Simplify buffer-growing algorithm. Just double it each time.

diff --git a/dstr.c b/dstr.c
index 86cde6e27c962db9eaeb18e59c8b7bea4d605ddd..e43e1386068dd95fbfd5a750d36ff1f9f080de54 100644 (file)
--- a/dstr.c
+++ b/dstr.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: dstr.c,v 1.8 1999/06/01 09:47:52 mdw Exp $
+ * $Id: dstr.c,v 1.9 1999/07/06 19:16:06 mdw Exp $
  *
  * Handle dynamically growing strings
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------*
  *
  * $Log: dstr.c,v $
+ * Revision 1.9  1999/07/06 19:16:06  mdw
+ * Simplify buffer-growing algorithm.  Just double it each time.
+ *
  * Revision 1.8  1999/06/01 09:47:52  mdw
  * Fix nasty bugs in `dstr_vputf'.
  *
@@ -72,8 +75,21 @@
 
 /*----- Tunable constants -------------------------------------------------*/
 
+/* --- Buffer expansion parameters --- *
+ *
+ * If the buffer is empty, it is set to @DSTR_INITSZ@ bytes in size.
+ * Otherwise, it's set to the next power of two that's large enough.  This is
+ * memory-hungry, but efficient.
+ */
+
 #define DSTR_INITSZ 256                        /* Initial buffer size */
-#define DSTR_INCSZ 4096                        /* Threshhold for doubling */
+
+/* --- Parameters for @dstr_putf@ --- *
+ *
+ * For each format specifier, at least @DSTR_PUTFSTEP@ bytes are ensured
+ * before writing the formatted result.
+ */
+
 #define DSTR_PUTFSTEP 64               /* Buffer size for @putf@ */
 
 /*----- Main code ---------------------------------------------------------*/
@@ -132,22 +148,14 @@ void dstr_ensure(dstr *d, size_t sz)
   if (rq <= d->sz)
     return;
 
-  /* --- Grow the buffer --- *
-   *
-   * For small buffers, just double the size.  For big buffers, make them
-   * a multiple of some suitably large chunk size.
-   */
+  /* --- Grow the buffer --- */
 
   nsz = d->sz;
 
-  do {
-    if (nsz == 0)
-      nsz = DSTR_INITSZ;
-    else if (d->sz < 0x1000)
-      nsz <<= 1;
-    else
-      nsz = (rq + 0x0fff) & ~0x0fff;
-  } while (rq > nsz);
+  if (nsz == 0 && rq < DSTR_INITSZ)
+    nsz = DSTR_INITSZ;
+  else
+    do nsz <<= 1; while (nsz < rq);
 
   if (d->buf)
     d->buf = xrealloc(d->buf, nsz);