108 lines
2.0 KiB
Go
108 lines
2.0 KiB
Go
/*
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Copyright 2024 Josh Deprez
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package atalk
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import (
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"math/bits"
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"github.com/sfiera/multitalk/pkg/ethernet"
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"github.com/sfiera/multitalk/pkg/ethertalk"
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)
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// Inside AppleTalk, appendix D
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var toUpperMap = [256]byte{
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// The alphabet
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0x61: 0x41,
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0x62: 0x42,
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0x63: 0x43,
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0x64: 0x44,
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0x65: 0x45,
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0x66: 0x46,
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0x67: 0x47,
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0x68: 0x48,
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0x69: 0x49,
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0x6A: 0x4A,
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0x6B: 0x4B,
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0x6C: 0x4C,
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0x6D: 0x4D,
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0x6E: 0x4E,
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0x6F: 0x4F,
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0x70: 0x50,
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0x71: 0x51,
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0x72: 0x52,
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0x73: 0x53,
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0x74: 0x54,
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0x75: 0x55,
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0x76: 0x56,
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0x77: 0x57,
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0x78: 0x58,
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0x79: 0x59,
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0x7A: 0x5A,
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// Letters with diacritics, etc
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0x88: 0xCB,
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0x8A: 0x80,
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0x8B: 0xCC,
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0x8C: 0x81,
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0x8D: 0x82,
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0x8E: 0x83,
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0x96: 0x84,
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0x9A: 0x85,
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0x9B: 0xCD,
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0x9F: 0x86,
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0xBE: 0xAE,
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0xBF: 0xAF,
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0xCF: 0xCE,
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}
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func Checksum(s string) uint16 {
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// Inside AppleTalk, pp 4-17 and pp 8-18
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var cksum uint16
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for _, b := range []byte(s) {
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cksum += uint16(b)
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cksum = bits.RotateLeft16(cksum, -1)
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}
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if cksum == 0 {
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cksum = 0xFFFF
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}
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return cksum
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}
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func ToUpper(s string) string {
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// Inside Appletalk, appendix D
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sb := []byte(s)
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out := make([]byte, len(sb))
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for i, b := range sb {
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if u := toUpperMap[b]; u != 0 {
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out[i] = u
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} else {
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out[i] = b
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}
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}
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return string(out)
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}
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func MulticastAddr(zone string) ethernet.Addr {
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if zone == "" || zone == "*" {
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return ethertalk.AppleTalkBroadcast
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}
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// Inside AppleTalk, pp 3-10 and pp 8-18
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h := Checksum(ToUpper(zone))
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return ethernet.Addr{0x09, 0x00, 0x07, 0x00, 0x00, byte(h % 0xFD)}
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}
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