Update

libretro-common/include/rthreads/rthreads.h

@@ -131,6 +131,15 @@ void slock_free(slock_t *lock);
 **/
 void slock_lock(slock_t *lock);
 
+/**
+ * slock_try_lock:
+ * @lock                    : pointer to mutex object
+ *
+ * Attempts to lock a mutex. If a mutex is already locked by
+ * another thread, return false.  If the lock is acquired, return true.
+**/
+bool slock_try_lock(slock_t *lock);
+
 /**
  * slock_unlock:
  * @lock                    : pointer to mutex object

libretro-common/rthreads/rthreads.c

@@ -385,6 +385,24 @@ void slock_lock(slock_t *lock)
 #endif
 }
 
+/**
+ * slock_try_lock:
+ * @lock                    : pointer to mutex object
+ *
+ * Attempts to lock a mutex. If a mutex is already locked by
+ * another thread, return false.  If the lock is acquired, return true.
+**/
+bool slock_try_lock(slock_t *lock)
+{
+   if (!lock)
+      return false;
+#ifdef USE_WIN32_THREADS
+   return TryEnterCriticalSection(&lock->lock);
+#else
+   return pthread_mutex_trylock(&lock->lock)==0;
+#endif
+}
+
 /**
  * slock_unlock:
  * @lock                    : pointer to mutex object

libretro-common/streams/file_stream.c

@@ -204,9 +204,9 @@ int filestream_getc(RFILE *stream)
 {
    char c = 0;
    if (!stream)
-      return 0;
-   if(filestream_read(stream, &c, 1) == 1)
-      return (int)c;
+      return EOF;
+   if (filestream_read(stream, &c, 1) == 1)
+      return (int)(unsigned char)c;
    return EOF;
 }
 
@@ -427,7 +427,7 @@ int filestream_putc(RFILE *stream, int c)
    char c_char = (char)c;
    if (!stream)
       return EOF;
-   return filestream_write(stream, &c_char, 1)==1 ? c : EOF;
+   return filestream_write(stream, &c_char, 1)==1 ? (int)(unsigned char)c : EOF;
 }
 
 int filestream_vprintf(RFILE *stream, const char* format, va_list args)