src/util/string-helper.hpp

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
/**
 * Copyright (C) 2013 Regents of the University of California.
 * @author: Jeff Thompson <jefft0@remap.ucla.edu>
 * See COPYING for copyright and distribution information.
 */

#ifndef NDN_STRING_HELPER_HPP
#define NDN_STRING_HELPER_HPP

#include <string>
#include <sstream>

namespace ndn {

static const char *WHITESPACE_CHARS = " \n\r\t";

/**
 * Return the hex representation of the bytes in array.
 * @param array The array of bytes.
 * @return Hex string.
 */
inline std::string 
toHex(const uint8_t* array, size_t arraySize)
{
  if (array == 0 || arraySize == 0)
    return "";
  
  std::ostringstream result;
  result.flags(std::ios::hex | std::ios::uppercase);
  for (size_t i = 0; i < arraySize; ++i) {
    uint8_t x = array[i];
    if (x < 16)
      result << '0';
    result << (unsigned int)x;
  }

  return result.str();
}

/**
 * Modify str in place to erase whitespace on the left.
 * @param str
 */
inline void 
trimLeft(std::string& str)
{
  size_t found = str.find_first_not_of(WHITESPACE_CHARS);
  if (found != std::string::npos) {
    if (found > 0)
      str.erase(0, found);
  }
  else
    // All whitespace
    str.clear();    
}

/**
 * Modify str in place to erase whitespace on the right.
 * @param str
 */
inline void 
trimRight(std::string& str)
{
  size_t found = str.find_last_not_of(WHITESPACE_CHARS);
  if (found != std::string::npos) {
    if (found + 1 < str.size())
      str.erase(found + 1);
  }
  else
    // All whitespace
    str.clear();
}

/**
 * Modify str in place to erase whitespace on the left and right.
 * @param str
 */
inline void 
trim(std::string& str)
{
  trimLeft(str);
  trimRight(str);
}

/**
 * Convert the hex character to an integer from 0 to 15, or -1 if not a hex character.
 * @param c
 * @return 
 */
inline int 
fromHexChar(uint8_t c)
{
  if (c >= '0' && c <= '9')
    return (int)c - (int)'0';
  else if (c >= 'A' && c <= 'F')
    return (int)c - (int)'A' + 10;
  else if (c >= 'a' && c <= 'f')
    return (int)c - (int)'a' + 10;
  else
    return -1;
}

/**
 * Return a copy of str, converting each escaped "%XX" to the char value.
 * @param str
 */
inline std::string 
unescape(const std::string& str)
{
  std::ostringstream result;
  
  for (size_t i = 0; i < str.size(); ++i) {
    if (str[i] == '%' && i + 2 < str.size()) {
      int hi = fromHexChar(str[i + 1]);
      int lo = fromHexChar(str[i + 2]);
      
      if (hi < 0 || lo < 0)
        // Invalid hex characters, so just keep the escaped string.
        result << str[i] << str[i + 1] << str[i + 2];
      else
        result << (uint8_t)(16 * hi + lo);
      
      // Skip ahead past the escaped value.
      i += 2;
    }
    else
      // Just copy through.
      result << str[i];
  }
  
  return result.str();
}

} // namespace ndn

#endif // NDN_STRING_HELPER_HPP