rtc_base/stringencode.cc - platform/external/webrtc - Gitiles

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "rtc_base/stringencode.h"

 #include <stdio.h>
 #include <stdlib.h>

 #include "rtc_base/checks.h"
 #include "rtc_base/stringutils.h"

 namespace rtc {

 /////////////////////////////////////////////////////////////////////////////
 // String Encoding Utilities
 /////////////////////////////////////////////////////////////////////////////

 size_t escape(char * buffer, size_t buflen,
               const char * source, size_t srclen,
               const char * illegal, char escape) {
   RTC_DCHECK(buffer);  // TODO(grunell): estimate output size
   if (buflen <= 0)
     return 0;

   size_t srcpos = 0, bufpos = 0;
   while ((srcpos < srclen) && (bufpos + 1 < buflen)) {
     char ch = source[srcpos++];
     if ((ch == escape) || ::strchr(illegal, ch)) {
       if (bufpos + 2 >= buflen)
         break;
       buffer[bufpos++] = escape;
     }
     buffer[bufpos++] = ch;
   }

   buffer[bufpos] = '\0';
   return bufpos;
 }

 size_t url_decode(char * buffer, size_t buflen,
                   const char * source, size_t srclen) {
   if (nullptr == buffer)
     return srclen + 1;
   if (buflen <= 0)
     return 0;

   unsigned char h1, h2;
   size_t srcpos = 0, bufpos = 0;
   while ((srcpos < srclen) && (bufpos + 1 < buflen)) {
     unsigned char ch = source[srcpos++];
     if (ch == '+') {
       buffer[bufpos++] = ' ';
     } else if ((ch == '%')
                && (srcpos + 1 < srclen)
                && hex_decode(source[srcpos], &h1)
                && hex_decode(source[srcpos+1], &h2))
     {
       buffer[bufpos++] = (h1 << 4) | h2;
       srcpos += 2;
     } else {
       buffer[bufpos++] = ch;
     }
   }
   buffer[bufpos] = '\0';
   return bufpos;
 }

 size_t utf8_decode(const char* source, size_t srclen, unsigned long* value) {
   const unsigned char* s = reinterpret_cast<const unsigned char*>(source);
   if ((s[0] & 0x80) == 0x00) {                    // Check s[0] == 0xxxxxxx
     *value = s[0];
     return 1;
   }
   if ((srclen < 2) || ((s[1] & 0xC0) != 0x80)) {  // Check s[1] != 10xxxxxx
     return 0;
   }
   // Accumulate the trailer byte values in value16, and combine it with the
   // relevant bits from s[0], once we've determined the sequence length.
   unsigned long value16 = (s[1] & 0x3F);
   if ((s[0] & 0xE0) == 0xC0) {                    // Check s[0] == 110xxxxx
     *value = ((s[0] & 0x1F) << 6) | value16;
     return 2;
   }
   if ((srclen < 3) || ((s[2] & 0xC0) != 0x80)) {  // Check s[2] != 10xxxxxx
     return 0;
   }
   value16 = (value16 << 6) | (s[2] & 0x3F);
   if ((s[0] & 0xF0) == 0xE0) {                    // Check s[0] == 1110xxxx
     *value = ((s[0] & 0x0F) << 12) | value16;
     return 3;
   }
   if ((srclen < 4) || ((s[3] & 0xC0) != 0x80)) {  // Check s[3] != 10xxxxxx
     return 0;
   }
   value16 = (value16 << 6) | (s[3] & 0x3F);
   if ((s[0] & 0xF8) == 0xF0) {                    // Check s[0] == 11110xxx
     *value = ((s[0] & 0x07) << 18) | value16;
     return 4;
   }
   return 0;
 }

