14 files changed, 873 insertions, 0 deletions

diff --git a/v_windows/v/vlib/io/buffered_reader.v b/v_windows/v/vlib/io/buffered_reader.v
new file mode 100644
index 0000000..f336e2d
--- /dev/null
+++ b/v_windows/v/vlib/io/buffered_reader.v
@@ -0,0 +1,145 @@
+module io
+
+// BufferedReader provides a buffered interface for a reader
+struct BufferedReader {
+mut:
+	reader Reader
+	buf    []byte
+	offset int // current offset in the buffer
+	len    int
+	fails  int // how many times fill_buffer has read 0 bytes in a row
+	mfails int // maximum fails, after which we can assume that the stream has ended
+pub mut:
+	end_of_stream bool // whether we reached the end of the upstream reader
+}
+
+// BufferedReaderConfig are options that can be given to a reader
+pub struct BufferedReaderConfig {
+	reader  Reader
+	cap     int = 128 * 1024 // large for fast reading of big(ish) files
+	retries int = 2 // how many times to retry before assuming the stream ended
+}
+
+// new_buffered_reader creates new BufferedReader
+pub fn new_buffered_reader(o BufferedReaderConfig) &BufferedReader {
+	if o.cap <= 0 {
+		panic('new_buffered_reader should be called with a positive `cap`')
+	}
+	// create
+	r := &BufferedReader{
+		reader: o.reader
+		buf: []byte{len: o.cap, cap: o.cap}
+		offset: 0
+		mfails: o.retries
+	}
+	return r
+}
+
+// read fufills the Reader interface
+pub fn (mut r BufferedReader) read(mut buf []byte) ?int {
+	if r.end_of_stream {
+		return none
+	}
+	// read data out of the buffer if we dont have any
+	if r.needs_fill() {
+		if !r.fill_buffer() {
+			// end of stream
+			return none
+		}
+	}
+	read := copy(buf, r.buf[r.offset..r.len])
+	if read == 0 {
+		return none
+	}
+	r.offset += read
+	return read
+}
+
+pub fn (mut r BufferedReader) free() {
+	unsafe {
+		r.buf.free()
+	}
+}
+
+// fill_buffer attempts to refill the internal buffer
+// and returns whether it got any data
+fn (mut r BufferedReader) fill_buffer() bool {
+	if r.end_of_stream {
+		// we know we have already reached the end of stream
+		// so return early
+		return true
+	}
+	r.offset = 0
+	r.len = 0
+	r.len = r.reader.read(mut r.buf) or {
+		// end of stream was reached
+		r.end_of_stream = true
+		return false
+	}
+	if r.len == 0 {
+		r.fails++
+	} else {
+		r.fails = 0
+	}
+	if r.fails >= r.mfails {
+		// When reading 0 bytes several times in a row, assume the stream has ended.
+		// This prevents infinite loops ¯\_(ツ)_/¯ ...
