Mercurial > hgrepos > Python2 > PyMuPDF

annotate mupdf-source/docs/reference/c/fitz/memory.md @ 38:8934ac156ef5

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Allow to build with the PyPI package "clang" instead of "libclang". 1. It seems to be maintained. 2. In the FreeBSD base system there is no pre-built libclang.so. If you need this library you have to install llvm from ports additionally. 2. On FreeBSD there is no pre-built wheel "libclang" with a packaged libclang.so.
author Franz Glasner <fzglas.hg@dom66.de>
date Tue, 23 Sep 2025 10:27:15 +0200
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1 # Memory
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3 All memory in Fitz is allocated through an allocator, which allows you to use
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4 a custom allocator instead of the system malloc if you need to.
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6 ## Malloc & Free
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8 You should not need to do raw memory allocation using the Fitz context, but if
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9 you do, here are the functions you need. These work just like the regular C
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10 functions, but take a Fitz context and throw an exception if the allocation
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11 fails. They will **not** return `NULL`; either they will succeed or they will
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12 throw an exception.
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14 void *fz_malloc(fz_context *ctx, size_t size);
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15 void *fz_realloc(fz_context *ctx, void *old, size_t size);
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16 void *fz_calloc(fz_context *ctx, size_t count, size_t size);
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17 void fz_free(fz_context *ctx, void *ptr);
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19 There are also some macros that allocate structures and arrays, together with a type cast to catch typing errors.
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21 T *fz_malloc_struct(fz_context *ctx, T); // Allocate and zero the memory.
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22 T *fz_malloc_array(fz_context *ctx, size_t count, T); // Allocate uninitialized memory!
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23 T *fz_realloc_array(fz_context *ctx, T *old, size_t count, T);
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25 In the rare case that you need an allocation that returns `NULL` on failure,
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26 there are variants for that too: `fz_malloc_no_throw`, etc.
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28 ## Pool Allocator
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30 The pool allocator is used for allocating many small objects that live and die
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31 together. All objects allocated from the pool will be freed when the pool is
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32 freed.
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34 fz_pool *fz_new_pool(fz_context *ctx);
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35 void *fz_pool_alloc(fz_context *ctx, fz_pool *pool, size_t size);
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36 char *fz_pool_strdup(fz_context *ctx, fz_pool *pool, const char *s);
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37 void fz_drop_pool(fz_context *ctx, fz_pool *pool);
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39 ## Reference Counting
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41 Most objects in MuPDF use reference counting to keep track of when they are no
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42 longer used and can be freed. We use the verbs "keep" and "drop" to increment
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43 and decrement the reference count. For simplicity, we also use the word "drop"
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44 for non-reference counted objects (so that in case we change our minds and
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45 decide to add reference counting to an object, the code that uses it need not
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46 change).