1 /* $NetBSD: malloc-find.c,v 1.1.1.1 2016/01/13 21:42:18 christos Exp $ */ 2 3 /* Find the starting address of a malloc'd block, from anywhere inside it. 4 Copyright (C) 1995 Free Software Foundation, Inc. 5 6 This file is part of the GNU C Library. Its master source is NOT part of 7 the C library, however. The master source lives in /gd/gnu/lib. 8 9 The GNU C Library is free software; you can redistribute it and/or 10 modify it under the terms of the GNU Library General Public License as 11 published by the Free Software Foundation; either version 2 of the 12 License, or (at your option) any later version. 13 14 The GNU C Library is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 17 Library General Public License for more details. 18 19 You should have received a copy of the GNU Library General Public 20 License along with the GNU C Library; see the file COPYING.LIB. If 21 not, write to the Free Software Foundation, Inc., 675 Mass Ave, 22 Cambridge, MA 02139, USA. */ 23 24 #ifndef _MALLOC_INTERNAL 25 #define _MALLOC_INTERNAL 26 #include <malloc.h> 27 #endif 28 29 /* Given an address in the middle of a malloc'd object, 30 return the address of the beginning of the object. */ 31 32 __ptr_t 33 malloc_find_object_address (ptr) 34 __ptr_t ptr; 35 { 36 __malloc_size_t block = BLOCK (ptr); 37 int type = _heapinfo[block].busy.type; 38 39 if (type == 0) 40 { 41 /* The object is one or more entire blocks. */ 42 __malloc_ptrdiff_t sizevalue = _heapinfo[block].busy.info.size; 43 44 if (sizevalue < 0) 45 /* This is one of the blocks after the first. SIZEVALUE 46 says how many blocks to go back to find the first. */ 47 block += sizevalue; 48 49 /* BLOCK is now the first block of the object. 50 Its start is the start of the object. */ 51 return ADDRESS (block); 52 } 53 else 54 { 55 /* Get the size of fragments in this block. */ 56 __malloc_size_t size = 1 << type; 57 58 /* Turn off the low bits to find the start address of the fragment. */ 59 return _heapbase + (((char *) ptr - _heapbase) & ~(size - 1)); 60 } 61 } 62