add set-priority and get-priority

add clear_err_no and check-errno for dealing with get-priority

extra/io/priority/priority.factor

@@ -0,0 +1,5 @@
+USING: io.backend kernel ;
+IN: io.priority
+
+HOOK: get-priority io-backend ( -- n )
+HOOK: set-priority io-backend ( n -- )

extra/io/unix/backend/backend.factor

@@ -72,6 +72,9 @@ M: mx unregister-io-task ( task mx -- )
 
 : (io-error) ( -- * ) err_no strerror throw ;
 
+: check-errno ( -- )
+    err_no dup zero? [ drop ] [ strerror throw ] if ;
+
 : check-null ( n -- ) zero? [ (io-error) ] when ;
 
 : io-error ( n -- ) 0 < [ (io-error) ] when ;

extra/io/unix/priority/priority.factor

@@ -0,0 +1,21 @@
+USING: alien.syntax kernel io.priority io.unix.backend
+unix ;
+IN: io.unix.priority
+
+: PRIO_PROCESS 0 ; inline
+: PRIO_PGRP 1 ; inline
+: PRIO_USER 2 ; inline
+
+: PRIO_MIN -20 ; inline
+: PRIO_MAX 20 ; inline
+
+! which/who = 0 for current process
+FUNCTION: int getpriority ( int which, int who ) ;
+FUNCTION: int setpriority ( int which, int who, int prio ) ;
+
+M: unix-io get-priority ( -- n )
+    clear_err_no
+    0 0 getpriority dup -1 = [ check-errno ] when ;
+
+M: unix-io set-priority ( n -- )
+    0 0 rot setpriority io-error ;

extra/io/unix/unix.factor

@@ -1,5 +1,5 @@
 USING: io.unix.backend io.unix.files io.unix.sockets io.timeouts
-io.unix.launcher io.unix.mmap io.backend
+io.unix.launcher io.unix.mmap io.backend io.priority
 combinators namespaces system vocabs.loader sequences ;
 
 "io.unix." os append require

extra/unix/unix.factor

@@ -27,6 +27,7 @@ TYPEDEF: ulong size_t
 ! ! ! Unix functions
 LIBRARY: factor
 FUNCTION: int err_no ( ) ;
+FUNCTION: void clear_err_no ( ) ;
 
 LIBRARY: libc
 

vm/io.c

@@ -194,3 +194,8 @@ int err_no(void)
 {
 	return errno;
 }
+
+void clear_err_no(void)
+{
+	errno = 0;
+}

vm/io.h

@@ -1,6 +1,7 @@
 void init_c_io(void);
 void io_error(void);
 int err_no(void);
+void clear_err_no(void);
 
 DECLARE_PRIMITIVE(fopen);
 DECLARE_PRIMITIVE(fgetc);