+		r.end_of_stream = true
+		return false
+	}
+	// we got some data
+	return true
+}
+
+// needs_fill returns whether the buffer needs refilling
+fn (r BufferedReader) needs_fill() bool {
+	return r.offset >= r.len
+}
+
+// end_of_stream returns whether the end of the stream was reached
+pub fn (r BufferedReader) end_of_stream() bool {
+	return r.end_of_stream
+}
+
+// read_line attempts to read a line from the buffered reader
+// it will read until it finds a new line character (\n) or
+// the end of stream
+pub fn (mut r BufferedReader) read_line() ?string {
+	if r.end_of_stream {
+		return none
+	}
+	mut line := []byte{}
+	for {
+		if r.needs_fill() {
+			// go fetch some new data
+			if !r.fill_buffer() {
+				// We are at the end of the stream
+				if line.len == 0 {
+					// we had nothing so return nothing
+					return none
+				}
+				return line.bytestr()
+			}
+		}
+		// try and find a newline character
+		mut i := r.offset
+		for ; i < r.len; i++ {
+			c := r.buf[i]
+			if c == `\n` {
+				// great, we hit something
+				// do some checking for whether we hit \r\n or just \n
+				if i != 0 && r.buf[i - 1] == `\r` {
+					x := i - 1
+					line << r.buf[r.offset..x]
+				} else {
+					line << r.buf[r.offset..i]
+				}
+				r.offset = i + 1
+				return line.bytestr()
+			}
+		}
+		line << r.buf[r.offset..i]
+		r.offset = i
+	}
+	return none
+}
diff --git a/v_windows/v/vlib/io/custom_string_reading_test.v b/v_windows/v/vlib/io/custom_string_reading_test.v
new file mode 100644
index 0000000..76e3307
--- /dev/null
+++ b/v_windows/v/vlib/io/custom_string_reading_test.v
@@ -0,0 +1,57 @@
+import io
+
+struct StringReader {
+	text string
+mut:
+	place int
+}
+
+fn imin(a int, b int) int {
+	return if a < b { a } else { b }
+}
+
+fn (mut s StringReader) read(mut buf []byte) ?int {
+	$if debug {
+		eprintln('>>>> StringReader.read output buf.len: $buf.len')
+	}
+	if s.place > s.text.len + 1 {
+		return none
+	}
+	mut howmany := imin(buf.len, s.text.len - s.place)
+	xxx := s.text[s.place..s.place + howmany].bytes()
+	read := copy(buf, xxx)
+	s.place += read
+	return read
+}
+
+fn read_from_string(text string, capacity int) []byte {
+	mut str := StringReader{
+		text: text
+	}
+	mut stream := io.new_buffered_reader(reader: str, cap: capacity)
+	//
+	mut buf := []byte{len: 1}
+	mut res := []byte{}
+	mut i := 0
+	for {
+		z := stream.read(mut buf) or { break }
+		res << buf
+		$if debug {
+			println('capacity: $capacity, i: $i, buf: $buf | z: $z')
+		}
+		i++
+	}
+	return res
+}
+
+pub fn test_reading_from_a_string() {
+	for capacity in 1 .. 1000 {
+		assert read_from_string('a', capacity) == [byte(`a`)]
+		assert read_from_string('ab', capacity) == [byte(`a`), `b`]
+		assert read_from_string('abc', capacity) == [byte(`a`), `b`, `c`]
+		assert read_from_string('abcde', capacity) == [byte(`a`), `b`, `c`, `d`, `e`]
+		large_string_bytes := []byte{len: 1000, init: `x`}
+		large_string := large_string_bytes.bytestr()
+		assert read_from_string(large_string, capacity) == large_string_bytes
+	}
+}
diff --git a/v_windows/v/vlib/io/io.v b/v_windows/v/vlib/io/io.v
new file mode 100644
index 0000000..c07e074
--- /dev/null
+++ b/v_windows/v/vlib/io/io.v
@@ -0,0 +1,16 @@
+module io
+
+const (
+	buf_max_len = 1024
+)
+
+pub fn cp(src Reader, mut dst Writer) ? {
+	mut buf := []byte{len: io.buf_max_len}
+	for {
+		len := src.read(mut buf) or { break }
+		dst.write(buf[..len]) or { return err }
+	}
+	unsafe {
+		buf.free()
+	}
+}
diff --git a/v_windows/v/vlib/io/io_cp_test.v b/v_windows/v/vlib/io/io_cp_test.v
new file mode 100644
index 0000000..21c743a
--- /dev/null
+++ b/v_windows/v/vlib/io/io_cp_test.v
@@ -0,0 +1,13 @@
+import io
+import os
+
+fn test_cp() ? {
+	mut f := os.open(@FILE) or { panic(err) }
+	defer {
+		f.close()
+	}
+	mut r := io.new_buffered_reader(reader: f)
+	mut stdout := os.stdout()
+	io.cp(r, mut stdout) ?
