pcpcrypto_utils.go

package pcpcrypto

import (
	"bytes"
	"encoding/binary"
	"fmt"

	"golang.org/x/sys/windows"
)

// utf16BytesToString transforms a []byte which contains a wide char string in LE
// into its []uint16 corresponding representation,
// then returns the UTF-8 encoding of the UTF-16 sequence,
// with a terminating NUL removed. If after converting the []byte into
// a []uint16, there is a NUL uint16, the conversion to string stops
// at that NUL uint16.
func utf16BytesToString(buf []byte) (string, error) {

	if len(buf)%2 != 0 {
		return "", fmt.Errorf("input is not a valid byte representation of a wide char string in LE")
	}
	b := make([]uint16, len(buf)/2)

	// LPCSTR (Windows' representation of utf16) is always little endian.
	if err := binary.Read(bytes.NewReader(buf), binary.LittleEndian, b); err != nil {
		return "", err
	}
	return windows.UTF16ToString(b), nil
}

// stringToUtf16Bytes returns the UTF-16 encoding of the UTF-8 string
// str, as a byte array with a terminating NUL added. If str contains a NUL byte at any
// location, it returns (nil, EINVAL).
func stringToUtf16Bytes(str string) ([]byte, error) {
	if str == "" {
		return nil, nil
	}
	utf16Str, err := windows.UTF16FromString(str)
	if err != nil {
		return nil, err
	}
	bytesStr := make([]byte, len(utf16Str)*2)
	j := 0
	for _, utf16 := range utf16Str {
		b := make([]byte, 2)
		// LPCSTR (Windows' representation of utf16) is always little endian.
		binary.LittleEndian.PutUint16(b, utf16)
		bytesStr[j] = b[0]
		bytesStr[j+1] = b[1]
		j += 2
	}
	return bytesStr, nil
}