src/util.js
function (blob, callback) {
    readAsBinaryString(blob, function (content) {
        var hash = md5(content, true);
        callback(null, hash);
    });
}
function (blob, callback) {
    readAsBinaryString(blob, function (content) {
        var hash = md5(content, true);
        callback(null, hash);
    });
}
获取文件 md5 值