 size_t utf8_encode(char* buffer, size_t buflen, unsigned long value) {
   if ((value <= 0x7F) && (buflen >= 1)) {
     buffer[0] = static_cast<unsigned char>(value);
     return 1;
   }
   if ((value <= 0x7FF) && (buflen >= 2)) {
     buffer[0] = 0xC0 | static_cast<unsigned char>(value >> 6);
     buffer[1] = 0x80 | static_cast<unsigned char>(value & 0x3F);
     return 2;
   }
   if ((value <= 0xFFFF) && (buflen >= 3)) {
     buffer[0] = 0xE0 | static_cast<unsigned char>(value >> 12);
     buffer[1] = 0x80 | static_cast<unsigned char>((value >> 6) & 0x3F);
     buffer[2] = 0x80 | static_cast<unsigned char>(value & 0x3F);
     return 3;
   }
   if ((value <= 0x1FFFFF) && (buflen >= 4)) {
     buffer[0] = 0xF0 | static_cast<unsigned char>(value >> 18);
     buffer[1] = 0x80 | static_cast<unsigned char>((value >> 12) & 0x3F);
     buffer[2] = 0x80 | static_cast<unsigned char>((value >> 6) & 0x3F);
     buffer[3] = 0x80 | static_cast<unsigned char>(value & 0x3F);
     return 4;
   }
   return 0;
 }

 static const char HEX[] = "0123456789abcdef";

 char hex_encode(unsigned char val) {
   RTC_DCHECK_LT(val, 16);
   return (val < 16) ? HEX[val] : '!';
 }

 bool hex_decode(char ch, unsigned char* val) {
   if ((ch >= '0') && (ch <= '9')) {
     *val = ch - '0';
   } else if ((ch >= 'A') && (ch <= 'Z')) {
     *val = (ch - 'A') + 10;
   } else if ((ch >= 'a') && (ch <= 'z')) {
     *val = (ch - 'a') + 10;
   } else {
     return false;
   }
   return true;
 }

 size_t hex_encode(char* buffer, size_t buflen,
                   const char* csource, size_t srclen) {
   return hex_encode_with_delimiter(buffer, buflen, csource, srclen, 0);
 }

 size_t hex_encode_with_delimiter(char* buffer, size_t buflen,
                                  const char* csource, size_t srclen,
                                  char delimiter) {
   RTC_DCHECK(buffer);  // TODO(grunell): estimate output size
   if (buflen == 0)
     return 0;

   // Init and check bounds.
   const unsigned char* bsource =
       reinterpret_cast<const unsigned char*>(csource);
   size_t srcpos = 0, bufpos = 0;
   size_t needed = delimiter ? (srclen * 3) : (srclen * 2 + 1);
   if (buflen < needed)
     return 0;

   while (srcpos < srclen) {
     unsigned char ch = bsource[srcpos++];
     buffer[bufpos  ] = hex_encode((ch >> 4) & 0xF);
     buffer[bufpos+1] = hex_encode((ch     ) & 0xF);
     bufpos += 2;

     // Don't write a delimiter after the last byte.
     if (delimiter && (srcpos < srclen)) {
       buffer[bufpos] = delimiter;
       ++bufpos;
     }
   }

   // Null terminate.
   buffer[bufpos] = '\0';
   return bufpos;
 }

 std::string hex_encode(const std::string& str) {
   return hex_encode(str.c_str(), str.size());
 }

 std::string hex_encode(const char* source, size_t srclen) {
   return hex_encode_with_delimiter(source, srclen, 0);
 }

 std::string hex_encode_with_delimiter(const char* source, size_t srclen,
                                       char delimiter) {
   const size_t kBufferSize = srclen * 3;
   char* buffer = STACK_ARRAY(char, kBufferSize);
   size_t length = hex_encode_with_delimiter(buffer, kBufferSize,
                                             source, srclen, delimiter);
   RTC_DCHECK(srclen == 0 || length > 0);
   return std::string(buffer, length);
 }

 size_t hex_decode(char * cbuffer, size_t buflen,
                   const char * source, size_t srclen) {
   return hex_decode_with_delimiter(cbuffer, buflen, source, srclen, 0);
 }

 size_t hex_decode_with_delimiter(char* cbuffer, size_t buflen,
                                  const char* source, size_t srclen,
                                  char delimiter) {
   RTC_DCHECK(cbuffer);  // TODO(grunell): estimate output size
   if (buflen == 0)
     return 0;

