diff options
Diffstat (limited to 'sljit/sljitLir.h')
| -rw-r--r-- | sljit/sljitLir.h | 74 |
1 files changed, 35 insertions, 39 deletions
diff --git a/sljit/sljitLir.h b/sljit/sljitLir.h index 874b9ea..920f6d4 100644 --- a/sljit/sljitLir.h +++ b/sljit/sljitLir.h @@ -1353,56 +1353,52 @@ SLJIT_API_FUNC_ATTRIBUTE void SLJIT_FUNC sljit_release_lock(void); #if (defined SLJIT_UTIL_STACK && SLJIT_UTIL_STACK) -/* The sljit_stack is a utility extension of sljit, which provides - a top-down stack. The stack top is stored in base and the stack - goes down to max_limit, so the memory region for this stack is - between max_limit (inclusive) and base (exclusive). However the - application can only use the region between limit (inclusive) - and base (exclusive). The sljit_stack_resize can be used to - extend this region up to max_limit. +/* The sljit_stack structure and its manipulation functions provides + an implementation for a top-down stack. The stack top is stored + in the end field of the sljit_stack structure and the stack goes + down to the min_start field, so the memory region reserved for + this stack is between min_start (inclusive) and end (exclusive) + fields. However the application can only use the region between + start (inclusive) and end (exclusive) fields. The sljit_stack_resize + function can be used to extend this region up to min_start. This feature uses the "address space reserve" feature of modern - operating systems, so instead of allocating a huge memory block - applications can allocate a small region and extend it later - without moving the memory area. Hence the region is never moved - so pointers are valid after resize. */ - -/* Note: base and max_limit fields are aligned to PAGE_SIZE bytes - (usually 4 Kbyte or more). - Note: stack should grow in larger steps, e.g. 4Kbyte, 16Kbyte or more. - Note: this structure may not be supported by all operating systems. - Some kind of fallback mechanism is suggested when SLJIT_UTIL_STACK - is not defined. */ + operating systems. Instead of allocating a large memory block + applications can allocate a small memory region and extend it + later without moving the content of the memory area. Therefore + after a successful resize by sljit_stack_resize all pointers into + this region are still valid. + + Note: + this structure may not be supported by all operating systems. + end and max_limit fields are aligned to PAGE_SIZE bytes (usually + 4 Kbyte or more). + stack should grow in larger steps, e.g. 4Kbyte, 16Kbyte or more. */ struct sljit_stack { /* User data, anything can be stored here. - Starting with the same value as base. */ + Initialized to the same value as the end field. */ sljit_u8 *top; - /* These members are read only. */ - sljit_u8 *base; - sljit_u8 *limit; - sljit_u8 *max_limit; +/* These members are read only. */ + /* End address of the stack */ + sljit_u8 *end; + /* Current start address of the stack. */ + sljit_u8 *start; + /* Lowest start address of the stack. */ + sljit_u8 *min_start; }; -/* Returns NULL if unsuccessful. - - Note: - max_limit field contains the lower bound adress of the stack. - limit field contains the current starting address of the stack. - base field contains the end address of the stack. - top field is initialized to base. - +/* Allocates a new stack. Returns NULL if unsuccessful. Note: see sljit_create_compiler for the explanation of allocator_data. */ -SLJIT_API_FUNC_ATTRIBUTE struct sljit_stack* SLJIT_FUNC sljit_allocate_stack(sljit_uw limit, sljit_uw max_limit, void *allocator_data); +SLJIT_API_FUNC_ATTRIBUTE struct sljit_stack* SLJIT_FUNC sljit_allocate_stack(sljit_uw start_size, sljit_uw max_size, void *allocator_data); SLJIT_API_FUNC_ATTRIBUTE void SLJIT_FUNC sljit_free_stack(struct sljit_stack *stack, void *allocator_data); -/* Can be used to increase (allocate) or decrease (free) the memory area. - Returns with a non-zero value if unsuccessful. If new_limit is greater than - max_limit, it will fail. It is very easy to implement a stack data structure, - since the growth ratio can be added to the current limit, and sljit_stack_resize - will do all the necessary checks. The fields of the stack are not changed if - sljit_stack_resize fails. */ -SLJIT_API_FUNC_ATTRIBUTE sljit_sw SLJIT_FUNC sljit_stack_resize(struct sljit_stack *stack, sljit_u8 *new_limit); +/* Can be used to increase (extend) or decrease (shrink) the stack + memory area. Returns with new_start if successful and NULL otherwise. + It always fails if new_start is less than min_start or greater or equal + than end fields. The fields of the stack are not changed if the returned + value is NULL (the current memory content is never lost). */ +SLJIT_API_FUNC_ATTRIBUTE sljit_u8 *SLJIT_FUNC sljit_stack_resize(struct sljit_stack *stack, sljit_u8 *new_start); #endif /* (defined SLJIT_UTIL_STACK && SLJIT_UTIL_STACK) */ |