os: add open_file function

vlib/os/const.v

@@ -1,16 +1,6 @@
 module os
 // (Must be realized in Syscall) (Must be specified)
-// File modes.
-const (
-	O_RDONLY = 1 // open the file read-only.
-	O_WRONLY = 2 // open the file write-only.
-	O_RDWR = 3 // open the file read-write.
-	O_APPEND = 8 // append data to the file when writing.
-	O_CREATE = 16 // create a new file if none exists.
-	O_EXCL = 32 // used with O_CREATE, file must not exist.
-	O_SYNC = 64 // open for synchronous I/O.
-	O_TRUNC = 128 // truncate regular writable file when opened.
-)
+
 // ref: http://www.ccfit.nsu.ru/~deviv/courses/unix/unix/ng7c229.html
 const (
 	S_IFMT = 0xF000 // type of file

vlib/os/const_nix.v

@@ -0,0 +1,15 @@
+module os
+
+// File modes
+const (
+	O_RDONLY	= 000000000 // open the file read-only.
+	O_WRONLY	= 000000001 // open the file write-only.
+	O_RDWR		= 000000002 // open the file read-write.
+	O_CREATE	= 000000100 // create a new file if none exists.
+	O_EXCL		= 000000200 // used with O_CREATE, file must not exist.
+	O_NOCTTY	= 000000400 // if file is terminal, don't make it the controller terminal
+	O_TRUNC		= 000001000 // truncate regular writable file when opened.
+	O_APPEND	= 000002000 // append data to the file when writing.
+	O_NONBLOCK	= 000004000 // prevents blocking when opening files
+	O_SYNC		= 000010000 // open for synchronous I/O.
+)

vlib/os/const_windows.v

@@ -89,3 +89,16 @@ const (
     ENABLE_LVB_GRID_WORLDWIDE          = 0x0010
 )
 
+// File modes
+const (
+	O_RDONLY	= 0			// open the file read-only.
+	O_WRONLY	= 1			// open the file write-only.
+	O_RDWR		= 2			// open the file read-write.
+	O_APPEND	= 0x0008	// append data to the file when writing.
+	O_CREATE	= 0x0100	// create a new file if none exists.
+	O_TRUNC		= 0x0200	// truncate regular writable file when opened.
+	O_EXCL		= 0x0400	// used with O_CREATE, file must not exist.
+	O_SYNC		= 0			// open for synchronous I/O (ignored on Windows)
+	O_NOCTTY	= 0			// make file non-controlling tty (ignored on Windows)
+	O_NONBLOCK	= 0			// don't block on opening file (ignored on Windows)
+)

vlib/os/os.v

@@ -7,6 +7,7 @@ import filepath
 
 #include <sys/stat.h> // #include <signal.h>
 #include <errno.h>
+
 /*
 struct dirent {
      d_ino int
@@ -31,6 +32,7 @@ pub const (
 
 pub struct File {
 	cfile  voidptr // Using void* instead of FILE*
+pub:
 	fd     int
 mut:
 	opened bool
@@ -71,6 +73,12 @@ fn C.getenv(byteptr) &char
 fn C.sigaction(int, voidptr, int)
 
 
+fn C.open(charptr, int, int) int
+
+
+fn C.fdopen(int, string) voidptr
+
+
 pub fn (f File) is_opened() bool {
 	return f.opened
 }
@@ -292,6 +300,58 @@ pub fn open_append(path string) ?File {
 	return file
 }
 
+// open_file can be used to open or create a file with custom flags and permissions and returns a `File` object
+pub fn open_file(path string, mode string, options ...int) ?File {
+	mut flags := 0
+	for m in mode {
+		match m {
+			`r` { flags |= O_RDONLY }
+			`w` { flags |= O_CREATE | O_TRUNC }
+			`a` { flags |= O_CREATE | O_APPEND }
+			`s` { flags |= O_SYNC }
+			`n` { flags |= O_NONBLOCK }
+			`c` { flags |= O_NOCTTY }
+			`+`	{ flags |= O_RDWR }
+			else {}
+		}
+	}
+
+	mut permission := 0666
+	if options.len > 0 {
+		permission = options[0]
+	}
+
+	$if windows {
+		if permission < 0600 {
+			permission = 0x0100
+		}
+		else {
+			permission = 0x0100 | 0x0080
+		}
+	}
+
+	mut p := path
+	$if windows {
+		p = path.replace('/', '\\')
+	}
+
+	fd := C.open(charptr(p.str), flags, permission)
+	if fd == -1 {
+		return error(posix_get_error_msg(C.errno))
+	}
+
+	cfile := C.fdopen(fd, charptr(mode.str))
+	if isnil(cfile) {
+		return error('Failed to open or create file "$path"')
+	}
+
+	return File{
+		cfile: cfile
+		fd: fd
+		opened: true
+	}
+}
+
 /*
 pub fn (f mut File) write_bytes_at(data voidptr, size, pos int) {
 	$if linux {
@@ -344,6 +404,15 @@ fn posix_wait4_to_exit_status(waitret int) (int,bool) {
 	}
 }
 
