README.portability
1 CROSS-PLATFORM PORTABILITY GUIDELINES FOR GALLIUM3D
2
3
4= General Considerations =
5
6The state tracker and winsys driver support a rather limited number of
7platforms. However, the pipe drivers are meant to run in a wide number of
8platforms. Hence the pipe drivers, the auxiliary modules, and all public
9headers in general, should strictly follow these guidelines to ensure
10
11
12= Compiler Support =
13
14* Include the p_compiler.h.
15
16* Cast explicitly when converting to integer types of smaller sizes.
17
18* Cast explicitly when converting between float, double and integral types.
19
20* Don't use named struct initializers.
21
22* Don't use variable number of macro arguments. Use static inline functions
23instead.
24
25* Don't use C99 features.
26
27= Standard Library =
28
29* Avoid including standard library headers. Most standard library functions are
30not available in Windows Kernel Mode. Use the appropriate p_*.h include.
31
32== Memory Allocation ==
33
34* Use MALLOC, CALLOC, FREE instead of the malloc, calloc, free functions.
35
36* Use align_pointer() function defined in u_memory.h for aligning pointers
37 in a portable way.
38
39== Debugging ==
40
41* Use the functions/macros in p_debug.h.
42
43* Don't include assert.h, call abort, printf, etc.
44
45
46= Code Style =
47
48== Inherantice in C ==
49
50The main thing we do is mimic inheritance by structure containment.
51
52Here's a silly made-up example:
53
54/* base class */
55struct buffer
56{
57 int size;
58 void (*validate)(struct buffer *buf);
59};
60
61/* sub-class of bufffer */
62struct texture_buffer
63{
64 struct buffer base; /* the base class, MUST COME FIRST! */
65 int format;
66 int width, height;
67};
68
69
70Then, we'll typically have cast-wrapper functions to convert base-class
71pointers to sub-class pointers where needed:
72
73static inline struct vertex_buffer *vertex_buffer(struct buffer *buf)
74{
75 return (struct vertex_buffer *) buf;
76}
77
78
79To create/init a sub-classed object:
80
81struct buffer *create_texture_buffer(int w, int h, int format)
82{
83 struct texture_buffer *t = malloc(sizeof(*t));
84 t->format = format;
85 t->width = w;
86 t->height = h;
87 t->base.size = w * h;
88 t->base.validate = tex_validate;
89 return &t->base;
90}
91
92Example sub-class method:
93
94void tex_validate(struct buffer *buf)
95{
96 struct texture_buffer *tb = texture_buffer(buf);
97 assert(tb->format);
98 assert(tb->width);
99 assert(tb->height);
100}
101
102
103Note that we typically do not use typedefs to make "class names"; we use
104'struct whatever' everywhere.
105
106Gallium's pipe_context and the subclassed psb_context, etc are prime examples
107of this. There's also many examples in Mesa and the Mesa state tracker.
108