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#include <assert.h>
#include <errno.h>
#include <stddef.h> /* NULL, size_t */
#include <stdint.h> /* uintptr_t */
#include <stdio.h> /* fprintf */
#include <sys/mman.h> /* mmap */
#define MIN_ALIGNMENT 16
#ifndef MEMSIZE
#define MEMSIZE 1024*4*1024*1024l
#endif
#define unlikely(x) __builtin_expect((x),0)
typedef struct bumpptr {
uintptr_t end;
uintptr_t ptr;
} bumpptr_t;
__thread bumpptr_t* tsd = NULL;
static inline void* bump_up(size_t size, size_t align) {
assert(align % 2 == 0);
if (unlikely(tsd == NULL)) {
void* mem_start = mmap(NULL, MEMSIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB, -1, 0);
if(mem_start == MAP_FAILED) {
perror("mmap");
return NULL;
}
tsd = (bumpptr_t*)mem_start;
tsd->ptr = (uintptr_t)mem_start + sizeof(bumpptr_t);
tsd->end = (uintptr_t)mem_start + MEMSIZE;
}
// align ptr;
uintptr_t aligned = (tsd->ptr + align - 1) & ~(align - 1);
uintptr_t new_ptr = aligned + size;
if (new_ptr > tsd->end) {
errno = ENOMEM;
return NULL;
} else {
tsd->ptr = new_ptr;
return (void*)aligned;
}
}
void* malloc(size_t size) {
return bump_up(size, MIN_ALIGNMENT);
}
void free(__attribute__ ((unused)) void* ptr) {
}
void* memalign(size_t alignment, size_t size) {
return bump_up(size, alignment);
}
void malloc_stats() {
fprintf(stderr, "Bump pointer allocator by muhq\n");
fprintf(stderr, "Memsize: %zu, start address: %p, bump pointer %p\n", MEMSIZE, tsd, tsd->ptr);
}
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