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Merged
merged 5 commits into from
Aug 15, 2017
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byte sequence <> string #146

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byte sequence <> string
annevk Aug 15, 2017
d7c3cc4
use <code>
annevk Aug 15, 2017
f5e739a
isomorphic
annevk Aug 15, 2017
3723a5f
link things
annevk Aug 15, 2017
9570220
adjust note
annevk Aug 15, 2017
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22 changes: 20 additions & 2 deletions infra.bs
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Expand Up @@ -297,8 +297,9 @@ confusion with an actual <a>string</a>.
<p>Headers, such as `<code>Content-Type</code>`, are <a>byte sequences</a>.
</div>

<p class=note>To get a <a>byte sequence</a> out of a <a>string</a>, use an operation such as
<a>UTF-8 encode</a> from the Encoding Standard. [[ENCODING]]
<p class=note>To get a <a>byte sequence</a> out of a <a>string</a>, using <a>UTF-8 encode</a> from
the Encoding Standard is encouraged. In rare circumstances <a>isomorphic encode</a> might be needed.
[[ENCODING]]

<p>A <a>byte sequence</a>'s <dfn export for="byte sequence">length</dfn> is the number of
<a>bytes</a> it contains.
Expand All @@ -313,6 +314,11 @@ contains, in the range 0x61 (a) to 0x7A (z), inclusive, by 0x20.
<a>byte sequence</a> <var>B</var>, if the <a>byte-lowercase</a> of <var>A</var> is the
<a>byte-lowercase</a> of <var>B</var>.

<p>To <dfn export>isomorphic decode</dfn> a <a>byte sequence</a> <var>input</var>, return a
<a>string</a> whose <a for=string>length</a> is equal to <var>input</var>'s
<a for="byte sequence">length</a> and whose <a>code points</a> have the same values as
<var>input</var>'s <a>bytes</a>, in the same order.

<h3 id=code-points>Code points</h3>

<p>A <dfn export lt="code point|character">code point</dfn> is a Unicode code point and is
Expand Down Expand Up @@ -450,6 +456,18 @@ implementations of just <a>JavaScript strings</a> for performance and memory rea

<hr>

<p>To <dfn export>isomorphic encode</dfn> a <a>string</a> <var>input</var>, run these steps:</p>

<ol>
<li><p>Assert: <var>input</var> contains no <a>code points</a> greater than U+00FF.

<li><p>Return a <a>byte sequence</a> whose <a for="byte sequence">length</a> is equal to
<var>input</var>'s <a for=string>length</a> and whose <a>bytes</a> have the same values as
<var>input</var>'s <a>code points</a>, in the same order.
</ol>

<hr>

<p>An <dfn export>ASCII string</dfn> is a <a>string</a> whose <a>code points</a> are all
<a>ASCII code points</a>.

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