Revise backend libpq interfaces so that messages to the frontend

can be generated in a buffer and then sent to the frontend in a single
libpq call.  This solves problems with NOTICE and ERROR messages generated
in the middle of a data message or COPY OUT operation.

src/backend/lib/stringinfo.c

@@ -1,125 +1,171 @@
-/*
+/*-------------------------------------------------------------------------
+ *
  * stringinfo.c
- *	  These are routines that can be used to write informations to a string,
- *	  without having to worry about string lengths, space allocation etc.
- *	  Ideally the interface should look like the file i/o interface,
+ *
+ * StringInfo provides an indefinitely-extensible string data type.
+ * It can be used to buffer either ordinary C strings (null-terminated text)
+ * or arbitrary binary data.  All storage is allocated with palloc().
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- *	  $Id: stringinfo.c,v 1.14 1999/02/13 23:15:36 momjian Exp $
+ *	  $Id: stringinfo.c,v 1.15 1999/04/25 03:19:25 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
  */
 
 #include <stdio.h>
 #include <string.h>
 
-#include <stdarg.h>
-
-#include <postgres.h>
-
-#include <nodes/pg_list.h>
-#include <lib/stringinfo.h>
+#include "postgres.h"
+#include "lib/stringinfo.h"
 
 /*
  * makeStringInfo
  *
- * Create a StringInfoData & return a pointer to it.
- *
+ * Create an empty 'StringInfoData' & return a pointer to it.
  */
 StringInfo
-makeStringInfo()
+makeStringInfo(void)
 {
 	StringInfo	res;
-	int			size;
 
 	res = (StringInfo) palloc(sizeof(StringInfoData));
 	if (res == NULL)
-		elog(ERROR, "makeStringInfo: Out of memory!");
+		elog(ERROR, "makeStringInfo: Out of memory");
 
-	size = 256;					/* initial default size */
-	res->data = palloc(size);
-	if (res->data == NULL)
-	{
-		elog(ERROR,
-		   "makeStringInfo: Out of memory! (%d bytes requested)", size);
-	}
-	res->maxlen = size;
-	res->len = 0;
-	/* Make sure the string is empty initially. */
-	res->data[0] = '\0';
+	initStringInfo(res);
 
 	return res;
 }
 
 /*
- * appendStringInfo
- *
- * append to the current 'StringInfo' a new string.
- * If there is not enough space in the current 'data', then reallocate
- * some more...
- *
- * NOTE: if we reallocate space, we pfree the old one!
+ * initStringInfo
  *
+ * Initialize a StringInfoData struct (with previously undefined contents)
+ * to describe an empty string.
  */
 void
-appendStringInfo(StringInfo str, const char *fmt,...)
+initStringInfo(StringInfo str)
 {
-	int		buflen,
-				newlen,
-				needed;
-	char	*s,
-				buffer[512];
+	int			size = 256;		/* initial default buffer size */
 
-  va_list args;
-	va_start(args, fmt);
-  buflen = vsnprintf(buffer, 512, fmt, args);
-  va_end(args);
+	str->data = palloc(size);
+	if (str->data == NULL)
+		elog(ERROR,
+			 "initStringInfo: Out of memory (%d bytes requested)", size);
+	str->maxlen = size;
+	str->len = 0;
+	str->data[0] = '\0';
+}
+
+/*
+ * enlargeStringInfo
+ *
+ * Internal routine: make sure there is enough space for 'needed' more bytes
+ * ('needed' does not include the terminating null).
+ */
+static void
+enlargeStringInfo(StringInfo str, int needed)
+{
+	int		newlen;
+	char   *newdata;
+
+	needed += str->len + 1;		/* total space required now */
+	if (needed <= str->maxlen)
+		return;					/* got enough space already */
+
+	/*
+	 * We don't want to allocate just a little more space with each append;
+	 * for efficiency, double the buffer size each time it overflows.
+	 * Actually, we might need to more than double it if 'needed' is big...
+	 */
+	newlen = 2 * str->maxlen;
+	while (needed > newlen)
+		newlen = 2 * newlen;
+
+	newdata = palloc(newlen);
+	if (newdata == NULL)
+		elog(ERROR,
+			 "enlargeStringInfo: Out of memory (%d bytes requested)", newlen);
+
+	/* OK, transfer data into new buffer, and release old buffer */
+	memcpy(newdata, str->data, str->len + 1);
+	pfree(str->data);
+	str->data = newdata;
+	str->maxlen = newlen;
+}
+
+/*
+ * appendStringInfo
+ *
+ * Format text data under the control of fmt (an sprintf-like format string)
+ * 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 current implementation has a 1K limit on the amount of text
+ * generated in a single call (not on the total string length).
+ */
+void
+appendStringInfo(StringInfo str, const char *fmt, ...)
+{
+	va_list	args;
+	char	buffer[1024];
+	int		buflen;
 
 	Assert(str != NULL);
-	if (buflen == 0)
-		strcpy(buffer, "<>");
 
-	/*
-	 * do we have enough space to append the new string? (don't forget to
-	 * count the null string terminating char!) If no, then reallocate
-	 * some more.
-	 */
-	needed = str->len + buflen + 1;
-	if (needed > str->maxlen)
-	{
+	va_start(args, fmt);
+	buflen = vsnprintf(buffer, sizeof(buffer), fmt, args);
+	va_end(args);
 
-		/*
-		 * how much more space to allocate ? Let's say double the current
-		 * space... However we must check if this is enough!
-		 */
-		newlen = 2 * str->maxlen;
-		while (needed > newlen)
-			newlen = 2 * newlen;
+	/* Make more room if needed */
+	enlargeStringInfo(str, buflen);
 
-		/*
-		 * allocate enough space.
-		 */
-		s = palloc(newlen);
-		if (s == NULL)
-		{
-			elog(ERROR,
-				 "appendStringInfo: Out of memory (%d bytes requested)", newlen);
-		}
-		/*
-		 * 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;
-	}
-
-	/*
-	 * OK, we have enough space now, append 'buffer' at the end of the
-	 * string & update the string length. NOTE: strcat() would work,
-	 * but is certainly slower than just memcpy'ing the data to the right
-	 * place.
-	 */
+	/* OK, append the data, including the trailing null */
 	memcpy(str->data + str->len, buffer, buflen + 1);
 	str->len += buflen;
 }
+
+/*------------------------
+ * appendStringInfoChar
+ * Append a single byte to str.
+ * Like appendStringInfo(str, "%c", ch) but much faster.
+ */
+void
+appendStringInfoChar(StringInfo str, char ch)
+{
+	Assert(str != NULL);
+
+	/* Make more room if needed */
+	enlargeStringInfo(str, 1);
+
+	/* OK, append the character */
+	str->data[str->len] = ch;
+	str->len++;
+	str->data[str->len] = '\0';
+}
+
+/*
+ * appendBinaryStringInfo
+ *
+ * Append arbitrary binary data to a StringInfo, allocating more space
+ * if necessary.
+ */
+void
+appendBinaryStringInfo(StringInfo str, const char *data, int datalen)
+{
+	Assert(str != NULL);
+
+	/* Make more room if needed */
+	enlargeStringInfo(str, datalen);
+
+	/* OK, append the data */
+	memcpy(str->data + str->len, data, datalen);
+	str->len += datalen;
+
+	/* Keep a trailing null in place, even though it's probably useless
+	 * for binary data...
+	 */
+	str->data[str->len] = '\0';
+}