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//===-- Support/DJB.cpp ---DJB Hash -----------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains support for the DJ Bernstein hash function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/DJB.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ConvertUTF.h"
#include "llvm/Support/Unicode.h"
using namespace llvm;
static UTF32 chopOneUTF32(StringRef &Buffer) {
UTF32 C;
const UTF8 *const Begin8Const =
reinterpret_cast<const UTF8 *>(Buffer.begin());
const UTF8 *Begin8 = Begin8Const;
UTF32 *Begin32 = &C;
// In lenient mode we will always end up with a "reasonable" value in C for
// non-empty input.
assert(!Buffer.empty());
ConvertUTF8toUTF32(&Begin8, reinterpret_cast<const UTF8 *>(Buffer.end()),
&Begin32, &C + 1, lenientConversion);
Buffer = Buffer.drop_front(Begin8 - Begin8Const);
return C;
}
static StringRef toUTF8(UTF32 C, MutableArrayRef<UTF8> Storage) {
const UTF32 *Begin32 = &C;
UTF8 *Begin8 = Storage.begin();
// The case-folded output should always be a valid unicode character, so use
// strict mode here.
ConversionResult CR = ConvertUTF32toUTF8(&Begin32, &C + 1, &Begin8,
Storage.end(), strictConversion);
assert(CR == conversionOK && "Case folding produced invalid char?");
(void)CR;
return StringRef(reinterpret_cast<char *>(Storage.begin()),
Begin8 - Storage.begin());
}
static UTF32 foldCharDwarf(UTF32 C) {
// DWARF v5 addition to the unicode folding rules.
// Fold "Latin Small Letter Dotless I" and "Latin Capital Letter I With Dot
// Above" into "i".
if (C == 0x130 || C == 0x131)
return 'i';
return sys::unicode::foldCharSimple(C);
}
static std::optional<uint32_t> fastCaseFoldingDjbHash(StringRef Buffer,
uint32_t H) {
bool AllASCII = true;
for (unsigned char C : Buffer) {
H = H * 33 + ('A' <= C && C <= 'Z' ? C - 'A' + 'a' : C);
AllASCII &= C <= 0x7f;
}
if (AllASCII)
return H;
return std::nullopt;
}
uint32_t llvm::caseFoldingDjbHash(StringRef Buffer, uint32_t H) {
if (std::optional<uint32_t> Result = fastCaseFoldingDjbHash(Buffer, H))
return *Result;
std::array<UTF8, UNI_MAX_UTF8_BYTES_PER_CODE_POINT> Storage;
while (!Buffer.empty()) {
UTF32 C = foldCharDwarf(chopOneUTF32(Buffer));
StringRef Folded = toUTF8(C, Storage);
H = djbHash(Folded, H);
}
return H;
}
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