llvm-mirror/lib/Support/StringRef.cpp

//===-- 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"
using namespace llvm;

const size_t StringRef::npos;

static bool GetAsUnsignedInteger(StringRef Str, unsigned Radix,
                                 unsigned long long &Result) {
  // Autosense radix if not specified.
  if (Radix == 0) {
    if (Str[0] != '0') {
      Radix = 10;
    } else {
      if (Str.size() < 2) {
        Radix = 8;
      } else {
        if (Str[1] == 'x') {
          Str = Str.substr(2);
          Radix = 16;
        } else if (Str[1] == 'b') {
          Str = Str.substr(2);
          Radix = 2;
        } else {
          Radix = 8;
        }
      }
    }
  }
  
  // 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.
    if (Result < PrevResult)
      return true;

    Str = Str.substr(1);
  }
  
  return false;
}

bool StringRef::getAsInteger(unsigned Radix, unsigned long long &Result) const {
  return GetAsUnsignedInteger(*this, Radix, Result);
}