# HG changeset patch
# User Mike Becker <universe@uap-core.de>
# Date 1664904307 -7200
# Node ID 7df0bcaecffa6448c8429b05b3a14cf41318192f
# Parent  02a56701a5cb774e9e9a26ef0643e01d6ae74115
fix over-optimization of strstr

1. it's actually less performant to frequently read bytes
   from an array instead of using the native word length
2. the SBO buffer should be local and not static to allow
   multi-threading usage

diff -r 02a56701a5cb -r 7df0bcaecffa src/string.c
--- a/src/string.c	Tue Oct 04 18:55:20 2022 +0200
+++ b/src/string.c	Tue Oct 04 19:25:07 2022 +0200
@@ -227,14 +227,7 @@
     return (cxmutstr) {(char *) result.ptr, result.length};
 }
 
-#define ptable_r(dest, useheap, ptable, index) (dest = useheap ? \
-    ((size_t*)ptable)[index] : (size_t) ((uint8_t*)ptable)[index])
-
-#define ptable_w(useheap, ptable, index, src) do {\
-    if (!useheap) ((uint8_t*)ptable)[index] = (uint8_t) src;\
-    else ((size_t*)ptable)[index] = src;\
-    } while (0)
-
+#define STRSTR_SBO_BUFLEN 512
 
 cxstring cx_strstr(
         cxstring haystack,
@@ -257,14 +250,14 @@
      * and we want to avoid that.
      */
 
-    /* static prefix table */
-    static uint8_t s_prefix_table[512];
+    /* local prefix table */
+    size_t s_prefix_table[STRSTR_SBO_BUFLEN];
 
-    /* check pattern length and use appropriate prefix table */
+    /* check needle length and use appropriate prefix table */
     /* if the pattern exceeds static prefix table, allocate on the heap */
-    register int useheap = needle.length >= 512;
-    register void *ptable = useheap ? calloc(needle.length + 1,
-                                             sizeof(size_t)) : s_prefix_table;
+    bool useheap = needle.length >= STRSTR_SBO_BUFLEN;
+    register size_t *ptable = useheap ? calloc(needle.length + 1,
+                                               sizeof(size_t)) : s_prefix_table;
 
     /* keep counter in registers */
     register size_t i, j;
@@ -272,14 +265,14 @@
     /* fill prefix table */
     i = 0;
     j = 0;
-    ptable_w(useheap, ptable, i, j);
+    ptable[i] = j;
     while (i < needle.length) {
         while (j >= 1 && needle.ptr[j - 1] != needle.ptr[i]) {
-            ptable_r(j, useheap, ptable, j - 1);
+            j = ptable[j - 1];
         }
         i++;
         j++;
-        ptable_w(useheap, ptable, i, j);
+        ptable[i] = j;
     }
 
     /* search */
@@ -288,7 +281,7 @@
     j = 1;
     while (i < haystack.length) {
         while (j >= 1 && haystack.ptr[i] != needle.ptr[j - 1]) {
-            ptable_r(j, useheap, ptable, j - 1);
+            j = ptable[j - 1];
         }
         i++;
         j++;