shaka-player
Version:
DASH/EME video player library
280 lines (245 loc) • 9.34 kB
JavaScript
/**
* @license
* Copyright 2016 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
goog.provide('shaka.util.StringUtils');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.Error');
/**
* @namespace shaka.util.StringUtils
* @summary A set of string utility functions.
* @export
*/
/**
* Creates a string from the given buffer as UTF-8 encoding.
*
* @param {?BufferSource} data
* @return {string}
* @throws {shaka.util.Error}
* @export
*/
shaka.util.StringUtils.fromUTF8 = function(data) {
if (!data) return '';
let uint8 = new Uint8Array(data);
// If present, strip off the UTF-8 BOM.
if (uint8[0] == 0xef && uint8[1] == 0xbb && uint8[2] == 0xbf) {
uint8 = uint8.subarray(3);
}
// http://stackoverflow.com/a/13691499
let utf8 = shaka.util.StringUtils.fromCharCode(uint8);
// This converts each character in the string to an escape sequence. If the
// character is in the ASCII range, it is not converted; otherwise it is
// converted to a URI escape sequence.
// Example: '\x67\x35\xe3\x82\xac' -> 'g#%E3%82%AC'
let escaped = escape(utf8);
// Decode the escaped sequence. This will interpret UTF-8 sequences into the
// correct character.
// Example: 'g#%E3%82%AC' -> 'g#€'
try {
return decodeURIComponent(escaped);
} catch (e) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL, shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.BAD_ENCODING);
}
};
/**
* Creates a string from the given buffer as UTF-16 encoding.
*
* @param {?BufferSource} data
* @param {boolean} littleEndian true to read little endian, false to read big.
* @param {boolean=} noThrow true to avoid throwing in cases where we may
* expect invalid input. If noThrow is true and the data has an odd length,
* it will be truncated.
* @return {string}
* @throws {shaka.util.Error}
* @export
*/
shaka.util.StringUtils.fromUTF16 = function(data, littleEndian, noThrow) {
if (!data) return '';
if (!noThrow && data.byteLength % 2 != 0) {
shaka.log.error('Data has an incorrect length, must be even.');
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL, shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.BAD_ENCODING);
}
/** @type {ArrayBuffer} */
let buffer;
if (data instanceof ArrayBuffer) {
buffer = data;
} else {
// Have to create a new buffer because the argument may be a smaller
// view on a larger ArrayBuffer. We cannot use an ArrayBufferView in
// a DataView.
let temp = new Uint8Array(data.byteLength);
temp.set(new Uint8Array(data));
buffer = temp.buffer;
}
// Use a DataView to ensure correct endianness.
let length = Math.floor(data.byteLength / 2);
let arr = new Uint16Array(length);
let dataView = new DataView(buffer);
for (let i = 0; i < length; i++) {
arr[i] = dataView.getUint16(i * 2, littleEndian);
}
return shaka.util.StringUtils.fromCharCode(arr);
};
/**
* Creates a string from the given buffer, auto-detecting the encoding that is
* being used. If it cannot detect the encoding, it will throw an exception.
*
* @param {?BufferSource} data
* @return {string}
* @throws {shaka.util.Error}
* @export
*/
shaka.util.StringUtils.fromBytesAutoDetect = function(data) {
const StringUtils = shaka.util.StringUtils;
let uint8 = new Uint8Array(data);
if (uint8[0] == 0xef && uint8[1] == 0xbb && uint8[2] == 0xbf) {
return StringUtils.fromUTF8(uint8);
} else if (uint8[0] == 0xfe && uint8[1] == 0xff) {
return StringUtils.fromUTF16(uint8.subarray(2), false /* littleEndian */);
} else if (uint8[0] == 0xff && uint8[1] == 0xfe) {
return StringUtils.fromUTF16(uint8.subarray(2), true /* littleEndian */);
}
let isAscii = (function(arr, i) {
// arr[i] >= ' ' && arr[i] <= '~';
return arr.byteLength <= i || (arr[i] >= 0x20 && arr[i] <= 0x7e);
}.bind(null, uint8));
shaka.log.debug('Unable to find byte-order-mark, making an educated guess.');
if (uint8[0] == 0 && uint8[2] == 0) {
return StringUtils.fromUTF16(data, false /* littleEndian */);
} else if (uint8[1] == 0 && uint8[3] == 0) {
return StringUtils.fromUTF16(data, true /* littleEndian */);
} else if (isAscii(0) && isAscii(1) && isAscii(2) && isAscii(3)) {
return StringUtils.fromUTF8(data);
}
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.TEXT,
shaka.util.Error.Code.UNABLE_TO_DETECT_ENCODING);
};
/**
* Creates a ArrayBuffer from the given string, converting to UTF-8 encoding.
