@@ -38,7 +38,245 @@ var LibraryFetch = {
3838 '$fetchLoadCachedData' ,
3939 '$fetchDeleteCachedData' ,
4040#endif
41- ]
41+ #if FETCH_BACKEND == 'fetch'
42+ '$FetchXHR' ,
43+ #endif
44+ ] ,
45+ /**
46+ * A class that mimics the XMLHttpRequest API using the modern Fetch API.
47+ * This implementation is specifically tailored to only handle 'arraybuffer'
48+ * responses.
49+ */
50+ $FetchXHR : class {
51+ constructor ( ) {
52+ // --- Public XHR Properties ---
53+
54+ // Event Handlers
55+ this . onload = null ;
56+ this . onerror = null ;
57+ this . onprogress = null ;
58+ this . onreadystatechange = null ;
59+ this . ontimeout = null ;
60+
61+ // Request Configuration
62+ this . responseType = 'arraybuffer' ;
63+ this . withCredentials = false ;
64+ this . timeout = 0 ; // Standard XHR timeout property
65+
66+ // Response / State Properties
67+ this . readyState = 0 ; // 0: UNSENT
68+ this . response = null ;
69+ this . responseURL = '' ;
70+ this . status = 0 ;
71+ this . statusText = '' ;
72+
73+ // --- Internal Properties ---
74+ this . _method = '' ;
75+ this . _url = '' ;
76+ this . _headers = { } ;
77+ this . _abortController = null ;
78+ this . _aborted = false ;
79+ this . _responseHeaders = null ;
80+ }
81+
82+ // --- Private state management ---
83+ _changeReadyState ( state ) {
84+ this . readyState = state ;
85+ this . onreadystatechange ?. ( ) ;
86+ }
87+
88+ // --- Public XHR Methods ---
89+
90+ /**
91+ * Initializes a request.
92+ * @param {string } method The HTTP request method (e.g., 'GET', 'POST').
93+ * @param {string } url The URL to send the request to.
94+ * @param {boolean } [async=true] This parameter is ignored as Fetch is always async.
95+ * @param {string|null } [user=null] The username for basic authentication.
96+ * @param {string|null } [password=null] The password for basic authentication.
97+ */
98+ open ( method , url , async = true , user = null , password = null ) {
99+ if ( this . readyState !== 0 && this . readyState !== 4 ) {
100+ console . warn ( "FetchXHR.open() called while a request is in progress." ) ;
101+ this . abort ( ) ;
102+ }
103+
104+ // Reset internal state for the new request
105+ this . _method = method ;
106+ this . _url = url ;
107+ this . _headers = { } ;
108+ this . _responseHeaders = null ;
109+
110+ // The async parameter is part of the XHR API but is an error here because
111+ // the Fetch API is inherently asynchronous and does not support synchronous requests.
112+ if ( ! async ) {
113+ throw new Error ( "FetchXHR does not support synchronous requests." ) ;
114+ }
115+
116+ // Handle Basic Authentication if user/password are provided.
117+ // This creates a base64-encoded string and sets the Authorization header.
118+ if ( user ) {
119+ const credentials = btoa ( `${ user } ${ password || '' } ) ;
120+ this . _headers [ 'Authorization' ] = `Basic ${ credentials } ;
121+ }
122+
123+ this . _changeReadyState ( 1 ) ; // 1: OPENED
124+ }
125+
126+ /**
127+ * Sets the value of an HTTP request header.
128+ * @param {string } header The name of the header.
129+ * @param {string } value The value of the header.
130+ */
131+ setRequestHeader ( header , value ) {
132+ if ( this . readyState !== 1 ) {
133+ throw new Error ( 'setRequestHeader can only be called when state is OPENED.' ) ;
134+ }
135+ this . _headers [ header ] = value ;
136+ }
137+
138+ /**
139+ * This method is not effectively implemented because Fetch API relies on the
140+ * server's Content-Type header and does not support overriding the MIME type
141+ * on the client side in the same way as XHR.
142+ * @param {string } mimetype The MIME type to use.
143+ */
144+ overrideMimeType ( mimetype ) {
145+ throw new Error ( "overrideMimeType is not supported by the Fetch API and has no effect." ) ;
146+ }
147+
148+ /**
149+ * Returns a string containing all the response headers, separated by CRLF.
150+ * @returns {string } The response headers.
