varstruct-cstring/lib/index.js

Encode / decode C strings.

const vs = require('varstruct');
module.exports = function cstring(length, encoding = 'utf8') {
  const bufferCodec = vs.Buffer(length);
  function encode(value, buffer, offset) {
    const buf = Buffer.alloc(length);
    // we need last byte for '\0'
    if (value.length > length - 1) throw new Error(`varstruct-cstring: '${value}' length of ${value.length} is greater than the buffer length - 1 of ${length - 1}.`);
    buf.write(value, encoding);
    return bufferCodec.encode(buf, buffer, offset);
  }
  function decode(buffer, offset, end) {
    const buf = bufferCodec.decode(buffer, offset, end);
    const i = buf.indexOf(0);
    const sbuf = i === -1 ? buf : buf.slice(0, i);
    return sbuf.toString(encoding);
  }
  const encodingLength = () => length;

  // TODO: submit pr on varstruct if 'bytes' is undefined
  encode.bytes = decode.bytes = length;
  return {
    encode,
    decode,
    encodingLength
  };
};