   // Init and bounds check.
   unsigned char* bbuffer = reinterpret_cast<unsigned char*>(cbuffer);
   size_t srcpos = 0, bufpos = 0;
   size_t needed = (delimiter) ? (srclen + 1) / 3 : srclen / 2;
   if (buflen < needed)
     return 0;

   while (srcpos < srclen) {
     if ((srclen - srcpos) < 2) {
       // This means we have an odd number of bytes.
       return 0;
     }

     unsigned char h1, h2;
     if (!hex_decode(source[srcpos], &h1) ||
         !hex_decode(source[srcpos + 1], &h2))
       return 0;

     bbuffer[bufpos++] = (h1 << 4) | h2;
     srcpos += 2;

     // Remove the delimiter if needed.
     if (delimiter && (srclen - srcpos) > 1) {
       if (source[srcpos] != delimiter)
         return 0;
       ++srcpos;
     }
   }

   return bufpos;
 }

 size_t hex_decode(char* buffer, size_t buflen, const std::string& source) {
   return hex_decode_with_delimiter(buffer, buflen, source, 0);
 }
 size_t hex_decode_with_delimiter(char* buffer, size_t buflen,
                                  const std::string& source, char delimiter) {
   return hex_decode_with_delimiter(buffer, buflen,
                                    source.c_str(), source.length(), delimiter);
 }

 size_t transform(std::string& value, size_t maxlen, const std::string& source,
                  Transform t) {
   char* buffer = STACK_ARRAY(char, maxlen + 1);
   size_t length = t(buffer, maxlen + 1, source.data(), source.length());
   value.assign(buffer, length);
   return length;
 }

 std::string s_transform(const std::string& source, Transform t) {
   // Ask transformation function to approximate the destination size (returns upper bound)
   size_t maxlen = t(nullptr, 0, source.data(), source.length());
   char * buffer = STACK_ARRAY(char, maxlen);
   size_t len = t(buffer, maxlen, source.data(), source.length());
   std::string result(buffer, len);
   return result;
 }

 size_t tokenize(const std::string& source, char delimiter,
                 std::vector<std::string>* fields) {
   fields->clear();
   size_t last = 0;
   for (size_t i = 0; i < source.length(); ++i) {
     if (source[i] == delimiter) {
       if (i != last) {
         fields->push_back(source.substr(last, i - last));
       }
       last = i + 1;
     }
   }
   if (last != source.length()) {
     fields->push_back(source.substr(last, source.length() - last));
   }
   return fields->size();
 }

 size_t tokenize_with_empty_tokens(const std::string& source,
                                   char delimiter,
                                   std::vector<std::string>* fields) {
   fields->clear();
   size_t last = 0;
   for (size_t i = 0; i < source.length(); ++i) {
     if (source[i] == delimiter) {
       fields->push_back(source.substr(last, i - last));
       last = i + 1;
     }
   }
   fields->push_back(source.substr(last, source.length() - last));
   return fields->size();
 }

 size_t tokenize_append(const std::string& source, char delimiter,
                        std::vector<std::string>* fields) {
   if (!fields) return 0;

   std::vector<std::string> new_fields;
   tokenize(source, delimiter, &new_fields);
   fields->insert(fields->end(), new_fields.begin(), new_fields.end());
   return fields->size();
 }

 size_t tokenize(const std::string& source, char delimiter, char start_mark,
                 char end_mark, std::vector<std::string>* fields) {
   if (!fields) return 0;
   fields->clear();

   std::string remain_source = source;
   while (!remain_source.empty()) {
     size_t start_pos = remain_source.find(start_mark);
     if (std::string::npos == start_pos) break;
     std::string pre_mark;
     if (start_pos > 0) {
       pre_mark = remain_source.substr(0, start_pos - 1);
     }

     ++start_pos;
     size_t end_pos = remain_source.find(end_mark, start_pos);
     if (std::string::npos == end_pos) break;

