Fixed length "Buffer" type, for use in `ref-struct` type definitions.

ref-buffer-type.js

var ref = require('ref');

module.exports = BufferType;

/**
 * Fixed length "Buffer" type, for use in Struct type definitions.
 *
 * Optionally setting the `encoding` param will force to call
 * `toString(encoding)` on the buffer returning a String instead.
 */

function BufferType (length, encoding) {
  if (!(this instanceof BufferType)) return new BufferType(length);
  this.size = length | 0;
  this.encoding = encoding || null;
}
BufferType.prototype = Object.create(ref.types.byte, {
  constructor: {
    value: BufferType,
    enumerable: false,
    writable: true,
    configurable: true
  }
});

BufferType.prototype.get = function (buffer, offset) {
  var buf = buffer.slice(offset, offset + this.size);
  if (this.encoding !== null) {
    buf = buf.toString(this.encoding);
  }
  return buf;
};

BufferType.prototype.set = function (buffer, offset, value) {
  if ('string' === typeof value || Array.isArray(value)) {
    value = new Buffer(value, this.encoding);
  } else if (!Buffer.isBuffer(value)) {
    throw new TypeError('Buffer instance expected');
  }

  if (value.length > this.size) {
    throw new Error('Buffer given is ' + value.length + ' bytes, but only '
        + this.size + ' bytes available');
  }

  value.copy(buffer, offset);
};