58 lines · cpp
1//===- llvm/BinaryFormat/COFF.cpp - The COFF format -----------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "llvm/BinaryFormat/COFF.h"10#include "llvm/ADT/SmallVector.h"11#include "llvm/ADT/Twine.h"12 13// Maximum offsets for different string table entry encodings.14enum : unsigned { Max7DecimalOffset = 9999999U };15enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 016 17// Encode a string table entry offset in base 64, padded to 6 chars, and18// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...19// Buffer must be at least 8 bytes large. No terminating null appended.20static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {21 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&22 "Illegal section name encoding for value");23 24 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"25 "abcdefghijklmnopqrstuvwxyz"26 "0123456789+/";27 28 Buffer[0] = '/';29 Buffer[1] = '/';30 31 char *Ptr = Buffer + 7;32 for (unsigned i = 0; i < 6; ++i) {33 unsigned Rem = Value % 64;34 Value /= 64;35 *(Ptr--) = Alphabet[Rem];36 }37}38 39bool llvm::COFF::encodeSectionName(char *Out, uint64_t Offset) {40 if (Offset <= Max7DecimalOffset) {41 // Offsets of 7 digits or less are encoded in ASCII.42 SmallVector<char, COFF::NameSize> Buffer;43 Twine('/').concat(Twine(Offset)).toVector(Buffer);44 assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);45 std::memcpy(Out, Buffer.data(), Buffer.size());46 return true;47 }48 49 if (Offset <= MaxBase64Offset) {50 // Starting with 10,000,000, offsets are encoded as base64.51 encodeBase64StringEntry(Out, Offset);52 return true;53 }54 55 // The offset is too large to be encoded.56 return false;57}58