     // We have found the matching marks. First tokenize the pre-mask. Then add
     // the marked part as a single field. Finally, loop back for the post-mark.
     tokenize_append(pre_mark, delimiter, fields);
     fields->push_back(remain_source.substr(start_pos, end_pos - start_pos));
     remain_source = remain_source.substr(end_pos + 1);
   }

   return tokenize_append(remain_source, delimiter, fields);
 }

 bool tokenize_first(const std::string& source,
                     const char delimiter,
                     std::string* token,
                     std::string* rest) {
   // Find the first delimiter
   size_t left_pos = source.find(delimiter);
   if (left_pos == std::string::npos) {
     return false;
   }

   // Look for additional occurrances of delimiter.
   size_t right_pos = left_pos + 1;
   while (source[right_pos] == delimiter) {
     right_pos++;
   }

   *token = source.substr(0, left_pos);
   *rest = source.substr(right_pos);
   return true;
 }

 std::string join(const std::vector<std::string>& source, char delimiter) {
   if (source.size() == 0) {
     return std::string();
   }
   // Find length of the string to be returned to pre-allocate memory.
   size_t source_string_length = 0;
   for (size_t i = 0; i < source.size(); ++i) {
     source_string_length += source[i].length();
   }

   // Build the joined string.
   std::string joined_string;
   joined_string.reserve(source_string_length + source.size() - 1);
   for (size_t i = 0; i < source.size(); ++i) {
     if (i != 0) {
       joined_string += delimiter;
     }
     joined_string += source[i];
   }
   return joined_string;
 }

 size_t split(const std::string& source, char delimiter,
              std::vector<std::string>* fields) {
   RTC_DCHECK(fields);
   fields->clear();
   size_t last = 0;
   for (size_t i = 0; i < source.length(); ++i) {
     if (source[i] == delimiter) {
       fields->push_back(source.substr(last, i - last));
       last = i + 1;
     }
   }
   fields->push_back(source.substr(last, source.length() - last));
   return fields->size();
 }

 }  // namespace rtc
	/*
	* Copyright 2004 The WebRTC Project Authors. All rights reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "rtc_base/stringencode.h"

	#include <stdio.h>
	#include <stdlib.h>

	#include "rtc_base/checks.h"
	#include "rtc_base/stringutils.h"

	namespace rtc {

	/////////////////////////////////////////////////////////////////////////////
	// String Encoding Utilities
	/////////////////////////////////////////////////////////////////////////////

	size_t escape(char * buffer, size_t buflen,
	const char * source, size_t srclen,
	const char * illegal, char escape) {
	RTC_DCHECK(buffer); // TODO(grunell): estimate output size
	if (buflen <= 0)
	return 0;

	size_t srcpos = 0, bufpos = 0;
	while ((srcpos < srclen) && (bufpos + 1 < buflen)) {
	char ch = source[srcpos++];
	if ((ch == escape) \|\| ::strchr(illegal, ch)) {
	if (bufpos + 2 >= buflen)
	break;
	buffer[bufpos++] = escape;
	}
	buffer[bufpos++] = ch;
	}

	buffer[bufpos] = '\0';
	return bufpos;
	}

	size_t url_decode(char * buffer, size_t buflen,
	const char * source, size_t srclen) {
	if (nullptr == buffer)
	return srclen + 1;
	if (buflen <= 0)
	return 0;

	unsigned char h1, h2;
	size_t srcpos = 0, bufpos = 0;
	while ((srcpos < srclen) && (bufpos + 1 < buflen)) {
	unsigned char ch = source[srcpos++];
	if (ch == '+') {
	buffer[bufpos++] = ' ';
	} else if ((ch == '%')
	&& (srcpos + 1 < srclen)
	&& hex_decode(source[srcpos], &h1)
	&& hex_decode(source[srcpos+1], &h2))
	{
	buffer[bufpos++] = (h1 << 4) \| h2;
	srcpos += 2;
	} else {
	buffer[bufpos++] = ch;
	}
	}
	buffer[bufpos] = '\0';
	return bufpos;
	}

