rtc_base/stringencode.cc

/*
 *  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 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(kwiberg): 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(kwiberg): 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