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* Don't use the 'inline' keyword, use the INLINE macro in p_compiler.h instead.
17
18* Cast explicitly when converting to integer types of smaller sizes.
19
20* Cast explicitly when converting between float, double and integral types.
21
22* Don't use named struct initializers.
23
24* Don't use variable number of macro arguments. Use static inline functions
25instead.
26
27* Don't use C99 features.
28
29= Standard Library =
30
31* Avoid including standard library headers. Most standard library functions are
32not available in Windows Kernel Mode. Use the appropriate p_*.h include.
33
34== Memory Allocation ==
35
36* Use MALLOC, CALLOC, FREE instead of the malloc, calloc, free functions.
37
38* Use align_pointer() function defined in u_memory.h for aligning pointers
39 in a portable way.
40
41== Debugging ==
42
43* Use the functions/macros in p_debug.h.
44
45* Don't include assert.h, call abort, printf, etc.
46
47
48= Code Style =
49
50== Inherantice in C ==
51
52The main thing we do is mimic inheritance by structure containment.
53
54Here's a silly made-up example:
55
56/* base class */
57struct buffer
58{
59 int size;
60 void (*validate)(struct buffer *buf);
61};
62
63/* sub-class of bufffer */
64struct texture_buffer
65{
66 struct buffer base; /* the base class, MUST COME FIRST! */
67 int format;
68 int width, height;
69};
70
71
72Then, we'll typically have cast-wrapper functions to convert base-class
73pointers to sub-class pointers where needed:
74
75static inline struct vertex_buffer *vertex_buffer(struct buffer *buf)
76{
77 return (struct vertex_buffer *) buf;
78}
79
80
81To create/init a sub-classed object:
82
83struct buffer *create_texture_buffer(int w, int h, int format)
84{
85 struct texture_buffer *t = malloc(sizeof(*t));
86 t->format = format;
87 t->width = w;
88 t->height = h;
89 t->base.size = w * h;
90 t->base.validate = tex_validate;
91 return &t->base;
92}
93
94Example sub-class method:
95
96void tex_validate(struct buffer *buf)
97{
98 struct texture_buffer *tb = texture_buffer(buf);
99 assert(tb->format);
100 assert(tb->width);
101 assert(tb->height);
102}
103
104
105Note that we typically do not use typedefs to make "class names"; we use
106'struct whatever' everywhere.
107
108Gallium's pipe_context and the subclassed psb_context, etc are prime examples
109of this. There's also many examples in Mesa and the Mesa state tracker.
110