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- /* Copyright (c) 2008-2009, The Tor Project, Inc. */
- /* See LICENSE for licensing information */
- /** \file memarea.c
- * \brief Implementation for memarea_t, an allocator for allocating lots of
- * small objects that will be freed all at once.
- */
- #include "orconfig.h"
- #include <stdlib.h>
- #include "memarea.h"
- #include "util.h"
- #include "compat.h"
- #include "log.h"
- /** If true, we try to detect any attempts to write beyond the length of a
- * memarea. */
- #define USE_SENTINELS
- /** All returned pointers should be aligned to the nearest multiple of this
- * value. */
- #define MEMAREA_ALIGN SIZEOF_VOID_P
- #if MEMAREA_ALIGN == 4
- #define MEMAREA_ALIGN_MASK 3lu
- #elif MEMAREA_ALIGN == 8
- #define MEMAREA_ALIGN_MASK 7lu
- #else
- #error "void* is neither 4 nor 8 bytes long. I don't know how to align stuff."
- #endif
- #ifdef USE_SENTINELS
- #define SENTINEL_VAL 0x90806622u
- #define SENTINEL_LEN sizeof(uint32_t)
- #define SET_SENTINEL(chunk) \
- STMT_BEGIN \
- set_uint32( &(chunk)->u.mem[chunk->mem_size], SENTINEL_VAL ); \
- STMT_END
- #define CHECK_SENTINEL(chunk) \
- STMT_BEGIN \
- uint32_t sent_val = get_uint32(&(chunk)->u.mem[chunk->mem_size]); \
- tor_assert(sent_val == SENTINEL_VAL); \
- STMT_END
- #else
- #define SENTINEL_LEN 0
- #define SET_SENTINEL(chunk) STMT_NIL
- #define CHECK_SENTINEL(chunk) STMT_NIL
- #endif
- /** Increment <b>ptr</b> until it is aligned to MEMAREA_ALIGN. */
- static INLINE void *
- realign_pointer(void *ptr)
- {
- uintptr_t x = (uintptr_t)ptr;
- x = (x+MEMAREA_ALIGN_MASK) & ~MEMAREA_ALIGN_MASK;
- tor_assert(((void*)x) >= ptr); // XXXX021 remove this once bug 930 is solved
- return (void*)x;
- }
- /** Implements part of a memarea. New memory is carved off from chunk->mem in
- * increasing order until a request is too big, at which point a new chunk is
- * allocated. */
- typedef struct memarea_chunk_t {
- /** Next chunk in this area. Only kept around so we can free it. */
- struct memarea_chunk_t *next_chunk;
- size_t mem_size; /**< How much RAM is available in u.mem, total? */
- char *next_mem; /**< Next position in u.mem to allocate data at. If it's
- * greater than or equal to mem+mem_size, this chunk is
- * full. */
- union {
- char mem[1]; /**< Memory space in this chunk. */
- void *_void_for_alignment; /**< Dummy; used to make sure mem is aligned. */
- } u;
- } memarea_chunk_t;
- #define CHUNK_HEADER_SIZE STRUCT_OFFSET(memarea_chunk_t, u)
- #define CHUNK_SIZE 4096
- /** A memarea_t is an allocation region for a set of small memory requests
- * that will all be freed at once. */
- struct memarea_t {
- memarea_chunk_t *first; /**< Top of the chunk stack: never NULL. */
- };
- /** How many chunks will we put into the freelist before freeing them? */
- #define MAX_FREELIST_LEN 4
- /** The number of memarea chunks currently in our freelist. */
- static int freelist_len=0;
- /** A linked list of unused memory area chunks. Used to prevent us from
- * spinning in malloc/free loops. */
- static memarea_chunk_t *freelist = NULL;
- /** Helper: allocate a new memarea chunk of around <b>chunk_size</b> bytes. */
- static memarea_chunk_t *
- alloc_chunk(size_t sz, int freelist_ok)
- {
- if (freelist && freelist_ok) {
- memarea_chunk_t *res = freelist;
- freelist = res->next_chunk;
- res->next_chunk = NULL;
- --freelist_len;
- CHECK_SENTINEL(res);
- return res;
- } else {
- size_t chunk_size = freelist_ok ? CHUNK_SIZE : sz;
- memarea_chunk_t *res;
- chunk_size += SENTINEL_LEN;
- res = tor_malloc_roundup(&chunk_size);
- res->next_chunk = NULL;
- res->mem_size = chunk_size - CHUNK_HEADER_SIZE - SENTINEL_LEN;
- res->next_mem = res->u.mem;
- tor_assert(res->next_mem+res->mem_size+SENTINEL_LEN ==
- ((char*)res)+chunk_size);
- tor_assert(realign_pointer(res->next_mem) == res->next_mem);
- SET_SENTINEL(res);
- return res;
- }
- }
- /** Release <b>chunk</b> from a memarea, either by adding it to the freelist
- * or by freeing it if the freelist is already too big. */
- static void
- chunk_free_unchecked(memarea_chunk_t *chunk)
- {
- CHECK_SENTINEL(chunk);
- if (freelist_len < MAX_FREELIST_LEN) {
- ++freelist_len;
- chunk->next_chunk = freelist;
- freelist = chunk;
- chunk->next_mem = chunk->u.mem;
- } else {
- tor_free(chunk);
- }
- }
- /** Allocate and return new memarea. */
- memarea_t *
- memarea_new(void)
- {
- memarea_t *head = tor_malloc(sizeof(memarea_t));
- head->first = alloc_chunk(CHUNK_SIZE, 1);
- return head;
- }
- /** Free <b>area</b>, invalidating all pointers returned from memarea_alloc()
- * and friends for this area */
- void
- memarea_drop_all(memarea_t *area)
- {
