ref: c34f6ba17f2789b722eb3e3b34d9bbd873433a27
dir: /src/z_zone.c/
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005-2014 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// DESCRIPTION:
// Zone Memory Allocation. Neat.
//
#include <string.h>
#include "doomtype.h"
#include "i_system.h"
#include "m_argv.h"
#include "z_zone.h"
//
// ZONE MEMORY ALLOCATION
//
// There is never any space between memblocks,
// and there will never be two contiguous free memblocks.
// The rover can be left pointing at a non-empty block.
//
// It is of no value to free a cachable block,
// because it will get overwritten automatically if needed.
//
#define MEM_ALIGN sizeof(void *)
#define ZONEID 0x1d4a11
typedef struct memblock_s
{
int size; // including the header and possibly tiny fragments
void** user;
int tag; // PU_FREE if this is free
int id; // should be ZONEID
struct memblock_s* next;
struct memblock_s* prev;
} memblock_t;
typedef struct
{
// total bytes malloced, including header
int size;
// start / end cap for linked list
memblock_t blocklist;
memblock_t* rover;
} memzone_t;
static memzone_t *mainzone;
static boolean zero_on_free;
static boolean scan_on_free;
//
// Z_ClearZone
//
void Z_ClearZone (memzone_t* zone)
{
memblock_t* block;
// set the entire zone to one free block
zone->blocklist.next =
zone->blocklist.prev =
block = (memblock_t *)( (byte *)zone + sizeof(memzone_t) );
zone->blocklist.user = (void *)zone;
zone->blocklist.tag = PU_STATIC;
zone->rover = block;
block->prev = block->next = &zone->blocklist;
// a free block.
block->tag = PU_FREE;
block->size = zone->size - sizeof(memzone_t);
}
//
// Z_Init
//
void Z_Init (void)
{
memblock_t* block;
int size;
mainzone = (memzone_t *)I_ZoneBase (&size);
mainzone->size = size;
// set the entire zone to one free block
mainzone->blocklist.next =
mainzone->blocklist.prev =
block = (memblock_t *)( (byte *)mainzone + sizeof(memzone_t) );
mainzone->blocklist.user = (void *)mainzone;
mainzone->blocklist.tag = PU_STATIC;
mainzone->rover = block;
block->prev = block->next = &mainzone->blocklist;
// free block
block->tag = PU_FREE;
block->size = mainzone->size - sizeof(memzone_t);
// [Deliberately undocumented]
// Zone memory debugging flag. If set, memory is zeroed after it is freed
// to deliberately break any code that attempts to use it after free.
//
zero_on_free = M_ParmExists("-zonezero");
// [Deliberately undocumented]
// Zone memory debugging flag. If set, each time memory is freed, the zone
// heap is scanned to look for remaining pointers to the freed block.
//
scan_on_free = M_ParmExists("-zonescan");
}
// Scan the zone heap for pointers within the specified range, and warn about
// any remaining pointers.
static void ScanForBlock(void *start, void *end)
{
memblock_t *block;
void **mem;
int i, len, tag;
block = mainzone->blocklist.next;
while (block->next != &mainzone->blocklist)
{
tag = block->tag;
if (tag == PU_STATIC || tag == PU_LEVEL || tag == PU_LEVSPEC)
{
// Scan for pointers on the assumption that pointers are aligned
// on word boundaries (word size depending on pointer size):
mem = (void **) ((byte *) block + sizeof(memblock_t));
len = (block->size - sizeof(memblock_t)) / sizeof(void *);
for (i = 0; i < len; ++i)
{
if (start <= mem[i] && mem[i] <= end)
{
fprintf(stderr,
"%p has dangling pointer into freed block "
"%p (%p -> %p)\n",
mem, start, &mem[i], mem[i]);
}
}
}
block = block->next;
}
}
//
// Z_Free
//
void Z_Free (void* ptr)
{
memblock_t* block;
memblock_t* other;
block = (memblock_t *) ( (byte *)ptr - sizeof(memblock_t));
if (block->id != ZONEID)
I_Error ("Z_Free: freed a pointer without ZONEID");
if (block->tag != PU_FREE && block->user != NULL)
{
// clear the user's mark
*block->user = 0;
}
// mark as free
block->tag = PU_FREE;
block->user = NULL;
block->id = 0;
// If the -zonezero flag is provided, we zero out the block on free
// to break code that depends on reading freed memory.
