How Can I Correctly Read a UTF-16 Text File as a String in Go?

Reading a UTF-16 Text File as a String in Go

Understanding the Issue

When reading a UTF-16 text file into a byte array using standard input methods, the file's UTF-16 encoded characters may not be correctly interpreted. This can result in the bytes being treated as ASCII, leading to incorrect string representations.

Solution using UTF-16 Decoding

To properly read a UTF-16 text file, it is crucial to use methods specifically designed to handle UTF-16 encoding. The golang.org/x/text/encoding/unicode package provides the necessary functionality for this purpose.

ReadFileUTF16() Function

func ReadFileUTF16(filename string) ([]byte, error) {
    // Read the file into a byte array
    raw, err := ioutil.ReadFile(filename)
    if err != nil {
        return nil, err
    }

    // Create a transformer that converts MS-Windows default to UTF8
    win16be := unicode.UTF16(unicode.BigEndian, unicode.IgnoreBOM)

    // Override the BOM to ensure it is respected
    utf16bom := unicode.BOMOverride(win16be.NewDecoder())

    // Apply the transformer to the input byte array
    unicodeReader := transform.NewReader(bytes.NewReader(raw), utf16bom)

    // Decode the data into a new byte array
    decoded, err := ioutil.ReadAll(unicodeReader)
    return decoded, err
}

NewScannerUTF16() Function

For scenarios where reading the entire file is not feasible, the following function creates a scanner that uses the same UTF-16 decoding logic:

func NewScannerUTF16(filename string) (utfScanner, error) {
    // Read the file into a []byte
    file, err := os.Open(filename)
    if err != nil {
        return nil, err
    }

    // Create a transformer that converts MS-Windows default to UTF8
    win16be := unicode.UTF16(unicode.BigEndian, unicode.IgnoreBOM)

    // Override the BOM to ensure it is respected
    utf16bom := unicode.BOMOverride(win16be.NewDecoder())

    // Apply the transformer to the input file
    unicodeReader := transform.NewReader(file, utf16bom)
    return unicodeReader, nil
}

Discussion on BOM and Unicode Support

The golang.org/x/text/encoding/unicode package intelligently interprets Byte Order Marks (BOMs) to determine the encoding used in the file. However, it is important to note that the bufio package's ReadLine function does not support Unicode decoding.

Further Resources

For additional customization and options related to UTF-16 decoding, refer to the open source module at https://github.com/TomOnTime/utfutil/.

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