Index: llvm/include/llvm/ADT/StringExtras.h =================================================================== --- llvm/include/llvm/ADT/StringExtras.h +++ llvm/include/llvm/ADT/StringExtras.h @@ -67,22 +67,27 @@ /// /// If \p C is not a valid hex digit, -1U is returned. inline unsigned hexDigitValue(char C) { - struct HexTable { - unsigned LUT[255] = {}; - constexpr HexTable() { - // Default initialize everything to invalid. - for (int i = 0; i < 255; ++i) - LUT[i] = ~0U; - // Initialize `0`-`9`. - for (int i = 0; i < 10; ++i) - LUT['0' + i] = i; - // Initialize `A`-`F` and `a`-`f`. - for (int i = 0; i < 6; ++i) - LUT['A' + i] = LUT['a' + i] = 10 + i; - } + /* clang-format off */ + static const int16_t LUT[256] = { + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, // '0'..'9' + -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 'A'..'F' + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 'a'..'f' + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; - constexpr HexTable Table; - return Table.LUT[static_cast(C)]; + /* clang-format on */ + return LUT[static_cast(C)]; } /// Checks if character \p C is one of the 10 decimal digits. @@ -210,24 +215,31 @@ if (Input.empty()) return true; - Output.reserve((Input.size() + 1) / 2); + // If the input string is not properly aligned on 2 nibbles we pad out the + // front with a 0 prefix; e.g. `ABC` -> `0ABC`. + Output.resize((Input.size() + 1) / 2); + char *OutputPtr = const_cast(Output.data()); if (Input.size() % 2 == 1) { uint8_t Hex = 0; if (!tryGetHexFromNibbles('0', Input.front(), Hex)) return false; - - Output.push_back(Hex); + *OutputPtr++ = Hex; Input = Input.drop_front(); } - assert(Input.size() % 2 == 0); - while (!Input.empty()) { + // Convert the nibble pairs (e.g. `9C`) into bytes (0x9C). + // With the padding above we know the input is aligned and the output expects + // exactly half as many bytes as nibbles in the input. + size_t InputSize = Input.size(); + assert(InputSize % 2 == 0); + const char *InputPtr = Input.data(); + for (size_t OutputIndex = 0; OutputIndex < InputSize / 2; ++OutputIndex) { uint8_t Hex = 0; - if (!tryGetHexFromNibbles(Input[0], Input[1], Hex)) + if (!tryGetHexFromNibbles(InputPtr[OutputIndex * 2 + 0], // MSB + InputPtr[OutputIndex * 2 + 1], // LSB + Hex)) return false; - - Output.push_back(Hex); - Input = Input.drop_front(2); + OutputPtr[OutputIndex] = Hex; } return true; } Index: llvm/unittests/ADT/StringExtrasTest.cpp =================================================================== --- llvm/unittests/ADT/StringExtrasTest.cpp +++ llvm/unittests/ADT/StringExtrasTest.cpp @@ -90,7 +90,7 @@ EXPECT_EQ(EvenData, fromHex(EvenStr)); EXPECT_EQ(StringRef(EvenStr).lower(), toHex(EvenData, true)); - std::string InvalidStr = "A5ZX"; + std::string InvalidStr = "A50\xFF"; std::string IgnoredOutput; EXPECT_FALSE(tryGetFromHex(InvalidStr, IgnoredOutput)); }