151+ */
152+ getAllResponseHeaders ( ) {
153+ if ( ! this . _responseHeaders ) {
154+ return '' ;
155+ }
156+
157+ let headersString = '' ;
158+ // The Headers object is iterable.
159+ for ( const [ key , value ] of this . _responseHeaders . entries ( ) ) {
160+ headersString += `${ key } ${ value } ;
161+ }
162+ return headersString ;
163+ }
164+
165+ /**
166+ * Sends the request.
167+ * @param {any } body The body of the request.
168+ */
169+ async send ( body = null ) {
170+ if ( this . readyState !== 1 ) {
171+ throw new Error ( 'send() can only be called when state is OPENED.' ) ;
172+ }
173+
174+ this . _abortController = new AbortController ( ) ;
175+ const signal = this . _abortController . signal ;
176+
177+ // Handle timeout
178+ let timeoutID ;
179+ if ( this . timeout > 0 ) {
180+ timeoutID = setTimeout (
181+ ( ) => this . _abortController . abort ( new DOMException ( 'The user aborted a request.' , 'TimeoutError' ) ) ,
182+ this . timeout
183+ ) ;
184+ }
185+
186+ const fetchOptions = {
187+ method : this . _method ,
188+ headers : this . _headers ,
189+ body : body ,
190+ signal : signal ,
191+ credentials : this . withCredentials ? 'include' : 'same-origin' ,
192+ } ;
193+
194+ try {
195+ const response = await fetch ( this . _url , fetchOptions ) ;
196+
197+ // Populate response properties once headers are received
198+ this . status = response . status ;
199+ this . statusText = response . statusText ;
200+ this . responseURL = response . url ;
201+ this . _responseHeaders = response . headers ;
202+ this . _changeReadyState ( 2 ) ; // 2: HEADERS_RECEIVED
203+
204+ // Start processing the body
205+ this . _changeReadyState ( 3 ) ; // 3: LOADING
206+
207+ if ( ! response . body ) {
208+ throw new Error ( "Response has no body to read." ) ;
209+ }
210+
211+ const reader = response . body . getReader ( ) ;
212+ const contentLength = + response . headers . get ( 'Content-Length' ) ;
213+
214+ let receivedLength = 0 ;
215+ const chunks = [ ] ;
216+
217+ while ( true ) {
218+ const { done, value } = await reader . read ( ) ;
219+ if ( done ) {
220+ break ;
221+ }
222+
223+ chunks . push ( value ) ;
224+ receivedLength += value . length ;
225+
226+ if ( this . onprogress ) {
227+ // Convert to ArrayBuffer as requested by responseType.
228+ this . response = value . buffer ;
229+ const progressEvent = {
230+ lengthComputable : contentLength > 0 ,
231+ loaded : receivedLength ,
232+ total : contentLength
233+ } ;
234+ this . onprogress ( progressEvent ) ;
235+ }
236+ }
237+
238+ // Combine chunks into a single Uint8Array.
239+ const allChunks = new Uint8Array ( receivedLength ) ;
240+ let position = 0 ;
241+ for ( const chunk of chunks ) {
242+ allChunks . set ( chunk , position ) ;
243+ position += chunk . length ;
244+ }
245+
246+ // Convert to ArrayBuffer as requested by responseType
247+ this . response = allChunks . buffer ;
248+ } catch ( error ) {
249+ this . statusText = error . message ;
250+
251+ if ( error . name === 'AbortError' ) {
252+ // Do nothing.
253+ } else if ( error . name === 'TimeoutError' ) {
254+ this . ontimeout ?. ( ) ;
255+ } else {
256+ // This is a network error
257+ this . onerror ?. ( ) ;
258+ }
259+ } finally {
260+ clearTimeout ( timeoutID ) ;
261+ if ( ! this . _aborted ) {
262+ this . _changeReadyState ( 4 ) ; // 4: DONE
263+ // The XHR 'load' event fires for successful HTTP statuses (2xx) as well as
264+ // unsuccessful ones (4xx, 5xx). The 'error' event is for network failures.
265+ this . onload ?. ( ) ;
266+ }
267+ }
268+ }
269+
270+ /**
271+ * Aborts the request if it has already been sent.
272+ */
273+ abort ( ) {
274+ this . _aborted = true ;
275+ this . status = 0 ;
276+ this . _changeReadyState ( 4 ) ; // 4: DONE
277+ this . _abortController ?. abort ( ) ;
278+ }
279+ }
42280} ;
43281
44282addToLibrary ( LibraryFetch ) ;
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