Nils O. Selåsdal
126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
#ifndef UC_SARENA_H_
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#define UC_SARENA_H_
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** @file
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* Static arena allocator.
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*
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* An UCSArena allocates memory from a provided buffer.
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*
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* The backing buffer should be suitable aligned to the types
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* that will be allocated from it. Use .e.g
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* @code
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* _Alignas(16) char mem[1024];
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* @endcode
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* as the backing buffer.
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*
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* Once allocated, a piece of memory obtained from the
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* allocator cannot be free'd individually, only the entire SArena can
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* be free'd/reset
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*/
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typedef struct UCSArena UCSArena;
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struct UCSArena {
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unsigned char *start; // start of user buffer
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unsigned char *curr; // next alloc point
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unsigned char *end; // one past end of user buffer
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};
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/** Initialize a UCSArena with predefined backing array.
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*
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* @data must be an array type
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* Use as
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* @code
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* _Alignas(16) char v[128];
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* UCSArena a = UC_BV_STATIC_INITIALIZER(v);
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* @endcode
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*/
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#define UC_SAR_STATIC_INITIALIZER(data)\
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UC_SAR_INITIALIZER((data), sizeof(data))
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/** Initializer for UCSArena with predefined memory
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* Use as
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* @code
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* char v[128];
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* UCSArena a = UC_BV_STATIC_INITIALIZER(v, sizeof v);
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* @endcode
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* or
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* @code
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* char *m = malloc(128);
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* UCSArena a = UC_BV_INIT(m, 128);
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* @endcode
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*/
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#define UC_SAR_INITIALIZER(data, sz)\
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{\
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(data),\
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(data),\
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(data) + sz\
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}
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/** Initialize a UCSArena with an array as the backing memory to allocate from.
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* The macro can be used at local scope to allocate memory automatic on the stack,
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* or at global scope where the backing array will have static storage duration
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*
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* Use as:
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* @code
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* UC_SAR_ALLOC_DEF(my_allocator, 1024)
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* struct foo *foo = uc_sar_alloc(&my_allocator);
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* if (foo == NULL) {
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* // out of memory
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* }
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* @endcode
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*
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* @note, the backing buffer has alignment of 16. Use manual init if a different alignment
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* is needed.
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* @param var_name Variable name for the allocator
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* @param size_ byte size of the backing array
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*/
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#define UC_SAR_ALLOC_DEF(var_name, size_) \
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struct {\
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_Alignas(16) char memory[size_]; \
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} var_name ## _memory;\
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UCSArena var_name = UC_SAR_STATIC_INITIALIZER(var_name ## _memory.memory)
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/** Allocate space for @type_ , returned memory is aligned to requirements
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* of @type.
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*
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* Use as:
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* @code
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* UC_SAR_ALLOC_DEF(my_allocator, 1024)
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* struct foo *foo = UC_SAR_ALLOC_ALIGNED(&my_allocator, struct foo);
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* // Array types can be used too:
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* struct Foo *str = UC_SAR_ALLOC_ALIGNED(&my_allocator, struct Foo[32]);
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* @endcode
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*/
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#define UC_SAR_ALLOC_ALIGNED(allocator, type_) \
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uc_sar_alloc_aligned((allocator), sizeof (type_), _Alignof(type_))
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//Initialize an UCSArena to allocate from @mem which is @sz bytes
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static inline void uc_sar_init(UCSArena *a, void *mem, size_t sz)
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{
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a->start = a->curr = mem;
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a->end = a->start + sz;
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}
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// Allocate @sz bytes from the UCSArena. Returns NULL if not enough space
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void *uc_sar_alloc(UCSArena *a, size_t sz);
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// Allocate @sz bytes from the UCSArena, returned pointer is aligned to @align
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// Returns NULL if not enough space
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void *uc_sar_alloc_aligned(UCSArena *a, size_t sz, unsigned int align) [[gnu::alloc_align(2)]];
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static inline void uc_sar_reset(UCSArena *a)
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{
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a->curr = a->start;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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