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Previously, before interpreting a pages content stream we would
load it entirely into a buffer. Then we would interpret that
buffer. This has a cost in memory use.
Here, we update the code to read from a stream on the fly.
This has required changes in various different parts of the code.
Firstly, we have removed all use of the FILE lock - as stream
reads can now safely be interrupted by resource (or object) reads
from elsewhere in the file, the file lock becomes a very hard
thing to maintain, and doesn't actually benefit us at all. The
choices were to either use a recursive lock, or to remove it
entirely; I opted for the latter.
The file lock enum value remains as a placeholder for future use in
extendable data streams.
Secondly, we add a new 'concat' filter that concatenates a series of
streams together into one, optionally putting whitespace between each
stream (as the pdf parser requires this).
Finally, we change page/xobject/pattern content streams to work
on the fly, but we leave type3 glyphs using buffers (as presumably
these will be run repeatedly).
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Sebras pointed out that my previous (untested) fix was wrong,
as we don't resolve indirect objects until we attempt to interpret
them. The fix is just to move the interpretation (pdf_to_int())
into the unlocked section.
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Divides large format pdfs into a new pdf with multiple pages, that tile
the original PDF.
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When reading the xref, if certain objects are indirect references
(Size, Prev, XrefStm) we can 'relock' a lock we already hold.
Work around that here.
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We were mapping from one enum range to another, and then using
the unmapped value.
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Avoid recursion in pdf_load_page_tree_node.
Avoid recursion (most of the time) in pdf_read_xref_sections.
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Use this to reintroduce "Document Properties..." in mupdf viewer.
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When we fail to be able to cache an object, we warn and return NULL.
An indirection cycle should probably be treated the same way.
From SumatraMuPDF.patch - Many thanks.
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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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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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A huge amount (20%+ on some files) of our runtime is spent in
fz_atof. A survey of results on the net suggests we will get
much better speed by writing our own atof.
Part of the job of doing this involves parsing the string to
identify the component parts of the number - ludicrously, we
are already doing this as part of the lexing process, so it
would make sense to do the atoi/atof as part of this process.
In order to do this, we need somewhere to store the lexed
results; rather than add a float * and an int * to every single
pdf_lex call, we generalise the calls to pass a pdf_lexbuf *
pointer instead of separate buffer/max/string length pointers.
This should help us overall.
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CLUSTER_UNTESTED.
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Quartz generated PDFs (and maybe others too) seem to use
000000000 65536 n to mean "free object" in defiance of the
spec. Add special case code to mupdf to handle this.
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This is a significant change to the use of locks in MuPDF.
Previously, the user had the option of passing us lock/unlock
functions for a single mutex as part of the allocation struct.
Now we remove these entries from the allocation struct, and
make a separate 'locks' struct. This enables people to use
fz_alloc_default with locking.
If multithreaded operation is required, then the user is
required to create FZ_LOCK_MAX mutexes, which will be locked
or unlocked by MuPDF calling the lock/unlock functions within
the new fz_locks_context structure passed in at context creation.
These mutexes are not required to be recursive (they may be, but
MuPDF should never call them in this way). MuPDF avoids deadlocks
by imposing a locking ordering on itself; a thread will never take
lock n, if it already holds any lock i for which 0 <= i <= n.
Currently, there are 4 locks used within MuPDF.
Lock 0: The alloc lock; taken around all calls to user supplied
(or default) allocation functions. Also taken around all accesses
to the refs field of storable items.
Lock 1: The store lock; taken whenever the store data structures
(specifically the linked list pointers) are accessed.
Lock 2: The file lock; taken whenever a thread is accessing the raw
file. We use the debugging macros to insist that this is held
whenever we do a file based seek or read. We also insist that this
is never held when we resolve an indirect reference, as this can
have the effect of moving the file pointer.
Lock 3: The glyphcache lock; taken whenever a thread calls freetype,
or accesses the glyphcache data structures. This introduces some
complexities w.r.t type3 fonts.
Locking can be hugely problematic, so to ease our minds as to
the correctness of this code, we introduce some debugging macros.
These compile away to nothing unless FITZ_DEBUG_LOCKING is defined.
fz_assert_lock_held(ctx, lock) checks that we hold lock.
fz_assert_lock_not_held(ctx, lock) checks that we do not hold lock.
In addition fz_lock_debug_lock and fz_lock_debug_unlock are used
on every fz_lock/fz_unlock to check the validity of the operation
we are performing - in particular it checks that we do/do not already
hold the lock we are trying to take/drop, and that by taking this
lock we are not violating our defined locking order.
The RESOLVE macro (used throughout the code to check whether we need
to resolve an indirect reference) calls fz_assert_lock_not_held to
ensure that we aren't about to resolve an indirect reference (and
hence move the stream pointer) when the file is locked.
