Add fcntl(F_PREVFD) and fcntl(F_NEXTFD).

kernel/dtable.cpp

@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
 
     This file is part of Sortix.
 
@@ -219,4 +219,39 @@ int DescriptorTable::GetFlags(int index)
 	return entries[index].flags;
 }
 
+int DescriptorTable::Previous(int index)
+{
+	ScopedLock lock(&dtablelock);
+
+	if ( index < 0 )
+		index = numentries;
+
+	do index--;
+	while ( 0 <= index && !IsGoodEntry(index) );
+
+	if ( index < 0 )
+		return errno = EBADF, -1;
+
+	return index;
+}
+
+int DescriptorTable::Next(int index)
+{
+	ScopedLock lock(&dtablelock);
+
+	if ( index < 0 )
+		index = -1;
+
+	if ( numentries <= index )
+		return errno = EBADF, -1;
+
+	do index++;
+	while ( index < numentries && !IsGoodEntry(index) );
+
+	if ( numentries <= index )
+		return errno = EBADF, -1;
+
+	return index;
+}
+
 } // namespace Sortix

kernel/include/sortix/fcntl.h

@@ -99,6 +99,14 @@ __BEGIN_DECLS
 #define F_DUPFD_CLOEXEC F_ENCODE_CMD(F_ENCODE(F_DUPFD_NUM, FD_CLOEXEC), F_TYPE_INT)
 #define F_DUPFD_CLOFORK F_ENCODE_CMD(F_ENCODE(F_DUPFD_NUM, FD_CLOFORK), F_TYPE_INT)
 
+/* Find the previous file descriptor. */
+#define F_PREVFD_NUM 5
+#define F_PREVFD F_ENCODE_CMD(F_PREVFD_NUM, F_TYPE_VOID)
+
+/* Find the next file descriptor. */
+#define F_NEXTFD_NUM 6
+#define F_NEXTFD F_ENCODE_CMD(F_NEXTFD_NUM, F_TYPE_VOID)
+
 #define AT_FDCWD (-100)
 #define AT_REMOVEDIR (1<<0)
 #define AT_EACCESS (1<<1)

kernel/include/sortix/kernel/dtable.h

@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
 
     This file is part of Sortix.
 
@@ -52,6 +52,8 @@ public:
 	void OnExecute();
 	bool SetFlags(int index, int flags);
 	int GetFlags(int index);
+	int Previous(int index);
+	int Next(int index);
 
 private:
 	void Reset(); // Hey, reference counted. Don't call this.

kernel/io.cpp

@@ -316,6 +316,10 @@ static int sys_fcntl(int fd, int cmd, uintptr_t arg)
 {
 	// Operations on the descriptor table.
 	Ref<DescriptorTable> dtable = CurrentProcess()->GetDTable();
+	if ( cmd == F_PREVFD )
+		return dtable->Previous(fd);
+	if ( cmd == F_NEXTFD )
+		return dtable->Next(fd);
 
 	// Operations on the file descriptior.
 	if ( cmd == F_SETFD )