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JavaScript

/**
* Create a blob builder even when vendor prefixes exist
*/
var BlobBuilder = typeof BlobBuilder !== 'undefined' ? BlobBuilder :
typeof WebKitBlobBuilder !== 'undefined' ? WebKitBlobBuilder :
typeof MSBlobBuilder !== 'undefined' ? MSBlobBuilder :
typeof MozBlobBuilder !== 'undefined' ? MozBlobBuilder :
false;
/**
* Check if Blob constructor is supported
*/
var blobSupported = (function() {
try {
var a = new Blob(['hi']);
return a.size === 2;
} catch(e) {
return false;
}
})();
/**
* Check if Blob constructor supports ArrayBufferViews
* Fails in Safari 6, so we need to map to ArrayBuffers there.
*/
var blobSupportsArrayBufferView = blobSupported && (function() {
try {
var b = new Blob([new Uint8Array([1,2])]);
return b.size === 2;
} catch(e) {
return false;
}
})();
/**
* Check if BlobBuilder is supported
*/
var blobBuilderSupported = BlobBuilder
&& BlobBuilder.prototype.append
&& BlobBuilder.prototype.getBlob;
/**
* Helper function that maps ArrayBufferViews to ArrayBuffers
* Used by BlobBuilder constructor and old browsers that didn't
* support it in the Blob constructor.
*/
function mapArrayBufferViews(ary) {
return ary.map(function(chunk) {
if (chunk.buffer instanceof ArrayBuffer) {
var buf = chunk.buffer;
// if this is a subarray, make a copy so we only
// include the subarray region from the underlying buffer
if (chunk.byteLength !== buf.byteLength) {
var copy = new Uint8Array(chunk.byteLength);
copy.set(new Uint8Array(buf, chunk.byteOffset, chunk.byteLength));
buf = copy.buffer;
}
return buf;
}
return chunk;
});
}
function BlobBuilderConstructor(ary, options) {
options = options || {};
var bb = new BlobBuilder();
mapArrayBufferViews(ary).forEach(function(part) {
bb.append(part);
});
return (options.type) ? bb.getBlob(options.type) : bb.getBlob();
};
function BlobConstructor(ary, options) {
return new Blob(mapArrayBufferViews(ary), options || {});
};
if (typeof Blob !== 'undefined') {
BlobBuilderConstructor.prototype = Blob.prototype;
BlobConstructor.prototype = Blob.prototype;
}
module.exports = (function() {
if (blobSupported) {
return blobSupportsArrayBufferView ? Blob : BlobConstructor;
} else if (blobBuilderSupported) {
return BlobBuilderConstructor;
} else {
return undefined;
}
})();