SmartCardConnection.getAttribute() algorithm

index.html

@@ -1538,8 +1538,55 @@ <h3><dfn>control()</dfn> method</h3>
       </section>
       <section>
         <h3><dfn>getAttribute()</dfn> method</h3>
-        <p>Queries a card reader's attribute or capability value, given its tag.</p>
-        <div class="issue">Write an algorithm for this method.</div>
+        <p>The {{SmartCardConnection/getAttribute(tag)}} method steps are:</p>
+        <ol>
+          <li>Let |promise:Promise| be [=a new promise=].</li>
+          <li>If
+            [=this=].{{SmartCardConnection/[[context]]}}.{{SmartCardContext/[[operationInProgress]]}}
+            is `true`, [=reject=] |promise| with a "{{InvalidStateError}}"
+          {{DOMException}} and return |promise|.</li>
+          <li>If [=this=].{{SmartCardConnection/[[comm]]}} is `null`, [=reject=]
+            |promise| with a "{{InvalidStateError}}" {{DOMException}} and return
+            |promise|.</li>
+          <li>Set
+            [=this=].{{SmartCardConnection/[[context]]}}.{{SmartCardContext/[[operationInProgress]]}}
+            to `true`.</li>
+          <li>Run the following steps [=in parallel=]:
+            <ol>
+              <li>Let |pcscTag:DWORD| be a [[PCSC5]] `DWORD` containing |tag|.</li>
+              <li>Let |buffer:array of BYTE| be a [[PCSC5]] `BYTE[]` large
+                enough to hold this reader attribute, as determined by the
+                platform's [[PCSC5]] implementation.</li>
+              <li>Call [=this=].{{SmartCardConnection/[[comm]]}}.`GetReaderCapabilities()`
+                with |pcscTag| and |buffer| as arguments.</li>
+              <li>Let |responseCode:RESPONSECODE| be the returned
+                `RESPONSECODE`.</li>
+              <li>[=Queue a global task=] on the [=relevant global object=] of
+                [=this=] using the [=smart card task source=] which performs the
+                following steps:
+                <ol>
+                  <li>[=Clear the operationInProgress=] of
+                    [=this=].{{SmartCardConnection/[[context]]}}.</li>
+                  <li>If |responseCode| is not `SCARD_S_SUCCESS`, [=reject=]
+                    |promise| with an [=exception=]
+                    {{SmartCardError/corresponding}} to |responseCode| and abort
+                    these steps.</li>
+                  <li>Let |resultBytes:byte sequence| be the bytes of |buffer|
+                    containing the attribute read.</li>
+                  <li>[=Resolve=] |promise| with the result of
+                    [=ArrayBuffer/Create|creating=] an {{ArrayBuffer}} from
+                    |resultBytes| in [=this=]'s [=relevant Realm=].</li>
+                </ol>
+              </li>
+            </ol>
+          </li>
+          <li>Return |promise|.</li>
+        </ol>
+        <aside class="note" title="Output buffer size">
+          <p>Known [[PCSC5]] platform implementations allow either the output
+          buffer to be automatically allocated or to query the size needed for
+          it. This covers the gap left by [[PCSC5]] in that regard.</p>
+        </aside>
       </section>
       <section>
         <h3><dfn>setAttribute()</dfn> method</h3>