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/** \file halloc.c
A hierarchical memory allocation system. Works just like talloc
used in Samba, except that an arbitrary block allocated with
malloc() can be registered to be freed by halloc_free.
*/
#include "config.h"
#include <stdlib.h>
#include <unistd.h>
#include "fallback.h"
#include "util.h"
#include "common.h"
#include "halloc.h"
/**
Extra size to allocate whenever doing a halloc, in order to fill uyp smaller halloc calls
*/
#define HALLOC_BLOCK_SIZE 128
/**
Maximum size of trailing halloc space to refuse to discard
*/
#define HALLOC_SCRAP_SIZE 16
#ifdef HALLOC_DEBUG
/**
Debug statistic parameter
*/
static int child_count=0;
/**
Debug statistic parameter
*/
static int child_size=0;
/**
Debug statistic parameter
*/
static int alloc_count =0;
/**
Debug statistic parameter
*/
static int alloc_spill = 0;
/**
Debug statistic parameter
*/
static pid_t pid=0;
/**
Debug statistic parameter
*/
static int parent_count=0;
#endif
/**
The main datastructure for a main halloc context
*/
typedef struct halloc
{
/**
List of all addresses and functions to call on them
*/
array_list_t children;
/**
Memory scratch area used to fullfil smaller memory allocations
*/
void *scratch;
/**
Amount of free space in the scratch area
*/
size_t scratch_free;
#if __STDC_VERSION__ < 199901L
/**
The actual data. MAde to be of type long long to make sure memory alignment is in order.
*/
long long data[1]; // Waste one byte on non-C99 compilers... :-(
#else
long long data[];
#endif
}
halloc_t;
/**
Get the offset of the halloc structure before a data block
*/
static halloc_t *halloc_from_data( void *data )
{
return (halloc_t *)(((char *)data) - sizeof( halloc_t ) );
}
/**
A function that does nothing
*/
static void late_free( void *data)
{
}
#ifdef HALLOC_DEBUG
/**
Debug function, called at exit when in debug mode. Prints usage
statistics, like number of allocations and number of internal calls
to malloc.
*/
static void woot()
{
if( getpid() == pid )
{
debug( 1, L"%d parents, %d children with average child size of %.2f bytes caused %d allocs, average spill of %.2f bytes",
parent_count, child_count, (double)child_size/child_count,
parent_count+alloc_count, (double)alloc_spill/(parent_count+alloc_count) );
}
}
#endif
void *halloc( void *context, size_t size )
{
halloc_t *me, *parent;
if( context )
{
void *res;
#ifdef HALLOC_DEBUG
if( !child_count )
{
pid = getpid();
atexit( woot );
}
child_count++;
child_size += size;
#endif
parent = halloc_from_data( context );
if( size <= parent->scratch_free )
{
res = parent->scratch;
parent->scratch_free -= size;
parent->scratch = ((char *)parent->scratch)+size;
}
else
{
#ifdef HALLOC_DEBUG
alloc_count++;
#endif
if( parent->scratch_free < HALLOC_SCRAP_SIZE )
{
#ifdef HALLOC_DEBUG
alloc_spill += parent->scratch_free;
#endif
res = calloc( 1, size + HALLOC_BLOCK_SIZE );
parent->scratch = (char *)res + size;
parent->scratch_free = HALLOC_BLOCK_SIZE;
}
else
{
res = calloc( 1, size );
}
al_push( &parent->children, &late_free );
al_push( &parent->children, res );
}
return res;
}
else
{
me = (halloc_t *)calloc( 1, sizeof(halloc_t) + size + HALLOC_BLOCK_SIZE );
if( !me )
return 0;
#ifdef HALLOC_DEBUG
parent_count++;
#endif
me->scratch = ((char *)me) + sizeof(halloc_t) + size;
me->scratch_free = HALLOC_BLOCK_SIZE;
al_init( &me->children );
return &me->data;
}
}
void halloc_register_function( void *context, void (*func)(void *), void *data )
{
halloc_t *me;
if( !context )
return;
me = halloc_from_data( context );
al_push( &me->children, func );
al_push( &me->children, data );
}
void halloc_free( void *context )
{
halloc_t *me;
int i;
if( !context )
return;
me = halloc_from_data( context );
#ifdef HALLOC_DEBUG
alloc_spill += me->scratch_free;
#endif
for( i=0; i<al_get_count(&me->children); i+=2 )
{
void (*func)(void *) = (void (*)(void *))al_get( &me->children, i );
void * data = (void *)al_get( &me->children, i+1 );
if( func != &late_free )
func( data );
}
for( i=0; i<al_get_count(&me->children); i+=2 )
{
void (*func)(void *) = (void (*)(void *))al_get( &me->children, i );
void * data = (void *)al_get( &me->children, i+1 );
if( func == &late_free )
free( data );
}
al_destroy( &me->children );
free(me);
}
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