if (zero_on_free)
{
memset(ptr, 0, block->size - sizeof(memblock_t));
}
if (scan_on_free)
{
ScanForBlock(ptr,
(byte *) ptr + block->size - sizeof(memblock_t));
}
other = block->prev;
if (other->tag == PU_FREE)
{
// merge with previous free block
other->size += block->size;
other->next = block->next;
other->next->prev = other;
if (block == mainzone->rover)
mainzone->rover = other;
block = other;
}
other = block->next;
if (other->tag == PU_FREE)
{
// merge the next free block onto the end
block->size += other->size;
block->next = other->next;
block->next->prev = block;
if (other == mainzone->rover)
mainzone->rover = block;
}
}
//
// Z_Malloc
// You can pass a NULL user if the tag is < PU_PURGELEVEL.
//
#define MINFRAGMENT 64
void*
Z_Malloc
( int size,
int tag,
void* user )
{
int extra;
memblock_t* start;
memblock_t* rover;
memblock_t* newblock;
memblock_t* base;
void *result;
size = (size + MEM_ALIGN - 1) & ~(MEM_ALIGN - 1);
// scan through the block list,
// looking for the first free block
// of sufficient size,
// throwing out any purgable blocks along the way.
// account for size of block header
size += sizeof(memblock_t);
// if there is a free block behind the rover,
// back up over them
base = mainzone->rover;
if (base->prev->tag == PU_FREE)
base = base->prev;
rover = base;
start = base->prev;
do
{
if (rover == start)
{
// scanned all the way around the list
I_Error ("Z_Malloc: failed on allocation of %i bytes", size);
}
if (rover->tag != PU_FREE)
{
if (rover->tag < PU_PURGELEVEL)
{
// hit a block that can't be purged,
// so move base past it
base = rover = rover->next;
}
else
{
// free the rover block (adding the size to base)
// the rover can be the base block
base = base->prev;
Z_Free ((byte *)rover+sizeof(memblock_t));
base = base->next;
rover = base->next;
}
}
else
{
rover = rover->next;
}
} while (base->tag != PU_FREE || base->size < size);
// found a block big enough
extra = base->size - size;
if (extra > MINFRAGMENT)
{
// there will be a free fragment after the allocated block
newblock = (memblock_t *) ((byte *)base + size );
newblock->size = extra;
newblock->tag = PU_FREE;
newblock->user = NULL;
newblock->prev = base;
newblock->next = base->next;
newblock->next->prev = newblock;
base->next = newblock;
base->size = size;
}
if (user == NULL && tag >= PU_PURGELEVEL)
I_Error ("Z_Malloc: an owner is required for purgable blocks");
base->user = user;
base->tag = tag;
result = (void *) ((byte *)base + sizeof(memblock_t));
if (base->user)
{
*base->user = result;
}
// next allocation will start looking here
mainzone->rover = base->next;
base->id = ZONEID;
return result;
}
//
// Z_FreeTags
//
void
Z_FreeTags
( int lowtag,
int hightag )
{
memblock_t* block;
memblock_t* next;
for (block = mainzone->blocklist.next ;
block != &mainzone->blocklist ;
block = next)
{
// get link before freeing
next = block->next;
// free block?
if (block->tag == PU_FREE)
continue;
if (block->tag >= lowtag && block->tag <= hightag)
Z_Free ( (byte *)block+sizeof(memblock_t));
}
}
//
// Z_DumpHeap
// Note: TFileDumpHeap( stdout ) ?
