Avoid unnecessary memory reallocations during caching

* src/findkey.c (_gdbm_read_entry): Reallocate cache_entry->ca_data.dptr only
if necessary.
* src/gdbmdefs.h (data_cache_elem): New member: dsize
* src/gdbmdelete.c: Don't free cache_entry->ca_data.dptr
* src/gdbmopen.c (_gdbm_init_cache): Initialize ca_data.dsize

4 files changed, 38 insertions, 20 deletions

diff --git a/src/findkey.c b/src/findkey.c
index 9c8fd71..5560b28 100644
--- a/src/findkey.c
+++ b/src/findkey.c
@@ -46,6 +46,7 @@ _gdbm_read_entry (GDBM_FILE dbf, int elem_loc)
   int rc;
   int key_size;
   int data_size;
+  size_t dsize;
   off_t file_pos;
   data_cache_elem *data_ca;
 
@@ -62,24 +63,44 @@ _gdbm_read_entry (GDBM_FILE dbf, int elem_loc)
   /* Set sizes and pointers. */
   key_size = dbf->bucket->h_table[elem_loc].key_size;
   data_size = dbf->bucket->h_table[elem_loc].data_size;
+  dsize = key_size + data_size;
   data_ca = &dbf->cache_entry->ca_data;
-  
+
   /* Set up the cache. */
-  if (data_ca->dptr != NULL) free (data_ca->dptr);
   data_ca->key_size = key_size;
   data_ca->data_size = data_size;
   data_ca->elem_loc = elem_loc;
   data_ca->hash_val = dbf->bucket->h_table[elem_loc].hash_value;
 
-  if (key_size + data_size == 0)
-    data_ca->dptr = (char *) malloc (1);
+  if (dsize <= data_ca->dsize)
+    {
+      if (data_ca->dsize == 0)
+	{
+	  data_ca->dptr = malloc (1);
+	  if (data_ca->dptr)
+	    data_ca->dsize = 1;
+	  else
+	    {
+	      GDBM_SET_ERRNO2 (dbf, GDBM_MALLOC_ERROR, FALSE, GDBM_DEBUG_LOOKUP);
+	      _gdbm_fatal (dbf, _("malloc error"));
+	      return NULL;
+	    }
+	}
+    }
   else
-    data_ca->dptr = (char *) malloc (key_size + data_size);
-  if (data_ca->dptr == NULL)
     {
-      GDBM_SET_ERRNO2 (dbf, GDBM_MALLOC_ERROR, FALSE, GDBM_DEBUG_LOOKUP);
-      _gdbm_fatal (dbf, _("malloc error"));
-      return NULL;
+      char *p = realloc (data_ca->dptr, dsize);
+      if (p)
+	{
+	  data_ca->dptr = p;
+	  data_ca->dsize = dsize;
+	}
+      else
+	{
+	  GDBM_SET_ERRNO2 (dbf, GDBM_MALLOC_ERROR, FALSE, GDBM_DEBUG_LOOKUP);
+	  _gdbm_fatal (dbf, _("malloc error"));
+	  return NULL;
+	}
     }
 
   /* Read into the cache. */
diff --git a/src/gdbmdefs.h b/src/gdbmdefs.h
index 4ae646f..af6f09c 100644
--- a/src/gdbmdefs.h
+++ b/src/gdbmdefs.h
@@ -149,11 +149,12 @@ typedef struct
 
 typedef struct
 {
-  int   hash_val;
-  int   data_size;
-  int   key_size;
-  char *dptr;
-  int   elem_loc;
+  int     hash_val;
+  int     data_size;
+  int     key_size;
+  char    *dptr;
+  size_t  dsize;
+  int     elem_loc;
 } data_cache_elem;
 
 typedef struct
diff --git a/src/gdbmdelete.c b/src/gdbmdelete.c
index 5660d3a..ff13a1a 100644
--- a/src/gdbmdelete.c
+++ b/src/gdbmdelete.c
@@ -88,12 +88,7 @@ gdbm_delete (GDBM_FILE dbf, datum key)
   /* Set the flags. */
   dbf->bucket_changed = TRUE;
 
-  /* Clear out the data cache for the current bucket. */
-  if (dbf->cache_entry->ca_data.dptr != NULL)
-    {
-      free (dbf->cache_entry->ca_data.dptr);
-      dbf->cache_entry->ca_data.dptr = NULL;
-    }
+  /* Invalidate data cache for the current bucket. */
   dbf->cache_entry->ca_data.hash_val = -1;
   dbf->cache_entry->ca_data.key_size = 0;
   dbf->cache_entry->ca_data.elem_loc = -1;
diff --git a/src/gdbmopen.c b/src/gdbmopen.c
index 31d8fea..03cc4f4 100644
--- a/src/gdbmopen.c
+++ b/src/gdbmopen.c
@@ -663,6 +663,7 @@ _gdbm_init_cache (GDBM_FILE dbf, size_t size)
 	      return -1;
             }
 	  dbf->bucket_cache[index].ca_data.dptr = NULL;
+	  dbf->bucket_cache[index].ca_data.dsize = 0;
 	  _gdbm_cache_entry_invalidate (dbf, index);
         }
       dbf->bucket = dbf->bucket_cache[0].ca_bucket;