sprintf to snprintf conversion

Move out string operations to another file, and introduce a frontend
to snprintf for various situations.  This change is important for
catching and eliminating sprintf overflows, which are as of now many
times silently corrupting memory.

Signed-off-by: Dan Farina <drfarina@acm.org>
Signed-off-by: Peter van Hardenberg <pvh@heroku.com>

strutil.c

@@ -0,0 +1,72 @@
+/*
+ * strutil.c
+ *
+ * Copyright (c) Heroku, 2010
+ *
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "strutil.h"
+
+static int xvsnprintf(char *str, size_t size, const char *format, va_list ap);
+
+
+static int
+xvsnprintf(char *str, size_t size, const char *format, va_list ap)
+{
+	int retval;
+
+	retval = vsnprintf(str, size, format, ap);
+
+	if (retval >= size)
+	{
+		fprintf(stderr, "Buffer not large enough to format entire string\n");
+		exit(255);
+	}
+
+	return retval;
+}
+
+
+int
+xsnprintf(char *str, size_t size, const char *format, ...)
+{
+	va_list arglist;
+	int retval;
+
+	va_start(arglist, format);
+	retval = xvsnprintf(str, size, format, arglist);
+	va_end(arglist);
+
+	return retval;
+}
+
+
+int
+sqlquery_snprintf(char *str, const char *format, ...)
+{
+	va_list		arglist;
+	int			retval;
+
+	va_start(arglist, format);
+	retval = xvsnprintf(str, QUERY_STR_LEN, format, arglist);
+	va_end(arglist);
+
+	return retval;
+}
+
+
+int maxlen_snprintf(char *str, const char *format, ...)
+{
+	va_list		arglist;
+	int			retval;
+
+	va_start(arglist, format);
+	retval = xvsnprintf(str, MAXLEN, format, arglist);
+	va_end(arglist);
+
+	return retval;
+}