58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
//===- llvm/BinaryFormat/COFF.cpp - The COFF format -----------------------===//
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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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#include "llvm/BinaryFormat/COFF.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Twine.h"
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// Maximum offsets for different string table entry encodings.
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enum : unsigned { Max7DecimalOffset = 9999999U };
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enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0
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// Encode a string table entry offset in base 64, padded to 6 chars, and
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// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
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// Buffer must be at least 8 bytes large. No terminating null appended.
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static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
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assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
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"Illegal section name encoding for value");
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static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
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"abcdefghijklmnopqrstuvwxyz"
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"0123456789+/";
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Buffer[0] = '/';
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Buffer[1] = '/';
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char *Ptr = Buffer + 7;
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for (unsigned i = 0; i < 6; ++i) {
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unsigned Rem = Value % 64;
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Value /= 64;
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*(Ptr--) = Alphabet[Rem];
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}
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}
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bool llvm::COFF::encodeSectionName(char *Out, uint64_t Offset) {
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if (Offset <= Max7DecimalOffset) {
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// Offsets of 7 digits or less are encoded in ASCII.
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SmallVector<char, COFF::NameSize> Buffer;
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Twine('/').concat(Twine(Offset)).toVector(Buffer);
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assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
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std::memcpy(Out, Buffer.data(), Buffer.size());
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return true;
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}
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if (Offset <= MaxBase64Offset) {
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// Starting with 10,000,000, offsets are encoded as base64.
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encodeBase64StringEntry(Out, Offset);
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return true;
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}
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// The offset is too large to be encoded.
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return false;
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}
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