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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
/**
* Namespace for utility functions.
*/
var util = {
/**
* Returns a function that console.log's its arguments, prefixed by |msg|.
*
* @param {string} msg The message prefix to use in the log.
* @param {function(*)} opt_callback A function to invoke after logging.
*/
flog: function(msg, opt_callback) {
return function() {
var ary = Array.apply(null, arguments);
console.log(msg + ': ' + ary.join(', '));
if (opt_callback)
opt_callback.call(arguments);
};
},
/**
* Returns a function that throws an exception that includes its arguments
* prefixed by |msg|.
*
* @param {string} msg The message prefix to use in the exception.
*/
ferr: function(msg) {
return function() {
var ary = Array.apply(null, arguments);
throw new Error(msg + ': ' + ary.join(', '));
};
},
/**
* Install a sensible toString() on the FileError object.
*
* FileError.prototype.code is a numeric code describing the cause of the
* error. The FileError constructor has a named property for each possible
* error code, but provides no way to map the code to the named property.
* This toString() implementation fixes that.
*/
installFileErrorToString: function() {
FileError.prototype.toString = function() {
return '[object FileError: ' + util.getFileErrorMnemonic(this.code) + ']';
}
},
getFileErrorMnemonic: function(code) {
for (var key in FileError) {
if (key.search(/_ERR$/) != -1 && FileError[key] == code)
return key;
}
return code;
},
/**
* Utility function to invoke callback once for each entry in dirEntry.
*
* @param {DirectoryEntry} dirEntry The directory entry to enumerate.
* @param {function(Entry)} callback The function to invoke for each entry in
* dirEntry.
*/
forEachDirEntry: function(dirEntry, callback) {
var reader;
function onReadSome(results) {
if (results.length == 0)
return callback(null);
for (var i = 0; i < results.length; i++)
callback(results[i]);
reader.readEntries(onReadSome);
};
reader = dirEntry.createReader();
reader.readEntries(onReadSome);
},
/**
* Utility function to resolve multiple directories with a single call.
*
* The successCallback will be invoked once for each directory object
* found. The errorCallback will be invoked once for each
* path that could not be resolved.
*
* The successCallback is invoked with a null entry when all paths have
* been processed.
*
* @param {DirEntry} dirEntry The base directory.
* @param {Object} params The parameters to pass to the underlying
* getDirectory calls.
* @param {Array<string>} paths The list of directories to resolve.
* @param {function(!DirEntry)} successCallback The function to invoke for
* each DirEntry found. Also invoked once with null at the end of the
* process.
* @param {function(string, FileError)} errorCallback The function to invoke
* for each path that cannot be resolved.
*/
getDirectories: function(dirEntry, params, paths, successCallback,
errorCallback) {
// Copy the params array, since we're going to destroy it.
params = [].slice.call(params);
function onComplete() {
successCallback(null);
}
function getNextDirectory() {
var path = paths.shift();
if (!path)
return onComplete();
dirEntry.getDirectory(
path, params,
function(entry) {
successCallback(entry);
getNextDirectory();
},
function(err) {
errorCallback(path, err);
getNextDirectory();
});
}
getNextDirectory();
},
/**
* Lookup tables used by bytesToSi.
*/
units_: ['B', 'k', 'M', 'G', 'T', 'P'],
scale_: [1, 1e3, 1e6, 1e9, 1e12, 1e15],
/**
* Convert a number of bytes into an appropriate International System of
* Units (SI) representation, using the correct number separators.
*
* The first time this function is called it computes a lookup table which
* is cached for subsequent calls.
*
* @param {number} bytes The number of bytes.
*/
bytesToSi: function(bytes) {
function fmt(s, u) {
var rounded = Math.round(bytes / s * 10) / 10;
// TODO(rginda): Switch to v8Locale's number formatter when it's
// available.
return rounded.toLocaleString() + u;
}
// This loop index is used outside the loop if it turns out |bytes|
// requires the largest unit.
var i;
for (i = 0; i < this.units_.length - 1; i++) {
if (bytes < this.scale_[i + 1])
return fmt(this.scale_[i], this.units_[i]);
}
return fmt(this.scale_[i], this.units_[i]);
},
/**
* Utility function to read specified range of bytes from file
* @param file {File} file to read
* @param begin {int} starting byte(included)
* @param end {int} last byte(excluded)
* @param callback {function(File, Uint8Array)} callback to invoke
* @param onError {function(err)} error handler
*/
readFileBytes: function(file, begin, end, callback, onError) {
var fileReader = new FileReader();
fileReader.onerror = onError;
fileReader.onloadend = function() {
callback(file, new ByteReader(fileReader.result))
};
fileReader.readAsArrayBuffer(file.webkitSlice(begin, end));
}
};
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