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;
 }