+	assert true
+}
diff --git a/v_windows/v/vlib/io/io_test.v b/v_windows/v/vlib/io/io_test.v
new file mode 100644
index 0000000..fca17c2
--- /dev/null
+++ b/v_windows/v/vlib/io/io_test.v
@@ -0,0 +1,41 @@
+import io
+
+struct Buf {
+pub:
+	bytes []byte
+mut:
+	i int
+}
+
+struct Writ {
+pub mut:
+	bytes []byte
+}
+
+fn (mut b Buf) read(mut buf []byte) ?int {
+	if !(b.i < b.bytes.len) {
+		return none
+	}
+	n := copy(buf, b.bytes[b.i..])
+	b.i += n
+	return n
+}
+
+fn (mut w Writ) write(buf []byte) ?int {
+	if buf.len <= 0 {
+		return none
+	}
+	w.bytes << buf
+	return buf.len
+}
+
+fn test_copy() {
+	src := Buf{
+		bytes: 'abcdefghij'.repeat(10).bytes()
+	}
+	mut dst := Writ{
+		bytes: []byte{}
+	}
+	io.cp(src, mut dst) or { assert false }
+	assert dst.bytes == src.bytes
+}
diff --git a/v_windows/v/vlib/io/multi_writer.v b/v_windows/v/vlib/io/multi_writer.v
new file mode 100644
index 0000000..837ea30
--- /dev/null
+++ b/v_windows/v/vlib/io/multi_writer.v
@@ -0,0 +1,33 @@
+module io
+
+// new_multi_writer returns a Writer that writes to all writers. The write
+// function of the returned Writer writes to all writers of the MultiWriter,
+// returns the length of bytes written, and if any writer fails to write the
+// full length an error is returned and writing to other writers stops, and if
+// any writer returns an error the error is returned immediately and writing to
+// other writers stops.
+pub fn new_multi_writer(writers ...Writer) Writer {
+	return &MultiWriter{
+		writers: writers
+	}
+}
+
+// MultiWriter writes to all its writers.
+pub struct MultiWriter {
+pub mut:
+	writers []Writer
+}
+
+// write writes to all writers of the MultiWriter. Returns the length of bytes
+// written. If any writer fails to write the full length an error is returned
+// and writing to other writers stops. If any writer returns an error the error
+// is returned immediately and writing to other writers stops.
+pub fn (mut m MultiWriter) write(buf []byte) ?int {
+	for mut w in m.writers {
+		n := w.write(buf) ?
+		if n != buf.len {
+			return error('io: incomplete write to writer of MultiWriter')
+		}
+	}
+	return buf.len
+}
diff --git a/v_windows/v/vlib/io/multi_writer_test.v b/v_windows/v/vlib/io/multi_writer_test.v
new file mode 100644
index 0000000..2e317e8
--- /dev/null
+++ b/v_windows/v/vlib/io/multi_writer_test.v
@@ -0,0 +1,66 @@
+module io
+
+fn test_multi_writer_write_successful() {
+	w0 := TestWriter{}
+	w1 := TestWriter{}
+	mut mw := new_multi_writer(w0, w1)
+	n := mw.write('0123456789'.bytes()) or {
+		assert false
+		return
+	}
+	assert n == 10
+	assert w0.bytes == '0123456789'.bytes()
+	assert w1.bytes == '0123456789'.bytes()
+}
+
+fn test_multi_writer_write_incomplete() {
+	w0 := TestWriter{}
+	w1 := TestIncompleteWriter{}
+	mut mw := new_multi_writer(w0, w1)
+	n := mw.write('0123456789'.bytes()) or {
+		assert w0.bytes == '0123456789'.bytes()
+		assert w1.bytes == '012345678'.bytes()
+		return
+	}
+	assert false
+}
+
+fn test_multi_writer_write_error() {
+	w0 := TestWriter{}
+	w1 := TestErrorWriter{}
+	w2 := TestWriter{}
+	mut mw := new_multi_writer(w0, w1, w2)
+	n := mw.write('0123456789'.bytes()) or {
+		assert w0.bytes == '0123456789'.bytes()
+		assert w2.bytes == []
+		return
+	}
+	assert false
+}
+
+struct TestWriter {
+pub mut:
+	bytes []byte
+}
+
+fn (mut w TestWriter) write(buf []byte) ?int {
+	w.bytes << buf
+	return buf.len
+}
+
+struct TestIncompleteWriter {
