buffer-lite.js

// buffer-lite.js

var MAXBUFLEN = 8192;

exports.copy = copy;
exports.toString = toString;
exports.write = write;

/**
 * Buffer.prototype.write()
 *
 * @param string {String}
 * @param [offset] {Number}
 * @returns {Number}
 */

function write(string, offset) {
  var buffer = this;
  var index = offset || (offset |= 0);
  var length = string.length;
  var chr = 0;
  var i = 0;
  while (i < length) {
    chr = string.charCodeAt(i++);

    if (chr < 128) {
      buffer[index++] = chr;
    } else if (chr < 0x800) {
      // 2 bytes
      buffer[index++] = 0xC0 | (chr >>> 6);
      buffer[index++] = 0x80 | (chr & 0x3F);
    } else if (chr < 0xD800 || chr > 0xDFFF) {
      // 3 bytes
      buffer[index++] = 0xE0 | (chr  >>> 12);
      buffer[index++] = 0x80 | ((chr >>> 6)  & 0x3F);
      buffer[index++] = 0x80 | (chr          & 0x3F);
    } else {
      // 4 bytes - surrogate pair
      chr = (((chr - 0xD800) << 10) | (string.charCodeAt(i++) - 0xDC00)) + 0x10000;
      buffer[index++] = 0xF0 | (chr >>> 18);
      buffer[index++] = 0x80 | ((chr >>> 12) & 0x3F);
      buffer[index++] = 0x80 | ((chr >>> 6)  & 0x3F);
      buffer[index++] = 0x80 | (chr          & 0x3F);
    }
  }
  return index - offset;
}

/**
 * Buffer.prototype.toString()
 *
 * @param [encoding] {String} ignored
 * @param [start] {Number}
 * @param [end] {Number}
 * @returns {String}
 */

function toString(encoding, start, end) {
  var buffer = this;
  var index = start|0;
  if (!end) end = buffer.length;
  var string = '';
  var chr = 0;

  while (index < end) {
    chr = buffer[index++];
    if (chr < 128) {
      string += String.fromCharCode(chr);
      continue;
    }

    if ((chr & 0xE0) === 0xC0) {
      // 2 bytes
      chr = (chr & 0x1F) << 6 |
            (buffer[index++] & 0x3F);

    } else if ((chr & 0xF0) === 0xE0) {
      // 3 bytes
      chr = (chr & 0x0F)             << 12 |
            (buffer[index++] & 0x3F) << 6  |
            (buffer[index++] & 0x3F);

    } else if ((chr & 0xF8) === 0xF0) {
      // 4 bytes
      chr = (chr & 0x07)             << 18 |
            (buffer[index++] & 0x3F) << 12 |
            (buffer[index++] & 0x3F) << 6  |
            (buffer[index++] & 0x3F);
    }

    if (chr >= 0x010000) {
      // A surrogate pair
      chr -= 0x010000;

      string += String.fromCharCode((chr >>> 10) + 0xD800, (chr & 0x3FF) + 0xDC00);
    } else {
      string += String.fromCharCode(chr);
    }
  }

  return string;
}

/**
 * Buffer.prototype.copy()
 *
 * @param target {Buffer}
 * @param [targetStart] {Number}
 * @param [start] {Number}
 * @param [end] {Number}
 * @returns {number}
 */

function copy(target, targetStart, start, end) {
  var i;
  if (!start) start = 0;
  if (!end && end !== 0) end = this.length;
  if (!targetStart) targetStart = 0;
  var len = end - start;

  if (target === this && start < targetStart && targetStart < end) {
    // descending
    for (i = len - 1; i >= 0; i--) {
      target[i + targetStart] = this[i + start];
    }
  } else {
    // ascending
    for (i = 0; i < len; i++) {
      target[i + targetStart] = this[i + start];
    }
  }

  return len;
}