core: add BFile_Size syscall

include/gint/bfile.h

@@ -52,6 +52,12 @@ int BFile_Open(uint16_t const *file, enum BFile_OpenMode mode);
    Returns a BFile error code. */
 int BFile_Close(int fd);
 
+/* BFile_Size(): Retrieve size of an open file
+
+   @fd  File descriptor
+   Returns the file size in bytes, or a negative BFile error code*/
+int BFile_Size(int fd);
+
 /* BFile_Write(): Write data to an open file
    Second and third argument specify the data and length to write.
 

src/core/syscalls.S

@@ -23,6 +23,7 @@
 .global	_BFile_Create
 .global	_BFile_Open
 .global	_BFile_Close
+.global	_BFile_Size
 .global	_BFile_Write
 .global	_BFile_Read
 
@@ -71,6 +72,10 @@ _BFile_Open:
 _BFile_Close:
 	syscall(0x042d)
 
+# int BFile_Size(int handle)
+_BFile_Size:
+	syscall(0x042f)
+
 # int BFile_Write(int handle, const void *ram_buffer, int even_size)
 _BFile_Write:
 	syscall(0x0435)