text: //===-- StringRef.cpp - Lightweight String References ---------------------===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ADT/StringRef.h"
  #include "llvm/ADT/Hashing.h"
  #include "llvm/Support/Error.h"
  #include <bitset>
  
  using namespace llvm;
  
  // MSVC emits references to this into the translation units which reference it.
  #ifndef _MSC_VER
  constexpr size_t StringRef::npos;
  #endif
  
  // strncasecmp() is not available on non-POSIX systems, so define an
  // alternative function here.
  static int ascii_strncasecmp(const char *LHS, const char *RHS, size_t Length) {
    for (size_t I = 0; I < Length; ++I) {
      unsigned char LHC = toLower(LHS[I]);
      unsigned char RHC = toLower(RHS[I]);
      if (LHC != RHC)
        return LHC < RHC ? -1 : 1;
    }
    return 0;
  }
  
  /// compare_lower - Compare strings, ignoring case.
  int StringRef::compare_lower(StringRef RHS) const {
    if (int Res = ascii_strncasecmp(Data, RHS.Data, std::min(Length, RHS.Length)))
      return Res;
    if (Length == RHS.Length)
      return 0;
    return Length < RHS.Length ? -1 : 1;
  }
  
  /// Check if this string starts with the given \p Prefix, ignoring case.
  bool StringRef::startswith_lower(StringRef Prefix) const {
    return Length >= Prefix.Length &&
        ascii_strncasecmp(Data, Prefix.Data, Prefix.Length) == 0;
  }
  
  /// Check if this string ends with the given \p Suffix, ignoring case.
  bool StringRef::endswith_lower(StringRef Suffix) const {
    return Length >= Suffix.Length &&
        ascii_strncasecmp(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
  }
  
  size_t StringRef::find_lower(char C, size_t From) const {
    char L = toLower(C);
    return find_if([L](char D) { return toLower(D) == L; }, From);
  }
  
  /// compare_numeric - Compare strings, handle embedded numbers.
  int StringRef::compare_numeric(StringRef RHS) const {
    for (size_t I = 0, E = std::min(Length, RHS.Length); I != E; ++I) {
      // Check for sequences of digits.
      if (isDigit(Data[I]) && isDigit(RHS.Data[I])) {
        // The longer sequence of numbers is considered larger.
        // This doesn't really handle prefixed zeros well.
        size_t J;
        for (J = I + 1; J != E + 1; ++J) {
          bool ld = J < Length && isDigit(Data[J]);
          bool rd = J < RHS.Length && isDigit(RHS.Data[J]);
          if (ld != rd)
            return rd ? -1 : 1;
          if (!rd)
            break;
        }
        // The two number sequences have the same length (J-I), just memcmp them.
        if (int Res = compareMemory(Data + I, RHS.Data + I, J - I))
          return Res < 0 ? -1 : 1;
        // Identical number sequences, continue search after the numbers.
        I = J - 1;
        continue;
      }
      if (Data[I] != RHS.Data[I])
        return (unsigned char)Data[I] < (unsigned char)RHS.Data[I] ? -1 : 1;
    }
    if (Length == RHS.Length)
      return 0;
    return Length < RHS.Length ? -1 : 1;
  }
  
  //===----------------------------------------------------------------------===//
  // String Operations
  //===----------------------------------------------------------------------===//
  
  std::string StringRef::lower() const {
    std::string Result(size(), char());
    for (size_type i = 0, e = size(); i != e; ++i) {
      Result[i] = toLower(Data[i]);
    }
    return Result;
  }
  
  std::string StringRef::upper() const {
    std::string Result(size(), char());
    for (size_type i = 0, e = size(); i != e; ++i) {
      Result[i] = toUpper(Data[i]);
    }
    return Result;
  }
  
  //===----------------------------------------------------------------------===//
  // String Searching
  //===----------------------------------------------------------------------===//
  