//
void
Z_DumpHeap
( int lowtag,
int hightag )
{
memblock_t* block;
printf ("zone size: %i location: %p\n",
mainzone->size,mainzone);
printf ("tag range: %i to %i\n",
lowtag, hightag);
for (block = mainzone->blocklist.next ; ; block = block->next)
{
if (block->tag >= lowtag && block->tag <= hightag)
printf ("block:%p size:%7i user:%p tag:%3i\n",
block, block->size, block->user, block->tag);
if (block->next == &mainzone->blocklist)
{
// all blocks have been hit
break;
}
if ( (byte *)block + block->size != (byte *)block->next)
printf ("ERROR: block size does not touch the next block\n");
if ( block->next->prev != block)
printf ("ERROR: next block doesn't have proper back link\n");
if (block->tag == PU_FREE && block->next->tag == PU_FREE)
printf ("ERROR: two consecutive free blocks\n");
}
}
//
// Z_FileDumpHeap
//
void Z_FileDumpHeap (FILE* f)
{
memblock_t* block;
fprintf (f,"zone size: %i location: %p\n",mainzone->size,mainzone);
for (block = mainzone->blocklist.next ; ; block = block->next)
{
fprintf (f,"block:%p size:%7i user:%p tag:%3i\n",
block, block->size, block->user, block->tag);
if (block->next == &mainzone->blocklist)
{
// all blocks have been hit
break;
}
if ( (byte *)block + block->size != (byte *)block->next)
fprintf (f,"ERROR: block size does not touch the next block\n");
if ( block->next->prev != block)
fprintf (f,"ERROR: next block doesn't have proper back link\n");
if (block->tag == PU_FREE && block->next->tag == PU_FREE)
fprintf (f,"ERROR: two consecutive free blocks\n");
}
}
//
// Z_CheckHeap
//
void Z_CheckHeap (void)
{
memblock_t* block;
for (block = mainzone->blocklist.next ; ; block = block->next)
{
if (block->next == &mainzone->blocklist)
{
// all blocks have been hit
break;
}
if ( (byte *)block + block->size != (byte *)block->next)
I_Error ("Z_CheckHeap: block size does not touch the next block\n");
if ( block->next->prev != block)
I_Error ("Z_CheckHeap: next block doesn't have proper back link\n");
if (block->tag == PU_FREE && block->next->tag == PU_FREE)
I_Error ("Z_CheckHeap: two consecutive free blocks\n");
}
}
//
// Z_ChangeTag
//
void Z_ChangeTag2(void *ptr, int tag, const char *file, int line)
{
memblock_t* block;
block = (memblock_t *) ((byte *)ptr - sizeof(memblock_t));
if (block->id != ZONEID)
I_Error("%s:%i: Z_ChangeTag: block without a ZONEID!",
file, line);
if (tag >= PU_PURGELEVEL && block->user == NULL)
I_Error("%s:%i: Z_ChangeTag: an owner is required "
"for purgable blocks", file, line);
block->tag = tag;
}
void Z_ChangeUser(void *ptr, void **user)
{
memblock_t* block;
block = (memblock_t *) ((byte *)ptr - sizeof(memblock_t));
if (block->id != ZONEID)
{
I_Error("Z_ChangeUser: Tried to change user for invalid block!");
}
block->user = user;
*user = ptr;
}
//
// Z_FreeMemory
//
int Z_FreeMemory (void)
{
memblock_t* block;
int free;
free = 0;
for (block = mainzone->blocklist.next ;
block != &mainzone->blocklist;
block = block->next)
{
if (block->tag == PU_FREE || block->tag >= PU_PURGELEVEL)
free += block->size;
}
return free;
}
unsigned int Z_ZoneSize(void)
{
return mainzone->size;
}