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Rewrite HTTP cache integration
In particular: * Be more specific about terminology * Detail more clearly how requests are to be modified Tests: web-platform-tests/wpt#5137. During review we decided to postpone #144 (poorly implemented if at all) and #307 (also poorly implemented despite security implications). Fixes #336 and fixes #373.
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‎fetch.bs

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@@ -49,6 +49,9 @@ url: https://tools.ietf.org/html/rfc7234#section-1.2.1;text:delta-seconds;type:d
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"HTTP-CACHING": {
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"aliasOf": "RFC7234"
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},
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"HTTP-RANGE": {
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"aliasOf": "RFC7233"
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},
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"HTTP-AUTH": {
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"aliasOf": "RFC7235"
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},
@@ -95,7 +98,6 @@ url: https://tools.ietf.org/html/rfc7234#section-1.2.1;text:delta-seconds;type:d
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"href": "https://www.kb.cert.org/vuls/id/150227",
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"title": "HTTP proxy default configurations allow arbitrary TCP connections."
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}
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}
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</pre>
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@@ -3140,6 +3142,9 @@ steps:
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<p class=note><i>CORS flag</i> is still a bookkeeping detail. As is
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<i>authentication-fetch flag</i>.
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<p class=note>Some implementations might support caching of partial content, as per <cite>HTTP
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Range Requests</cite>. [[HTTP-RANGE]] However, this is not widely supported by browser caches.
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<ol>
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<li><p>Let <var>httpRequest</var> be null.
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@@ -3364,88 +3369,107 @@ steps:
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<var>httpRequest</var>'s
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<a for=request>credentials mode</a>.
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<li><p>Let <var>response</var> be null.
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<li><p>Let <var>response</var> and <var>storedResponse</var> be null.
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<li><p>Let the <var>revalidatingFlag</var> be unset.
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<li>
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<p>If <var>httpRequest</var>'s
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<a for=request>cache mode</a> is neither
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"<code>no-store</code>" nor "<code>reload</code>", and there is a <em>complete</em>
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<a for=/>response</a> in the HTTP cache for
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<var>httpRequest</var> run these substeps:
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<!-- XXX xref "HTTP cache" -->
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<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is neither "<code>no-store</code>"
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nor "<code>reload</code>", run these substeps:
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<ol>
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<li>
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<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
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"<code>force-cache</code>" or "<code>only-if-cached</code>", then set
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<var>response</var> to the <a for=/>response</a> in the HTTP cache for
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<var>httpRequest</var>.
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<p>Set <var>storedResponse</var> to the result of selecting a response from the HTTP cache,
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possibly needing validation, as per the
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"<a href=https://tools.ietf.org/html/rfc7234#section-4>Constructing Responses from Caches</a>"
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chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]], if any.
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<p class=note>As mandated by HTTP, this still takes the `<code>Vary</code>`
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<a>header</a> into account.
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<li><p>If <var>storedResponse</var> is null, then abort these substeps.
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3387-
<li><p>Otherwise, if <var>httpRequest</var>'s
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<a for=request>cache mode</a> is "<code>default</code>" and the
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<a for=/>response</a> in the HTTP cache for <var>httpRequest</var> does
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not require revalidation, then set <var>response</var> to that
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<a for=/>response</a>.
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<!-- XXX xref "revalidation" -->
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<!-- cache hit -->
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<li><p>If <var>storedResponse</var> requires validation (i.e., it is not fresh), then set the
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<var>revalidatingFlag</var>.
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<li><p>Otherwise, if <var>httpRequest</var>'s
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<a for=request>cache mode</a> is either "<code>default</code>"
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or "<code>no-cache</code>", modify <var>httpRequest</var>'s
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<a for=request>header list</a> with revalidation
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<a>headers</a>.
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<!-- XXX modify, revalidation headers -->
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</ol>
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<li>
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<p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is "<code>force-cache</code>" or
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"<code>only-if-cached</code>", then set <var>response</var> to <var>storedResponse</var> and
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abort these substeps.
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<li><p>Otherwise, if <var>httpRequest</var>'s
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<a for=request>cache mode</a> is either
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"<code>default</code>" or "<code>force-cache</code>", and there is a
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<em>partial</em> <a for=/>response</a> in the HTTP cache for
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<var>httpRequest</var>, modify <var>httpRequest</var>'s
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<a for=request>header list</a> with resume
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<a>headers</a>.
