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#include "framer.h"
/* Installs a MemFramer at the specified address */
MemFramer *mem_framer_install(void *addr, usize end, uint blksz) {
MemFramer *self = addr;
usize selfend = (usize)(self + 1);
usize next = ALIGN_UP(selfend, blksz);
*self = (MemFramer) {
.allocator = (MemAllocator) {
.alloc = mem_framer_alloc,
.free = mem_framer_free
},
.next = next,
.end = end,
.blksz = blksz
};
return self;
}
/* Allocates a frame */
void *mem_framer_alloc(MemAllocator *inner, usize n) {
/* When allocating a frame, we have two paths:
1. The freelist is not empty: give away
the last freed frame
2. The freelist is empty: bump away the next
frame (pointed at by the next member)
The alloc must fail the freelist is empty and that
the next is beyond the end of the region */
MemFramer *self = (MemFramer*)inner;
/* The implementation does not support more than
one frame */
if (n == 0 || n > self->blksz)
return nil;
void *ptr = nil;
if (self->free) {
ptr = self->free;
self->free = self->free->next;
} else if (self->next + self->blksz <= self->end) {
ptr = (void*)self->next;
self->next += self->blksz;
}
return ptr;
}
/* Frees a frame */
void mem_framer_free(MemAllocator *inner, void *ptr) {
/* NOTE: this implementation does make the assumption
that the given pointer is the base of the allocated
region without correction */
MemFramer *self = (MemFramer*)inner;
MemFramerFreed *freed = ptr;
freed->next = self->free;
self->free = freed;
}
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