uniden-header/index.js

Parse RIFF fields from uniden home-patrol and bearcat scanner recordings

/**
The MIT License (MIT)

Copyright (c) 2015 Tal Achituv

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

@author Tal Achituv <tal@media.mit.edu>


*/
var fs = require('fs');
var path = require('path');

var DEBUG = false;

module.exports = function(fname, callback) {
	var err;
	var chunkData = { };

	chunkData['filename'] = path.basename(fname);

	if (typeof fname === 'undefined' || "" == fname) {
		err = new Error("No Filename provided!");
	} else if (!fs.existsSync(fname)) {
		err = new Error("File does not exist! ["+fname+"]");
	}

	if (DEBUG) { console.log("Parsing "+fname); }
	var file = fs.openSync(fname, 'r');


	if (!verifyFourCC(file, "RIFF", 0)) { err = new Error("File parsing error [missing RIFF marker]"); }
	chunkData['riff-length'] = getRecordLength(file,0); //the total length as reported by the header (might differ from file size in some conditions)
	if (!verifyFourCC(file, "WAVE", 8)) { if (DEBUG) { console.log("WARNING! WAVE marker not detected. This really should not happen..."); } }
	if (!verifyFourCC(file, "LIST", 12)) { err = new Error("LIST chunk not detected"); }

	var listLength = getRecordLength(file,12);
	if (!verifyFourCC(file, "INFO", 20)) { if (DEBUG) { console.log("WARNING! INFO chunk not detected!"); } }
	var unidChunkPresent = verifyFourCC(file, "unid", 12 + 4 + 4 + listLength);

	if (typeof err === 'undefined') {
		var pos = 24; //starting position of first subchunk (should be INFO) of LIST.
		var length = 0;

		var b = new Buffer(1);
		do {
			fs.readSync(file, b, 0, 1, pos)
			if (0x00==b[0]) { pos++; }
		} while (0x00==b[0] && (pos<(24+listLength)));

		while ((pos+length)<getNextChunkStartPos(file,12)) {
			var chunkName = getDataFromChunkAt(file, pos, chunkData);
			pos = getNextChunkStartPos(file,pos);

			length = getRecordLength(file,pos);
			if (DEBUG) { console.log("Next: "+pos+"("+length+")"); }
		}

		if (unidChunkPresent) {
			var pos = getNextChunkStartPos(file,12);
			getDataFromChunkAt(file,pos,chunkData);
		}
	}

	fs.closeSync(file);

	if (DEBUG) {
		console.log(chunkData);
		if (chunkData.hasOwnProperty('unid')) { console.log(chunkData['unid']['rawdata'].toString()); }
	}

	callback(err, chunkData);
}



function getFourCCAt(file, position) {
	var b = new Buffer(4);
	fs.readSync(file, b, 0, 4, position);
	return b.toString();
}

function verifyFourCC(file, fourcc, position) {
	var b = getFourCCAt(file,position);
	if (fourcc == b) {
		if (DEBUG) { console.log("Detected FourCC '"+fourcc+"' in expected position of "+position); }
		return true;
	} else {
		if (DEBUG) { console.log("Expected '"+fourcc+"' at "+position+" but found '"+b+"'"); }
		return false;
	}
}

function getRecordLength(file, position) {
	var b = new Buffer(4);
	fs.readSync(file, b, 0, 4, position+4);
	var result = (b[3]<<24)+(b[2]<<16)+(b[1]<<8)+b[0];
	if (DEBUG) { console.log("Found Record Length: "+result); }
	return result;
}



//given the starting position of a known chunk, return the starting position of the next chunk, if any. (not guaranteed that there is one, compare to expected total record length to verify you don't step out of bounds.
function getNextChunkStartPos(file,pos) {
	var chunklength = getRecordLength(file,pos);
	return pos+8+chunklength;
}

//return the position of first occorance of null, or the length of the buffer otherwise
function getNullPosition(b) {
	for (i=0; i<b.length; i++) {
		if (0x00 == b[i]) {
			return i;
		}
	}
	return i;
}


function getDataFromChunkAt(file,pos,o) {
	var fourcc = getFourCCAt(file,pos);
	var chunklength = getRecordLength(file,pos);
	var b = new Buffer(chunklength);
	fs.readSync(file, b, 0, chunklength, pos+8);

	j = 0;
	k = 0;
	dataArr = [];
	lastWasNull=false;
	for (i=0; i<chunklength; i++) {
		if (0x00 == b[i]) {
			k=0;
			lastWasNull=true;
		} else {
			if (lastWasNull && null != dataArr[0]) {
				j=j+1;
			}
			lastWasNull=false;

			if (null == dataArr[j]) {
				dataArr[j] = [];
			}
			dataArr[j][k++] = b[i];

		}
	}

	o[fourcc] = { };
	o[fourcc]['elements'] = dataArr;
	o[fourcc]['string'] = String.fromCharCode.apply(null, dataArr[0]);
	o[fourcc]['rawdata'] = b;

	if (DEBUG) { console.log("Set '"+fourcc+"' to: ["+o[fourcc]+"]:["+b+"]"); }
	return fourcc;
}