StringRef.cpp

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//===-- StringRef.cpp - Lightweight String References ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/edit_distance.h"
#include <bitset>

using namespace llvm;

// MSVC emits references to this into the translation units which reference it.
#ifndef _MSC_VER
const size_t StringRef::npos;
#endif

static char ascii_tolower(char x) {
  if (x >= 'A' && x <= 'Z')
    return x - 'A' + 'a';
  return x;
}

static char ascii_toupper(char x) {
  if (x >= 'a' && x <= 'z')
    return x - 'a' + 'A';
  return x;
}

static bool ascii_isdigit(char x) {
  return x >= '0' && x <= '9';
}

// 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 = ascii_tolower(LHS[I]);
    unsigned char RHC = ascii_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;
}

/// 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 (ascii_isdigit(Data[I]) && ascii_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 && ascii_isdigit(Data[J]);
        bool rd = J < RHS.Length && ascii_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;
}

// Compute the edit distance between the two given strings.
unsigned StringRef::edit_distance(llvm::StringRef Other,
                                  bool AllowReplacements,
                                  unsigned MaxEditDistance) const {
  return llvm::ComputeEditDistance(
      makeArrayRef(data(), size()),
      makeArrayRef(Other.data(), Other.size()),
      AllowReplacements, MaxEditDistance);
}

//===----------------------------------------------------------------------===//
// String Operations
//===----------------------------------------------------------------------===//

std::string StringRef::lower() const {
  std::string Result(size(), char());
  for (size_type i = 0, e = size(); i != e; ++i) {
    Result[i] = ascii_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] = ascii_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 {
  size_t N = Str.size();
  if (N > Length)
    return npos;

  // For short haystacks or unsupported needles fall back to the naive algorithm
  if (Length < 16 || N > 255 || N == 0) {
    for (size_t e = Length - N + 1, i = std::min(From, e); i != e; ++i)
      if (substr(i, N).equals(Str))
        return i;
    return npos;
  }

  if (From >= Length)
    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;

  unsigned Len = Length-From, Pos = From;
  while (Len >= N) {
    if (substr(Pos, N).equals(Str)) // See if this is the correct substring.
      return Pos;

    // Otherwise skip the appropriate number of bytes.
    uint8_t Skip = BadCharSkip[(uint8_t)(*this)[Pos+N-1]];
    Len -= Skip;
    Pos += Skip;
  }

  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;
}

/// 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 Separators, int MaxSplit,
                      bool KeepEmpty) const {
  StringRef rest = *this;

  // rest.data() is used to distinguish cases like "a," that splits into
  // "a" + "" and "a" that splits into "a" + 0.
  for (int splits = 0;
       rest.data() != nullptr && (MaxSplit < 0 || splits < MaxSplit);
       ++splits) {
    std::pair<StringRef, StringRef> p = rest.split(Separators);

    if (KeepEmpty || p.first.size() != 0)
      A.push_back(p.first);
    rest = p.second;
  }
  // If we have a tail left, add it.
  if (rest.data() != nullptr && (rest.size() != 0 || KeepEmpty))
    A.push_back(rest);
}

//===----------------------------------------------------------------------===//
// 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 > Length)
    return 0;
  for (size_t i = 0, e = Length - N + 1; i != e; ++i)
    if (substr(i, N).equals(Str))
      ++Count;
  return Count;
}

static unsigned GetAutoSenseRadix(StringRef &Str) {
  if (Str.startswith("0x")) {
    Str = Str.substr(2);
    return 16;
  }
  
  if (Str.startswith("0b")) {
    Str = Str.substr(2);
    return 2;
  }

  if (Str.startswith("0o")) {
    Str = Str.substr(2);
    return 8;
  }

  if (Str.startswith("0"))
    return 8;
  
  return 10;
}


/// GetAsUnsignedInteger - Workhorse method that converts a integer character
/// sequence of radix up to 36 to an unsigned long long value.
bool llvm::getAsUnsignedInteger(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.
  Result = 0;
  while (!Str.empty()) {
    unsigned CharVal;
    if (Str[0] >= '0' && Str[0] <= '9')
      CharVal = Str[0]-'0';
    else if (Str[0] >= 'a' && Str[0] <= 'z')
      CharVal = Str[0]-'a'+10;
    else if (Str[0] >= 'A' && Str[0] <= 'Z')
      CharVal = Str[0]-'A'+10;
    else
      return true;

    // If the parsed value is larger than the integer radix, the string is
    // invalid.
    if (CharVal >= Radix)
      return true;

    // 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;

    Str = Str.substr(1);
  }

  return false;
}

bool llvm::getAsSignedInteger(StringRef Str, unsigned Radix,
                              long long &Result) {
  unsigned long long ULLVal;

  // Handle positive strings first.
  if (Str.empty() || Str.front() != '-') {
    if (getAsUnsignedInteger(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.
  if (getAsUnsignedInteger(Str.substr(1), 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;

  Result = -ULLVal;
  return false;
}

bool StringRef::getAsInteger(unsigned Radix, APInt &Result) const {
  StringRef Str = *this;

  // Autosense radix if not specified.
  if (Radix == 0)
    Radix = GetAutoSenseRadix(Str);

  assert(Radix > 1 && Radix <= 36);

  // Empty strings (after the radix autosense) are invalid.
  if (Str.empty()) return true;

  // Skip leading zeroes.  This can be a significant improvement if
  // it means we don't need > 64 bits.
  while (!Str.empty() && Str.front() == '0')
    Str = Str.substr(1);

  // If it was nothing but zeroes....
  if (Str.empty()) {
    Result = APInt(64, 0);
    return false;
  }

  // (Over-)estimate the required number of bits.
  unsigned Log2Radix = 0;
  while ((1U << Log2Radix) < Radix) Log2Radix++;
  bool IsPowerOf2Radix = ((1U << Log2Radix) == Radix);

  unsigned BitWidth = Log2Radix * Str.size();
  if (BitWidth < Result.getBitWidth())
    BitWidth = Result.getBitWidth(); // don't shrink the result
  else if (BitWidth > Result.getBitWidth())
    Result = Result.zext(BitWidth);

  APInt RadixAP, CharAP; // unused unless !IsPowerOf2Radix
  if (!IsPowerOf2Radix) {
    // These must have the same bit-width as Result.
    RadixAP = APInt(BitWidth, Radix);
    CharAP = APInt(BitWidth, 0);
  }

  // Parse all the bytes of the string given this radix.
  Result = 0;
  while (!Str.empty()) {
    unsigned CharVal;
    if (Str[0] >= '0' && Str[0] <= '9')
      CharVal = Str[0]-'0';
    else if (Str[0] >= 'a' && Str[0] <= 'z')
      CharVal = Str[0]-'a'+10;
    else if (Str[0] >= 'A' && Str[0] <= 'Z')
      CharVal = Str[0]-'A'+10;
    else
      return true;

    // If the parsed value is larger than the integer radix, the string is
    // invalid.
    if (CharVal >= Radix)
      return true;

    // Add in this character.
    if (IsPowerOf2Radix) {
      Result <<= Log2Radix;
      Result |= CharVal;
    } else {
      Result *= RadixAP;
      CharAP = CharVal;
      Result += CharAP;
    }

    Str = Str.substr(1);
  }

  return false;
}


// Implementation of StringRef hashing.
hash_code llvm::hash_value(StringRef S) {
  return hash_combine_range(S.begin(), S.end());
}