ref: 1258e68dd96e65545956fb658b9235e52c99d6a4
dir: /src/libc/stdlib/realloc.c/
#include <stdlib.h> #include <string.h> #include "malloc.h" #undef realloc void * realloc(void *ptr, size_t nbytes) { Header *oh, *prev, *next, *new; size_t nunits, avail, onbytes, n; if (nbytes == 0) return NULL; if (!ptr) return malloc(nbytes); nunits = (nbytes + sizeof(Header) - 1) / sizeof(Header) + 1; oh = (Header*) ptr - 1; if (oh->h.size == nunits) return ptr; new = oh + nunits; if (nunits < oh->h.size - 1) { new->h.size = oh->h.size - nunits; oh->h.size = nunits; free(new + 1); return oh + 1; } prev = _prevchunk(oh); if (oh + oh->h.size == prev->h.next) { /* * if there is free space adjacent * to the current memory */ next = prev->h.next; avail = oh->h.size + next->h.size; if (avail == nunits) { oh->h.size = nunits; prev->h.next = next->h.next; return oh + 1; } if (avail > nunits) { oh->h.size = nunits; prev->h.next = new; new->h.next = next; new->h.size = avail - nunits; return oh + 1; } } onbytes = (oh->h.size - 1) * sizeof(Header); if ((new = malloc(nbytes)) == NULL) return NULL; n = (onbytes > nbytes) ? nbytes : onbytes; memcpy(new, ptr, n); free(ptr); return new; }