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/*
* Some additional glue functions for using Harfbuzz with
* custom allocators.
*/
#include "mupdf/fitz.h"
#include "hb.h"
/* Harfbuzz has some major design flaws.
*
* It is utterly thread unsafe. It uses statics to hold
* structures in, meaning that if it is ever called from
* more than one thread at a time, access to such
* structures can race. We work around this by imposing
* a lock on our calls to harfbuzz (we reuse the freetype
* lock).
*
* This does not protect us against the possibility of
* other people calling harfbuzz; for instance, if we
* link MuPDF into an app that either calls harfbuzz
* itself, or uses another library that calls harfbuzz,
* there is no guarantee that that library will take
* the same lock while calling harfbuzz. This leaves
* us open to the possibility of crashes. The only
* way around this would be to use completely separate
* harfbuzz instances.
*
* In order to ensure that allocations throughout mupdf
* are done consistently, we get harfbuzz to call our
* own hb_malloc/realloc/calloc/free functions that
* call down to fz_malloc/realloc/calloc/free. These
* require context variables, so we get our hb_lock
* and unlock to set these. Any attempt to call through
* without setting these will be detected.
*
* It is therefore vital that any fz_lock/fz_unlock
* handlers are shared between all the fz_contexts in
* use at a time.
*
* Finally, harfbuzz stores various malloced structures
* in statics. These can either be left to leak on
* closedown, or (if HAVE_ATEXIT is defined), they will
* be freed using various 'atexit' callbacks. Unfortunately
* this won't reset the fz_context value, so the allocators
* can't free them correctly.
*
* Consequently, we leave them to leak, and warn Memento
* about this.
*/
/* Potentially we can write different versions
* of get_context and set_context for different
* threading systems.
*
* This simple version relies on harfbuzz never
* trying to make 2 allocations at once on
* different threads. The only way that can happen
* is when one of those other threads is someone
* outside MuPDF calling harfbuzz while MuPDF
* is running. This will cause us such huge
* problems that for now, we'll just forbid it.
*/
static fz_context *hb_secret = NULL;
static void set_hb_context(fz_context *ctx)
{
hb_secret = ctx;
}
static fz_context *get_hb_context()
{
return hb_secret;
}
void hb_lock(fz_context *ctx)
{
fz_lock(ctx, FZ_LOCK_FREETYPE);
set_hb_context(ctx);
}
void hb_unlock(fz_context *ctx)
{
set_hb_context(NULL);
fz_unlock(ctx, FZ_LOCK_FREETYPE);
}
void *hb_malloc(size_t size)
{
fz_context *ctx = get_hb_context();
assert(ctx != NULL);
return fz_malloc_no_throw(ctx, size);
}
void *hb_calloc(size_t n, size_t size)
{
fz_context *ctx = get_hb_context();
assert(ctx != NULL);
return fz_calloc_no_throw(ctx, n, size);
}
void *hb_realloc(void *ptr, size_t size)
{
fz_context *ctx = get_hb_context();
assert(ctx != NULL);
return fz_resize_array_no_throw(ctx, ptr, 1, size);
}
void hb_free(void *ptr)
{
fz_context *ctx = get_hb_context();
assert(ctx != NULL);
fz_free(ctx, ptr);
}
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