	size_t utf8_decode(const char* source, size_t srclen, unsigned long* value) {
	const unsigned char* s = reinterpret_cast<const unsigned char*>(source);
	if ((s[0] & 0x80) == 0x00) { // Check s[0] == 0xxxxxxx
	*value = s[0];
	return 1;
	}
	if ((srclen < 2) \|\| ((s[1] & 0xC0) != 0x80)) { // Check s[1] != 10xxxxxx
	return 0;
	}
	// Accumulate the trailer byte values in value16, and combine it with the
	// relevant bits from s[0], once we've determined the sequence length.
	unsigned long value16 = (s[1] & 0x3F);
	if ((s[0] & 0xE0) == 0xC0) { // Check s[0] == 110xxxxx
	*value = ((s[0] & 0x1F) << 6) \| value16;
	return 2;
	}
	if ((srclen < 3) \|\| ((s[2] & 0xC0) != 0x80)) { // Check s[2] != 10xxxxxx
	return 0;
	}
	value16 = (value16 << 6) \| (s[2] & 0x3F);
	if ((s[0] & 0xF0) == 0xE0) { // Check s[0] == 1110xxxx
	*value = ((s[0] & 0x0F) << 12) \| value16;
	return 3;
	}
	if ((srclen < 4) \|\| ((s[3] & 0xC0) != 0x80)) { // Check s[3] != 10xxxxxx
	return 0;
	}
	value16 = (value16 << 6) \| (s[3] & 0x3F);
	if ((s[0] & 0xF8) == 0xF0) { // Check s[0] == 11110xxx
	*value = ((s[0] & 0x07) << 18) \| value16;
	return 4;
	}
	return 0;
	}

	size_t utf8_encode(char* buffer, size_t buflen, unsigned long value) {
	if ((value <= 0x7F) && (buflen >= 1)) {
	buffer[0] = static_cast<unsigned char>(value);
	return 1;
	}
	if ((value <= 0x7FF) && (buflen >= 2)) {
	buffer[0] = 0xC0 \| static_cast<unsigned char>(value >> 6);
	buffer[1] = 0x80 \| static_cast<unsigned char>(value & 0x3F);
	return 2;
	}
	if ((value <= 0xFFFF) && (buflen >= 3)) {
	buffer[0] = 0xE0 \| static_cast<unsigned char>(value >> 12);
	buffer[1] = 0x80 \| static_cast<unsigned char>((value >> 6) & 0x3F);
	buffer[2] = 0x80 \| static_cast<unsigned char>(value & 0x3F);
	return 3;
	}
	if ((value <= 0x1FFFFF) && (buflen >= 4)) {
	buffer[0] = 0xF0 \| static_cast<unsigned char>(value >> 18);
	buffer[1] = 0x80 \| static_cast<unsigned char>((value >> 12) & 0x3F);
	buffer[2] = 0x80 \| static_cast<unsigned char>((value >> 6) & 0x3F);
	buffer[3] = 0x80 \| static_cast<unsigned char>(value & 0x3F);
	return 4;
	}
	return 0;
	}

	static const char HEX[] = "0123456789abcdef";

	char hex_encode(unsigned char val) {
	RTC_DCHECK_LT(val, 16);
	return (val < 16) ? HEX[val] : '!';
	}

	bool hex_decode(char ch, unsigned char* val) {
	if ((ch >= '0') && (ch <= '9')) {
	*val = ch - '0';
	} else if ((ch >= 'A') && (ch <= 'Z')) {
	*val = (ch - 'A') + 10;
	} else if ((ch >= 'a') && (ch <= 'z')) {
	*val = (ch - 'a') + 10;
	} else {
	return false;
	}
	return true;
	}

	size_t hex_encode(char* buffer, size_t buflen,
	const char* csource, size_t srclen) {
	return hex_encode_with_delimiter(buffer, buflen, csource, srclen, 0);
	}

	size_t hex_encode_with_delimiter(char* buffer, size_t buflen,
	const char* csource, size_t srclen,
	char delimiter) {
	RTC_DCHECK(buffer); // TODO(grunell): estimate output size
	if (buflen == 0)
	return 0;

