1 #include <stdlib.h> 2 #include <errno.h> 3 #include "meta.h" 4 aligned_alloc(size_t align,size_t len)5void *aligned_alloc(size_t align, size_t len) 6 { 7 if ((align & -align) != align) { 8 errno = EINVAL; 9 return 0; 10 } 11 12 if (len > SIZE_MAX - align || align >= (1ULL<<31)*UNIT) { 13 errno = ENOMEM; 14 return 0; 15 } 16 17 if (DISABLE_ALIGNED_ALLOC) { 18 errno = ENOMEM; 19 return 0; 20 } 21 22 if (align <= UNIT) align = UNIT; 23 24 unsigned char *p = malloc(len + align - UNIT); 25 if (!p) 26 return 0; 27 28 struct meta *g = get_meta(p); 29 int idx = get_slot_index(p); 30 size_t stride = get_stride(g); 31 unsigned char *start = g->mem->storage + stride*idx; 32 unsigned char *end = g->mem->storage + stride*(idx+1) - IB; 33 size_t adj = -(uintptr_t)p & (align-1); 34 35 if (!adj) { 36 set_size(p, end, len); 37 return p; 38 } 39 p += adj; 40 uint32_t offset = (size_t)(p-g->mem->storage)/UNIT; 41 if (offset <= 0xffff) { 42 *(uint16_t *)(p-2) = offset; 43 p[-4] = 0; 44 } else { 45 // use a 32-bit offset if 16-bit doesn't fit. for this, 46 // 16-bit field must be zero, [-4] byte nonzero. 47 *(uint16_t *)(p-2) = 0; 48 *(uint32_t *)(p-8) = offset; 49 p[-4] = 1; 50 } 51 p[-3] = idx; 52 set_size(p, end, len); 53 // store offset to aligned enframing. this facilitates cycling 54 // offset and also iteration of heap for debugging/measurement. 55 // for extreme overalignment it won't fit but these are classless 56 // allocations anyway. 57 *(uint16_t *)(start - 2) = (size_t)(p-start)/UNIT; 58 start[-3] = 7<<5; 59 return p; 60 } 61