  
  /// find - Search for the first string \arg Str in the string.
  ///
  /// \return - The index of the first occurrence of \arg Str, or npos if not
  /// found.
  size_t StringRef::find(StringRef Str, size_t From) const {
    if (From > Length)
      return npos;
  
    const char *Start = Data + From;
    size_t Size = Length - From;
  
    const char *Needle = Str.data();
    size_t N = Str.size();
    if (N == 0)
      return From;
    if (Size < N)
      return npos;
    if (N == 1) {
      const char *Ptr = (const char *)::memchr(Start, Needle[0], Size);
      return Ptr == nullptr ? npos : Ptr - Data;
    }
  
    const char *Stop = Start + (Size - N + 1);
  
    // For short haystacks or unsupported needles fall back to the naive algorithm
    if (Size < 16 || N > 255) {
      do {
        if (std::memcmp(Start, Needle, N) == 0)
          return Start - Data;
        ++Start;
      } while (Start < Stop);
      return npos;
    }
  
    // Build the bad char heuristic table, with uint8_t to reduce cache thrashing.
    uint8_t BadCharSkip[256];
    std::memset(BadCharSkip, N, 256);
    for (unsigned i = 0; i != N-1; ++i)
      BadCharSkip[(uint8_t)Str[i]] = N-1-i;
  
    do {
      uint8_t Last = Start[N - 1];
      if (LLVM_UNLIKELY(Last == (uint8_t)Needle[N - 1]))
        if (std::memcmp(Start, Needle, N - 1) == 0)
          return Start - Data;
  
      // Otherwise skip the appropriate number of bytes.
      Start += BadCharSkip[Last];
    } while (Start < Stop);
  
    return npos;
  }
  
  size_t StringRef::find_lower(StringRef Str, size_t From) const {
    StringRef This = substr(From);
    while (This.size() >= Str.size()) {
      if (This.startswith_lower(Str))
        return From;
      This = This.drop_front();
      ++From;
    }
    return npos;
  }
  
  size_t StringRef::rfind_lower(char C, size_t From) const {
    From = std::min(From, Length);
    size_t i = From;
    while (i != 0) {
      --i;
      if (toLower(Data[i]) == toLower(C))
        return i;
    }
    return npos;
  }
  
  /// rfind - Search for the last string \arg Str in the string.
  ///
  /// \return - The index of the last occurrence of \arg Str, or npos if not
  /// found.
  size_t StringRef::rfind(StringRef Str) const {
    size_t N = Str.size();
    if (N > Length)
      return npos;
    for (size_t i = Length - N + 1, e = 0; i != e;) {
      --i;
      if (substr(i, N).equals(Str))
        return i;
    }
    return npos;
  }
  
  size_t StringRef::rfind_lower(StringRef Str) const {
    size_t N = Str.size();
    if (N > Length)
      return npos;
    for (size_t i = Length - N + 1, e = 0; i != e;) {
      --i;
      if (substr(i, N).equals_lower(Str))
        return i;
    }
    return npos;
  }
  
  /// find_first_of - Find the first character in the string that is in \arg
  /// Chars, or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  StringRef::size_type StringRef::find_first_of(StringRef Chars,
                                                size_t From) const {
    std::bitset<1 << CHAR_BIT> CharBits;
    for (size_type i = 0; i != Chars.size(); ++i)
      CharBits.set((unsigned char)Chars[i]);
  
    for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
      if (CharBits.test((unsigned char)Data[i]))
        return i;
    return npos;
  }
  
  /// find_first_not_of - Find the first character in the string that is not
  /// \arg C or npos if not found.
  StringRef::size_type StringRef::find_first_not_of(char C, size_t From) const {
    for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
      if (Data[i] != C)
        return i;
    return npos;
  }
  
  /// find_first_not_of - Find the first character in the string that is not
  /// in the string \arg Chars, or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  StringRef::size_type StringRef::find_first_not_of(StringRef Chars,
                                                    size_t From) const {
    std::bitset<1 << CHAR_BIT> CharBits;
    for (size_type i = 0; i != Chars.size(); ++i)
      CharBits.set((unsigned char)Chars[i]);
  
    for (size_type i = std::min(From, Length), e = Length; i != e; ++i)
      if (!CharBits.test((unsigned char)Data[i]))
        return i;
    return npos;
  }
  
