Simple JS function to parse a C enum definition. Helpful for looking up enum key from debug logs without manual counting or whatsoever.

parse_c_enum.js

/**
 * Simple function to parse a C enum definition. E.g. Given a string like:
 *   A = 0,
 *   B,
 *   C = B,
 *   D
 * 
 *  Returns a map like: {"A": 0, "B": 1, "C": 1, "D": 2}
 * 
 * @param str The enum definition string to parse.
 * @returns {!Map<string, number>} Enum key as string, enum value as value.
 */
function parseCEnum(str) {
  // Remove all comments then all unnecessary spaces.
  str = str.replace(/\/\/.*$/gm, '').replace(/^\s/gm, '');
  const enumMap = {};
  let valueIndex = 0;
  str.split(',').forEach(line => {
    if (line.length == 0) {
      // Blank line.
      return;
    }
    const lineSplit = line.split('=');
    if (lineSplit.length != 1 && lineSplit.length != 2) {
      throw new Error('Syntax error: ' + line);
    }
    const enumKey = lineSplit[0].trim();
    if (lineSplit.length == 2) {
      // The assignment value could be a previous enum key.
      const assignmentValue = lineSplit[1].trim();
      valueIndex = isNaN(assignmentValue) ? enumMap[assignmentValue]
                                          : Number(assignmentValue);
    }
    enumMap[enumKey] = valueIndex;
    valueIndex++;
  });
  return enumMap;
}

/**
 * 
 * @param str Enum definition to be flattened. E.g. "A = 0, B, C = B, D"
 * @returns {string} The flattened definition. E.g. "A = 0, B = 1, C = 1, D = 2"
 */
function flattenEnumDef(str) {
  const enumMap = parseCEnum(str);
  let newDef = '';
  for (let k in enumMap) {
    newDef += k + ' = ' + enumMap[k] + ',\n';
  }
  return newDef;
}