In order to implement the file locking properly, pdf_open_stream
(and friends) now lock the file as a side effect (because they
fz_seek to the start of the stream). The lock is automatically
dropped on an fz_close of such streams.
Previously, the glyph cache was created in a context when it was first
required; this presents problems as it can be shared between several
contexts or not, depending on whether it is created before the
contexts are cloned. We now always create it at startup, so it is
always shared.
This means that we need reference counting for the glyph caches.
Added here.
In fz_render_glyph, we take the glyph cache lock, and check to see
whether the glyph is in the cache. If it is, we bump the refcount,
drop the lock and returned the cached character. If it is not, we
need to render the character.
For freetype based fonts we keep the lock throughout the rendering
process, thus ensuring that freetype is only called in a single
threaded manner.
For type3 fonts, however, we need to invoke the interpreter again
to render the glyph streams. This can require reentrance to this
routine. We therefore drop the glyph cache lock, call the
interpreter to render us our pixmap, and take the lock again.
This dropping and retaking of the lock introduces a possible race
condition; 2 threads may try to render the same character at the
same time. We therefore modify our hash table insert routines to
behave differently if it comes to insert an entry only to find
that an entry with the same key is already there.
We spot this case; if we have just rendered a type3 glyph and when
we try to insert it into the cache discover that someone has beaten
us to it, we just discard our entry and use the cached one.
Hopefully this will seldom be a problem in practise; to solve it
properly would require greater complexity (probably involving
spotting that another thread is already working on the desired
rendering, and sleeping on a semaphore until it completes).
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This was causing a SEGV in cluster testing of Bug690724.pdf.
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Require that clients call pdf_needs_password/pdf_authenticate_password
instead. For dumb clients, we still allow for decrypting a file with
a blank password without calling those functions.
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pdf_resolve_indirect(x) = pdf_resolve_indirect(pdf_resolve_indirect(x))
now - as long as it doesn't throw an exception.
Update the rest of the code to minimise unnecessary function calls.
Previously, we were calling one function to find out if an object was
a dict, only for that to call a function to see if it needed to
resolve the object, then calling another function to actually get the
dict, only to have that call the function to check for the dict
needing resolving again!
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Fixes a bug where objects remained in the store and would
keep stable pointers to the freed xref, later on those
objects could lead to false positive hits.
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Fix 2 places where we were filling a stroked pattern rather than
stroking it.
Cope with being asked to run a NULL buffer.
If running a stream fails, warn and return what we have, rather than
giving up entirely. Should really set a return code for each render.
Only look at the Print flag bit for Print renders. Only look at the
View flag bit for view renders.
If we find an unexpected ) or > during object parsing, warn and continue
rather than giving up entirely.
If optional content groups are broken, render the rest of the page
anyway.
Previously indirect objects that point to another indirection would
cause a failure; now attempt to resolve these. We set an arbitrary
limit of 10 such redirections to avoid infinite loops.
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gcc 4.4.5 gives helpful warnings about variables that can become
unset due to setjmp/longjmp usage. Fix that here.
Thanks to Sebras.
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Fixes for leaks (and SEGVs, division by zeros etc) seen when
Memsqueezing.
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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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When adding the exception handling in, I'd mis-indented some code.
This caused all the file to be read.
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Also: use 'cannot' instead of 'failed to' in error messages.
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When using exceptions (which are implemented using setjmp/longjmp), we
need to be careful to ensure that variable values get written back
before any exception happens.
Previously we've done that using volatile, but that produces nasty
warnings (and unduly limits the compilers freedom to optimise). Here
we introduce a new macro fz_var that passes the address of the variable
out of scope. This means that the compiler has to ensure that any
changes to its value are written back to memory before calling any
out of scope function.
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In converting from error return to exception throwing I was over
enthusiatic and removed more than I should. Add missing code back
in. Problem was seen with "0 - password password (crypt level 5).pdf"
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The code was dereferencing xref to get ctx before checking whether it
was NULL or not. Simple fix to move the test up a bit.
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When opening a file, create a pdf_ocg_descriptor that lists the OCGs
in a file. Add a new function to allow us to set the configuration
in use (currently just the default one).
This sets the states of the OCGs as appropriate. When decoding the
file respect the states of the OCGs.
This results in Invite.pdf rendering correctly.
There is more to be done in this area (with automatic setting of
OCGs by language/zoom level etc), but this is a good start.
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This frees us from passing errors back everywhere, and hence enables us
to pass results back as return values.
Rather than having to explicitly check for errors everywhere and bubble
them, we now allow exception handling to do the work for us; the
downside to this is that we no longer emit as much debugging information
as we did before (though this could be put back in). For now, the
debugging information we have lost has been retained in comments
with 'RJW:' at the start.
This code needs fuller testing, but is being committed as a work in
progress.
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