protodef/src/datatypes/conditional.js

A simple yet powerful way to define binary protocols

const { getField, getFieldInfo, tryDoc, PartialReadError} = require('../utils');

module.exports = {
  'switch': [readSwitch, writeSwitch, sizeOfSwitch, require('../../ProtoDef/schemas/conditional')["switch"]],
  'option': [readOption, writeOption, sizeOfOption, require('../../ProtoDef/schemas/conditional')["option"]]
};

function readSwitch(buffer, offset, {compareTo,fields,compareToValue,"default":defVal}, rootNode) {
  compareTo = compareToValue!==undefined ? compareToValue : getField(compareTo, rootNode);
  if (typeof fields[compareTo] === 'undefined' && typeof defVal === "undefined")
    throw new Error(compareTo + " has no associated fieldInfo in switch");

  const caseDefault=typeof fields[compareTo] === 'undefined';
  const resultingType = caseDefault ? defVal : fields[compareTo];
  const fieldInfo = getFieldInfo(resultingType);
  return tryDoc(() => this.read(buffer, offset, fieldInfo, rootNode),caseDefault ? "default" : compareTo);
}

function writeSwitch(value, buffer, offset, {compareTo,fields,compareToValue,"default":defVal}, rootNode) {
  compareTo = compareToValue!==undefined ? compareToValue : getField(compareTo, rootNode);
  if (typeof fields[compareTo] === 'undefined' && typeof defVal === "undefined")
    throw new Error(compareTo + " has no associated fieldInfo in switch");

  const caseDefault=typeof fields[compareTo] === 'undefined';
  const fieldInfo = getFieldInfo(caseDefault ? defVal : fields[compareTo]);
  return tryDoc(() => this.write(value, buffer, offset, fieldInfo, rootNode),caseDefault ? "default" : compareTo);
}

function sizeOfSwitch(value, {compareTo,fields,compareToValue,"default":defVal}, rootNode) {
  compareTo = compareToValue!==undefined ? compareToValue : getField(compareTo, rootNode);
  if (typeof fields[compareTo] === 'undefined' && typeof defVal === "undefined")
    throw new Error(compareTo + " has no associated fieldInfo in switch");

  const caseDefault=typeof fields[compareTo] === 'undefined';
  const fieldInfo = getFieldInfo(caseDefault ? defVal : fields[compareTo]);
  return tryDoc(() => this.sizeOf(value, fieldInfo, rootNode),caseDefault ? "default" : compareTo);
}

function readOption(buffer, offset, typeArgs, context) {
  if(buffer.length<offset+1)
    throw new PartialReadError();
  const val = buffer.readUInt8(offset++);
  if (val !== 0) {
    const retval = this.read(buffer, offset, typeArgs, context);
    retval.size++;
    return retval;
  }
  else
    return {size: 1};
}

function writeOption(value, buffer, offset, typeArgs, context) {
  if (value != null) {
    buffer.writeUInt8(1, offset++);
    offset=this.write(value, buffer, offset, typeArgs, context);
  }
  else
    buffer.writeUInt8(0, offset++);
  return offset;
}

function sizeOfOption(value, typeArgs, context) {
  return value == null ? 1 : this.sizeOf(value, typeArgs, context) + 1;
}