+// posix_get_error_msg return error code representation in string.
+pub fn posix_get_error_msg(code int) string {
+	ptr_text := C.strerror(code) // voidptr?
+	if ptr_text == 0 {
+		return ''
+	}
+	return tos3(ptr_text)
+}
+
 fn vpclose(f voidptr) int {
 	$if windows {
 		return C._pclose(f)

vlib/os/os_nix.v

@@ -2,6 +2,8 @@ module os
 
 #include <dirent.h>
 #include <unistd.h>
+#include <fcntl.h>
+
 pub const (
 	path_separator = '/'
 )
@@ -14,7 +16,6 @@ const (
 
 fn C.symlink(charptr, charptr) int
 
-
 pub fn init_os_args(argc int, argv &byteptr) []string {
 	mut args := []string
 	for i in 0 .. argc {
@@ -23,15 +24,6 @@ pub fn init_os_args(argc int, argv &byteptr) []string {
 	return args
 }
 
-// get_error_msg return error code representation in string.
-pub fn get_error_msg(code int) string {
-	ptr_text := C.strerror(code) // voidptr?
-	if ptr_text == 0 {
-		return ''
-	}
-	return tos3(ptr_text)
-}
-
 pub fn ls(path string) ?[]string {
 	mut res := []string
 	dir := C.opendir(path.str)
@@ -68,9 +60,8 @@ 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 {
-	mut file := File{}
   /*
 	$if linux {
 		$if !android {
@@ -85,9 +76,8 @@ pub fn open(path string) ?File {
 		}
 	}
   */
-	cpath := path.str
-	file = File{
-		cfile: C.fopen(charptr(cpath), 'rb')
+	file := File{
+		cfile: C.fopen(charptr(path.str), 'rb')
 		opened: true
 	}
 	if isnil(file.cfile) {
@@ -96,10 +86,8 @@ pub fn open(path string) ?File {
 	return file
 }
 
-// create creates a file at a specified location and returns a writable `File` object.
+// create creates or opens a file at a specified location and returns a write-only `File` object
 pub fn create(path string) ?File {
-	mut fd := 0
-	mut file := File{}
   /*
 	// NB: android/termux/bionic is also a kind of linux,
 	// but linux syscalls there sometimes fail,
@@ -123,7 +111,7 @@ pub fn create(path string) ?File {
 		}
 	}
   */
-	file = File{
+	file := File{
 		cfile: C.fopen(charptr(path.str), 'wb')
 		opened: true
 	}
@@ -187,7 +175,7 @@ pub fn mkdir(path string) ?bool {
 		$if !android {
 			ret := C.syscall(sys_mkdir, apath.str, 511)
 			if ret == -1 {
-				return error(get_error_msg(C.errno))
+				return error(posix_get_error_msg(C.errno))
 			}
 			return true
 		}
@@ -195,7 +183,7 @@ pub fn mkdir(path string) ?bool {
   */
 	r := C.mkdir(apath.str, 511)
 	if r == -1 {
-		return error(get_error_msg(C.errno))
+		return error(posix_get_error_msg(C.errno))
 	}
 	return true
 }
@@ -231,7 +219,12 @@ pub fn symlink(origin, target string) ?bool {
 	if res == 0 {
 		return true
 	}
-	return error(get_error_msg(C.errno))
+	return error(posix_get_error_msg(C.errno))
+}
+
+// get_error_msg return error code representation in string.
+pub fn get_error_msg(code int) string {
+	return posix_get_error_msg(code)
 }
 
 // convert any value to []byte (LittleEndian) and write it

vlib/os/os_test.v

@@ -24,6 +24,27 @@ fn test_unsetenv() {
   assert os.getenv('foo') == ''
 }
 
+fn test_open_file() {
+  filename := './test1.txt'
+  hello := 'hello world!'
+  os.open_file(filename, "r+", 0666) or {
+    assert err == "No such file or directory"
+  }
+
+  mut file := os.open_file(filename, "w+", 0666) or { panic(err) }
+  file.write(hello)
+  file.close()
+  
+  assert hello.len == os.file_size(filename)
+
+  read_hello := os.read_file(filename) or {
+    panic('error reading file $filename')
+  }
+  assert hello == read_hello
+
+  os.rm(filename)
+}
+
 fn test_write_and_read_string_to_file() {
   filename := './test1.txt'
   hello := 'hello world!'