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Diffstat (limited to 'src/accessor.h')
| -rw-r--r-- | src/accessor.h | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/src/accessor.h b/src/accessor.h new file mode 100644 index 0000000..0da1209 --- /dev/null +++ b/src/accessor.h @@ -0,0 +1,79 @@ +/* + * Copyright © 2024 Michael Smith <mikesmiffy128@gmail.com> + * + * Permission to use, copy, modify, and/or distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH + * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY + * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, + * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM + * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR + * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR + * PERFORMANCE OF THIS SOFTWARE. + */ + +#ifndef INC_ACCESSOR_H +#define INC_ACCESSOR_H + +#include "intdefs.h" +#include "mem.h" + +#if defined(__GNUC__) || defined(__clang__) +#define _ACCESSOR_UNUSED __attribute__((unused)) +#else +#define _ACCESSOR_UNUSED +#endif + +/* + * Defines a function to offset a pointer from a struct/class to a field based + * on a corresponding offset value off_<field>. Such an offset would be + * generally defined in gamedata. The function will be named getptr_<field>. + * Essentially allows easy access to an opaque thing contained with another + * opaque thing. + */ +#define DEF_PTR_ACCESSOR(type, field) \ + _ACCESSOR_UNUSED static inline typeof(type) *getptr_##field(void *obj) { \ + return mem_offset(obj, off_##field); \ + } + +/* + * Does the same as DEF_PTR_ACCESSOR, and also adds direct get/get functions. + * Requires that the field type is complete - that is, either scalar or a fully + * defined struct. + */ +#define DEF_ACCESSORS(type, field) \ + DEF_PTR_ACCESSOR(type, field) \ + _ACCESSOR_UNUSED static inline typeof(type) get_##field(const void *obj) { \ + return *getptr_##field((void *)obj); \ + } \ + _ACCESSOR_UNUSED static inline void set_##field(const void *obj, \ + typeof(type) val) { \ + *getptr_##field((void *)obj) = val; \ + } + +/* + * Defines an array indexing function arrayidx_<class> which allows offsetting + * an opaque pointer by sz_<class> bytes. This size value would generally be + * defined in gamedata. Allows iterating over structs/classes with sizes that + * vary by game and are thus unknown at compile time. + * + * Note that idx is signed so this can also be used for relative pointer offsets + * in either direction. + * + * Note on performance: obviously doing n * size requires a multiplication by a + * global, which poses a bit of an optimisation challenge in loops. Based on + * some testing though it seems like this *should* usually be optimised into a + * single load of the global followed by repeated addition with no need for + * multiplication, given that we use LTO, so... don't worry about it! It's fine! + */ +#define DEF_ARRAYIDX_ACCESSOR(class) \ + _ACCESSOR_UNUSED static inline struct class *arrayidx_##class(void *array, \ + ssize idx) { \ + return mem_offset(array, idx * sz_##class); \ + } + +#endif + +// vi: sw=4 ts=4 noet tw=80 cc=80 |