text: //===-- llvm/ADT/StringExtras.h - Useful string functions -------*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file contains some functions that are useful when dealing with strings.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_ADT_STRINGEXTRAS_H
  #define LLVM_ADT_STRINGEXTRAS_H
  
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/DataTypes.h"
  
  namespace llvm {
  template<typename T> class SmallVectorImpl;
  
  /// hexdigit - Return the hexadecimal character for the
  /// given number \p X (which should be less than 16).
  static inline char hexdigit(unsigned X, bool LowerCase = false) {
    const char HexChar = LowerCase ? 'a' : 'A';
    return X < 10 ? '0' + X : HexChar + X - 10;
  }
  
  /// Interpret the given character \p C as a hexadecimal digit and return its
  /// value.
  ///
  /// If \p C is not a valid hex digit, -1U is returned.
  static inline unsigned hexDigitValue(char C) {
    if (C >= '0' && C <= '9') return C-'0';
    if (C >= 'a' && C <= 'f') return C-'a'+10U;
    if (C >= 'A' && C <= 'F') return C-'A'+10U;
    return -1U;
  }
  
  /// utohex_buffer - Emit the specified number into the buffer specified by
  /// BufferEnd, returning a pointer to the start of the string.  This can be used
  /// like this: (note that the buffer must be large enough to handle any number):
  ///    char Buffer[40];
  ///    printf("0x%s", utohex_buffer(X, Buffer+40));
  ///
  /// This should only be used with unsigned types.
  ///
  template<typename IntTy>
  static inline char *utohex_buffer(IntTy X, char *BufferEnd) {
    char *BufPtr = BufferEnd;
    *--BufPtr = 0;      // Null terminate buffer.
    if (X == 0) {
      *--BufPtr = '0';  // Handle special case.
      return BufPtr;
    }
  
    while (X) {
      unsigned char Mod = static_cast<unsigned char>(X) & 15;
      *--BufPtr = hexdigit(Mod);
      X >>= 4;
    }
    return BufPtr;
  }
  
  static inline std::string utohexstr(uint64_t X) {
    char Buffer[17];
    return utohex_buffer(X, Buffer+17);
  }
  
  static inline std::string utostr_32(uint32_t X, bool isNeg = false) {
    char Buffer[11];
    char *BufPtr = Buffer+11;
  
    if (X == 0) *--BufPtr = '0';  // Handle special case...
  
    while (X) {
      *--BufPtr = '0' + char(X % 10);
      X /= 10;
    }
  
    if (isNeg) *--BufPtr = '-';   // Add negative sign...
  
    return std::string(BufPtr, Buffer+11);
  }
  
  static __declspec(noinline) inline std::string utostr(uint64_t X, bool isNeg = false) {
    char Buffer[21];
    char *BufPtr = Buffer+21;
  
    if (X == 0) *--BufPtr = '0';  // Handle special case...
  
    while (X) {
      *--BufPtr = '0' + char(X % 10);
      X /= 10;
    }
  
    if (isNeg) *--BufPtr = '-';   // Add negative sign...
    return std::string(BufPtr, Buffer+21);
  }
  
  
  static inline std::string itostr(int64_t X) {
    if (X < 0)
      return utostr(static_cast<uint64_t>(-X), true);
    else
      return utostr(static_cast<uint64_t>(X));
  }
  
  /// StrInStrNoCase - Portable version of strcasestr.  Locates the first
  /// occurrence of string 's1' in string 's2', ignoring case.  Returns
  /// the offset of s2 in s1 or npos if s2 cannot be found.
  StringRef::size_type StrInStrNoCase(StringRef s1, StringRef s2);
  
  /// getToken - This function extracts one token from source, ignoring any
  /// leading characters that appear in the Delimiters string, and ending the
  /// token at any of the characters that appear in the Delimiters string.  If
  /// there are no tokens in the source string, an empty string is returned.
  /// The function returns a pair containing the extracted token and the
  /// remaining tail string.
  std::pair<StringRef, StringRef> getToken(StringRef Source,
                                           StringRef Delimiters = " \t\n\v\f\r");
  
  /// SplitString - Split up the specified string according to the specified
  /// delimiters, appending the result fragments to the output list.
  void SplitString(StringRef Source,
                   SmallVectorImpl<StringRef> &OutFragments,
                   StringRef Delimiters = " \t\n\v\f\r");
  
  /// HashString - Hash function for strings.
  ///
  /// This is the Bernstein hash function.
  //
  // FIXME: Investigate whether a modified bernstein hash function performs
  // better: http://eternallyconfuzzled.com/tuts/algorithms/jsw_tut_hashing.aspx
  //   X*33+c -> X*33^c
  static inline unsigned HashString(StringRef Str, unsigned Result = 0) {
    for (unsigned i = 0, e = Str.size(); i != e; ++i)
      Result = Result * 33 + (unsigned char)Str[i];
    return Result;
  }
  
  /// Returns the English suffix for an ordinal integer (-st, -nd, -rd, -th).
  static inline StringRef getOrdinalSuffix(unsigned Val) {
    // It is critically important that we do this perfectly for
    // user-written sequences with over 100 elements.
    switch (Val % 100) {
    case 11:
    case 12:
    case 13:
      return "th";
    default:
      switch (Val % 10) {
        case 1: return "st";
        case 2: return "nd";
        case 3: return "rd";
        default: return "th";
      }
    }
  }
  
  } // End llvm namespace
  
  #endif
  