os: fix binary mode read/write on windows (#6431)

vlib/os/const_nix.c.v

@@ -6,6 +6,7 @@ const (
 	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_binary    = 000008000 // input and output is not translated.
 	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.

vlib/os/const_windows.c.v

@@ -100,6 +100,7 @@ const (
 	o_rdwr                             = 0x0002 // 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_binary                           = 0x8000 // input and output is not translated.
 	o_trunc                            = 0x0200 // truncate regular writable file when opened.
 	o_excl                             = 0x0400 // used with o_create, file must not exist.
 	o_sync                             = 0x0000 // open for synchronous I/O (ignored on Windows)

vlib/os/os.v

@@ -267,6 +267,7 @@ pub fn open_file(path string, mode string, options ...int) ?File {
 		match m {
 			`r` { flags |= o_rdonly }
 			`w` { flags |= o_create | o_trunc }
+			`b` { flags |= o_binary }
 			`a` { flags |= o_create | o_append }
 			`s` { flags |= o_sync }
 			`n` { flags |= o_nonblock }

vlib/os/os_test.v

@@ -43,6 +43,27 @@ fn test_open_file() {
 	os.rm(filename)
 }
 
+fn test_open_file_binary() {
+	filename := './test1.dat'
+	hello := 'hello \n world!'
+	os.open_file(filename, 'r+', 0o666) or {
+		assert err == 'No such file or directory'
+		os.File{}
+	}
+	mut file := os.open_file(filename, 'wb+', 0o666) or {
+		panic(err)
+	}
+	bytes := hello.bytes()
+	file.write_bytes(bytes.data, bytes.len)
+	file.close()
+	assert hello.len == os.file_size(filename)
+	read_hello := os.read_bytes(filename) or {
+		panic('error reading file $filename')
+	}
+	assert bytes == read_hello
+	os.rm(filename)
+}
+
 fn test_file_get_line() {
 	filename := './fgetline.txt'
 	os.write_file(filename, 'line 1\nline 2')
@@ -50,8 +71,12 @@ fn test_file_get_line() {
 		assert false
 		return
 	}
-	line1 := f.get_line() or { '' }
+	line1 := f.get_line() or {
-	line2 := f.get_line() or { '' }
+		''
+	}
+	line2 := f.get_line() or {
+		''
+	}
 	f.close()
 	//
 	// eprintln('line1: $line1')
@@ -119,33 +144,25 @@ fn test_write_and_read_string_to_file() {
 fn test_write_and_read_bytes() {
 	file_name := './byte_reader_writer.tst'
 	payload := [byte(`I`), `D`, `D`, `Q`, `D`]
-
 	mut file_write := os.create(os.real_path(file_name)) or {
 		eprintln('failed to create file $file_name')
 		return
 	}
-
 	// We use the standard write_bytes function to write the payload and
 	// compare the length of the array with the file size (have to match).
 	file_write.write_bytes(payload.data, 5)
-
 	file_write.close()
-
 	assert payload.len == os.file_size(file_name)
-
 	mut file_read := os.open(os.real_path(file_name)) or {
 		eprintln('failed to open file $file_name')
 		return
 	}
-
 	// We only need to test read_bytes because this function calls
 	// read_bytes_at with second parameter zeroed (size, 0).
 	rbytes := file_read.read_bytes(5)
-
 	// eprintln('rbytes: $rbytes')
 	// eprintln('payload: $payload')
 	assert rbytes == payload
-
 	// check that trying to read data from EOF doesn't error and returns 0
 	mut a := []byte{len: 5}
 	nread := file_read.read_bytes_into(5, a) or {
@@ -153,7 +170,6 @@ fn test_write_and_read_bytes() {
 		int(-1)
 	}
 	assert nread == 0
-
 	file_read.close()
 	// We finally delete the test file.
 	os.rm(file_name)