  /// find_last_of - Find the last character in the string that is in \arg C,
  /// or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  StringRef::size_type StringRef::find_last_of(StringRef Chars,
                                               size_t From) const {
    std::bitset<1 << CHAR_BIT> CharBits;
    for (size_type i = 0; i != Chars.size(); ++i)
      CharBits.set((unsigned char)Chars[i]);
  
    for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
      if (CharBits.test((unsigned char)Data[i]))
        return i;
    return npos;
  }
  
  /// find_last_not_of - Find the last character in the string that is not
  /// \arg C, or npos if not found.
  StringRef::size_type StringRef::find_last_not_of(char C, size_t From) const {
    for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
      if (Data[i] != C)
        return i;
    return npos;
  }
  
  /// find_last_not_of - Find the last character in the string that is not in
  /// \arg Chars, or npos if not found.
  ///
  /// Note: O(size() + Chars.size())
  StringRef::size_type StringRef::find_last_not_of(StringRef Chars,
                                                   size_t From) const {
    std::bitset<1 << CHAR_BIT> CharBits;
    for (size_type i = 0, e = Chars.size(); i != e; ++i)
      CharBits.set((unsigned char)Chars[i]);
  
    for (size_type i = std::min(From, Length) - 1, e = -1; i != e; --i)
      if (!CharBits.test((unsigned char)Data[i]))
        return i;
    return npos;
  }
  
  void StringRef::split(SmallVectorImpl<StringRef> &A,
                        StringRef Separator, int MaxSplit,
                        bool KeepEmpty) const {
    StringRef S = *this;
  
    // Count down from MaxSplit. When MaxSplit is -1, this will just split
    // "forever". This doesn't support splitting more than 2^31 times
    // intentionally; if we ever want that we can make MaxSplit a 64-bit integer
    // but that seems unlikely to be useful.
    while (MaxSplit-- != 0) {
      size_t Idx = S.find(Separator);
      if (Idx == npos)
        break;
  
      // Push this split.
      if (KeepEmpty || Idx > 0)
        A.push_back(S.slice(0, Idx));
  
      // Jump forward.
      S = S.slice(Idx + Separator.size(), npos);
    }
  
    // Push the tail.
    if (KeepEmpty || !S.empty())
      A.push_back(S);
  }
  
  void StringRef::split(SmallVectorImpl<StringRef> &A, char Separator,
                        int MaxSplit, bool KeepEmpty) const {
    StringRef S = *this;
  
    // Count down from MaxSplit. When MaxSplit is -1, this will just split
    // "forever". This doesn't support splitting more than 2^31 times
    // intentionally; if we ever want that we can make MaxSplit a 64-bit integer
    // but that seems unlikely to be useful.
    while (MaxSplit-- != 0) {
      size_t Idx = S.find(Separator);
      if (Idx == npos)
        break;
  
      // Push this split.
      if (KeepEmpty || Idx > 0)
        A.push_back(S.slice(0, Idx));
  
      // Jump forward.
      S = S.slice(Idx + 1, npos);
    }
  
    // Push the tail.
    if (KeepEmpty || !S.empty())
      A.push_back(S);
  }
  
  //===----------------------------------------------------------------------===//
  // Helpful Algorithms
  //===----------------------------------------------------------------------===//
  
  /// count - Return the number of non-overlapped occurrences of \arg Str in
  /// the string.
  size_t StringRef::count(StringRef Str) const {
    size_t Count = 0;
    size_t N = Str.size();
    if (!N || N > Length)
      return 0;
    for (size_t i = 0, e = Length - N + 1; i < e;) {
      if (substr(i, N).equals(Str)) {
        ++Count;
        i += N;
      }
      else
        ++i;
    }
    return Count;
  }
  
  static unsigned GetAutoSenseRadix(StringRef &Str) {
    if (Str.empty())
      return 10;
  