+pub mut:
+	bytes []byte
+}
+
+fn (mut w TestIncompleteWriter) write(buf []byte) ?int {
+	b := buf[..buf.len - 1]
+	w.bytes << b
+	return b.len
+}
+
+struct TestErrorWriter {}
+
+fn (mut w TestErrorWriter) write(buf []byte) ?int {
+	return error('error writer errored')
+}
diff --git a/v_windows/v/vlib/io/os_file_reader_test.v b/v_windows/v/vlib/io/os_file_reader_test.v
new file mode 100644
index 0000000..1ed3a1f
--- /dev/null
+++ b/v_windows/v/vlib/io/os_file_reader_test.v
@@ -0,0 +1,29 @@
+import os
+import io
+
+fn read_file(file string, cap int) []string {
+	mut lines := []string{}
+	mut f := os.open(file) or { panic(err) }
+	defer {
+		f.close()
+	}
+	mut r := io.new_buffered_reader(reader: f, cap: cap)
+	for {
+		l := r.read_line() or { break }
+		lines << l
+		// println('Line: $l')
+	}
+	assert lines.len > 0
+	assert r.end_of_stream == true
+	println('------------------------------------------------ cap: ${cap:6}; read: ${lines.len:3} lines')
+	return lines
+}
+
+fn test_file_reader() {
+	for cap := 1; cap <= 10000; cap += 256 {
+		lines := read_file(@FILE, cap)
+		assert lines.last() == '// my last line'
+	}
+}
+
+// my last line
diff --git a/v_windows/v/vlib/io/reader.v b/v_windows/v/vlib/io/reader.v
new file mode 100644
index 0000000..61f566f
--- /dev/null
+++ b/v_windows/v/vlib/io/reader.v
@@ -0,0 +1,66 @@
+module io
+
+// Reader represents a stream of data that can be read
+pub interface Reader {
+	// read reads up to buf.len bytes and places
+	// them into buf.
+	// A type that implements this should return
+	// `none` on end of stream (EOF) instead of just returning 0
+	read(mut buf []byte) ?int
+}
+
+const (
+	read_all_len      = 10 * 1024
+	read_all_grow_len = 1024
+)
+
+// ReadAllConfig allows options to be passed for the behaviour
+// of read_all
+pub struct ReadAllConfig {
+	reader                Reader
+	read_to_end_of_stream bool
+}
+
+// read_all reads all bytes from a reader until either a 0 length read
+// or if read_to_end_of_stream is true then the end of the stream (`none`)
+pub fn read_all(config ReadAllConfig) ?[]byte {
+	r := config.reader
+	read_till_eof := config.read_to_end_of_stream
+
+	mut b := []byte{len: io.read_all_len}
+	mut read := 0
+	for {
+		new_read := r.read(mut b[read..]) or { break }
+		read += new_read
+		if !read_till_eof && read == 0 {
+			break
+		}
+		if b.len == read {
+			unsafe { b.grow_len(io.read_all_grow_len) }
+		}
+	}
+	return b[..read]
+}
+
+// read_any reads any available bytes from a reader
+// (until the reader returns a read of 0 length)
+pub fn read_any(r Reader) ?[]byte {
+	mut b := []byte{len: io.read_all_len}
+	mut read := 0
+	for {
+		new_read := r.read(mut b[read..]) or { break }
+		read += new_read
+		if new_read == 0 {
+			break
+		}
+		if b.len == read {
+			unsafe { b.grow_len(io.read_all_grow_len) }
+		}
+	}
+	return b[..read]
+}
+
+// RandomReader represents a stream of data that can be read from at a random location
+interface RandomReader {
+	read_from(pos u64, mut buf []byte) ?int
+}
diff --git a/v_windows/v/vlib/io/reader_test.v b/v_windows/v/vlib/io/reader_test.v
new file mode 100644
index 0000000..c7a2265
--- /dev/null
+++ b/v_windows/v/vlib/io/reader_test.v
@@ -0,0 +1,130 @@
+module io
+
+struct Buf {
+pub:
+	bytes []byte
+mut:
+	i int
+}
+
+fn (mut b Buf) read(mut buf []byte) ?int {
+	if !(b.i < b.bytes.len) {
+		return none
+	}
+	n := copy(buf, b.bytes[b.i..])
