localforage
Version:
Offline storage, improved.
246 lines (216 loc) • 8.82 kB
JavaScript
/* eslint-disable no-bitwise */
import createBlob from './createBlob';
// Sadly, the best way to save binary data in WebSQL/localStorage is serializing
// it to Base64, so this is how we store it to prevent very strange errors with less
// verbose ways of binary <-> string data storage.
var BASE_CHARS =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
var BLOB_TYPE_PREFIX = '~~local_forage_type~';
var BLOB_TYPE_PREFIX_REGEX = /^~~local_forage_type~([^~]+)~/;
var SERIALIZED_MARKER = '__lfsc__:';
var SERIALIZED_MARKER_LENGTH = SERIALIZED_MARKER.length;
// OMG the serializations!
var TYPE_ARRAYBUFFER = 'arbf';
var TYPE_BLOB = 'blob';
var TYPE_INT8ARRAY = 'si08';
var TYPE_UINT8ARRAY = 'ui08';
var TYPE_UINT8CLAMPEDARRAY = 'uic8';
var TYPE_INT16ARRAY = 'si16';
var TYPE_INT32ARRAY = 'si32';
var TYPE_UINT16ARRAY = 'ur16';
var TYPE_UINT32ARRAY = 'ui32';
var TYPE_FLOAT32ARRAY = 'fl32';
var TYPE_FLOAT64ARRAY = 'fl64';
var TYPE_SERIALIZED_MARKER_LENGTH =
SERIALIZED_MARKER_LENGTH + TYPE_ARRAYBUFFER.length;
var toString = Object.prototype.toString;
function stringToBuffer(serializedString) {
// Fill the string into a ArrayBuffer.
var bufferLength = serializedString.length * 0.75;
var len = serializedString.length;
var i;
var p = 0;
var encoded1, encoded2, encoded3, encoded4;
if (serializedString[serializedString.length - 1] === '=') {
bufferLength--;
if (serializedString[serializedString.length - 2] === '=') {
bufferLength--;
}
}
var buffer = new ArrayBuffer(bufferLength);
var bytes = new Uint8Array(buffer);
for (i = 0; i < len; i += 4) {
encoded1 = BASE_CHARS.indexOf(serializedString[i]);
encoded2 = BASE_CHARS.indexOf(serializedString[i + 1]);
encoded3 = BASE_CHARS.indexOf(serializedString[i + 2]);
encoded4 = BASE_CHARS.indexOf(serializedString[i + 3]);
/*jslint bitwise: true */
bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
}
return buffer;
}
// Converts a buffer to a string to store, serialized, in the backend
// storage library.
function bufferToString(buffer) {
// base64-arraybuffer
var bytes = new Uint8Array(buffer);
var base64String = '';
var i;
for (i = 0; i < bytes.length; i += 3) {
/*jslint bitwise: true */
base64String += BASE_CHARS[bytes[i] >> 2];
base64String += BASE_CHARS[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
base64String +=
BASE_CHARS[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
base64String += BASE_CHARS[bytes[i + 2] & 63];
}
if (bytes.length % 3 === 2) {
base64String = base64String.substring(0, base64String.length - 1) + '=';
} else if (bytes.length % 3 === 1) {
base64String =
base64String.substring(0, base64String.length - 2) + '==';
}
return base64String;
}
// Serialize a value, afterwards executing a callback (which usually
// instructs the `setItem()` callback/promise to be executed). This is how
// we store binary data with localStorage.
function serialize(value, callback) {
var valueType = '';
if (value) {
valueType = toString.call(value);
}
// Cannot use `value instanceof ArrayBuffer` or such here, as these
// checks fail when running the tests using casper.js...