    if (Str.startswith("0x") || Str.startswith("0X")) {
      Str = Str.substr(2);
      return 16;
    }
  
    if (Str.startswith("0b") || Str.startswith("0B")) {
      Str = Str.substr(2);
      return 2;
    }
  
    if (Str.startswith("0o")) {
      Str = Str.substr(2);
      return 8;
    }
  
    if (Str[0] == '0' && Str.size() > 1 && isDigit(Str[1])) {
      Str = Str.substr(1);
      return 8;
    }
  
    return 10;
  }
  
  bool __swift::__runtime::llvm::consumeUnsignedInteger(
      StringRef &Str, unsigned Radix, unsigned long long &Result) {
    // Autosense radix if not specified.
    if (Radix == 0)
      Radix = GetAutoSenseRadix(Str);
  
    // Empty strings (after the radix autosense) are invalid.
    if (Str.empty()) return true;
  
    // Parse all the bytes of the string given this radix.  Watch for overflow.
    StringRef Str2 = Str;
    Result = 0;
    while (!Str2.empty()) {
      unsigned CharVal;
      if (Str2[0] >= '0' && Str2[0] <= '9')
        CharVal = Str2[0] - '0';
      else if (Str2[0] >= 'a' && Str2[0] <= 'z')
        CharVal = Str2[0] - 'a' + 10;
      else if (Str2[0] >= 'A' && Str2[0] <= 'Z')
        CharVal = Str2[0] - 'A' + 10;
      else
        break;
  
      // If the parsed value is larger than the integer radix, we cannot
      // consume any more characters.
      if (CharVal >= Radix)
        break;
  
      // Add in this character.
      unsigned long long PrevResult = Result;
      Result = Result * Radix + CharVal;
  
      // Check for overflow by shifting back and seeing if bits were lost.
      if (Result / Radix < PrevResult)
        return true;
  
      Str2 = Str2.substr(1);
    }
  
    // We consider the operation a failure if no characters were consumed
    // successfully.
    if (Str.size() == Str2.size())
      return true;
  
    Str = Str2;
    return false;
  }
  
  bool __swift::__runtime::llvm::consumeSignedInteger(
      StringRef &Str, unsigned Radix, long long &Result) {
    unsigned long long ULLVal;
  
    // Handle positive strings first.
    if (Str.empty() || Str.front() != '-') {
      if (consumeUnsignedInteger(Str, Radix, ULLVal) ||
          // Check for value so large it overflows a signed value.
          (long long)ULLVal < 0)
        return true;
      Result = ULLVal;
      return false;
    }
  
    // Get the positive part of the value.
    StringRef Str2 = Str.drop_front(1);
    if (consumeUnsignedInteger(Str2, Radix, ULLVal) ||
        // Reject values so large they'd overflow as negative signed, but allow
        // "-0".  This negates the unsigned so that the negative isn't undefined
        // on signed overflow.
        (long long)-ULLVal > 0)
      return true;
  
    Str = Str2;
    Result = -ULLVal;
    return false;
  }
  
  /// GetAsUnsignedInteger - Workhorse method that converts a integer character
  /// sequence of radix up to 36 to an unsigned long long value.
  bool __swift::__runtime::llvm::getAsUnsignedInteger(
      StringRef Str, unsigned Radix, unsigned long long &Result) {
    if (consumeUnsignedInteger(Str, Radix, Result))
      return true;
  
    // For getAsUnsignedInteger, we require the whole string to be consumed or
    // else we consider it a failure.
    return !Str.empty();
  }
  
  bool __swift::__runtime::llvm::getAsSignedInteger(
      StringRef Str, unsigned Radix, long long &Result) {
    if (consumeSignedInteger(Str, Radix, Result))
      return true;
  
    // For getAsSignedInteger, we require the whole string to be consumed or else
    // we consider it a failure.
    return !Str.empty();
  }
  
  // Implementation of StringRef hashing.
  hash_code __swift::__runtime::llvm::hash_value(StringRef S) {
    return hash_combine_range(S.begin(), S.end());
  }
  