# All files / node_modules/upng-js/node_modules/pako/lib/utils strings.js

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     // String encode/decode helpers
    'use strict';

    var utils = require('./common');

    // Quick check if we can use fast array to bin string conversion
    //
    // - apply(Array) can fail on Android 2.2
    // - apply(Uint8Array) can fail on iOS 5.1 Safari
    //
    var STR_APPLY_OK = true;
    var STR_APPLY_UIA_OK = true;

    try { String.fromCharCode.apply(null, [ 0 ]); } catch (__) { STR_APPLY_OK = false; }
    try { String.fromCharCode.apply(null, new Uint8Array(1)); } catch (__) { STR_APPLY_UIA_OK = false; }

    // Table with utf8 lengths (calculated by first byte of sequence)
    // Note, that 5 & 6-byte values and some 4-byte values can not be represented in JS,
    // because max possible codepoint is 0x10ffff
    var _utf8len = new utils.Buf8(256);
    for (var q = 0; q < 256; q++) {
      _utf8len[q] = (q >= 252 ? 6 : q >= 248 ? 5 : q >= 240 ? 4 : q >= 224 ? 3 : q >= 192 ? 2 : 1);
    }
    _utf8len[254] = _utf8len[254] = 1; // Invalid sequence start

    // convert string to array (typed, when possible)
    exports.string2buf = function (str) {
      var buf, c, c2, m_pos, i, str_len = str.length, buf_len = 0;

      // count binary size
      for (m_pos = 0; m_pos < str_len; m_pos++) {
        c = str.charCodeAt(m_pos);
    I    if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) {
          c2 = str.charCodeAt(m_pos + 1);
    I      if ((c2 & 0xfc00) === 0xdc00) {
            c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00);
            m_pos++;
          }
        }
        buf_len += c < 0x80 ? 1 : c < 0x800 ? 2 : c < 0x10000 ? 3 : 4;
      }

      // allocate buffer
      buf = new utils.Buf8(buf_len);

      // convert
      for (i = 0, m_pos = 0; i < buf_len; m_pos++) {
        c = str.charCodeAt(m_pos);
    I    if ((c & 0xfc00) === 0xd800 && (m_pos + 1 < str_len)) {
          c2 = str.charCodeAt(m_pos + 1);
    I      if ((c2 & 0xfc00) === 0xdc00) {
            c = 0x10000 + ((c - 0xd800) << 10) + (c2 - 0xdc00);
            m_pos++;
          }
        }
        if (c < 0x80) {
          /* one byte */
          buf[i++] = c;
        } else if (c < 0x800) {
          /* two bytes */
          buf[i++] = 0xC0 | (c >>> 6);
          buf[i++] = 0x80 | (c & 0x3f);
        } else if (c < 0x10000) {
          /* three bytes */
          buf[i++] = 0xE0 | (c >>> 12);
          buf[i++] = 0x80 | (c >>> 6 & 0x3f);
          buf[i++] = 0x80 | (c & 0x3f);
        } else {
          /* four bytes */
          buf[i++] = 0xf0 | (c >>> 18);
          buf[i++] = 0x80 | (c >>> 12 & 0x3f);
          buf[i++] = 0x80 | (c >>> 6 & 0x3f);
          buf[i++] = 0x80 | (c & 0x3f);
        }
      }

      return buf;
    };

    // Helper (used in 2 places)
    function buf2binstring(buf, len) {
      // On Chrome, the arguments in a function call that are allowed is `65534`.
      // If the length of the buffer is smaller than that, we can use this optimization,
      // otherwise we will take a slower path.
    I  if (len < 65534) {
    I    if ((buf.subarray && STR_APPLY_UIA_OK) || (!buf.subarray && STR_APPLY_OK)) {
          return String.fromCharCode.apply(null, utils.shrinkBuf(buf, len));
        }
      }

      var result = '';
      for (var i = 0; i < len; i++) {
        result += String.fromCharCode(buf[i]);
      }
      return result;
    }

    // Convert byte array to binary string
    exports.buf2binstring = function (buf) {
      return buf2binstring(buf, buf.length);
    };

    // Convert binary string (typed, when possible)
    exports.binstring2buf = function (str) {
      var buf = new utils.Buf8(str.length);
      for (var i = 0, len = buf.length; i < len; i++) {
        buf[i] = str.charCodeAt(i);
      }
      return buf;
    };

    // convert array to string
    exports.buf2string = function (buf, max) {
      var i, out, c, c_len;
      var len = max || buf.length;

      // Reserve max possible length (2 words per char)
      // NB: by unknown reasons, Array is significantly faster for
      //     String.fromCharCode.apply than Uint16Array.
      var utf16buf = new Array(len * 2);

      for (out = 0, i = 0; i < len;) {
        c = buf[i++];
        // quick process ascii
    I    if (c < 0x80) { utf16buf[out++] = c; continue; }

        c_len = _utf8len[c];
        // skip 5 & 6 byte codes
    I    if (c_len > 4) { utf16buf[out++] = 0xfffd; i += c_len - 1; continue; }

        // apply mask on first byte
        c &= c_len === 2 ? 0x1f : c_len === 3 ? 0x0f : 0x07;
        // join the rest
        while (c_len > 1 && i < len) {
          c = (c << 6) | (buf[i++] & 0x3f);
          c_len--;
        }

        // terminated by end of string?
    I    if (c_len > 1) { utf16buf[out++] = 0xfffd; continue; }

        if (c < 0x10000) {
          utf16buf[out++] = c;
        } else {
          c -= 0x10000;
          utf16buf[out++] = 0xd800 | ((c >> 10) & 0x3ff);
          utf16buf[out++] = 0xdc00 | (c & 0x3ff);
        }
      }

      return buf2binstring(utf16buf, out);
    };

    // Calculate max possible position in utf8 buffer,
    // that will not break sequence. If that's not possible
    // - (very small limits) return max size as is.
    //
    // buf[] - utf8 bytes array
    // max   - length limit (mandatory);
    exports.utf8border = function (buf, max) {
      var pos;

      max = max || buf.length;
    I  if (max > buf.length) { max = buf.length; }

      // go back from last position, until start of sequence found
      pos = max - 1;
      while (pos >= 0 && (buf[pos] & 0xC0) === 0x80) { pos--; }

      // Very small and broken sequence,
      // return max, because we should return something anyway.
    I  if (pos < 0) { return max; }

      // If we came to start of buffer - that means buffer is too small,
      // return max too.
    I  if (pos === 0) { return max; }

      return (pos + _utf8len[buf[pos]] > max) ? pos : max;
    };