go-windows-mbcs

Convert between UTF-8 and ANSI (non-UTF-8) character encodings using Windows APIs: MultiByteToWideChar and WideCharToMultiByte.

Although this library primarily uses Windows APIs, it also emulates similar functionality on Linux by inspecting the $LANG or $LC_ALL environment variables. (See below for details.)

Convert from ANSI-bytes to UTF8-strings

package main

import (
    "bufio"
    "fmt"
    "os"

    "github.com/nyaosorg/go-windows-mbcs"
)

func main() {
    sc := bufio.NewScanner(os.Stdin)
    for sc.Scan() {
        text, err := mbcs.AnsiToUtf8(sc.Bytes(), mbcs.ACP)
        if err != nil {
            fmt.Fprintln(os.Stderr, err.Error())
            os.Exit(1)
        }
        fmt.Println(text)
    }
    if err := sc.Err(); err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        os.Exit(1)
    }
}

mbcs.ACP represents the current code page.

On Windows

$ chcp 932
$ go run examples\AnsiToUtf8.go < testdata\jugemu-cp932.txt | nkf32 --guess
UTF-8 (LF)

On Linux

$ env LC_ALL=ja_JP.Shift_JIS go run examples/AnsiToUtf8.go < testdata/jugemu-cp932.txt | nkf --guess
UTF-8 (LF)

On non-Windows systems, the current encoding is determined based on the $LC_ALL and $LANG environment variables.

Convert from UTF8-strings to ANSI-bytes

package main

import (
    "bufio"
    "fmt"
    "os"

    "github.com/nyaosorg/go-windows-mbcs"
)

func main() {
    sc := bufio.NewScanner(os.Stdin)
    for sc.Scan() {
        bytes, err := mbcs.Utf8ToAnsi(sc.Text(), mbcs.ACP)
        if err != nil {
            fmt.Fprintln(os.Stderr, err.Error())
            os.Exit(1)
        }
        os.Stdout.Write(bytes)
        os.Stdout.Write([]byte{'\n'})
    }
    if err := sc.Err(); err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        os.Exit(1)
    }
}

On Windows

$ chcp 932
$ go run examples\Utf8ToAnsi.go < testdata\jugemu-utf8.txt | nkf32 --guess
Shift_JIS (LF)

On Linux

$ env LC_ALL=ja_JP.Shift_JIS go run examples/Utf8ToAnsi.go < testdata/jugemu-utf8.txt | nkf --guess
Shift_JIS (LF)

Use golang.org/x/text/transform

Convert from an ANSI reader to a UTF-8 reader

package main

import (
    "bufio"
    "fmt"
    "os"

    "golang.org/x/text/transform"

    "github.com/nyaosorg/go-windows-mbcs"
)

func main() {
    sc := bufio.NewScanner(transform.NewReader(os.Stdin, mbcs.NewDecoder(mbcs.ACP)))
    for sc.Scan() {
        fmt.Println(sc.Text())
    }
    if err := sc.Err(); err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        os.Exit(1)
    }
}

On Windows

$ chcp 932
$ go run examples\NewDecoder.go < testdata\jugemu-cp932.txt | nkf32 --guess
UTF-8 (LF)

On Linux

$ env LC_ALL=ja_JP.Shift_JIS go run examples/NewDecoder.go < testdata/jugemu-cp932.txt  | nkf --guess
UTF-8 (LF)

Convert from a UTF-8 reader to an ANSI reader

package main

import (
    "bufio"
    "fmt"
    "os"

    "golang.org/x/text/transform"

    "github.com/nyaosorg/go-windows-mbcs"
)

func main() {
    sc := bufio.NewScanner(transform.NewReader(os.Stdin, mbcs.NewEncoder(mbcs.ACP)))
    for sc.Scan() {
        os.Stdout.Write(sc.Bytes())
        os.Stdout.Write([]byte{'\n'})
    }
    if err := sc.Err(); err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        os.Exit(1)
    }
}

On Windows

$ chcp 932
$ go run examples\NewEncoder.go < testdata/jugemu-utf8.txt  | nkf32 --guess
Shift_JIS (LF)

On Linux

$ env LC_ALL=ja_JP.Shift_JIS go run examples/NewEncoder.go < testdata/jugemu-utf8.txt  | nkf --guess
Shift_JIS (LF)

Platform notes

On non-Windows (e.g. Linux)

This library also supports Linux and other non-Windows platforms, where Windows API is not available.

On such platforms, the current encoding is heuristically determined using the environment variables $LC_ALL and $LANG. The encoding name specified in these variables (such as ja_JP.SJIS) is matched against known encodings via golang.org/x/text/encoding/ianaindex.IANA. If a suitable match is found, the library will convert between UTF-8 and the specified encoding accordingly.

⚠️ Note: This approach is best-effort and currently verified only for Japanese encodings. Use with caution in other locales.

Author

hymkor (HAYAMA Kaoru)

License

MIT LICENSE