6024e5c395
clang 20.0.0 (based on r547379) from build 12806354. Bug: http://b/379133546 Test: N/A Change-Id: I2eb8938af55d809de674be63cb30cf27e801862b Upstream-Commit: ad834e67b1105d15ef907f6255d4c96e8e733f57
53 lines
2.0 KiB
C++
53 lines
2.0 KiB
C++
//===--- SipHash.h - An ABI-stable string SipHash ---------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// An implementation of SipHash, a hash function optimized for speed on
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// short inputs. Based on the SipHash reference implementation.
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//
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// Also provides one specific wrapper on top of SipHash-2-4-64 to compute
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// compute ABI-stable ptrauth discriminators.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_SIPHASH_H
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#define LLVM_SUPPORT_SIPHASH_H
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#include <cstdint>
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namespace llvm {
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template <typename T> class ArrayRef;
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class StringRef;
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/// Computes a SipHash-2-4 64-bit result.
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void getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
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uint8_t (&Out)[8]);
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/// Computes a SipHash-2-4 128-bit result.
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void getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
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uint8_t (&Out)[16]);
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/// Compute a stable non-zero 16-bit hash of the given string.
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///
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/// The exact algorithm is the little-endian interpretation of the
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/// non-doubled (i.e. 64-bit) result of applying a SipHash-2-4 using
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/// a specific seed value which can be found in the source.
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/// This 64-bit result is truncated to a non-zero 16-bit value.
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///
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/// We use a 16-bit discriminator because ARM64 can efficiently load
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/// a 16-bit immediate into the high bits of a register without disturbing
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/// the remainder of the value, which serves as a nice blend operation.
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/// 16 bits is also sufficiently compact to not inflate a loader relocation.
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/// We disallow zero to guarantee a different discriminator from the places
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/// in the ABI that use a constant zero.
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uint16_t getPointerAuthStableSipHash(StringRef S);
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} // end namespace llvm
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#endif
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