bird/lib/mempool.c

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/*
* BIRD Resource Manager -- Memory Pools
*
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* (c) 1998--2000 Martin Mares <mj@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
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/**
* DOC: Linear memory pools
*
* Linear memory pools are collections of memory blocks which
* support very fast allocation of new blocks, but are able to free only
* the whole collection at once.
*
* Example: Each configuration is described by a complex system of structures,
* linked lists and function trees which are all allocated from a single linear
* pool, thus they can be freed at once when the configuration is no longer used.
*/
#include <stdlib.h>
#include "nest/bird.h"
#include "lib/resource.h"
#include "lib/string.h"
struct lp_chunk {
struct lp_chunk *next;
unsigned int size;
uintptr_t data_align[0];
byte data[0];
};
struct linpool {
resource r;
byte *ptr, *end;
struct lp_chunk *first, *current, **plast; /* Normal (reusable) chunks */
struct lp_chunk *first_large; /* Large chunks */
unsigned chunk_size, threshold, total, total_large;
};
static void lp_free(resource *);
static void lp_dump(resource *);
static resource *lp_lookup(resource *, unsigned long);
static struct resclass lp_class = {
"LinPool",
sizeof(struct linpool),
lp_free,
lp_dump,
lp_lookup
};
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/**
* lp_new - create a new linear memory pool
* @p: pool
* @blk: block size
*
* lp_new() creates a new linear memory pool resource inside the pool @p.
* The linear pool consists of a list of memory chunks of size at least
* @blk.
*/
linpool
*lp_new(pool *p, unsigned blk)
{
linpool *m = ralloc(p, &lp_class);
m->ptr = m->end = NULL;
m->first = m->current = NULL;
m->plast = &m->first;
m->first_large = NULL;
m->chunk_size = blk;
m->threshold = 3*blk/4;
m->total = m->total_large = 0;
return m;
}
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/**
* lp_alloc - allocate memory from a &linpool
* @m: linear memory pool
* @size: amount of memory
*
* lp_alloc() allocates @size bytes of memory from a &linpool @m
* and it returns a pointer to the allocated memory.
*
* It works by trying to find free space in the last memory chunk
* associated with the &linpool and creating a new chunk of the standard
* size (as specified during lp_new()) if the free space is too small
* to satisfy the allocation. If @size is too large to fit in a standard
* size chunk, an "overflow" chunk is created for it instead.
*/
void *
lp_alloc(linpool *m, unsigned size)
{
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byte *a = (byte *) BIRD_ALIGN((unsigned long) m->ptr, CPU_STRUCT_ALIGN);
byte *e = a + size;
if (e <= m->end)
{
m->ptr = e;
return a;
}
else
{
struct lp_chunk *c;
if (size >= m->threshold)
{
/* Too large => allocate large chunk */
c = xmalloc(sizeof(struct lp_chunk) + size);
m->total_large += size;
c->next = m->first_large;
m->first_large = c;
c->size = size;
}
else
{
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if (m->current)
{
/* Still have free chunks from previous incarnation (before lp_flush()) */
c = m->current;
m->current = c->next;
}
else
{
/* Need to allocate a new chunk */
c = xmalloc(sizeof(struct lp_chunk) + m->chunk_size);
m->total += m->chunk_size;
*m->plast = c;
m->plast = &c->next;
c->next = NULL;
c->size = m->chunk_size;
}
m->ptr = c->data + size;
m->end = c->data + m->chunk_size;
}
return c->data;
}
}
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/**
* lp_allocu - allocate unaligned memory from a &linpool
* @m: linear memory pool
* @size: amount of memory
*
* lp_allocu() allocates @size bytes of memory from a &linpool @m
* and it returns a pointer to the allocated memory. It doesn't
* attempt to align the memory block, giving a very efficient way
* how to allocate strings without any space overhead.
*/
void *
lp_allocu(linpool *m, unsigned size)
{
byte *a = m->ptr;
byte *e = a + size;
if (e <= m->end)
{
m->ptr = e;
return a;
}
return lp_alloc(m, size);
}
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/**
* lp_allocz - allocate cleared memory from a &linpool
* @m: linear memory pool
* @size: amount of memory
*
* This function is identical to lp_alloc() except that it
* clears the allocated memory block.
*/
void *
lp_allocz(linpool *m, unsigned size)
{
void *z = lp_alloc(m, size);
bzero(z, size);
return z;
}
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/**
* lp_flush - flush a linear memory pool
* @m: linear memory pool
*
* This function frees the whole contents of the given &linpool @m,
* but leaves the pool itself.
*/
void
lp_flush(linpool *m)
{
struct lp_chunk *c;
/* Relink all normal chunks to free list and free all large chunks */
m->ptr = m->end = NULL;
m->current = m->first;
while (c = m->first_large)
{
m->first_large = c->next;
xfree(c);
}
m->total_large = 0;
}
static void
lp_free(resource *r)
{
linpool *m = (linpool *) r;
struct lp_chunk *c, *d;
for(d=m->first; d; d = c)
{
c = d->next;
xfree(d);
}
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for(d=m->first_large; d; d = c)
{
c = d->next;
xfree(d);
}
}
static void
lp_dump(resource *r)
{
linpool *m = (linpool *) r;
struct lp_chunk *c;
int cnt, cntl;
for(cnt=0, c=m->first; c; c=c->next, cnt++)
;
for(cntl=0, c=m->first_large; c; c=c->next, cntl++)
;
debug("(chunk=%d threshold=%d count=%d+%d total=%d+%d)\n",
m->chunk_size,
m->threshold,
cnt,
cntl,
m->total,
m->total_large);
}
static resource *
lp_lookup(resource *r, unsigned long a)
{
linpool *m = (linpool *) r;
struct lp_chunk *c;
for(c=m->first; c; c=c->next)
if ((unsigned long) c->data <= a && (unsigned long) c->data + c->size > a)
return r;
for(c=m->first_large; c; c=c->next)
if ((unsigned long) c->data <= a && (unsigned long) c->data + c->size > a)
return r;
return NULL;
}