forked from OSchip/llvm-project
86 lines
2.8 KiB
C++
86 lines
2.8 KiB
C++
//===-- Support/DJB.cpp ---DJB Hash -----------------------------*- 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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// This file contains support for the DJ Bernstein hash function.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/DJB.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/ConvertUTF.h"
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#include "llvm/Support/Unicode.h"
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using namespace llvm;
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static UTF32 chopOneUTF32(StringRef &Buffer) {
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UTF32 C;
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const UTF8 *const Begin8Const =
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reinterpret_cast<const UTF8 *>(Buffer.begin());
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const UTF8 *Begin8 = Begin8Const;
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UTF32 *Begin32 = &C;
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// In lenient mode we will always end up with a "reasonable" value in C for
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// non-empty input.
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assert(!Buffer.empty());
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ConvertUTF8toUTF32(&Begin8, reinterpret_cast<const UTF8 *>(Buffer.end()),
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&Begin32, &C + 1, lenientConversion);
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Buffer = Buffer.drop_front(Begin8 - Begin8Const);
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return C;
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}
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static StringRef toUTF8(UTF32 C, MutableArrayRef<UTF8> Storage) {
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const UTF32 *Begin32 = &C;
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UTF8 *Begin8 = Storage.begin();
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// The case-folded output should always be a valid unicode character, so use
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// strict mode here.
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ConversionResult CR = ConvertUTF32toUTF8(&Begin32, &C + 1, &Begin8,
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Storage.end(), strictConversion);
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assert(CR == conversionOK && "Case folding produced invalid char?");
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(void)CR;
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return StringRef(reinterpret_cast<char *>(Storage.begin()),
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Begin8 - Storage.begin());
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}
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static UTF32 foldCharDwarf(UTF32 C) {
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// DWARF v5 addition to the unicode folding rules.
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// Fold "Latin Small Letter Dotless I" and "Latin Capital Letter I With Dot
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// Above" into "i".
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if (C == 0x130 || C == 0x131)
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return 'i';
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return sys::unicode::foldCharSimple(C);
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}
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static uint32_t caseFoldingDjbHashCharSlow(StringRef &Buffer, uint32_t H) {
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UTF32 C = chopOneUTF32(Buffer);
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C = foldCharDwarf(C);
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std::array<UTF8, UNI_MAX_UTF8_BYTES_PER_CODE_POINT> Storage;
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StringRef Folded = toUTF8(C, Storage);
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return djbHash(Folded, H);
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}
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uint32_t llvm::caseFoldingDjbHash(StringRef Buffer, uint32_t H) {
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while (!Buffer.empty()) {
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unsigned char C = Buffer.front();
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if (LLVM_LIKELY(C <= 0x7f)) {
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// US-ASCII, encoded as one character in utf-8.
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// This is by far the most common case, so handle this specially.
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if (C >= 'A' && C <= 'Z')
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C = 'a' + (C - 'A'); // fold uppercase into lowercase
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H = (H << 5) + H + C;
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Buffer = Buffer.drop_front();
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continue;
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}
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H = caseFoldingDjbHashCharSlow(Buffer, H);
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}
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return H;
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}
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