From 0632a35b184119f82b53d3e39fd6672e55c3033d Mon Sep 17 00:00:00 2001
From: Randy Heit <rheit@zdoom.fake>
Date: Wed, 2 Jul 2008 18:08:06 +0000
Subject: [PATCH] - Rewrote myvsnprintf to use the StringFormat routines
 directly so that no   additional memory needs to be allocated from the heap.

SVN r1062 (trunk)
---
 docs/rh-log.txt        |  4 ++++
 src/win32/i_system.cpp | 50 +++++++++++++++++++++++++++++++++++-------
 2 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index aa6f81b50b..5a8c18b90b 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,3 +1,7 @@
+July 2, 2008
+- Rewrote myvsnprintf to use the StringFormat routines directly so that no
+  additional memory needs to be allocated from the heap.
+
 July 1, 2008
 - Polyobject sounds now play from their lines, similar to the way sector
   sounds are handled.
diff --git a/src/win32/i_system.cpp b/src/win32/i_system.cpp
index bf42589c95..8739d182d7 100644
--- a/src/win32/i_system.cpp
+++ b/src/win32/i_system.cpp
@@ -517,15 +517,49 @@ bool gameisdead;
 
 // We should use ZDoom's internal formatting routine here so that the extended
 // format specifiers work here as well.
-// However, since throwing FStrings around causes some problems in VC++ the
-// error message is still copied to a local buffer.
-static void myvsnprintf(char *DstBuf, size_t MaxCount, const char * Format, va_list ArgList)
-{
-	FString formatstr;
 
-	formatstr.VFormat(Format, ArgList);
-	strncpy(DstBuf, formatstr.GetChars(), MaxCount);
-	DstBuf[MaxCount-1] = 0;
+struct snprintf_state
+{
+	char *buffer;
+	size_t maxlen;
+	size_t curlen;
+	bool overflow;
+};
+
+static int myvsnprintf_helper(void *data, const char *cstr, int cstr_len)
+{
+	snprintf_state *state = (snprintf_state *)data;
+
+	if (state->curlen + cstr_len > state->maxlen)
+	{
+		cstr_len = (int)(state->maxlen - state->curlen);
+		state->overflow = true;
+	}
+	if (cstr_len > 0)
+	{
+		memcpy(state->buffer + state->curlen, cstr, cstr_len);
+		state->curlen += cstr_len;
+	}
+	return cstr_len;
+}
+
+// Unlike the standard C library function snprintf, this one always writes
+// a terminating null character to the buffer.
+int myvsnprintf(char *buffer, size_t count, const char *format, va_list argptr)
+{
+	snprintf_state state = { buffer, count - 1, 0, false };
+	StringFormat::VWorker(myvsnprintf_helper, &state, format, argptr);
+	buffer[state.curlen] = '\0';
+	return state.overflow ? -1 : (int)state.curlen;
+}
+
+int mysnprintf(char *buffer, size_t count, const char *format, ...)
+{
+	va_list argptr;
+	va_start(argptr, format);
+	int len = myvsnprintf(buffer, count, format, argptr);
+	va_end(argptr);
+	return len;
 }
 
 void STACK_ARGS I_FatalError (const char *error, ...)