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net_instaweb::CssFlattenImportsContext Class Reference

Context used by CssFilter under async flow that flattens . More...

#include "css_flatten_imports_context.h"

Inheritance diagram for net_instaweb::CssFlattenImportsContext:
net_instaweb::SingleRewriteContext net_instaweb::RewriteContext

Public Member Functions

 CssFlattenImportsContext (RewriteContext *parent, CssFilter *filter, CssFilter::Context *rewriter, CssHierarchy *hierarchy)
virtual GoogleString CacheKeySuffix () const
virtual void RewriteSingle (const ResourcePtr &input_resource, const OutputResourcePtr &output_resource)
 Subclasses of SingleRewriteContext must override this: More...
void Harvest ()
bool PolicyPermitsRendering () const
virtual void Render ()
virtual const char * id () const
 Returns the filter ID.
virtual OutputResourceKind kind () const
- Public Member Functions inherited from net_instaweb::SingleRewriteContext
 SingleRewriteContext (RewriteDriver *driver, RewriteContext *parent, ResourceContext *resource_context)
- Public Member Functions inherited from net_instaweb::RewriteContext
 RewriteContext (RewriteDriver *driver, RewriteContext *parent, ResourceContext *resource_context)
int num_slots () const
ResourceSlotPtr slot (int index) const
int num_outputs () const
OutputResourcePtr output (int i) const
int num_output_partitions () const
const CachedResult * output_partition (int i) const
CachedResult * mutable_output_partition (int i)
bool chained () const
void AddSlot (const ResourceSlotPtr &slot)
void RemoveLastSlot ()
void AddNestedContext (RewriteContext *context)
void CallFetchInputs ()
void CallLockFailed ()
void CallStartFetchImpl ()
void Initiate ()
bool Fetch (const OutputResourcePtr &output_resource, AsyncFetch *fetch, MessageHandler *message_handler)
bool slow () const
bool is_metadata_cache_miss () const
 This particular rewrite was a metadata cache miss.
bool has_parent () const
 Returns true if this is a nested rewriter.
bool IsNestedIn (StringPiece id) const
void CheckNotFrozen ()
RewriteContextparent ()
 Allows a nested rewriter to walk up its parent hierarchy.
const RewriteContextparent () const
int num_nested () const
 Accessors for the nested rewrites.
RewriteContextnested (int i) const
RewriteDriverDriver () const
void set_force_rewrite (bool x)
 If called with true, forces a rewrite and re-generates the output.
bool rewrite_uncacheable () const
void set_rewrite_uncacheable (bool rewrite_uncacheable)
const ResourceContext * resource_context () const
GoogleString ToString () const
 Returns debug information about this RewriteContext.
GoogleString ToStringWithPrefix (StringPiece prefix) const

