From: Mark Wooding <mdw@distorted.org.uk>
Date: Tue, 9 Jul 2024 17:07:01 +0000 (+0100)
Subject: @@@ tvec buffer align power-of-two
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/mLib/commitdiff_plain/c70f2c2c1135366f8fc41575e741c2482b0a3948?ds=inline

@@@ tvec buffer align power-of-two
---

diff --git a/test/tvec-types.c b/test/tvec-types.c
index 27381b5..9e7a35f 100644
--- a/test/tvec-types.c
+++ b/test/tvec-types.c
@@ -3976,17 +3976,18 @@ void tvec_initbuffer(union tvec_regval *rv,
 void tvec_allocbuffer(union tvec_regval *rv)
 {
   unsigned char *p; size_t n;
+  size_t m = rv->buf.m, a = rv->buf.a, off;
 
   if (rv->buf.p) free(rv->buf.p - rv->buf.off);
 
-  if (rv->buf.m < 2) {
-    rv->buf.p = x_alloc(&arena_stdlib, rv->buf.sz); rv->buf.off = 0;
+  if (m < 2) {
+    p = x_alloc(&arena_stdlib, rv->buf.sz); off = 0;
   } else {
-    p = x_alloc(&arena_stdlib, rv->buf.sz + rv->buf.m - 1);
-    n = (size_t)p%rv->buf.m;
-    rv->buf.off = (rv->buf.a - n + rv->buf.m)%rv->buf.m;
-    rv->buf.p = p + rv->buf.off;
+    p = x_alloc(&arena_stdlib, rv->buf.sz + m - 1);
+    if (!(m&(m - 1))) off = (a - (size_t)p)&(m - 1);
+    else off = (a + m - (size_t)p%m)%m;
   }
+  rv->buf.p = p + off; rv->buf.off = off;
   memset(rv->buf.p, '?', rv->buf.sz);
 }