src/lib/mempool-alloconly.c

	mempool-alloconly.c revision 01a170c984df9e5fc0f28aa7695e0cbbdb3c9029
/* Copyright (c) 2002-2008 Dovecot authors, see the included COPYING file */

/* @UNSAFE: whole file */
#include "lib.h"
#include "safe-memset.h"
#include "mempool.h"

#include <stdlib.h>

#ifdef HAVE_GC_GC_H
#  include <gc/gc.h>
#elif defined (HAVE_GC_H)
#  include <gc.h>
#endif

#define MAX_ALLOC_SIZE SSIZE_T_MAX

struct alloconly_pool {
    struct pool pool;
    int refcount;

    struct pool_block *block;
#ifdef DEBUG
    const char *name;
    size_t base_size;
    bool disable_warning;
#endif
    bool clean_frees;
};

struct pool_block {
    struct pool_block *prev;

    size_t size;
    size_t left;
    size_t last_alloc_size;

    /* unsigned char data[]; */
};
#define SIZEOF_POOLBLOCK (MEM_ALIGN(sizeof(struct pool_block)))

#define POOL_BLOCK_DATA(block) \
    ((char *) (block) + SIZEOF_POOLBLOCK)

#define DEFAULT_BASE_SIZE MEM_ALIGN(sizeof(struct alloconly_pool))

static const char *pool_alloconly_get_name(pool_t pool);
static void pool_alloconly_ref(pool_t pool);
static void pool_alloconly_unref(pool_t *pool);
static void *pool_alloconly_malloc(pool_t pool, size_t size);
static void pool_alloconly_free(pool_t pool, void *mem);
static void *pool_alloconly_realloc(pool_t pool, void *mem,
                    size_t old_size, size_t new_size);
static void pool_alloconly_clear(pool_t pool);
static size_t pool_alloconly_get_max_easy_alloc_size(pool_t pool);

static void block_alloc(struct alloconly_pool *pool, size_t size);

static const struct pool_vfuncs static_alloconly_pool_vfuncs = {
    pool_alloconly_get_name,

    pool_alloconly_ref,
    pool_alloconly_unref,

    pool_alloconly_malloc,
    pool_alloconly_free,

    pool_alloconly_realloc,

    pool_alloconly_clear,
    pool_alloconly_get_max_easy_alloc_size
};

static const struct pool static_alloconly_pool = {
    MEMBER(v) &static_alloconly_pool_vfuncs,

    MEMBER(alloconly_pool) TRUE,
    MEMBER(datastack_pool) FALSE
};

#ifdef DEBUG
static void check_nuls(struct pool_block *block)
{
    const char *data = POOL_BLOCK_DATA(block);
    size_t i;

    for (i = block->size - block->left; i < block->size; i++) {
        if (data[i] != '\0')
            i_unreached();
    }
    if (block->prev != NULL)
        check_nuls(block->prev);
}
#endif

pool_t pool_alloconly_create(const char *name ATTR_UNUSED, size_t size)
{
    struct alloconly_pool apool, *new_apool;
    size_t min_alloc = MEM_ALIGN(sizeof(struct alloconly_pool)) +
        SIZEOF_POOLBLOCK;

#ifdef DEBUG
    min_alloc += MEM_ALIGN(strlen(name) + 1);
#endif

    /* create a fake alloconly_pool so we can call block_alloc() */
    memset(&apool, 0, sizeof(apool));
    apool.pool = static_alloconly_pool;
    apool.refcount = 1;

    if (size < min_alloc)
        size = nearest_power(size + min_alloc);
    block_alloc(&apool, size);

    /* now allocate the actual alloconly_pool from the created block */
    new_apool = p_new(&apool.pool, struct alloconly_pool, 1);
    *new_apool = apool;
    /* the pool allocation must be from the first block */
    i_assert(apool.block->prev == NULL);
#ifdef DEBUG
    if (strncmp(name, MEMPOOL_GROWING, strlen(MEMPOOL_GROWING)) == 0) {
        name += strlen(MEMPOOL_GROWING);
        new_apool->disable_warning = TRUE;
    }
    new_apool->name = p_strdup(&new_apool->pool, name);

    /* set base_size so p_clear() doesn't trash alloconly_pool structure. */
    new_apool->base_size = new_apool->block->size - new_apool->block->left;
    new_apool->block->last_alloc_size = 0;
#endif

    return &new_apool->pool;
}

pool_t pool_alloconly_create_clean(const char *name, size_t size)
{
    struct alloconly_pool *apool;
    pool_t pool;

    pool = pool_alloconly_create(name, size);
    apool = (struct alloconly_pool *)pool;
    apool->clean_frees = TRUE;
    return pool;
}

static void pool_alloconly_destroy(struct alloconly_pool *apool)
{
    void *block;

    /* destroy all but the last block */
    pool_alloconly_clear(&apool->pool);

    /* destroy the last block */
    block = apool->block;
#ifdef DEBUG
    safe_memset(block, 0xde, SIZEOF_POOLBLOCK + apool->block->size);
#else
    if (apool->clean_frees)
        safe_memset(block, 0, SIZEOF_POOLBLOCK + apool->block->size);
#endif

