0,0 → 1,109 |
CROSS-PLATFORM PORTABILITY GUIDELINES FOR GALLIUM3D |
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= General Considerations = |
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The state tracker and winsys driver support a rather limited number of |
platforms. However, the pipe drivers are meant to run in a wide number of |
platforms. Hence the pipe drivers, the auxiliary modules, and all public |
headers in general, should strictly follow these guidelines to ensure |
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= Compiler Support = |
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* Include the p_compiler.h. |
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* Don't use the 'inline' keyword, use the INLINE macro in p_compiler.h instead. |
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* Cast explicitly when converting to integer types of smaller sizes. |
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* Cast explicitly when converting between float, double and integral types. |
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* Don't use named struct initializers. |
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* Don't use variable number of macro arguments. Use static inline functions |
instead. |
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* Don't use C99 features. |
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= Standard Library = |
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* Avoid including standard library headers. Most standard library functions are |
not available in Windows Kernel Mode. Use the appropriate p_*.h include. |
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== Memory Allocation == |
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* Use MALLOC, CALLOC, FREE instead of the malloc, calloc, free functions. |
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* Use align_pointer() function defined in u_memory.h for aligning pointers |
in a portable way. |
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== Debugging == |
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* Use the functions/macros in p_debug.h. |
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* Don't include assert.h, call abort, printf, etc. |
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= Code Style = |
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== Inherantice in C == |
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The main thing we do is mimic inheritance by structure containment. |
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Here's a silly made-up example: |
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/* base class */ |
struct buffer |
{ |
int size; |
void (*validate)(struct buffer *buf); |
}; |
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/* sub-class of bufffer */ |
struct texture_buffer |
{ |
struct buffer base; /* the base class, MUST COME FIRST! */ |
int format; |
int width, height; |
}; |
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Then, we'll typically have cast-wrapper functions to convert base-class |
pointers to sub-class pointers where needed: |
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static inline struct vertex_buffer *vertex_buffer(struct buffer *buf) |
{ |
return (struct vertex_buffer *) buf; |
} |
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To create/init a sub-classed object: |
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struct buffer *create_texture_buffer(int w, int h, int format) |
{ |
struct texture_buffer *t = malloc(sizeof(*t)); |
t->format = format; |
t->width = w; |
t->height = h; |
t->base.size = w * h; |
t->base.validate = tex_validate; |
return &t->base; |
} |
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Example sub-class method: |
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void tex_validate(struct buffer *buf) |
{ |
struct texture_buffer *tb = texture_buffer(buf); |
assert(tb->format); |
assert(tb->width); |
assert(tb->height); |
} |
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Note that we typically do not use typedefs to make "class names"; we use |
'struct whatever' everywhere. |
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Gallium's pipe_context and the subclassed psb_context, etc are prime examples |
of this. There's also many examples in Mesa and the Mesa state tracker. |