github.com/afumu/libc@v0.0.6/musl/src/malloc/mallocng/donate.c (about)

     1  #include <stdlib.h>
     2  #include <stdint.h>
     3  #include <limits.h>
     4  #include <string.h>
     5  #include <sys/mman.h>
     6  #include <errno.h>
     7  
     8  #include "meta.h"
     9  
    10  static void donate(unsigned char *base, size_t len)
    11  {
    12  	uintptr_t a = (uintptr_t)base;
    13  	uintptr_t b = a + len;
    14  	a += -a & (UNIT-1);
    15  	b -= b & (UNIT-1);
    16  	memset(base, 0, len);
    17  	for (int sc=47; sc>0 && b>a; sc-=4) {
    18  		if (b-a < (size_classes[sc]+1)*UNIT) continue;
    19  		struct meta *m = alloc_meta();
    20  		m->avail_mask = 0;
    21  		m->freed_mask = 1;
    22  		m->mem = (void *)a;
    23  		m->mem->meta = m;
    24  		m->last_idx = 0;
    25  		m->freeable = 0;
    26  		m->sizeclass = sc;
    27  		m->maplen = 0;
    28  		*((unsigned char *)m->mem+UNIT-4) = 0;
    29  		*((unsigned char *)m->mem+UNIT-3) = 255;
    30  		m->mem->storage[size_classes[sc]*UNIT-4] = 0;
    31  		queue(&ctx.active[sc], m);
    32  		a += (size_classes[sc]+1)*UNIT;
    33  	}
    34  }
    35  
    36  void __malloc_donate(char *start, char *end)
    37  {
    38  	donate((void *)start, end-start);
    39  }