#ifndef USE_GC
    free(block);
#endif
}

static const char *pool_alloconly_get_name(pool_t pool ATTR_UNUSED)
{
#ifdef DEBUG
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;

    return apool->name;
#else
    return "alloconly";
#endif
}

static void pool_alloconly_ref(pool_t pool)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;

    apool->refcount++;
}

static void pool_alloconly_unref(pool_t *pool)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)*pool;

    if (--apool->refcount > 0)
        return;

    /* erase the pointer before freeing anything, as the pointer may
       exist inside the pool's memory area */
    *pool = NULL;

    pool_alloconly_destroy(apool);
}

static void block_alloc(struct alloconly_pool *apool, size_t size)
{
    struct pool_block *block;

    i_assert(size > SIZEOF_POOLBLOCK);

    if (apool->block != NULL) {
        /* each block is at least twice the size of the previous one */
        if (size <= apool->block->size)
            size += apool->block->size;

        size = nearest_power(size);
#ifdef DEBUG
        if (!apool->disable_warning) {
            i_warning("Growing pool '%s' with: %"PRIuSIZE_T,
                  apool->name, size);
        }
#endif
    }

#ifndef USE_GC
    block = calloc(size, 1);
#else
    block = GC_malloc(size);
#endif
    if (unlikely(block == NULL))
        i_fatal_status(FATAL_OUTOFMEM, "block_alloc(): Out of memory");
    block->prev = apool->block;
    apool->block = block;

    block->size = size - SIZEOF_POOLBLOCK;
    block->left = block->size;
}

static void *pool_alloconly_malloc(pool_t pool, size_t size)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;
    void *mem;

    if (unlikely(size == 0 || size > SSIZE_T_MAX))
        i_panic("Trying to allocate %"PRIuSIZE_T" bytes", size);

    size = MEM_ALIGN(size);

    if (apool->block->left < size) {
        /* we need a new block */
        block_alloc(apool, size + SIZEOF_POOLBLOCK);
    }

    mem = POOL_BLOCK_DATA(apool->block) +
        (apool->block->size - apool->block->left);

    apool->block->left -= size;
    apool->block->last_alloc_size = size;
    return mem;
}

static void pool_alloconly_free(pool_t pool, void *mem)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;

    /* we can free only the last allocation */
    if (POOL_BLOCK_DATA(apool->block) +
        (apool->block->size - apool->block->left -
         apool->block->last_alloc_size) == mem) {
        memset(mem, 0, apool->block->last_alloc_size);
        apool->block->left += apool->block->last_alloc_size;
                apool->block->last_alloc_size = 0;
    }
}

static bool pool_try_grow(struct alloconly_pool *apool, void *mem, size_t size)
{
    /* see if we want to grow the memory we allocated last */
    if (POOL_BLOCK_DATA(apool->block) +
        (apool->block->size - apool->block->left -
         apool->block->last_alloc_size) == mem) {
        /* yeah, see if we can grow */
        if (apool->block->left >= size-apool->block->last_alloc_size) {
            /* just shrink the available size */
            apool->block->left -=
                size - apool->block->last_alloc_size;
            apool->block->last_alloc_size = size;
            return TRUE;
        }
    }

    return FALSE;
}

static void *pool_alloconly_realloc(pool_t pool, void *mem,
                    size_t old_size, size_t new_size)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;
    unsigned char *new_mem;

    if (unlikely(new_size == 0 || new_size > SSIZE_T_MAX))
        i_panic("Trying to allocate %"PRIuSIZE_T" bytes", new_size);

    if (mem == NULL)
        return pool_alloconly_malloc(pool, new_size);

    if (new_size <= old_size)
        return mem;

    new_size = MEM_ALIGN(new_size);

    /* see if we can directly grow it */
    if (!pool_try_grow(apool, mem, new_size)) {
        /* slow way - allocate + copy */
        new_mem = pool_alloconly_malloc(pool, new_size);
        memcpy(new_mem, mem, old_size);
        mem = new_mem;
    }

        return mem;
}

static void pool_alloconly_clear(pool_t pool)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;
    struct pool_block *block;
    size_t base_size, avail_size;

#ifdef DEBUG
    check_nuls(apool->block);
#endif

    /* destroy all blocks but the oldest, which contains the
       struct alloconly_pool allocation. */
    while (apool->block->prev != NULL) {
        block = apool->block;
        apool->block = block->prev;

#ifdef DEBUG
        safe_memset(block, 0xde, SIZEOF_POOLBLOCK + block->size);
#else
        if (apool->clean_frees)
            safe_memset(block, 0, SIZEOF_POOLBLOCK + block->size);
#endif
#ifndef USE_GC
        free(block);
#endif
    }

    /* clear the first block */
#ifdef DEBUG
    base_size = apool->base_size;
#else
    base_size = DEFAULT_BASE_SIZE;
#endif
    avail_size = apool->block->size - base_size;
    safe_memset(PTR_OFFSET(POOL_BLOCK_DATA(apool->block), base_size), 0,
            avail_size - apool->block->left);
    apool->block->left = avail_size;
    apool->block->last_alloc_size = 0;
}

static size_t pool_alloconly_get_max_easy_alloc_size(pool_t pool)
{
    struct alloconly_pool *apool = (struct alloconly_pool *)pool;

    return apool->block->left;
}