--- JSON-XS/XS.xs	2007/06/25 06:57:42	1.45
+++ JSON-XS/XS.xs	2007/06/25 22:11:39	1.46
@@ -1025,25 +1025,62 @@
   else
     for (;;)
       {
-        SV *key, *value;
-
         decode_ws (dec); EXPECT_CH ('"');
 
-        key = decode_str (dec);
-        if (!key)
-          goto fail;
-
-        decode_ws (dec); EXPECT_CH (':');
-
-        value = decode_sv (dec);
-        if (!value)
-          {
-            SvREFCNT_dec (key);
-            goto fail;
-          }
-
-        hv_store_ent (hv, key, value, 0);
-        SvREFCNT_dec (key);
+        // heuristic: assume that
+        // a) decode_str + hv_store_ent are abysmally slow
+        // b) most hash keys are short, simple ascii text
+        // so try to "fast-match" such strings to avoid
+        // the overhead of hv_store_ent.
+        {
+          SV *value;
+          char *p = dec->cur;
+          char *e = p + 24; // only try up to 24 bytes
+
+          for (;;)
+            {
+              if (p == e || *p < 0x20 || *p >= 0x80 || *p == '\\')
+                {
+                  // slow path, back up and use decode_str
+                  SV *key = decode_str (dec);
+                  if (!key)
+                    goto fail;
+
+                  decode_ws (dec); EXPECT_CH (':');
+
+                  value = decode_sv (dec);
+                  if (!value)
+                    {
+                      SvREFCNT_dec (key);
+                      goto fail;
+                    }
+
+                  hv_store_ent (hv, key, value, 0);
+                  SvREFCNT_dec (key);
+
+                  break;
+                }
+              else if (*p == '"')
+                {
+                  // fast path, got a simple key
+                  char *key = dec->cur;
+                  int len = p - key;
+                  dec->cur = p + 1;
+
+                  decode_ws (dec); EXPECT_CH (':');
+
+                  value = decode_sv (dec);
+                  if (!value)
+                    goto fail;
+
+                  hv_store (hv, key, len, value, 0);
+
+                  break;
+                }
+
+              ++p;
+            }
+        }
 
         decode_ws (dec);