Modify libpq's pqexpbuffer to eliminate length restriction on how much

data can be formatted per call.  This requires relying on vsnprintf().
On machines that haven't got vsnprintf, link in the version from
backend/port/.

1 files changed, 73 insertions, 30 deletions

diff --git a/src/interfaces/libpq/pqexpbuffer.c b/src/interfaces/libpq/pqexpbuffer.c
index ddaca7e67b..bedf456b3c 100644
--- a/src/interfaces/libpq/pqexpbuffer.c
+++ b/src/interfaces/libpq/pqexpbuffer.c
@@ -8,11 +8,15 @@
  *
  * This module is essentially the same as the backend's StringInfo data type,
  * but it is intended for use in frontend libpq and client applications.
- * Thus, it does not rely on palloc(), elog(), nor vsnprintf().
+ * Thus, it does not rely on palloc() nor elog().
+ *
+ * It does rely on vsnprintf(); if configure finds that libc doesn't provide
+ * a usable vsnprintf(), then a copy of our own implementation of it will
+ * be linked into libpq.
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.1 1999/08/31 01:37:37 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.2 2000/01/17 02:59:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -148,27 +152,47 @@ enlargePQExpBuffer(PQExpBuffer str, int needed)
  * and insert it into str.  More space is allocated to str if necessary.
  * This is a convenience routine that does the same thing as
  * resetPQExpBuffer() followed by appendPQExpBuffer().
- *
- * CAUTION: the frontend version of this routine WILL FAIL if the result of
- * the sprintf formatting operation exceeds 1KB of data (but the size of the
- * pre-existing string in the buffer doesn't matter).  We could make it
- * support larger strings, but that requires vsnprintf() which is not
- * universally available.  Currently there is no need for long strings to be
- * formatted in the frontend.  We could support it, if necessary, by
- * conditionally including a vsnprintf emulation.
  */
 void
 printfPQExpBuffer(PQExpBuffer str, const char *fmt,...)
 {
 	va_list		args;
-	char		buffer[1024];
-
-	va_start(args, fmt);
-	vsprintf(buffer, fmt, args);
-	va_end(args);
+	int			avail,
+				nprinted;
 
 	resetPQExpBuffer(str);
-	appendPQExpBufferStr(str, buffer);
+
+	for (;;)
+	{
+		/*----------
+		 * Try to format the given string into the available space;
+		 * but if there's hardly any space, don't bother trying,
+		 * just fall through to enlarge the buffer first.
+		 *----------
+		 */
+		avail = str->maxlen - str->len - 1;
+		if (avail > 16)
+		{
+			va_start(args, fmt);
+			nprinted = vsnprintf(str->data + str->len, avail,
+								 fmt, args);
+			va_end(args);
+			/*
+			 * Note: some versions of vsnprintf return the number of chars
+			 * actually stored, but at least one returns -1 on failure.
+			 * Be conservative about believing whether the print worked.
+			 */
+			if (nprinted >= 0 && nprinted < avail-1)
+			{
+				/* Success.  Note nprinted does not include trailing null. */
+				str->len += nprinted;
+				break;
+			}
+		}
+		/* Double the buffer size and try again. */
+		if (! enlargePQExpBuffer(str, str->maxlen))
+			return;				/* oops, out of memory */
+	}
 }
 
 /*------------------------
@@ -178,26 +202,45 @@ printfPQExpBuffer(PQExpBuffer str, const char *fmt,...)
  * and append it to whatever is already in str.  More space is allocated
  * to str if necessary.  This is sort of like a combination of sprintf and
  * strcat.
- *
- * CAUTION: the frontend version of this routine WILL FAIL if the result of
- * the sprintf formatting operation exceeds 1KB of data (but the size of the
- * pre-existing string in the buffer doesn't matter).  We could make it
- * support larger strings, but that requires vsnprintf() which is not
- * universally available.  Currently there is no need for long strings to be
- * formatted in the frontend.  We could support it, if necessary, by
- * conditionally including a vsnprintf emulation.
  */
 void
 appendPQExpBuffer(PQExpBuffer str, const char *fmt,...)
 {
 	va_list		args;
-	char		buffer[1024];
-
-	va_start(args, fmt);
-	vsprintf(buffer, fmt, args);
-	va_end(args);
+	int			avail,
+				nprinted;
 
-	appendPQExpBufferStr(str, buffer);
+	for (;;)
+	{
+		/*----------
+		 * Try to format the given string into the available space;
+		 * but if there's hardly any space, don't bother trying,
+		 * just fall through to enlarge the buffer first.
+		 *----------
+		 */
+		avail = str->maxlen - str->len - 1;
+		if (avail > 16)
+		{
+			va_start(args, fmt);
+			nprinted = vsnprintf(str->data + str->len, avail,
+								 fmt, args);
+			va_end(args);
+			/*
+			 * Note: some versions of vsnprintf return the number of chars
+			 * actually stored, but at least one returns -1 on failure.
+			 * Be conservative about believing whether the print worked.
+			 */
+			if (nprinted >= 0 && nprinted < avail-1)
+			{
+				/* Success.  Note nprinted does not include trailing null. */
+				str->len += nprinted;
+				break;
+			}
+		}
+		/* Double the buffer size and try again. */
+		if (! enlargePQExpBuffer(str, str->maxlen))
+			return;				/* oops, out of memory */
+	}
 }
 
 /*------------------------