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<!-- XXX xref partial, modify, resume headers -->
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<p class=note>As mandated by HTTP, this still takes the `<code>Vary</code>` <a>header</a>
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into account.
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<li>
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<p>If <var>response</var> is null, run these substeps:
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<li>
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<p>If the <var>revalidatingFlag</var> is set, then:
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3414-
<ol>
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<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
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"<code>only-if-cached</code>", then return a
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<a>network error</a>.
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<ol>
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<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
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<a for="header list">contains</a> `<code>ETag</code>`, then <a for="header list">append</a>
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`<code>If-None-Match</code>` with its value to <var>httpRequest</var>'s
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<a for=request>header list</a>.
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<li><p>Set <var>response</var> to the result of making an
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<a>HTTP-network fetch</a> using <var>httpRequest</var>
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with <i>credentials flag</i> if set.
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<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
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<a for="header list">contains</a> `<code>Last-Modified</code>`, then
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<a for="header list">append</a> `<code>If-Modified-Since</code>` with its value to
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<var>httpRequest</var>'s <a for=request>header list</a>.
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</ol>
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<p class=note>See also the
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"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Sending a Validation Request</a>"
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chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]].
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<li><p>Otherwise, if the <var>revalidatingFlag</var> is unset, then set <var>response</var> to
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<var>storedResponse</var>.
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</ol>
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<li>
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<p>If <var>response</var>'s <a for=response>status</a> is <code>304</code> and
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<var>httpRequest</var>'s <a for=request>cache mode</a> is either
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"<code>default</code>" or "<code>no-cache</code>", run these substeps:
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<!-- If response is still null, we require a forwarded request. -->
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<p>If <var>response</var> is null, then run these substeps:
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34293428
<ol>
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<li><p>Set <var>cachedResponse</var> to the result of selecting a stored
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<a for=/>response</a> from the HTTP cache using <var>httpRequest</var>, as
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per the
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"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
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chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
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<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is
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"<code>only-if-cached</code>", then return a <a>network error</a>.
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<li><p>If <var>cachedResponse</var> is null (i.e., one cannot be selected), return a
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<a>network error</a>.
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<li><p>Set <var>forwardResponse</var> to the result of making an <a>HTTP-network fetch</a> using
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<var>httpRequest</var> with <i>credentials flag</i> if set.
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<li><p>If <var>httpRequest</var>'s <var>method</var> is
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<a href=https://tools.ietf.org/html/rfc7231#safe.methods>unsafe</a> and
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<var>forwardResponse</var>'s <a for=response>status</a> is in the range <code>200</code> to
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<code>399</code>, inclusive, invalidate appropriate stored responses in the HTTP cache, as per
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the "<a href=https://tools.ietf.org/html/rfc7234#section-4.4>Invalidation</a>" chapter of
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<cite>HTTP Caching</cite>, and set <var>storedResponse</var> to null. [[!HTTP-CACHING]]
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<li>
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<p>If the <var>revalidatingFlag</var> is set and <var>forwardResponse</var>'s
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<a for=response>status</a> is <code>304</code>, then:
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<ol>
3447+
<li>
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<p>Update <var>storedResponse</var>'s <a for=response>header list</a> using
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<var>forwardResponse</var>'s <a for=response>header list</a>, as per the
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"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
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chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
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<p class="note">This updates the stored response in cache as well.
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<li><p>Update <var>cachedResponse</var>'s <a for=response>header list</a>
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using <var>response</var>'s <a for=response>header list</a>, as per the
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"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Freshening Stored Responses upon Validation</a>"
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chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
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<li><p>Set <var>response</var> to <var>storedResponse</var>.
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3457+
</ol>
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34443459
<li>
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<p>Set <var>response</var> to the <var>cachedResponse</var>.
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<p>If <var>response</var> is null, then:
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3447-
<p class="note no-backref">This changes <var>response</var> entirely, including its
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<a for=response>status</a> which is most likely <code>200</code> now.
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<ol>
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<li><p>Set <var>response</var> to <var>forwardResponse</var>.
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<li>
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<p>Store <var>httpRequest</var> and <var>forwardResponse</var> in the HTTP cache, as per the
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"<a href=https://tools.ietf.org/html/rfc7234#section-3>Storing Responses in Caches</a>"
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chapter of <cite>HTTP Caching</cite>. [[!HTTP-CACHING]]
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<p class=note>If <var>forwardResponse</var> is a <a>network error</a>, this effectively caches
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the network error, which is sometimes known as "negative caching".
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</ol>
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</ol>
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<li>

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