querystring.js

'use strict';

const { ERR_INVALID_URI } = require('internal/errors').codes;

const hexTable = new Array(256);
for (let i = 0; i < 256; ++i)
  hexTable[i] = '%' + ((i < 16 ? '0' : '') + i.toString(16)).toUpperCase();

const isHexTable = [
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0 - 15
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16 - 31
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 32 - 47
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, // 48 - 63
  0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 64 - 79
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 80 - 95
  0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 96 - 111
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 112 - 127
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 128 ...
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0  // ... 256
];

function encodeStr(str, noEscapeTable, hexTable) {
  const len = str.length;
  if (len === 0)
    return '';

  let out = '';
  let lastPos = 0;

  for (let i = 0; i < len; i++) {
    let c = str.charCodeAt(i);

    // ASCII
    if (c < 0x80) {
      if (noEscapeTable[c] === 1)
        continue;
      if (lastPos < i)
        out += str.slice(lastPos, i);
      lastPos = i + 1;
      out += hexTable[c];
      continue;
    }

    if (lastPos < i)
      out += str.slice(lastPos, i);

    // Multi-byte characters ...
    if (c < 0x800) {
      lastPos = i + 1;
      out += hexTable[0xC0 | (c >> 6)] +
             hexTable[0x80 | (c & 0x3F)];
      continue;
    }
    if (c < 0xD800 || c >= 0xE000) {
      lastPos = i + 1;
      out += hexTable[0xE0 | (c >> 12)] +
             hexTable[0x80 | ((c >> 6) & 0x3F)] +
             hexTable[0x80 | (c & 0x3F)];
      continue;
    }
    // Surrogate pair
    ++i;

    // This branch should never happen because all URLSearchParams entries
    // should already be converted to USVString. But, included for
    // completion's sake anyway.
    if (i >= len)
      throw new ERR_INVALID_URI();

    const c2 = str.charCodeAt(i) & 0x3FF;

    lastPos = i + 1;
    c = 0x10000 + (((c & 0x3FF) << 10) | c2);
    out += hexTable[0xF0 | (c >> 18)] +
           hexTable[0x80 | ((c >> 12) & 0x3F)] +
           hexTable[0x80 | ((c >> 6) & 0x3F)] +
           hexTable[0x80 | (c & 0x3F)];
  }
  if (lastPos === 0)
    return str;
  if (lastPos < len)
    return out + str.slice(lastPos);
  return out;
}

module.exports = {
  encodeStr,
  hexTable,
  isHexTable
};