os: cleanup code duplication for os.create and os.open

vlib/builtin/cfns.c.v

@@ -54,6 +54,9 @@ fn C.fseek() int
 fn C.fopen() voidptr
 
 
+fn C.fileno(voidptr) int
+
+
 fn C.fwrite() int
 
 

vlib/os/os.v

@@ -223,7 +223,10 @@ pub fn mv_by_cp(source string, target string) ?bool {
 	return true
 }
 
-fn vfopen(path, mode string) &C.FILE {
+// vfopen returns an opened C file, given its path and open mode.
+// NB: os.vfopen is useful for compatibility with C libraries, that expect `FILE *`.
+// If you write pure V code, os.create or os.open are more convenient.
+pub fn vfopen(path, mode string) &C.FILE {
 	$if windows {
 		return C._wfopen(path.to_wide(), mode.to_wide())
 	} $else {
@@ -231,6 +234,15 @@ fn vfopen(path, mode string) &C.FILE {
 	}
 }
 
+// fileno returns the file descriptor of an opened C file
+pub fn fileno(cfile voidptr) int {
+	$if windows {
+		return C._fileno(cfile)
+	} $else {
+		return C.fileno(cfile)
+	}
+}
+
 // read_lines reads the file in `path` into an array of lines.
 pub fn read_lines(path string) ?[]string {
 	buf := read_file(path) or {
@@ -1246,3 +1258,102 @@ pub fn resource_abs_path(path string) string {
 	}
 	return os.real_path(os.join_path(base_path, path))
 }
+
+
+// open tries to open a file for reading and returns back a read-only `File` object
+pub fn open(path string) ?File {
+  /*
+	$if linux {
+		$if !android {
+			fd := C.syscall(sys_open, path.str, 511)
+			if fd == -1 {
+				return error('failed to open file "$path"')
+			}
+			return File{
+				fd: fd
+				opened: true
+			}
+		}
+	}
+  */
+	cfile := vfopen(path, 'rb')
+	if cfile == 0 {
+		return error('failed to open file "$path"')
+	}
+	fd := fileno(cfile)
+	return File {
+		cfile: cfile
+		fd: fd
+		opened: true
+	}
+}
+
+// create creates or opens a file at a specified location and returns a write-only `File` object
+pub fn create(path string) ?File {
+  /*
+	// NB: android/termux/bionic is also a kind of linux,
+	// but linux syscalls there sometimes fail,
+	// while the libc version should work.
+	$if linux {
+		$if !android {
+			//$if macos {
+			//	fd = C.syscall(398, path.str, 0x601, 0x1b6)
+			//}
+			//$if linux {
+			fd = C.syscall(sys_creat, path.str, 511)
+			//}
+			if fd == -1 {
+				return error('failed to create file "$path"')
+			}
+			file = File{
+				fd: fd
+				opened: true
+			}
+			return file
+		}
+	}
+  */
+	cfile := vfopen(path, 'wb')
+	if cfile == 0 {
+		return error('failed to create file "$path"')
+	}
+	fd := fileno(cfile)
+	return File {
+		cfile: cfile
+		fd: fd
+		opened: true
+	}
+}
+
+pub fn (mut f File) write(s string) {
+	if !f.opened {
+		return
+	}
+  /*
+	$if linux {
+		$if !android {
+			C.syscall(sys_write, f.fd, s.str, s.len)
+			return
+		}
+	}
+  */
+	C.fputs(s.str, f.cfile)
+}
+
+pub fn (mut f File) writeln(s string) {
+	if !f.opened {
+		return
+	}
+  /*
+	$if linux {
+		$if !android {
+			snl := s + '\n'
+			C.syscall(sys_write, f.fd, snl.str, snl.len)
+			return
+		}
+	}
+  */
+	// TODO perf
+	C.fputs(s.str, f.cfile)
+	C.fputs('\n', f.cfile)
+}

