Spark-MD5获取文件MD5的使用

function calculate(file,callBack){
var fileReader = new FileReader(),
blobSlice = File.prototype.mozSlice || File.prototype.webkitSlice || File.prototype.slice,
chunkSize = 2097152,
// read in chunks of 2MB
chunks = Math.ceil(file.size / chunkSize),
currentChunk = 0,
spark = new SparkMD5();

fileReader.onload = function(e) {
spark.appendBinary(e.target.result); // append binary string
currentChunk++;

if (currentChunk < chunks) {
loadNext();
}
else {
callBack(spark.end());
}
};

function loadNext() {
var start = currentChunk * chunkSize,
end = start + chunkSize >= file.size ? file.size : start + chunkSize;

fileReader.readAsBinaryString(blobSlice.call(file, start, end));
};

loadNext();
}