v.gen.js, os_js: port the OS module to JS (#10872)

vlib/os_js/file.js.v

@@ -0,0 +1,130 @@
+module os_js
+
+pub struct File {
+pub:
+	fd int
+pub mut:
+	is_opened bool
+}
+
+#const $buffer = require('buffer');
+
+// todo(playX):   __as_cast is broken here
+/*
+pub struct ErrFileNotOpened {
+	msg  string = 'os: file not opened'
+	code int
+}
+pub struct ErrSizeOfTypeIs0 {
+	msg  string = 'os: size of type is 0'
+	code int
+}
+fn error_file_not_opened() IError {
+	return IError(&ErrFileNotOpened{})
+}
+fn error_size_of_type_0() IError {
+	return IError(&ErrSizeOfTypeIs0{})
+}
+*/
+pub fn open_file(path string, mode string, options ...int) ?File {
+	mut res := File{}
+	$if js_node {
+		#if (!options) { options = new array([]); }
+		#let permissions = 0o666
+		#if (options.arr.length > 0) { permissions = options.arr[0]; }
+		#try {
+		#res.fd = new int($fs.openSync(''+path,''+mode,permissions))
+		#} catch (e) {
+		#return builtin.error('' + e);
+		#}
+
+		res.is_opened = true
+	} $else {
+		error('cannot open file on non NodeJS runtime')
+	}
+	return res
+}
+
+// open tries to open a file for reading and returns back a read-only `File` object.
+pub fn open(path string) ?File {
+	f := open_file(path, 'r') ?
+	return f
+}
+
+pub fn create(path string) ?File {
+	f := open_file(path, 'w') ?
+	return f
+}
+
+pub fn stdin() File {
+	return File{
+		fd: 0
+		is_opened: true
+	}
+}
+
+pub fn stdout() File {
+	return File{
+		fd: 1
+		is_opened: true
+	}
+}
+
+pub fn stderr() File {
+	return File{
+		fd: 2
+		is_opened: true
+	}
+}
+
+pub fn (f &File) read(mut buf []byte) ?int {
+	if buf.len == 0 {
+		return 0
+	}
+	mut nbytes := 0
+	#try {
+	#let buffer = $fs.readFileSync(f.fd.valueOf());
+	#
+	#for (const val of buffer.values()) { buf.arr[nbytes++] = val; }
+	#}
+	#catch (e) { return builtin.error('' + e); }
+
+	return nbytes
+}
+
+pub fn (mut f File) write(buf []byte) ?int {
+	if !f.is_opened {
+		return error('file is not opened')
+	}
+	mut nbytes := 0
+	#const b = $buffer.Buffer.from(buf.arr.map((x) => x.valueOf()))
+	#try { $fs.writeSync(f.fd.valueOf(),b,0,buf.len.valueOf(),0); } catch (e) { return builtin.error('' + e); }
+
+	return nbytes
+}
+
+// writeln writes the string `s` into the file, and appends a \n character.
+// It returns how many bytes were written, including the \n character.
+pub fn (mut f File) writeln(s string) ?int {
+	mut nbytes := f.write(s.bytes()) ?
+	nbytes += f.write('\n'.bytes()) ?
+	return nbytes
+}
+
+pub fn (mut f File) write_to(pos u64, buf []byte) ?int {
+	if !f.is_opened {
+		return error('file is not opened')
+	}
+	mut nbytes := 0
+	#const b = $buffer.Buffer.from(buf.arr.map((x) => x.valueOf()))
+	#try { $fs.writeSync(f.fd.valueOf(),b,0,buf.len.valueOf(),pos.valueOf()); } catch (e) { return builtin.error('' + e); }
+
+	return nbytes
+}
+
+// write_string writes the string `s` into the file
+// It returns how many bytes were actually written.
+pub fn (mut f File) write_string(s string) ?int {
+	nbytes := f.write(s.bytes()) ?
+	return nbytes
+}