+	b.i += n
+	return n
+}
+
+fn test_read_all() {
+	buf := Buf{
+		bytes: '123'.repeat(10).bytes()
+	}
+	res := read_all(reader: buf) or {
+		assert false
+		''.bytes()
+	}
+	assert res == '123'.repeat(10).bytes()
+}
+
+fn test_read_all_huge() {
+	buf := Buf{
+		bytes: '123'.repeat(100000).bytes()
+	}
+	res := read_all(reader: buf) or {
+		assert false
+		''.bytes()
+	}
+	assert res == '123'.repeat(100000).bytes()
+}
+
+struct StringReader {
+	text string
+mut:
+	place int
+}
+
+fn (mut s StringReader) read(mut buf []byte) ?int {
+	if s.place >= s.text.len {
+		return none
+	}
+	read := copy(buf, s.text[s.place..].bytes())
+	s.place += read
+	return read
+}
+
+const (
+	newline_count = 100000
+)
+
+fn test_stringreader() {
+	text := '12345\n'.repeat(io.newline_count)
+	mut s := StringReader{
+		text: text
+	}
+	mut r := new_buffered_reader(reader: s)
+	for i := 0; true; i++ {
+		if _ := r.read_line() {
+		} else {
+			assert i == io.newline_count
+			break
+		}
+	}
+	if _ := r.read_line() {
+		assert false
+	}
+	leftover := read_all(reader: r) or {
+		assert false
+		panic('bad')
+	}
+	if leftover.len > 0 {
+		assert false
+	}
+}
+
+fn test_stringreader2() {
+	text := '12345\r\n'.repeat(io.newline_count)
+	mut s := StringReader{
+		text: text
+	}
+	mut r := new_buffered_reader(reader: s)
+	for i := 0; true; i++ {
+		if _ := r.read_line() {
+		} else {
+			assert i == io.newline_count
+			break
+		}
+	}
+	if _ := r.read_line() {
+		assert false
+	}
+	leftover := read_all(reader: r) or {
+		assert false
+		panic('bad')
+	}
+	if leftover.len > 0 {
+		assert false
+	}
+}
+
+fn test_leftover() {
+	text := 'This is a test\r\nNice try!'
+	mut s := StringReader{
+		text: text
+	}
+	mut r := new_buffered_reader(reader: s)
+	_ := r.read_line() or {
+		assert false
+		panic('bad')
+	}
+	line2 := r.read_line() or {
+		assert false
+		panic('bad')
+	}
+	assert line2 == 'Nice try!'
+	if _ := r.read_line() {
+		assert false
+		panic('bad')
+	}
+	assert r.end_of_stream()
+}
diff --git a/v_windows/v/vlib/io/readerwriter.v b/v_windows/v/vlib/io/readerwriter.v
new file mode 100644
index 0000000..ba44172
--- /dev/null
+++ b/v_windows/v/vlib/io/readerwriter.v
@@ -0,0 +1,34 @@
+module io
+
+// ReaderWriter represents a stream that can be read from and wrote to
+pub interface ReaderWriter {
+	// from Reader
+	read(mut buf []byte) ?int
+	// from Writer
+	write(buf []byte) ?int
+}
+
+// ReaderWriterImpl is a ReaderWriter that can be made from
+// a seperate reader and writer (see fn make_readerwriter)
+struct ReaderWriterImpl {
+	r Reader
+mut:
+	w Writer
+}
+
+pub fn (mut r ReaderWriterImpl) read(mut buf []byte) ?int {
+	return r.r.read(mut buf)
+}
+
+pub fn (mut r ReaderWriterImpl) write(buf []byte) ?int {
+	return r.w.write(buf)
+}
+
+// make_readerwriter takes a rstream and a wstream and makes
+// an rwstream with them
+pub fn make_readerwriter(r Reader, w Writer) ReaderWriterImpl {
+	return ReaderWriterImpl{
+		r: r
+		w: w
+	}
+}
diff --git a/v_windows/v/vlib/io/util/util.v b/v_windows/v/vlib/io/util/util.v
new file mode 100644
index 0000000..6f0d93f
--- /dev/null
+++ b/v_windows/v/vlib/io/util/util.v
@@ -0,0 +1,104 @@
+module util
+
+import os
+import rand
+import rand.seed as rseed
+
+const (
+	retries = 10000
+)
+
+pub struct TempFileOptions {
+	path    string = os.temp_dir()
+	pattern string
+}
+
+// temp_file returns an uniquely named, open, writable, `os.File` and it's path
+pub fn temp_file(tfo TempFileOptions) ?(os.File, string) {
+	mut d := tfo.path
+	if d == '' {
+		d = os.temp_dir()
+	}
+	os.is_writable_folder(d) or {
+		return error(@FN +
+			' could not create temporary file in "$d". Please ensure write permissions.')