Additional Inherited Members

- Public Types inherited from net_instaweb::RewriteContext
typedef std::vector< InputInfo * > InputInfoStarVector
- Static Public Member Functions inherited from net_instaweb::RewriteContext
static void InitStats (Statistics *stats)
 Initializes statistics.
- Static Public Attributes inherited from net_instaweb::RewriteContext
static const char kNumRewritesAbandonedForLockContention []
static const char kNumDeadlineAlarmInvocations []
static const char kHashMismatchMessage []
- Protected Types inherited from net_instaweb::RewriteContext
typedef std::vector< GoogleUrl * > GoogleUrlStarVector
- Protected Member Functions inherited from net_instaweb::SingleRewriteContext
virtual bool Partition (OutputPartitions *partitions, OutputResourceVector *outputs)
 SingleRewriteContext takes care of these methods from RewriteContext:
virtual void Rewrite (int partition_index, CachedResult *partition, const OutputResourcePtr &output)
void AddLinkRelCanonical (const ResourcePtr &input, ResponseHeaders *output)
 Adds a link: rel=canonical header pointing to the input URL as canonical.
void AddLinkRelCanonicalForFallbackHeaders (ResponseHeaders *output)
 Helper for using above in FixFetchFallbackHeaders()
- Protected Member Functions inherited from net_instaweb::RewriteContext
ServerContextFindServerContext () const
const RewriteOptionsOptions () const
OutputPartitions * partitions ()
void AddRecheckDependency ()
virtual bool OptimizationOnly () const
virtual void PartitionAsync (OutputPartitions *partitions, OutputResourceVector *outputs)
void PartitionDone (RewriteResult result)
void CrossThreadPartitionDone (RewriteResult result)
void RewriteDone (RewriteResult result, int partition_index)
virtual bool SendFallbackResponse (StringPiece output_url_base, StringPiece contents, AsyncFetch *async_fetch, MessageHandler *handler)
void StartNestedTasks ()
bool AreOutputsAllowedByCsp (CspDirective role) const
 Helper that checks that all output resources are OK with CSP as given role.
virtual void WillNotRender ()
virtual void Cancel ()
virtual const UrlSegmentEncoderencoder () const
virtual GoogleString UserAgentCacheKey (const ResourceContext *context) const
virtual void EncodeUserAgentIntoResourceContext (ResourceContext *context)
void AttachDependentRequestTrace (const StringPiece &label)
RequestTracedependent_request_trace ()
void TracePrintf (const char *fmt,...)
virtual void StartFetchReconstruction ()
void DetachFetch ()
virtual bool DecodeFetchUrls (const OutputResourcePtr &output_resource, MessageHandler *message_handler, GoogleUrlStarVector *url_vector)
virtual void FixFetchFallbackHeaders (const CachedResult &cached_result, ResponseHeaders *headers)
virtual void FetchCallbackDone (bool success)
virtual void FetchTryFallback (const GoogleString &url, const StringPiece &hash)
void Freshen ()
 Freshens resources proactively to avoid expiration in the near future.
bool notify_driver_on_fetch_done () const
void set_notify_driver_on_fetch_done (bool value)
AsyncFetchasync_fetch ()
 Note that the following must only be called in the fetch flow.
bool FetchContextDetached ()
 Is fetch_ detached? Only call this in the fetch flow.
MessageHandlerfetch_message_handler ()
 The message handler for the fetch.
bool stale_rewrite () const
 Indicates whether we are serving a stale rewrite.
virtual int64 GetRewriteDeadlineAlarmMs () const
virtual bool CreationLockBeforeStartFetch () const
 Should the context call LockForCreation before checking the cache?
virtual bool FailOnHashMismatch () const
virtual bool ScheduleViaCentralController ()
virtual bool ScheduleNestedContextViaCentalController () const
void ObtainLockForCreation (ServerContext *server_context, Function *callback)
void ReleaseCreationLock (bool succeeded)
- Static Protected Member Functions inherited from net_instaweb::RewriteContext
static bool LookupMetadataForOutputResourceImpl (OutputResourcePtr output_resource, const GoogleUrl &gurl, RewriteContext *rewrite_context, RewriteDriver *driver, GoogleString *error_out, CacheLookupResultCallback *callback)

Detailed Description

Context used by CssFilter under async flow that flattens .

Constructor & Destructor Documentation

net_instaweb::CssFlattenImportsContext::CssFlattenImportsContext ( RewriteContext parent,
CssFilter filter,
CssFilter::Context rewriter,
CssHierarchy hierarchy 

no resource_context

Member Function Documentation

virtual GoogleString net_instaweb::CssFlattenImportsContext::CacheKeySuffix ( ) const

Allows subclasses to add additional text to be appended to the metadata cache key. The default implementation returns "".

We have to include the media that applies to this context in its key so that, if someone 's the same file but with a different set of media on the rule, we don't fetch the cached file, since it has been minified based on the original set of applicable media.