*
* @param {string} str
* @return {!ArrayBuffer}
* @export
*/
shaka.util.StringUtils.toUTF8 = function(str) {
// http://stackoverflow.com/a/13691499
// Converts the given string to a URI encoded string. If a character falls
// in the ASCII range, it is not converted; otherwise it will be converted to
// a series of URI escape sequences according to UTF-8.
// Example: 'g#€' -> 'g#%E3%82%AC'
let encoded = encodeURIComponent(str);
// Convert each escape sequence individually into a character. Each escape
// sequence is interpreted as a code-point, so if an escape sequence happens
// to be part of a multi-byte sequence, each byte will be converted to a
// single character.
// Example: 'g#%E3%82%AC' -> '\x67\x35\xe3\x82\xac'
let utf8 = unescape(encoded);
let result = new Uint8Array(utf8.length);
for (let i = 0; i < utf8.length; ++i) {
result[i] = utf8.charCodeAt(i);
}
return result.buffer;
};
/**
* Creates a ArrayBuffer from the given string, converting to UTF-16 encoding.
*
* @param {string} str
* @param {boolean} littleEndian
* @return {!ArrayBuffer}
* @export
*/
shaka.util.StringUtils.toUTF16 = function(str, littleEndian) {
const result = new Uint8Array(str.length * 2);
const view = new DataView(result.buffer);
for (let i = 0; i < str.length; ++i) {
const value = str.charCodeAt(i);
view.setUint16(/* position= */ i * 2, value, littleEndian);
}
return result.buffer;
};
/**
* Creates a new string from the given array of char codes.
*
* Using String.fromCharCode.apply is risky because you can trigger stack errors
* on very large arrays. This breaks up the array into several pieces to avoid
* this.
*
* @param {!TypedArray} array
* @return {string}
*/
shaka.util.StringUtils.fromCharCode = function(array) {
// Check the browser for what chunk sizes it supports. Cache the result
// in an impl method to avoid checking several times.
if (!shaka.util.StringUtils.fromCharCodeImpl_) {
const supportsChunkSize = (size) => {
try {
// The compiler will complain about suspicious value if this isn't
// stored in a variable and used.
const buffer = new Uint8Array(size);
// This can't use the spread operator, or it blows up on Xbox One.
// So we use apply() instead, which is normally not allowed.
// See issue #2186 for more details.
// eslint-disable-next-line no-restricted-syntax
const foo = String.fromCharCode.apply(null, buffer);
goog.asserts.assert(foo, 'Should get value');
return foo.length > 0; // Actually use "foo", so it's not compiled out.
} catch (error) {
return false;
}
};
// Different browsers support different chunk sizes; find out the largest
// this browser supports so we can use larger chunks on supported browsers
// but still support lower-end devices that require small chunks.
// 64k is supported on all major desktop browsers.
for (let size = 64 * 1024; size > 0; size /= 2) {
if (supportsChunkSize(size)) {
shaka.util.StringUtils.fromCharCodeImpl_ = (buffer) => {
let ret = '';
for (let i = 0; i < buffer.length; i += size) {
const subArray = buffer.subarray(i, i + size);
// This can't use the spread operator, or it blows up on Xbox One.
// So we use apply() instead, which is normally not allowed.
// See issue #2186 for more details.
// eslint-disable-next-line no-restricted-syntax
ret += String.fromCharCode.apply(null, subArray); // Issue #2186
}
return ret;
};
break;
}
}
}
goog.asserts.assert(
shaka.util.StringUtils.fromCharCodeImpl_,
'Unable to create a fromCharCode method');
return shaka.util.StringUtils.fromCharCodeImpl_(array);
};
/** @private {?function(!TypedArray):string} */
shaka.util.StringUtils.fromCharCodeImpl_ = null;
/**
* Resets the fromCharCode method's implementation.
* For debug use.
* @export
*/
shaka.util.StringUtils.resetFromCharCode = function() {
shaka.util.StringUtils.fromCharCodeImpl_ = null;
};