Allow src and dest buffers to be overlapped in Q_strncpy() for QVM co…

…mpatibility reasons

code/qcommon/q_shared.c

@@ -1309,24 +1309,56 @@ void Q_strncpyz( char *dest, const char *src, int destsize )
 /*
 =============
 Q_strncpy
+
+allows src and dest to be overlapped for QVM compatibility purposes
 =============
 */
-char *Q_strncpy( char *dest, const char *src, int destsize )
+char *Q_strncpy( char *dest, char *src, int destsize )
 {
- char *start = dest;
+ char *s = src, *start = dest;
+ int src_len;
 
- while ( destsize > 0 && (*dest++ = *src++) != '\0' ) {
- --destsize;
+ while ( *s != '\0' )
+ ++s;
+ src_len = (int)(s - src);
+
+ if ( src_len > destsize ) {
+ src_len = destsize;
+ }
+ destsize -= src_len;
+
+ if ( dest > src && dest < src + src_len ) {
+ int i;
+#ifdef _DEBUG
+ Com_Printf( S_COLOR_YELLOW "Q_strncpy: overlapped (dest > src) buffers\n" );
+#endif
+ for ( i = src_len - 1; i >= 0; --i ) {
+ dest[i] = src[i]; // back overlapping
+ }
+ dest += src_len;
+ } else {
+#ifdef _DEBUG
+ if ( src >= dest && src < dest + src_len ) {
+ Com_Printf( S_COLOR_YELLOW "Q_strncpy: overlapped (src >= dst) buffers\n" );
+#ifdef _MSC_VER
+ // __debugbreak();
+#endif 
+ }
+#endif
+ while ( src_len > 0 ) {
+ *dest++ = *src++;
+ --src_len;
+ }
  }
 
- while ( --destsize > 0 ) {
+ while ( destsize > 0 ) {
  *dest++ = '\0';
+ --destsize;
  }
 
  return start;
 }
 
-
 /*
 =============
 Q_stricmpn

code/qcommon/q_shared.h

@@ -842,7 +842,7 @@ void Q_strcat( char *dest, int size, const char *src );
 int Q_replace( const char *str1, const char *str2, char *src, int max_len );
 
 char *Q_stradd( char *dst, const char *src );
-char *Q_strncpy( char *dest, const char *src, int destsize );
+char *Q_strncpy( char *dest, char *src, int destsize );
 
 // strlen that discounts Quake color sequences
 int Q_PrintStrlen( const char *string );

code/server/sv_game.c

@@ -487,7 +487,7 @@ static intptr_t SV_GameSystemCalls( intptr_t *args ) {
  return 0;
  case G_GET_ENTITY_TOKEN:
  {
- const char *s = COM_Parse( &sv.entityParsePoint );
+ char *s = (char*)COM_Parse( &sv.entityParsePoint );
  VM_CHECKBOUNDS( gvm, args[1], args[2] );
  //Q_strncpyz( VMA(1), s, args[2] );
  // we can't use our optimized Q_strncpyz() function