//
// Copyright (c) SAS Institute Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

package authenticode

// MSI table names are packed in pairs into a Chinese codepoint which then
// becomes 2 bytes of UTF-16. This seems to be an attempt to support longer
// table names than CDF would otherwise allow but it's incredibly silly.
func msiDecodeName(msiName string) string {
	out := ""
	for _, x := range msiName {
		if x >= 0x3800 && x < 0x4800 {
			x -= 0x3800
			out += string(msiDecodeRune(x&0x3f)) + string(msiDecodeRune(x>>6))
		} else if x >= 0x4800 && x < 0x4840 {
			x -= 0x4800
			out += string(msiDecodeRune(x))
		} else if x == 0x4840 {
			out += "Table."
		} else {
			out += string(x)
		}
	}
	return out
}

func msiDecodeRune(x rune) rune {
	if x < 10 {
		return x + '0'
	} else if x < 10+26 {
		return x - 10 + 'A'
	} else if x < 10+26+26 {
		return x - 10 - 26 + 'a'
	} else if x == 10+26+26 {
		return '.'
	} else {
		return '_'
	}
}