[rrd-developers] [PATCH 1/2] Add utility functions to allocate pointers in variable size chunks.

[kevin brintnall]

---
 doc/librrd.pod  |   18 ++++++++++++++++++
 src/rrd.h       |    4 ++++
 src/rrd_utils.c |   53 ++++++++++++++++++++++++++++++++++++++++++-----------
 3 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/doc/librrd.pod b/doc/librrd.pod
index 038746c..396e50c 100644
--- a/doc/librrd.pod
+++ b/doc/librrd.pod
@@ -81,6 +81,16 @@ end of the new C<dest>.  Returns 1 on success, 0 on failure.
     if (!rrd_add_ptr(&arr, &arr_size, elem))
         handle_failure();
 
+=item B<rrd_add_ptr_chunk(void ***dest, size_t *dest_size, void *src, size_t *alloc, size_t chunk)>
+
+Like C<rrd_add_ptr>, except the destination is allocated in chunks of
+C<chunk>.  C<alloc> points to the number of entries allocated, whereas
+C<dest_size> points to the number of valid pointers.  If more pointers are
+needed, C<chunk> pointers are allocated and C<alloc> is increased
+accordingly.  C<alloc> must be E<gt>= C<dest_size>.
+
+This method improves performance on hosts with expensive C<realloc()>.
+
 =item B<rrd_add_strdup(char ***dest, size_t *dest_size, char *src)>
 
 Like C<rrd_add_ptr>, except adds a C<strdup> of the source string.
@@ -91,6 +101,14 @@ Like C<rrd_add_ptr>, except adds a C<strdup> of the source string.
     if (!rrd_add_strdup(&arr, &arr_size, str))
         handle_failure();
 
+=item B<rrd_add_strdup_chunk(char ***dest, size_t *dest_size, char *src, size_t *alloc, size_t chunk)>
+
+Like C<rrd_add_strdup>, except the destination is allocated in chunks of
+C<chunk>.  C<alloc> points to the number of entries allocated, whereas
+C<dest_size> points to the number of valid pointers.  If more pointers are
+needed, C<chunk> pointers are allocated and C<alloc> is increased
+accordingly.  C<alloc> must be E<gt>= C<dest_size>.
+
 =item B<rrd_free_ptrs(void ***src, size_t *cnt)>
 
 Free an array of pointers allocated by C<rrd_add_ptr> or
diff --git a/src/rrd.h b/src/rrd.h
index ce7e749..6008794 100644
--- a/src/rrd.h
+++ b/src/rrd.h
@@ -333,8 +333,12 @@ int       rrd_proc_start_end(
 
     long rrd_random(void);
 
+    int rrd_add_ptr_chunk(void ***dest, size_t *dest_size, void *src,
+                          size_t *alloc, size_t chunk);
     int rrd_add_ptr(void ***dest, size_t *dest_size, void *src);
     int rrd_add_strdup(char ***dest, size_t *dest_size, char *src);
+    int rrd_add_strdup_chunk(char ***dest, size_t *dest_size, char *src,
+                             size_t *alloc, size_t chunk);
     void rrd_free_ptrs(void ***src, size_t *cnt);
 
     int rrd_mkdir_p(const char *pathname, mode_t mode);
diff --git a/src/rrd_utils.c b/src/rrd_utils.c
index 3936cff..6853c66 100644
--- a/src/rrd_utils.c
+++ b/src/rrd_utils.c
@@ -50,29 +50,53 @@ long rrd_random(void)
     return random();
 }
 
-/* rrd_add_ptr: add a pointer to a dynamically sized array of pointers,
- * realloc as necessary.  returns 1 on success, 0 on failure.
+/* rrd_add_ptr_chunk: add a pointer to a dynamically sized array of
+ * pointers, realloc as necessary in multiples of "chunk".
+ *
+ * "alloc" is the number of pointers allocated
+ * "dest_size" is the number of valid pointers
+ *
+ * returns 1 on success, 0 on failure.
  */
 
-int rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
+int rrd_add_ptr_chunk(void ***dest, size_t *dest_size, void *src,
+                      size_t *alloc, size_t chunk)
 {
     void **temp;
 
     assert(dest != NULL);
+    assert(alloc != NULL);
+    assert(*alloc >= *dest_size);
 
-    temp = (void **) rrd_realloc(*dest, (*dest_size+1) * sizeof(*dest));
-    if (!temp)
-        return 0;
+    if (*alloc == *dest_size)
+    {
+        temp = (void **) rrd_realloc(*dest, (*alloc+chunk) * sizeof(*dest));
+        if (!temp)
+            return 0;
 
-    *dest = temp;
-    temp[*dest_size] = src;
+        *dest = temp;
+        *alloc += chunk;
+    }
+
+    (*dest)[*dest_size] = src;
     (*dest_size)++;
 
     return 1;
 }
 
-/* like rrd_add_ptr, but calls strdup() on a string first. */
-int rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
+/* rrd_add_ptr: add a pointer to a dynamically sized array of pointers,
+ * realloc as necessary.  returns 1 on success, 0 on failure.
+ */
+int rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
+{
+    size_t alloc = *dest_size;
+
+    return rrd_add_ptr_chunk(dest, dest_size, src, &alloc, 1);
+}
+
+/* like rrd_add_ptr_chunk, but calls strdup() on a string first. */
+int rrd_add_strdup_chunk(char ***dest, size_t *dest_size, char *src,
+                         size_t *alloc, size_t chunk)
 {
     char *dup_src;
     int add_ok;
@@ -84,13 +108,20 @@ int rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
     if (!dup_src)
         return 0;
 
-    add_ok = rrd_add_ptr((void ***)dest, dest_size, (void *)dup_src);
+    add_ok = rrd_add_ptr_chunk((void ***)dest, dest_size, (void *)dup_src, alloc, chunk);
     if (!add_ok)
         free(dup_src);
 
     return add_ok;
 }
 
+int rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
+{
+    size_t alloc = *dest_size;
+
+    return rrd_add_strdup_chunk(dest, dest_size, src, &alloc, 1);
+}
+
 void rrd_free_ptrs(void ***src, size_t *cnt)
 {
     void **sp;
-- 
1.6.4