	// Init and check bounds.
	const unsigned char* bsource =
	reinterpret_cast<const unsigned char*>(csource);
	size_t srcpos = 0, bufpos = 0;
	size_t needed = delimiter ? (srclen * 3) : (srclen * 2 + 1);
	if (buflen < needed)
	return 0;

	while (srcpos < srclen) {
	unsigned char ch = bsource[srcpos++];
	buffer[bufpos ] = hex_encode((ch >> 4) & 0xF);
	buffer[bufpos+1] = hex_encode((ch ) & 0xF);
	bufpos += 2;

	// Don't write a delimiter after the last byte.
	if (delimiter && (srcpos < srclen)) {
	buffer[bufpos] = delimiter;
	++bufpos;
	}
	}

	// Null terminate.
	buffer[bufpos] = '\0';
	return bufpos;
	}

	std::string hex_encode(const std::string& str) {
	return hex_encode(str.c_str(), str.size());
	}

	std::string hex_encode(const char* source, size_t srclen) {
	return hex_encode_with_delimiter(source, srclen, 0);
	}

	std::string hex_encode_with_delimiter(const char* source, size_t srclen,
	char delimiter) {
	const size_t kBufferSize = srclen * 3;
	char* buffer = STACK_ARRAY(char, kBufferSize);
	size_t length = hex_encode_with_delimiter(buffer, kBufferSize,
	source, srclen, delimiter);
	RTC_DCHECK(srclen == 0 \|\| length > 0);
	return std::string(buffer, length);
	}

	size_t hex_decode(char * cbuffer, size_t buflen,
	const char * source, size_t srclen) {
	return hex_decode_with_delimiter(cbuffer, buflen, source, srclen, 0);
	}

	size_t hex_decode_with_delimiter(char* cbuffer, size_t buflen,
	const char* source, size_t srclen,
	char delimiter) {
	RTC_DCHECK(cbuffer); // TODO(grunell): estimate output size
	if (buflen == 0)
	return 0;

	// Init and bounds check.
	unsigned char* bbuffer = reinterpret_cast<unsigned char*>(cbuffer);
	size_t srcpos = 0, bufpos = 0;
	size_t needed = (delimiter) ? (srclen + 1) / 3 : srclen / 2;
	if (buflen < needed)
	return 0;

	while (srcpos < srclen) {
	if ((srclen - srcpos) < 2) {
	// This means we have an odd number of bytes.
	return 0;
	}

	unsigned char h1, h2;
	if (!hex_decode(source[srcpos], &h1) \|\|
	!hex_decode(source[srcpos + 1], &h2))
	return 0;

	bbuffer[bufpos++] = (h1 << 4) \| h2;
	srcpos += 2;

	// Remove the delimiter if needed.
	if (delimiter && (srclen - srcpos) > 1) {
	if (source[srcpos] != delimiter)
	return 0;
	++srcpos;
	}
	}

	return bufpos;
	}

	size_t hex_decode(char* buffer, size_t buflen, const std::string& source) {
	return hex_decode_with_delimiter(buffer, buflen, source, 0);
	}
	size_t hex_decode_with_delimiter(char* buffer, size_t buflen,
	const std::string& source, char delimiter) {
	return hex_decode_with_delimiter(buffer, buflen,
	source.c_str(), source.length(), delimiter);
	}

	size_t transform(std::string& value, size_t maxlen, const std::string& source,
	Transform t) {
	char* buffer = STACK_ARRAY(char, maxlen + 1);
	size_t length = t(buffer, maxlen + 1, source.data(), source.length());
	value.assign(buffer, length);
	return length;
	}

	std::string s_transform(const std::string& source, Transform t) {
	// Ask transformation function to approximate the destination size (returns upper bound)
	size_t maxlen = t(nullptr, 0, source.data(), source.length());
	char * buffer = STACK_ARRAY(char, maxlen);
	size_t len = t(buffer, maxlen, source.data(), source.length());
	std::string result(buffer, len);
	return result;
	}

