Small cleanup to aomstats.c

- Multiplicative re-size instead of additive (amortized constant
  time -- although in practice, I could not see a difference).
  Still, multiplicative re-size is the gold standard.
- Ensure that there is enough room for the data being written out,
  when growing the array
- Readability cleanup (remove one level of nesting)

Change-Id: I424617e845814cf1acb7dd5a08027964078cc9ae

stats/aomstats.c

diff --git a/stats/aomstats.c b/stats/aomstats.c
index 4a15adf..8d59377 100644
--- a/stats/aomstats.c
+++ b/stats/aomstats.c
@@ -11,10 +11,12 @@
 
 #include "stats/aomstats.h"
 
+#include <assert.h>
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "aom_dsp/aom_dsp_common.h"
 #include "common/tools_common.h"
 
 int stats_open_file(stats_io_t *stats, const char *fpf, int pass) {
@@ -83,24 +85,28 @@
 void stats_write(stats_io_t *stats, const void *pkt, size_t len) {
   if (stats->file) {
     (void)fwrite(pkt, 1, len, stats->file);
-  } else {
-    if (stats->buf.sz + len > stats->buf_alloc_sz) {
-      size_t new_sz = stats->buf_alloc_sz + 64 * 1024;
-      char *new_ptr = realloc(stats->buf.buf, new_sz);
-
-      if (new_ptr) {
-        stats->buf_ptr = new_ptr + (stats->buf_ptr - (char *)stats->buf.buf);
-        stats->buf.buf = new_ptr;
-        stats->buf_alloc_sz = new_sz;
-      } else {
-        fatal("Failed to realloc firstpass stats buffer.");
-      }
-    }
-
-    memcpy(stats->buf_ptr, pkt, len);
-    stats->buf.sz += len;
-    stats->buf_ptr += len;
+    return;
   }
+  assert(stats->buf.sz <= stats->buf_alloc_sz);
+  assert(0 < stats->buf_alloc_sz);
+  if (stats->buf.sz + len > stats->buf_alloc_sz) {
+    // Grow by a factor of 1.5 each time, for amortized constant time.
+    // Also make sure there is enough room for the data.
+    size_t new_sz = AOMMAX((3 * stats->buf_alloc_sz) / 2, stats->buf.sz + len);
+    char *new_ptr = realloc(stats->buf.buf, new_sz);
+
+    if (new_ptr) {
+      stats->buf_ptr = new_ptr + (stats->buf_ptr - (char *)stats->buf.buf);
+      stats->buf.buf = new_ptr;
+      stats->buf_alloc_sz = new_sz;
+    } else {
+      fatal("Failed to realloc firstpass stats buffer.");
+    }
+  }
+
+  memcpy(stats->buf_ptr, pkt, len);
+  stats->buf.sz += len;
+  stats->buf_ptr += len;
 }
 
 aom_fixed_buf_t stats_get(stats_io_t *stats) { return stats->buf; }