Parses an SCP-ECG file and prints the demographics/data acquisition information (in Section 1)

parse_scpecg.js

var fs = require('fs')

var DEBUG = true;

var log = console.log;
if (!DEBUG)
	log = function() {};

function parse_scp_time(fval) {
	var hour = fval.readInt8(0);
	var min = fval.readInt8(1);
	var sec = fval.readInt8(2);
	return hour + ":" + min + ":" + sec;

}
function parse_scp_date(fval) {
	var year = fval.readUInt16LE(0);
	var month = fval.readInt8(2);
	var day = fval.readInt8(3);
	return day + "/" + month + "/"+ year;

}

function parse_scp_ecg_demo(b) {
	var secHdrLen = 16;
	var ptrFldLen = 2 + 4 + 4; // Section Number | Section Length | Index to section
	var section0_start = 6;
	var section0_data_start = section0_start + secHdrLen;
	var ptrFld1_start = section0_data_start + ptrFldLen; // Move over Section0 pointer field
	var section1_len = b.readUInt32LE(ptrFld1_start + 2);
	var section1_start = b.readUInt32LE(ptrFld1_start + 2 + 4)-1; // It appers to be 1-based not 0-based pointer

	var section1_end = section1_start+section1_len;
	// var section1_hdr = b.slice(section1_start, section1_start +secHdrLen);
	// var section1_data = b.slice(section1_start+secHdrLen, section1_end);

	// log('== Section ' + section1_hdr.readUInt16LE(2));
	var fstart = section1_start + secHdrLen;
	var js = {};
	while (fstart < section1_end) {
		var tag = b.readUInt8(fstart);
		if (tag == 255) {
			// log('Found Demographic section terminator!');
			break;
		}
		var flen = b.readUInt16LE(fstart+1);
		var val_start = fstart + 3;
		var fval= b.slice(val_start, val_start+flen);
		var val_str = fval.slice(0, flen-1).toString(); // Strings are null terminated!
		var val_int = b.readUInt16LE(val_start);
		var val_b = b.readUInt8(val_start);
		//log(tag + " (" + flen + ") ==>" + b.readInt8(val_start));
		switch (tag) {
			case 0:  log('Last name: ' + val_str); js.lname = val_str; break;
			case 1:  log('First name: ' + val_str); js.fname = val_str; break;
			case 2:  log('Patient ID: ' + val_str); js.patid = val_str; break;
			case 3:  log('2nd Last name: ' + val_str); break;
			case 4:  log('Age: ' + val_int); js.age = val_int; break;
			case 5:  log('DoB: ' + parse_scp_date(fval)); break;
			case 6:  log('Height: ' + val_int + "cm"); js.height = val_int; break;
			case 7:  log('Weight: ' + val_int + "kg"); js.weight = val_int; break;
			case 8:  log('Sex: ' + (val_b==1? "Male" : (val_b==2 ? "Female" : "Other"))); break;
			case 11: log('Sys Pressure: ' + val_int + "mmHg"); js.syspres = val_int; break;
			case 12: log('Dia Pressure: ' + val_int + "mmHg"); js.diapres = val_int; break;
			case 25: log('Date of Acq. : ' + parse_scp_date(fval)); break;
			case 26: log('Time of Acq. : ' + parse_scp_time(fval)); break;
			default:
				//log(tag + " (" + flen + ") ==>" + val_str);
		}
		fstart = fstart + 3 + flen;
	}
	return js;
}
var fns = ['ECGSamples/scp_redred/P120N00.scp'];
var args = process.argv.slice(2);
if (args.length > 0)
	fns = args;

fns.forEach(function(fn) {
	fs.readFile(fn, function (err, data) {
		if (err)
			throw err;
		log("====== " + fn );
		var js = parse_scp_ecg_demo(data);
		if (!DEBUG) {
			console.log(fn +"==> " + JSON.stringify(js));
		}
	});
});