	size_t tokenize(const std::string& source, char delimiter,
	std::vector<std::string>* fields) {
	fields->clear();
	size_t last = 0;
	for (size_t i = 0; i < source.length(); ++i) {
	if (source[i] == delimiter) {
	if (i != last) {
	fields->push_back(source.substr(last, i - last));
	}
	last = i + 1;
	}
	}
	if (last != source.length()) {
	fields->push_back(source.substr(last, source.length() - last));
	}
	return fields->size();
	}

	size_t tokenize_with_empty_tokens(const std::string& source,
	char delimiter,
	std::vector<std::string>* fields) {
	fields->clear();
	size_t last = 0;
	for (size_t i = 0; i < source.length(); ++i) {
	if (source[i] == delimiter) {
	fields->push_back(source.substr(last, i - last));
	last = i + 1;
	}
	}
	fields->push_back(source.substr(last, source.length() - last));
	return fields->size();
	}

	size_t tokenize_append(const std::string& source, char delimiter,
	std::vector<std::string>* fields) {
	if (!fields) return 0;

	std::vector<std::string> new_fields;
	tokenize(source, delimiter, &new_fields);
	fields->insert(fields->end(), new_fields.begin(), new_fields.end());
	return fields->size();
	}

	size_t tokenize(const std::string& source, char delimiter, char start_mark,
	char end_mark, std::vector<std::string>* fields) {
	if (!fields) return 0;
	fields->clear();

	std::string remain_source = source;
	while (!remain_source.empty()) {
	size_t start_pos = remain_source.find(start_mark);
	if (std::string::npos == start_pos) break;
	std::string pre_mark;
	if (start_pos > 0) {
	pre_mark = remain_source.substr(0, start_pos - 1);
	}

	++start_pos;
	size_t end_pos = remain_source.find(end_mark, start_pos);
	if (std::string::npos == end_pos) break;

	// We have found the matching marks. First tokenize the pre-mask. Then add
	// the marked part as a single field. Finally, loop back for the post-mark.
	tokenize_append(pre_mark, delimiter, fields);
	fields->push_back(remain_source.substr(start_pos, end_pos - start_pos));
	remain_source = remain_source.substr(end_pos + 1);
	}

	return tokenize_append(remain_source, delimiter, fields);
	}

	bool tokenize_first(const std::string& source,
	const char delimiter,
	std::string* token,
	std::string* rest) {
	// Find the first delimiter
	size_t left_pos = source.find(delimiter);
	if (left_pos == std::string::npos) {
	return false;
	}

	// Look for additional occurrances of delimiter.
	size_t right_pos = left_pos + 1;
	while (source[right_pos] == delimiter) {
	right_pos++;
	}

	*token = source.substr(0, left_pos);
	*rest = source.substr(right_pos);
	return true;
	}

	std::string join(const std::vector<std::string>& source, char delimiter) {
	if (source.size() == 0) {
	return std::string();
	}
	// Find length of the string to be returned to pre-allocate memory.
	size_t source_string_length = 0;
	for (size_t i = 0; i < source.size(); ++i) {
	source_string_length += source[i].length();
	}

	// Build the joined string.
	std::string joined_string;
	joined_string.reserve(source_string_length + source.size() - 1);
	for (size_t i = 0; i < source.size(); ++i) {
	if (i != 0) {
	joined_string += delimiter;
	}
	joined_string += source[i];
	}
	return joined_string;
	}

	size_t split(const std::string& source, char delimiter,
	std::vector<std::string>* fields) {
	RTC_DCHECK(fields);
	fields->clear();
	size_t last = 0;
	for (size_t i = 0; i < source.length(); ++i) {
	if (source[i] == delimiter) {
	fields->push_back(source.substr(last, i - last));
	last = i + 1;
	}
	}
	fields->push_back(source.substr(last, source.length() - last));
	return fields->size();
	}

	} // namespace rtc