Fix a potential infinite loop in appendStringInfo: would lock

up if first string to be appended to an empty StringInfo was longer
than the initial space allocation.
Also speed it up slightly.

diff --git a/src/backend/lib/stringinfo.c b/src/backend/lib/stringinfo.c
index 5dbfde953f3cd0134a4d7cd0378b6946c59d0f5f..1c5a0f4f578ff43db4983cfd19bc0c811e3751c5 100644 (file)
--- a/src/backend/lib/stringinfo.c
+++ b/src/backend/lib/stringinfo.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/lib/stringinfo.c,v 1.11 1998/09/01 03:22:39 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/lib/stringinfo.c,v 1.12 1998/11/08 19:22:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,27 +31,22 @@ StringInfo
 makeStringInfo()
 {
    StringInfo  res;
-   long        size;
+   int         size;
 
    res = (StringInfo) palloc(sizeof(StringInfoData));
    if (res == NULL)
        elog(ERROR, "makeStringInfo: Out of memory!");
 
-   size = 100;
+   size = 256;                 /* initial default size */
    res->data = palloc(size);
    if (res->data == NULL)
    {
        elog(ERROR,
-          "makeStringInfo: Out of memory! (%ld bytes requested)", size);
+          "makeStringInfo: Out of memory! (%d bytes requested)", size);
    }
    res->maxlen = size;
    res->len = 0;
-
-   /*
-    * NOTE: we must initialize `res->data' to the empty string because we
-    * use 'strcat' in 'appendStringInfo', which of course it always
-    * expects a null terminated string.
-    */
+   /* Make sure the string is empty initially. */
    res->data[0] = '\0';
 
    return res;
@@ -71,7 +66,8 @@ void
 appendStringInfo(StringInfo str, char *buffer)
 {
    int         buflen,
-               newlen;
+               newlen,
+               needed;
    char       *s;
 
    Assert(str != NULL);
@@ -84,15 +80,16 @@ appendStringInfo(StringInfo str, char *buffer)
     * some more.
     */
    buflen = strlen(buffer);
-   if (buflen + str->len >= str->maxlen - 1)
+   needed = str->len + buflen + 1;
+   if (needed > str->maxlen)
    {
 
        /*
         * how much more space to allocate ? Let's say double the current
         * space... However we must check if this is enough!
         */
-       newlen = 2 * str->len;
-       while (buflen + str->len >= newlen - 1)
+       newlen = 2 * str->maxlen;
+       while (needed > newlen)
            newlen = 2 * newlen;
 
        /*
@@ -105,7 +102,11 @@ appendStringInfo(StringInfo str, char *buffer)
                 "appendStringInfo: Out of memory (%d bytes requested)",
                 newlen);
        }
-       memmove(s, str->data, str->len + 1);
+       /*
+        * transfer the data.  strcpy() would work, but is probably a tad
+        * slower than memcpy(), and since we know the string length...
+        */
+       memcpy(s, str->data, str->len + 1);
        pfree(str->data);
        str->maxlen = newlen;
        str->data = s;
@@ -113,10 +114,10 @@ appendStringInfo(StringInfo str, char *buffer)
 
    /*
     * OK, we have enough space now, append 'buffer' at the end of the
-    * string & update the string length. NOTE: this is a text string
-    * (i.e. printable characters) so 'strcat' will do the job (no need to
-    * use 'bcopy' et all...)
+    * string & update the string length. NOTE: strcat() would work,
+    * but is certainly slower than just memcpy'ing the data to the right
+    * place.
     */
-   strcat(str->data, buffer);
+   memcpy(str->data + str->len, buffer, buflen + 1);
    str->len += buflen;
 }