+	}
+	d = d.trim_right(os.path_separator)
+	mut rng := rand.new_default()
+	prefix, suffix := prefix_and_suffix(tfo.pattern) or { return error(@FN + ' ' + err.msg) }
+	for retry := 0; retry < util.retries; retry++ {
+		path := os.join_path(d, prefix + random_number(mut rng) + suffix)
+		mut mode := 'rw+'
+		$if windows {
+			mode = 'w+'
+		}
+		mut file := os.open_file(path, mode, 0o600) or {
+			rng.seed(rseed.time_seed_array(2))
+			continue
+		}
+		if os.exists(path) && os.is_file(path) {
+			return file, path
+		}
+	}
+	return error(@FN +
+		' could not create temporary file in "$d". Retry limit ($util.retries) exhausted. Please ensure write permissions.')
+}
+
+pub struct TempDirOptions {
+	path    string = os.temp_dir()
+	pattern string
+}
+
+// temp_dir returns an uniquely named, writable, directory path
+pub fn temp_dir(tdo TempFileOptions) ?string {
+	mut d := tdo.path
+	if d == '' {
+		d = os.temp_dir()
+	}
+	os.is_writable_folder(d) or {
+		return error(@FN +
+			' could not create temporary directory "$d". Please ensure write permissions.')
+	}
+	d = d.trim_right(os.path_separator)
+	mut rng := rand.new_default()
+	prefix, suffix := prefix_and_suffix(tdo.pattern) or { return error(@FN + ' ' + err.msg) }
+	for retry := 0; retry < util.retries; retry++ {
+		path := os.join_path(d, prefix + random_number(mut rng) + suffix)
+		os.mkdir_all(path) or {
+			rng.seed(rseed.time_seed_array(2))
+			continue
+		}
+		if os.is_dir(path) && os.exists(path) {
+			os.is_writable_folder(path) or {
+				return error(@FN +
+					' could not create temporary directory "$d". Please ensure write permissions.')
+			}
+			return path
+		}
+	}
+	return error(@FN +
+		' could not create temporary directory "$d". Retry limit ($util.retries) exhausted. Please ensure write permissions.')
+}
+
+// * Utility functions
+fn random_number(mut rng rand.PRNG) string {
+	s := (u32(1e9) + (u32(os.getpid()) + rng.u32() % u32(1e9))).str()
+	return s.substr(1, s.len)
+}
+
+fn prefix_and_suffix(pattern string) ?(string, string) {
+	mut pat := pattern
+	if pat.contains(os.path_separator) {
+		return error('pattern cannot contain path separators ($os.path_separator).')
+	}
+	pos := pat.last_index('*') or { -1 }
+	mut prefix := ''
+	mut suffix := ''
+	if pos != -1 {
+		prefix = pat.substr(0, pos)
+		suffix = pat.substr(pos + 1, pat.len)
+	} else {
+		prefix = pat
+	}
+	return prefix, suffix
+}
diff --git a/v_windows/v/vlib/io/util/util_test.v b/v_windows/v/vlib/io/util/util_test.v
new file mode 100644
index 0000000..18f0164
--- /dev/null
+++ b/v_windows/v/vlib/io/util/util_test.v
@@ -0,0 +1,127 @@
+import os
+import io.util
+
+const (
+	// tfolder will contain all the temporary files/subfolders made by
+	// the different tests. It would be removed in testsuite_end(), so
+	// individual os tests do not need to clean up after themselves.
