Formalize reading bodies

Closes #661.
whatwg · Feb 17, 2021 · 672ed2e · 672ed2e
1 parent 72be227
commit 672ed2e
Showing 1 changed file with 127 additions and 14 deletions.
diff --git a/fetch.bs b/fetch.bs
@@ -1037,6 +1037,131 @@ worked on in <a href=https://github.com/whatwg/fetch/issues/1156>issue #1156</a>
  <var>body</var>.
 </ol>
 
+<hr>
+
+<p>To <dfn export for=body>incrementally read</dfn> a <a for=/>body</a> <var>body</var>, given an
+algorithm <var>processBodyChunk</var>, an algorithm <var>processError</var>, an optional null or
+algorithm <dfn export for="body/incrementally read"><var>processEndOfBody</var></dfn> (default
+null), and an optional null or <a for=/>global object</a>
+<dfn export for="body/incrementally read">taskDestination</dfn> (default null), run these steps:
+
+<ol>
+ <li><p>Assert: <var>body</var>'s <a for=body>stream</a> is non-null.
+
+ <li><p>If <var>taskDestination</var> is null, then set <var>taskDestination</var> to the result of
+ <a>starting a new parallel queue</a>.
+
+ <li>
+  <p>Let <var>reader</var> be the result of <a for=ReadableStream>getting a reader</a> for
+  <var>body</var>'s <a for=body>stream</a>.
+
+  <p class="note no-backref">This operation cannot throw an exception.
+
+ <li><p>Perform the <a>incrementally-read loop</a> given <var>reader</var>,
+ <var>taskDestination</var>, <var>processBodyChunk</var>, <var>processError</var>, and
+ <var>processEndOfBody</var>.
+</ol>
+
+<p>To perform the <dfn>incrementally-read loop</dfn>, given a {{ReadableStreamDefaultReader}} object
+<var>reader</var>, <a>parallel queue</a> or <a for=/>global object</a> <var>taskDestination</var>,
+algorithm <var>processBodyChunk</var>, algorithm <var>processError</var>, and null or algorithm
+<var>processEndOfBody</var>:
+
+<ol>
+ <li>
+  <p>Let <var>readRequest</var> be the following <a>read request</a>:
+
+  <dl>
+   <dt><a for="read request">chunk steps</a>, given <var>chunk</var>
+   <dd>
+    <ol>
+     <li><p>Let <var>continueAlgorithm</var> be null.
+
+     <li><p>If <var>chunk</var> is not a {{Uint8Array}} object, then set
+     <var>continueAlgorithm</var> to this step: run <var>processError</var> given a {{TypeError}}.
+
+     <li>
+      <p>Otherwise:
+
+      <ol>
+       <li><p>Let <var>bytes</var> be a <a lt="get a copy of the buffer source">copy of</a>
+       <var>chunk</var>.
+
+       <li>
+        <p>Set <var>continueAlgorithm</var> to these steps:
+
+        <ol>
+         <li><p>Run <var>processBodyChunk</var> given <var>bytes</var>.
+
+         <li><p>Perform the <a>incrementally-read loop</a> given <var>reader</var>,
+         <var>taskDestination</var>, <var>processBodyChunk</var>, <var>processError</var>, and
+         <var>processEndOfBody</var>.
+        </ol>
+      </ol>
+
+     <li><p><a>Queue a fetch task</a> given <var>continueAlgorithm</var> and
+     <var>taskDestination</var>.
+    </ol>
+
+   <dt><a for="read request">close steps</a>
+   <dd><ol><li><p>If <var>processEndOfBody</var> is non-null, then <a>queue a fetch task</a> given
+   <var>processEndOfBody</var> and <var>taskDestination</var>.</ol>
+
+   <dt><a for="read request">error steps</a>, given <var>e</var>
+   <dd>
+    <ol>
+     <li><p>Let <var>errorAlgorithm</var> be this step: run <var>processError</var> given
+     <var>e</var>.
+
+     <li><p><a>Queue a fetch task</a> given <var>errorAlgorithm</var> and
+     <var>taskDestination</var>.
+    </ol>
+  </dl>
+
+ <li><p><a for=ReadableStreamDefaultReader>Read a chunk</a> from <var>reader</var> given
+ <var>readRequest</var>.
+</ol>
+
+<p>To <dfn export for=body>fully read</dfn> a <a for=/>body</a> <var>body</var>, given an algorithm
+<dfn export for="body/fully read"><var>processBody</var></dfn>, an optional algorithm
+<dfn export for="body/fully read"><var>processError</var></dfn>, and an optional null or
+<a for=/>global object</a> <dfn export for="body/fully read">taskDestination</dfn> (default null),
+run these steps:
+
+<ol>
+ <li><p>If <var>taskDestination</var> is null, then set <var>taskDestination</var> to the result of
+ <a>starting a new parallel queue</a>.
+
+ <li><p>Let <var>promise</var> be the result of <a>fully reading body as promise</a> given
+ <var>body</var>.
+
+ <li><p>Let <var>fulfilledSteps</var> given a <a>byte sequence</a> <var>bytes</var> be to
+ <a>queue a fetch task</a> to run <var>processBody</var> given <var>bytes</var>, with
+ <var>taskDestination</var>.
+
+ <li><p>Let <var>rejectedSteps</var> be to <a>queue a fetch task</a> to run <var>processError</var>,
+ with <var>taskDestination</var>.
+
+ <li><p><a for=promise>React</a> to <var>promise</var> with <var>fulfilledSteps</var> and
+ <var>rejectedSteps</var>.
+</ol>
+
+<p>To <dfn export lt="fully reading body as promise">fully read body as promise</dfn>, given a
+<a for=/>body</a> <var>body</var>, run these steps:
+
+<ol>
+ <li><p>Assert: <var>body</var>'s <a for=body>stream</a> is non-null.
+
+ <li><p>Let <var>reader</var> be the result of <a for=ReadableStream>getting a reader</a> for
+ <var>body</var>'s <a for=body>stream</a>. If that threw an exception, then return
+ <a>a promise rejected with</a> that exception.
+
+ <li><p>Return the result of <a for=ReadableStreamDefaultReader>reading all bytes</a> from
+ <var>reader</var>.
+</ol>
+
+<hr>
+
 <p>To <dfn export>handle content codings</dfn> given <var>codings</var> and <var>bytes</var>, run
 these steps:
 
@@ -5727,20 +5852,8 @@ the associated steps:
  <li><p>Let <var>promise</var> be <a>a promise resolved with</a> an empty
  <a for=/>byte sequence</a>.
 
- <li>
-  <p>If <var>object</var>'s <a for=Body>body</a> is non-null, then:
-
-  <ol>
-   <li><p>Let <var>stream</var> be <var>object</var>'s <a for=Body>body</a>'s
-   <a for=body>stream</a>.
-
-   <li><p>Let <var>reader</var> be the result of <a for=ReadableStream>getting a reader</a> from
-   <var>stream</var>. If that threw an exception, then return <a>a promise rejected with</a> that
-   exception.
-
-   <li><p>Set <var>promise</var> to the result of
-   <a for=ReadableStreamDefaultReader>reading all bytes</a> from <var>reader</var>.
-  </ol>
+ <li><p>If <var>object</var>'s <a for=Body>body</a> is non-null, then set <var>promise</var> to the
+ result of <a>fully reading body as promise</a> given <var>object</var>'s <a for=Body>body</a>.
 
  <li><p>Let <var>steps</var> be to return the result of <a>package data</a> with the first argument
  given, <var>type</var>, and <var>object</var>'s <a for=Body>MIME type</a>.