vlib/os/os_nix.c.v

@@ -66,112 +66,12 @@ pub fn is_dir(path string) bool {
 }
 */
 
-// open opens a file at the specified and returns back a read-only `File` object
-pub fn open(path string) ?File {
-  /*
-	$if linux {
-		$if !android {
-			fd := C.syscall(sys_open, path.str, 511)
-			if fd == -1 {
-				return error('failed to open file "$path"')
-			}
-			return File{
-				fd: fd
-				opened: true
-			}
-		}
-	}
-  */
-	file := File{
-		cfile: C.fopen(charptr(path.str), 'rb')
-		fd: 0
-		opened: true
-	}
-	if isnil(file.cfile) {
-		return error('failed to open file "$path"')
-	}
-	return file
-}
-
-// create creates or opens a file at a specified location and returns a write-only `File` object
-pub fn create(path string) ?File {
-  /*
-	// NB: android/termux/bionic is also a kind of linux,
-	// but linux syscalls there sometimes fail,
-	// while the libc version should work.
-	$if linux {
-		$if !android {
-			//$if macos {
-			//	fd = C.syscall(398, path.str, 0x601, 0x1b6)
-			//}
-			//$if linux {
-			fd = C.syscall(sys_creat, path.str, 511)
-			//}
-			if fd == -1 {
-				return error('failed to create file "$path"')
-			}
-			file = File{
-				fd: fd
-				opened: true
-			}
-			return file
-		}
-	}
-  */
-	file := File{
-		cfile: C.fopen(charptr(path.str), 'wb')
-		fd: 0
-		opened: true
-	}
-	if isnil(file.cfile) {
-		return error('failed to create file "$path"')
-	}
-	return file
-}
-
 /*
 pub fn (mut f File) fseek(pos, mode int) {
 }
 */
 
 
-pub fn (mut f File) write(s string) {
-	if !f.opened {
-		return
-	}
-  /*
-	$if linux {
-		$if !android {
-			C.syscall(sys_write, f.fd, s.str, s.len)
-			return
-		}
-	}
-  */
-	C.fputs(s.str, f.cfile)
-	// C.fwrite(s.str, 1, s.len, f.cfile)
-}
-
-pub fn (mut f File) writeln(s string) {
-	if !f.opened {
-		return
-	}
-  /*
-	$if linux {
-		$if !android {
-			snl := s + '\n'
-			C.syscall(sys_write, f.fd, snl.str, snl.len)
-			return
-		}
-	}
-  */
-	// C.fwrite(s.str, 1, s.len, f.cfile)
-	// ss := s.clone()
-	// TODO perf
-	C.fputs(s.str, f.cfile)
-	// ss.free()
-	C.fputs('\n', f.cfile)
-}
-
 // mkdir creates a new directory with the specified path.
 pub fn mkdir(path string) ?bool {
 	if path == '.' {

vlib/os/os_windows.c.v

@@ -130,47 +130,6 @@ pub fn is_dir(path string) bool {
 }
 */
 
-pub fn open(path string) ?File {
-	mode := 'rb'
-	file := File {
-		cfile: C._wfopen(path.to_wide(), mode.to_wide())
-		opened: true
-	}
-	if isnil(file.cfile) {
-		return error('failed to open file "$path"')
-	}
-	return file
-}
-
-// create creates a file at a specified location and returns a writable `File` object.
-pub fn create(path string) ?File {
-	mode := 'wb'
-	file := File {
-		cfile: C._wfopen(path.to_wide(), mode.to_wide())
-		opened: true
-	}
-	if isnil(file.cfile) {
-		return error('failed to create file "$path"')
-	}
-	return file
-}
-
-pub fn (mut f File) write(s string) {
-	if !f.opened {
-		return
-	}
-	C.fputs(s.str, f.cfile)
-}
-
-pub fn (mut f File) writeln(s string) {
-	if !f.opened {
-		return
-	}
-	// TODO perf
-	C.fputs(s.str, f.cfile)
-	C.fputs('\n', f.cfile)
-}
-
 
 // mkdir creates a new directory with the specified path.
 pub fn mkdir(path string) ?bool {
@@ -185,12 +144,11 @@ pub fn mkdir(path string) ?bool {
 // Ref - https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/get-osfhandle?view=vs-2019
 // get_file_handle retrieves the operating-system file handle that is associated with the specified file descriptor.
 pub fn get_file_handle(path string) HANDLE {
-    mode := 'rb'
+    cfile := vfopen(path, 'rb')
-    fd := C._wfopen(path.to_wide(), mode.to_wide())
+    if cfile == 0 {
-    if fd == 0 {
 	    return HANDLE(INVALID_HANDLE_VALUE)
     }
-    handle := HANDLE(C._get_osfhandle(C._fileno(fd))) // CreateFile? - hah, no -_-
+    handle := HANDLE(C._get_osfhandle(fileno(cfile))) // CreateFile? - hah, no -_-
     return handle
 }