uint32_t value2a = static_cast<uint32_t>(value2 & 0xffffffff); - uint32_t value2b = static_cast<uint32_t>((value2 >> 32) & 0xffffffff); - - uint64_t product1 = static_cast<uint64_t>(value1a) * short_random1; - uint64_t product2 = static_cast<uint64_t>(value1b) * short_random2; - uint64_t product3 = static_cast<uint64_t>(value2a) * short_random3; - uint64_t product4 = static_cast<uint64_t>(value2b) * short_random4; - - uint64_t hash64 = product1 + product2 + product3 + product4; - - if (sizeof(size_t) >= sizeof(uint64_t)) - return static_cast<size_t>(hash64); - - uint64_t odd_random = 1578233944LL << 32 | 194370989LL; - uint32_t shift_random = 20591U << 16; - - hash64 = hash64 * odd_random + shift_random; - size_t high_bits = static_cast<size_t>( - hash64 >> (8 * (sizeof(uint64_t) - sizeof(size_t)))); - return high_bits; -} - -template<typename T1, typename T2> -inline size_t HashInts(T1 value1, T2 value2) { - // This condition is expected to be compile-time evaluated and optimised away - // in release builds. - if (sizeof(T1) > sizeof(uint32_t) || (sizeof(T2) > sizeof(uint32_t))) - return HashInts64(value1, value2); - - return HashInts32(value1, value2); -} - -// A templated hasher for pairs of integer types. -template<typename T> struct IntPairHash; - -template<typename Type1, typename Type2> -struct IntPairHash<std::pair<Type1, Type2>> { - size_t operator()(std::pair<Type1, Type2> value) const { - return HashInts(value.first, value.second); - } -}; - } // namespace base #endif // BASE_HASH_H_ |