//
// TODO: See why those tests fail and use a better solution.
if (
value &&
(valueType === '[object ArrayBuffer]' ||
(value.buffer &&
toString.call(value.buffer) === '[object ArrayBuffer]'))
) {
// Convert binary arrays to a string and prefix the string with
// a special marker.
var buffer;
var marker = SERIALIZED_MARKER;
if (value instanceof ArrayBuffer) {
buffer = value;
marker += TYPE_ARRAYBUFFER;
} else {
buffer = value.buffer;
if (valueType === '[object Int8Array]') {
marker += TYPE_INT8ARRAY;
} else if (valueType === '[object Uint8Array]') {
marker += TYPE_UINT8ARRAY;
} else if (valueType === '[object Uint8ClampedArray]') {
marker += TYPE_UINT8CLAMPEDARRAY;
} else if (valueType === '[object Int16Array]') {
marker += TYPE_INT16ARRAY;
} else if (valueType === '[object Uint16Array]') {
marker += TYPE_UINT16ARRAY;
} else if (valueType === '[object Int32Array]') {
marker += TYPE_INT32ARRAY;
} else if (valueType === '[object Uint32Array]') {
marker += TYPE_UINT32ARRAY;
} else if (valueType === '[object Float32Array]') {
marker += TYPE_FLOAT32ARRAY;
} else if (valueType === '[object Float64Array]') {
marker += TYPE_FLOAT64ARRAY;
} else {
callback(new Error('Failed to get type for BinaryArray'));
}
}
callback(marker + bufferToString(buffer));
} else if (valueType === '[object Blob]') {
// Conver the blob to a binaryArray and then to a string.
var fileReader = new FileReader();
fileReader.onload = function() {
// Backwards-compatible prefix for the blob type.
var str =
BLOB_TYPE_PREFIX +
value.type +
'~' +
bufferToString(this.result);
callback(SERIALIZED_MARKER + TYPE_BLOB + str);
};
fileReader.readAsArrayBuffer(value);
} else {
try {
callback(JSON.stringify(value));
} catch (e) {
console.error("Couldn't convert value into a JSON string: ", value);
callback(null, e);
}
}
}
// Deserialize data we've inserted into a value column/field. We place
// special markers into our strings to mark them as encoded; this isn't
// as nice as a meta field, but it's the only sane thing we can do whilst
// keeping localStorage support intact.
//
// Oftentimes this will just deserialize JSON content, but if we have a
// special marker (SERIALIZED_MARKER, defined above), we will extract
// some kind of arraybuffer/binary data/typed array out of the string.
function deserialize(value) {
// If we haven't marked this string as being specially serialized (i.e.
// something other than serialized JSON), we can just return it and be
// done with it.
if (value.substring(0, SERIALIZED_MARKER_LENGTH) !== SERIALIZED_MARKER) {
return JSON.parse(value);
}
// The following code deals with deserializing some kind of Blob or
// TypedArray. First we separate out the type of data we're dealing
// with from the data itself.
var serializedString = value.substring(TYPE_SERIALIZED_MARKER_LENGTH);
var type = value.substring(
SERIALIZED_MARKER_LENGTH,
TYPE_SERIALIZED_MARKER_LENGTH
);
var blobType;
// Backwards-compatible blob type serialization strategy.
// DBs created with older versions of localForage will simply not have the blob type.
if (type === TYPE_BLOB && BLOB_TYPE_PREFIX_REGEX.test(serializedString)) {
var matcher = serializedString.match(BLOB_TYPE_PREFIX_REGEX);
blobType = matcher[1];
serializedString = serializedString.substring(matcher[0].length);
}
var buffer = stringToBuffer(serializedString);
// Return the right type based on the code/type set during
// serialization.
switch (type) {
case TYPE_ARRAYBUFFER:
return buffer;
case TYPE_BLOB:
return createBlob([buffer], { type: blobType });
case TYPE_INT8ARRAY:
return new Int8Array(buffer);
case TYPE_UINT8ARRAY:
return new Uint8Array(buffer);
case TYPE_UINT8CLAMPEDARRAY:
return new Uint8ClampedArray(buffer);
case TYPE_INT16ARRAY:
return new Int16Array(buffer);
case TYPE_UINT16ARRAY:
return new Uint16Array(buffer);
case TYPE_INT32ARRAY:
return new Int32Array(buffer);
case TYPE_UINT32ARRAY:
return new Uint32Array(buffer);
case TYPE_FLOAT32ARRAY:
return new Float32Array(buffer);
case TYPE_FLOAT64ARRAY:
return new Float64Array(buffer);
default:
throw new Error('Unkown type: ' + type);
}
}
var localforageSerializer = {
serialize: serialize,
deserialize: deserialize,
stringToBuffer: stringToBuffer,
bufferToString: bufferToString
};
export default localforageSerializer;