+	tfolder = os.join_path(os.temp_dir(), 'v', 'tests', 'io_util_test')
+)
+
+fn testsuite_begin() {
+	eprintln('testsuite_begin, tfolder = $tfolder')
+	os.rmdir_all(tfolder) or {}
+	assert !os.is_dir(tfolder)
+	os.mkdir_all(tfolder) or { panic(err) }
+	os.chdir(tfolder) or {}
+	assert os.is_dir(tfolder)
+}
+
+fn testsuite_end() {
+	os.chdir(os.wd_at_startup) or {}
+	os.rmdir_all(tfolder) or {}
+	assert !os.is_dir(tfolder)
+	// eprintln('testsuite_end  , tfolder = $tfolder removed.')
+}
+
+fn test_temp_file() {
+	// Test defaults
+	mut f, mut path := util.temp_file() or {
+		assert false
+		return
+	}
+	mut prev_path := path
+	defer {
+		f.close()
+	}
+	assert os.is_file(path)
+	assert f.is_opened
+	// Test pattern
+	f.close()
+	f, path = util.temp_file(
+		pattern: 'some_*_test.file'
+	) or {
+		assert false
+		return
+	}
+	assert path != prev_path
+	assert os.is_file(path)
+	assert f.is_opened
+	mut filename := os.file_name(path)
+	assert filename.contains('_test.file')
+	// Check for 9 digits where the wildcard is placed in the pattern
+	for i, c in filename {
+		if i > 4 && i <= 4 + 9 {
+			assert c.is_digit()
+		}
+	}
+	// Test custom path
+	prev_path = path
+	f.close()
+	f, path = util.temp_file(
+		path: tfolder
+	) or {
+		assert false
+		return
+	}
+	assert path != prev_path
+	assert os.is_file(path)
+	assert path.contains(tfolder)
+	assert f.is_opened
+	filename = os.file_name(path)
+	for c in filename {
+		assert c.is_digit()
+	}
+}
+
+fn test_temp_dir() {
+	// Test defaults
+	mut path := util.temp_dir() or {
+		assert false
+		return
+	}
+	assert os.is_dir(path)
+	mut writable := os.is_writable_folder(path) or {
+		assert false
+		return
+	}
+	assert writable
+	mut prev_path := path
+	// Test pattern
+	path = util.temp_dir(
+		pattern: 'some_*_test_dir'
+	) or {
+		assert false
+		return
+	}
+	assert path != prev_path
+	assert os.is_dir(path)
+	mut filename := os.file_name(path)
+	assert filename.contains('_test_dir')
+	// Check for 9 digits where the wildcard is placed in the pattern
+	for i, c in filename {
+		if i > 4 && i <= 4 + 9 {
+			assert c.is_digit()
+		}
+	}
+	// Test custom path
+	prev_path = path
+	path = util.temp_dir(
+		path: tfolder
+	) or {
+		assert false
+		return
+	}
+	assert path != prev_path
+	assert os.is_dir(path)
+	writable = os.is_writable_folder(path) or {
+		assert false
+		return
+	}
+	assert writable
+	assert path.contains(tfolder)
+	filename = os.file_name(path)
+	for c in filename {
+		assert c.is_digit()
+	}
+}
diff --git a/v_windows/v/vlib/io/writer.v b/v_windows/v/vlib/io/writer.v
new file mode 100644
index 0000000..322dd45
--- /dev/null
+++ b/v_windows/v/vlib/io/writer.v
@@ -0,0 +1,12 @@
+module io
+
+// Writer represents a stream of data that can be wrote to
+pub interface Writer {
+	write(buf []byte) ?int
+}
+
+// RandomWriter represents a stream of data that can be wrote to
+// at a random pos
+pub interface RandomWriter {
+	write_to(pos u64, buf []byte) ?int
+}