document one more function

[simgrid.git] / src / xbt / mmalloc / mmalloc.c

diff --git a/src/xbt/mmalloc/mmalloc.c b/src/xbt/mmalloc/mmalloc.c
index a5a0192..355b24c 100644 (file)
--- a/src/xbt/mmalloc/mmalloc.c
+++ b/src/xbt/mmalloc/mmalloc.c
@@ -16,18 +16,25 @@
 
 /* Prototypes for local functions */
 
-static int initialize(struct mdesc *mdp);
-static void *morecore(struct mdesc *mdp, size_t size);
-static void *align(struct mdesc *mdp, size_t size);
-
-/* Aligned allocation.  */
+static int initialize(xbt_mheap_t mdp);
+static void *register_morecore(xbt_mheap_t mdp, size_t size);
+static void *align(xbt_mheap_t mdp, size_t size);
 
+/* Allocation aligned on block boundary */
 static void *align(struct mdesc *mdp, size_t size)
 {
   void *result;
   unsigned long int adj;
 
   result = mmorecore(mdp, size);
+
+  /* if this reservation does not fill up the last block of our resa,
+   * complete the reservation by also asking for the full lastest block.
+   *
+   * Also, the returned block is aligned to the end of block (but I've
+   * no fucking idea of why, actually -- http://abstrusegoose.com/432 --
+   * but not doing so seems to lead to issues).
+   */
   adj = RESIDUAL(result, BLOCKSIZE);
   if (adj != 0) {
     adj = BLOCKSIZE - adj;
@@ -37,9 +44,9 @@ static void *align(struct mdesc *mdp, size_t size)
   return (result);
 }
 
-/* Set everything up and remember that we have.  */
-
-static int initialize(struct mdesc *mdp)
+/* Finish the initialization of the mheap. If we want to inline it
+ * properly, we need to make the align function publicly visible, too  */
+static int initialize(xbt_mheap_t mdp)
 {
   mdp->heapsize = HEAP / BLOCKSIZE;
   mdp->heapinfo = (malloc_info *)
@@ -56,10 +63,9 @@ static int initialize(struct mdesc *mdp)
   return (1);
 }
 
-/* Get neatly aligned memory, initializing or
-   growing the heap info table as necessary. */
-
-static void *morecore(struct mdesc *mdp, size_t size)
+/* Get neatly aligned memory from the low level layers, and register it
+ * into the heap info table as necessary. */
+static void *register_morecore(struct mdesc *mdp, size_t size)
 {
   void *result;
   malloc_info *newinfo, *oldinfo;
@@ -70,26 +76,25 @@ static void *morecore(struct mdesc *mdp, size_t size)
     return (NULL);
   }
 
-  /* Check if we need to grow the info table.  */
+  /* Check if we need to grow the info table (in a multiplicative manner)  */
   if ((size_t) BLOCK((char *) result + size) > mdp->heapsize) {
+
     newsize = mdp->heapsize;
-    while ((size_t) BLOCK((char *) result + size) > newsize) {
+    while ((size_t) BLOCK((char *) result + size) > newsize)
       newsize *= 2;
-    }
-    newinfo = (malloc_info *) align(mdp, newsize * sizeof(malloc_info));
-    if (newinfo == NULL) {
-      mmorecore(mdp, -size);
-      return (NULL);
-    }
-    memset((void *) newinfo, 0, newsize * sizeof(malloc_info));
-    memcpy((void *) newinfo, (void *) mdp->heapinfo,
-           mdp->heapsize * sizeof(malloc_info));
+
+    /* Copy old info into new location */
     oldinfo = mdp->heapinfo;
+    newinfo = (malloc_info *) align(mdp, newsize * sizeof(malloc_info));
+    memset(newinfo, 0, newsize * sizeof(malloc_info));
+    memcpy(newinfo, oldinfo, mdp->heapsize * sizeof(malloc_info));
+    mdp->heapinfo = newinfo;
+
+    /* mark the space previously occupied by the block info as free by first marking it
+     * as occupied in the regular way, and then freing it */
     newinfo[BLOCK(oldinfo)].busy.type = 0;
-    newinfo[BLOCK(oldinfo)].busy.info.block.size
-        = BLOCKIFY(mdp->heapsize * sizeof(malloc_info));
+    newinfo[BLOCK(oldinfo)].busy.info.block.size = BLOCKIFY(mdp->heapsize * sizeof(malloc_info));
     newinfo[BLOCK(oldinfo)].busy.info.block.busy_size = size;
-    mdp->heapinfo = newinfo;
     __mmalloc_free(mdp, (void *) oldinfo);
     mdp->heapsize = newsize;
   }
@@ -199,7 +204,7 @@ void *mmalloc(xbt_mheap_t mdp, size_t size)
         if (mdp->heaplimit != 0 &&
             block + lastblocks == mdp->heaplimit &&
             mmorecore(mdp, 0) == ADDRESS(block + lastblocks) &&
-            (morecore(mdp, (blocks - lastblocks) * BLOCKSIZE)) != NULL) {
+            (register_morecore(mdp, (blocks - lastblocks) * BLOCKSIZE)) != NULL) {
           /* Which block we are extending (the `final free
              block' referred to above) might have changed, if
              it got combined with a freed info table.  */
@@ -208,7 +213,7 @@ void *mmalloc(xbt_mheap_t mdp, size_t size)
           mdp->heapinfo[block].free.size += (blocks - lastblocks);
           continue;
         }
-        result = morecore(mdp, blocks * BLOCKSIZE);
+        result = register_morecore(mdp, blocks * BLOCKSIZE);
         if (result == NULL) {
           return (NULL);
         }