- memarea_chunk_t *chunk, *next;
- for (chunk = area->first; chunk; chunk = next) {
- next = chunk->next_chunk;
- chunk_free_unchecked(chunk);
- }
- area->first = NULL; /*fail fast on */
- tor_free(area);
- }
- /** Forget about having allocated anything in <b>area</b>, and free some of
- * the backing storage associated with it, as appropriate. Invalidates all
- * pointers returned from memarea_alloc() for this area. */
- void
- memarea_clear(memarea_t *area)
- {
- memarea_chunk_t *chunk, *next;
- if (area->first->next_chunk) {
- for (chunk = area->first->next_chunk; chunk; chunk = next) {
- next = chunk->next_chunk;
- chunk_free_unchecked(chunk);
- }
- area->first->next_chunk = NULL;
- }
- area->first->next_mem = area->first->u.mem;
- }
- /** Remove all unused memarea chunks from the internal freelist. */
- void
- memarea_clear_freelist(void)
- {
- memarea_chunk_t *chunk, *next;
- freelist_len = 0;
- for (chunk = freelist; chunk; chunk = next) {
- next = chunk->next_chunk;
- tor_free(chunk);
- }
- freelist = NULL;
- }
- /** Return true iff <b>p</b> is in a range that has been returned by an
- * allocation from <b>area</b>. */
- int
- memarea_owns_ptr(const memarea_t *area, const void *p)
- {
- memarea_chunk_t *chunk;
- const char *ptr = p;
- for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
- if (ptr >= chunk->u.mem && ptr < chunk->next_mem)
- return 1;
- }
- return 0;
- }
- /** Return a pointer to a chunk of memory in <b>area</b> of at least <b>sz</b>
- * bytes. <b>sz</b> should be significantly smaller than the area's chunk
- * size, though we can deal if it isn't. */
- void *
- memarea_alloc(memarea_t *area, size_t sz)
- {
- memarea_chunk_t *chunk = area->first;
- char *result;
- tor_assert(chunk);
- CHECK_SENTINEL(chunk);
- if (sz == 0)
- sz = 1;
- if (chunk->next_mem+sz > chunk->u.mem+chunk->mem_size) {
- if (sz+CHUNK_HEADER_SIZE >= CHUNK_SIZE) {
- /* This allocation is too big. Stick it in a special chunk, and put
- * that chunk second in the list. */
- memarea_chunk_t *new_chunk = alloc_chunk(sz+CHUNK_HEADER_SIZE, 0);
- new_chunk->next_chunk = chunk->next_chunk;
- chunk->next_chunk = new_chunk;
- chunk = new_chunk;
- } else {
- memarea_chunk_t *new_chunk = alloc_chunk(CHUNK_SIZE, 1);
- new_chunk->next_chunk = chunk;
- area->first = chunk = new_chunk;
- }
- tor_assert(chunk->mem_size >= sz);
- }
- result = chunk->next_mem;
- chunk->next_mem = chunk->next_mem + sz;
- // XXXX021 remove these once bug 930 is solved.
- tor_assert(chunk->next_mem >= chunk->u.mem);
- tor_assert(chunk->next_mem <= chunk->u.mem+chunk->mem_size);
- chunk->next_mem = realign_pointer(chunk->next_mem);
- return result;
- }
- /** As memarea_alloc(), but clears the memory it returns. */
- void *
- memarea_alloc_zero(memarea_t *area, size_t sz)
- {
- void *result = memarea_alloc(area, sz);
- memset(result, 0, sz);
- return result;
- }
- /** As memdup, but returns the memory from <b>area</b>. */
- void *
- memarea_memdup(memarea_t *area, const void *s, size_t n)
- {
- char *result = memarea_alloc(area, n);
- memcpy(result, s, n);
- return result;
- }
- /** As strdup, but returns the memory from <b>area</b>. */
- char *
- memarea_strdup(memarea_t *area, const char *s)
- {
- return memarea_memdup(area, s, strlen(s)+1);
- }
- /** As strndup, but returns the memory from <b>area</b>. */
- char *
- memarea_strndup(memarea_t *area, const char *s, size_t n)
- {
- size_t ln;
- char *result;
- const char *cp, *end = s+n;
- for (cp = s; cp < end && *cp; ++cp)
- ;
- /* cp now points to s+n, or to the 0 in the string. */
- ln = cp-s;
- result = memarea_alloc(area, ln+1);
- memcpy(result, s, ln);
- result[ln]='\0';
- return result;
- }
- /** Set <b>allocated_out</b> to the number of bytes allocated in <b>area</b>,
- * and <b>used_out</b> to the number of bytes currently used. */
- void
- memarea_get_stats(memarea_t *area, size_t *allocated_out, size_t *used_out)
- {
- size_t a = 0, u = 0;
- memarea_chunk_t *chunk;
- for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
- CHECK_SENTINEL(chunk);
- a += CHUNK_HEADER_SIZE + chunk->mem_size;
- tor_assert(chunk->next_mem >= chunk->u.mem);
- u += CHUNK_HEADER_SIZE + (chunk->next_mem - chunk->u.mem);
- }
- *allocated_out = a;
- *used_out = u;
- }
- /** Assert that <b>area</b> is okay. */
- void
- memarea_assert_ok(memarea_t *area)
- {
- memarea_chunk_t *chunk;
- tor_assert(area->first);
- for (chunk = area->first; chunk; chunk = chunk->next_chunk) {
- CHECK_SENTINEL(chunk);
- tor_assert(chunk->next_mem >= chunk->u.mem);
- tor_assert(chunk->next_mem <=
- (char*) realign_pointer(chunk->u.mem+chunk->mem_size));
- }
- }
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