index.js

'use strict';

var promisify = require('util').promisify;
var fs = require('fs');
var exifReader = require('exif-reader');

var open = promisify(fs.open);
var read = promisify(fs.read);
var close = promisify(fs.close);

module.exports = {
  read: readExif
};

function readExif (filename, maxIterations) {
	if (maxIterations === true) { // former isDeepSearch boolean argument
		maxIterations = Number.MAX_SAFE_INTEGER;
	}
	if (maxIterations === undefined) {
		maxIterations = 1;
	}
	return open(filename, 'r').then(function (fd) {
		var buffer = new Buffer(512);
		return searchExif(fd, buffer, 0, maxIterations)
			.then(function (exifBuffer) {
				return exifBuffer && exifReader(exifBuffer);
			})
			.finally(function () {
				return close(fd);
			});
	});
}

function searchExif (fd, buffer, fileOffset, remainingIterations) {
	var offset = 0, length = buffer.length;
	return read(fd, buffer, 0, length, null).then(function (bytesRead) {
		if (!bytesRead) {
			return null;
		}
		while (offset < length) {
			if (buffer[offset++] == 0xFF && buffer[offset] == 0xE1) {
				var exifBuffer = new Buffer(buffer.readUInt16BE(++offset));
				return read(fd, exifBuffer, 0, exifBuffer.length, fileOffset + offset + 2).return(exifBuffer);
			}
		}
		return remainingIterations > 1 ? searchExif(fd, buffer, fileOffset + length, remainingIterations - 1) : null;
	});
}