Reimplemented from net_instaweb::RewriteContext.

void net_instaweb::CssFlattenImportsContext::Harvest ( )

Once any nested rewrites have completed, the results of these can be incorporated into the rewritten data. For contexts that do not require any nested RewriteContexts, it is OK to skip overriding this method – the empty default implementation is fine.

Propagate any info on images from child rewrites.

Roll up the rewritten CSS(s) regardless of success or failure. Failure means we can't flatten it for some reason, such as incompatible charsets or invalid CSS, but we still need to cache the unflattened version so we don't try to flatten it again and again, so even in that case we don't return kRewriteFailed.

Our result is the combination of all our imports and our own rules.

Reimplemented from net_instaweb::RewriteContext.

virtual OutputResourceKind net_instaweb::CssFlattenImportsContext::kind ( ) const

Rewrites come in three flavors, as described in output_resource_kind.h, so this method must be defined by subclasses to indicate which it is.

For example, we will avoid caching output_resource content in the HTTP cache for rewrites that are so quick to complete that it's fine to do the rewrite on every request. extend_cache is obviously in this category, and it's arguable we could treat js minification that way too (though we don't at the moment).

Implements net_instaweb::RewriteContext.

bool net_instaweb::CssFlattenImportsContext::PolicyPermitsRendering ( ) const

This method gives the context a chance to verify that rendering the result is consistent with the current document's (Content Security) Policy, which may be different than that of the page for which the result was first computed + cached. Most subclasses can just call AreOutputsAllowedByCsp(), with appropriate role.

We apply CSP policy for flattening at top-level, not here.

Implements net_instaweb::RewriteContext.

virtual void net_instaweb::CssFlattenImportsContext::Render ( )

Performs rendering activities that span multiple HTML slots. For example, in a filter that combines N slots to 1, N-1 of the HTML elements might need to be removed. That can be performed in Render(). This method is optional; the base-class implementation is empty.

Note that unlike Harvest(), this method runs in the HTML thread (for top-level rewrites), and only runs if the rewrite completes prior to the rewrite-deadline. If the rewrite does make it by the deadline, RewriteContext::Render() will be invoked regardless of whether any slots were actually optimized successfully.

If we have flattened the imported file ...

If Harvest() was called, directly or from RewriteSingle(), then the minified contents are already set as are the stylesheet and input contents - in that case we don't actually have to do anything. If they haven't been called then the minified contents are empty and the result was found in the cache, in which case we have to set the input and minified contents to this result; the minified because we know that cached values are minified (we only cache minified contents), the input because we will need that to generate the stylesheet from when RollUpStylesheets is eventually called.

Parse() will compute flattening_succeeded_, which needs to be restored. See

Something has gone wrong earlier. It could be that the resource is not valid and cacheable (see SingleRewriteContext::Partition) or it could be that we're handling a cached failure, but it's hard to tell. So, mark flattening as failed but don't record a failure statistic nor a failure reason.

Reimplemented from net_instaweb::RewriteContext.

virtual void net_instaweb::CssFlattenImportsContext::RewriteSingle ( const ResourcePtr input,
const OutputResourcePtr output 

Subclasses of SingleRewriteContext must override this:

We have to fix relative URLs in the CSS as they break if used in a CSS file that itself was loaded via a relative path from the base (for example, if styles/screen.css references ../images/icon.png, then the correct path for the image is /images/icon.png). We also need to absolutify or left-trim URLs in flattened CSS if no other rewriter is going to do it (cache extend, css image rewriter, etc), but it's hard to tell if that will happen so we transform URLs here regardless and note that for CssHierarchy::css_resolution_base().

If we rewrite the input resource's contents we need somewhere to store it; that's what the hierarchy's backing store is for.

See RewriteDriver::ResolveCssUrls about why we disable trimming in proxy mode. We also disable it if trimming is not enabled.

If we cannot parse the CSS then we cannot flatten it.

< Initiates rewriting of 'd files.

< Harvest centralizes all the output generation.

Implements net_instaweb::SingleRewriteContext.

The documentation for this class was generated from the following file: