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Debug printing functions: debug -> print.
Accessors: get noun attribute -> noun attribute.
Find -> lookup when the returned value is not reference counted.
pixmap_with_rect -> pixmap_with_bbox.
We are reserving the word "find" to mean lookups that give ownership
of objects to the caller. Lookup is used in other places where the
ownership is not transferred, or simple values are returned.
The rename is done by the sed script in scripts/rename3.sed
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Attempt to separate public API from internal functions.
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When we attempt to insert a key/value pair into the store, we have
to allow for the possibility that a racing thread may have already
inserted an equivalent key/value. We have special code in place to
handle this eventuality; if we spot an existing entry, we take the
existing one in preference to our new key/value pair.
This means that fz_store_item needs to take a new reference to any
existing thing it finds before returning it.
Currently the only store user that is exposed to this possibility
is pdf_image; it spots an existing tile being returned, and was
inadvertently double freeing the key.
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Currently, we are in the slightly strange position of having
the PDF specific object types as part of fitz. Here we pull
them out into the pdf layer instead. This has been made possible
by the recent changes to make the store no longer be tied to
having fz_obj's as keys.
Most of this work is a simple huge rename; to help customers who
may have code that use such functions we have provided a sed
script to do the renaming; scripts/rename2.sed.
Various other small tweaks are required; the store used to have
some debugging code that still required knowledge of fz_obj
types - we extract that into a nicer 'type' based function
pointer. Also, the type 3 font handling used to have an fz_obj
pointer for type 3 resources, and therefore needed to know how
to free this; this has become a void * with a function to free
it.
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Introduce a new 'fz_image' type; this type contains rudimentary
information about images (such as native, size, colorspace etc)
and a function to call to get a pixmap of that image (with a
size hint).
Instead of passing pixmaps through the device interface (and
holding pixmaps in the display list) we now pass images instead.
The rendering routines therefore call fz_image_to_pixmap to get
pixmaps to render, and fz_pixmap_drop those afterwards.
The file format handling routines therefore need to produce
images rather than pixmaps; xps and cbz currently just wrap
pixmaps as images. PDF is more involved.
The stream handling routines in PDF have been altered so that
they can recognise when the last stream entry in a filter
dictionary is an image decoding filter. Rather than applying
this filter, they read and store the parameters into a
pdf_image_params structure, and stop decoding at that point.
This allows us to read the compressed data for an image into
memory as a block. We can then restart the image decode process
later.
pdf_images therefore consist of the compressed image data for
images. When a pixmap is requested for such an image, the code
checks to see if we have one (of an appropriate size), and if
not, decodes it.
The size hint is used to determine whether it is possible to
subsample the image; currently this is only supported for
JPEGs, but we could add generic subsampling code later.
In order to handle caching the produced images, various changes
have been made to the store and the underlying hash table.
Previously the store was indexed purely by fz_obj keys; we don't
have an fz_obj key any more, so have extended the store by adding
a concept of a key 'type'. A key type is a pointer to a set of
functions that keep/drop/compare and make a hashable key from
a key pointer.
We make a pdf_store.c file that contains functions to offer the
existing fz_obj based functions, and add a new 'type' for keys
(based on the fz_image handle, and the subsample factor) in the
pdf_image.c file.
While working on this, a problem became apparent in the existing
store codel; fz_obj objects had no protection on their reference
counts, hence an interpreter thread could try to alter a ref count
at the same time as a malloc caused an eviction from the store.
This has been solved by using the alloc lock as protection. This in
turn requires some tweaks to the code to make sure we don't try
and keep/drop fz_obj's from the store code while the alloc lock is
held.
A side effect of this work is that when a hash table is created, we
inform it what lock should be used to protect its innards (if any).
If the alloc lock is used, the insert method knows to drop/retake it
to allow it to safely expand the hash table. Callers to the hash
functions have the responsibility of taking/dropping the appropriate
lock, and ensuring that they cope with the possibility that insert
might drop the alloc lock, causing race conditions.
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Firstly, we rename pdf_store to fz_store, reflecting the fact that
there are no pdf specific dependencies on it.
Next, we rework it so that all the objects that can be stored in
the store start with an fz_storable structure. This consists of
a reference count, and a function used to free the object when
the reference count reaches zero.
All the keep/drop functions are then reimplemented by calling
fz_keep_sharable/fz_drop_sharable. The 'drop' functions as supplied
by the callers are thus now 'free' functions, only called if
the reference count drops to 0.
The store changes to keep all the items in the store in the linked
list (which becomes a doubly linked one). We still make use of
the hashtable to index into this list quickly, but we now have
the objects in an LRU ordering within the list.
Every object is put into the store, with a size record; this is
an estimate of how much memory would be freed by freeing that
object.
The store is moved into the context and given a maximum size;
when new things are inserted into the store, care is taken to
ensure that we do not expand beyond this size. We evict any
stored items (that are not in use) starting from the least
recently used.
Finding an object in the store now takes a reference to it already.
LOCK and UNLOCK comments are used to indicate where locks need to
be taken and released to ensure thread safety.
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Also: use 'cannot' instead of 'failed to' in error messages.
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Huge pervasive change to lots of files, adding a context for exception
handling and allocation.
In time we'll move more statics into there.
Also fix some for(i = 0; i < function(...); i++) calls.
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The run-together words are dead! Long live the underscores!
The postscript inspired naming convention of using all run-together
words has served us well, but it is now time for more readable code.
In this commit I have also added the sed script, rename.sed, that I used
to convert the source. Use it on your patches and application code.
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