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Add simpler reading methods to Blob interface. #117

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Merged
merged 5 commits into from
Apr 12, 2019
Merged

Add simpler reading methods to Blob interface. #117

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26bf46a
Add simpler reading methods to Blob interface.
mkruisselbrink Feb 22, 2019
b997a56
fix typo
mkruisselbrink Mar 7, 2019
d0b650a
Address some comments.
mkruisselbrink Mar 8, 2019
1b65277
Rebase to match FileReader changes.
mkruisselbrink Mar 15, 2019
42f8a45
Address last few comments
mkruisselbrink Mar 26, 2019
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44 changes: 42 additions & 2 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,9 @@ spec: url
text: url; for:/
type: interface
text: URL
spec: fetch
type:interface
text:ReadableStream
</pre>

<pre class="anchors">
Expand Down Expand Up @@ -215,7 +218,7 @@ which must be initially set to the state of the underlying storage,
if any such underlying storage exists.
Further normative definition of <a>snapshot state</a> can be found for {{File}}s.

<pre class="idl">
<xmp class="idl">
[Constructor(optional sequence&lt;BlobPart> blobParts,
optional BlobPropertyBag options),
Exposed=(Window,Worker), Serializable]
Expand All @@ -228,6 +231,11 @@ interface Blob {
Blob slice(optional [Clamp] long long start,
optional [Clamp] long long end,
optional DOMString contentType);

// read from the Blob.
[NewObject] ReadableStream stream();
[NewObject] Promise<USVString> text();
[NewObject] Promise<ArrayBuffer> arrayBuffer();
};

enum EndingType { "transparent", "native" };
Expand All @@ -238,7 +246,7 @@ dictionary BlobPropertyBag {
};

typedef (BufferSource or Blob or USVString) BlobPart;
</pre>
</xmp>

{{Blob}} objects are [=serializable objects=]. Their [=serialization steps=],
given |value| and |serialized|, are:
Expand Down Expand Up @@ -561,6 +569,38 @@ It must act as follows:
</pre>
</div>

### The {{Blob/stream()}} method ### {#stream-method-algo}

The <dfn method for=Blob>stream()</dfn> method, when invoked, must return
the result of calling [=get stream=] on the [=context object=].

### The {{Blob/text()}} method ### {#text-method-algo}

The <dfn method for=Blob>text()</dfn> method, when invoked, must run these steps:

1. Let |stream| be the result of calling [=get stream=] on the [=context object=].
1. Let |reader| be the result of [=get a reader|getting a reader=] from |stream|.
If that threw an exception, return a new promise rejected with that exception.
1. Let |promise| be the result of [=read all bytes|reading all bytes=] from |stream| with |reader|.
1. Return the result of transforming |promise| by a fulfillment handler that returns the result of
running [=UTF-8 decode=] on its first argument.

Note: This is different from the behavior of {{FileReader/readAsText()}} to align better
with the behavior of {{Body/text()|Fetch's text()}}. Specifically this method will always
use UTF-8 as encoding, while {{FileReader}} can use a different encoding depending on
the blob's type and passed in encoding name.

### The {{Blob/arrayBuffer()}} method ### {#arraybuffer-method-algo}

The <dfn method for=Blob>arrayBuffer()</dfn> method, when invoked, must run these steps:

1. Let |stream| be the result of calling [=get stream=] on the [=context object=].
1. Let |reader| be the result of [=get a reader|getting a reader=] from |stream|.
If that threw an exception, return a new promise rejected with that exception.
1. Let |promise| be the result of [=read all bytes|reading all bytes=] from |stream| with |reader|.
1. Return the result of transforming |promise| by a fulfillment handler that returns
a new {{ArrayBuffer}} whose contents are its first argument.

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