File: bitdump.go 1 /* 2 The MIT License (MIT) 3 4 Copyright © 2025 pacman64 5 6 Permission is hereby granted, free of charge, to any person obtaining a copy of 7 this software and associated documentation files (the “Software”), to deal 8 in the Software without restriction, including without limitation the rights to 9 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies 10 of the Software, and to permit persons to whom the Software is furnished to do 11 so, subject to the following conditions: 12 13 The above copyright notice and this permission notice shall be included in all 14 copies or substantial portions of the Software. 15 16 THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 19 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 21 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 SOFTWARE. 23 */ 24 25 /* 26 To compile a smaller-sized command-line app, you can use the `go` command as 27 follows: 28 29 go build -ldflags "-s -w" -trimpath bitdump.go 30 */ 31 32 package main 33 34 import ( 35 "bufio" 36 "errors" 37 "io" 38 "os" 39 "strconv" 40 ) 41 42 // Note: the code is avoiding using the fmt package to save hundreds of 43 // kilobytes on the resulting executable, which is a noticeable difference. 44 45 const info = ` 46 bitdump [options...] [filenames...] 47 48 49 Show all bits for all input bytes, starting each output line with the 50 leading byte's offset. 51 52 All (optional) leading options start with either single or double-dash: 53 54 -h show this help message 55 -help show this help message 56 ` 57 58 const itemsPerLine = 8 59 60 // errNoMoreOutput is a dummy error whose message is ignored, and which 61 // causes the app to quit immediately and successfully 62 var errNoMoreOutput = errors.New(`no more output`) 63 64 func main() { 65 if len(os.Args) > 1 { 66 switch os.Args[1] { 67 case `-h`, `--h`, `-help`, `--help`: 68 os.Stderr.WriteString(info[1:]) 69 return 70 } 71 } 72 73 if err := run(os.Stdout, os.Args[1:]); isActualError(err) { 74 os.Stderr.WriteString(err.Error()) 75 os.Stderr.WriteString("\n") 76 os.Exit(1) 77 } 78 } 79 80 func run(w io.Writer, args []string) error { 81 offset := 0 82 bw := bufio.NewWriter(w) 83 defer func() { 84 if offset%itemsPerLine == 0 && offset > 0 { 85 bw.WriteByte('\n') 86 } 87 bw.Flush() 88 }() 89 90 if len(args) == 0 { 91 return bitdump(bw, os.Stdin, &offset) 92 } 93 94 for _, name := range args { 95 if err := handleFile(bw, name, &offset); err != nil { 96 return err 97 } 98 } 99 return nil 100 } 101 102 func handleFile(w *bufio.Writer, name string, offset *int) error { 103 if name == `` || name == `-` { 104 return bitdump(w, os.Stdin, offset) 105 } 106 107 f, err := os.Open(name) 108 if err != nil { 109 return errors.New(`can't read from file named "` + name + `"`) 110 } 111 defer f.Close() 112 113 return bitdump(w, f, offset) 114 } 115 116 // isActualError is to figure out whether not to ignore an error, and thus 117 // show it as an error message 118 func isActualError(err error) bool { 119 return err != nil && err != io.EOF && err != errNoMoreOutput 120 } 121 122 func bitdump(w *bufio.Writer, r io.Reader, offset *int) error { 123 var buf [32 * 1024]byte 124 defer w.Flush() 125 126 for { 127 n, err := r.Read(buf[:]) 128 if n < 1 && err == io.EOF { 129 return nil 130 } 131 132 if err != nil && err != io.EOF { 133 return err 134 } 135 136 chunk := buf[:n] 137 138 for len(chunk) >= itemsPerLine { 139 if err := emitChunk(w, chunk[:itemsPerLine], offset); err != nil { 140 return err 141 } 142 143 chunk = chunk[itemsPerLine:] 144 *offset += itemsPerLine 145 } 146 147 if len(chunk) > 0 { 148 if err := emitChunk(w, chunk, offset); err != nil { 149 return err 150 } 151 152 *offset += len(chunk) 153 } 154 } 155 } 156 157 func emitChunk(w *bufio.Writer, chunk []byte, offset *int) error { 158 const pad = `00000000` 159 var str [24]byte 160 161 if *offset%itemsPerLine == 0 { 162 if *offset > 0 { 163 if err := w.WriteByte('\n'); err != nil { 164 // assume a write error is the consequence of stdout 165 // being closed, perhaps by another app along a pipe 166 return errNoMoreOutput 167 } 168 } 169 170 s := strconv.AppendInt(str[:0], int64(*offset), 10) 171 // pad small offsets with leading zeros 172 if len(s) < len(pad) { 173 w.WriteString(pad[len(s):]) 174 } 175 w.Write(s) 176 } 177 178 for _, b := range chunk { 179 w.WriteByte(' ') 180 w.WriteString(bits[b]) 181 } 182 return nil 183 } 184 185 /* 186 tlp = '(f"{bin(v)[2:]:>08}" for v in range(256))' | lineup 6 | 187 gsub '\t' '`, `' | tlp 'f"\t`{l}`,"' 188 */ 189 var bits = [256]string{ 190 `00000000`, `00000001`, `00000010`, `00000011`, `00000100`, `00000101`, 191 `00000110`, `00000111`, `00001000`, `00001001`, `00001010`, `00001011`, 192 `00001100`, `00001101`, `00001110`, `00001111`, `00010000`, `00010001`, 193 `00010010`, `00010011`, `00010100`, `00010101`, `00010110`, `00010111`, 194 `00011000`, `00011001`, `00011010`, `00011011`, `00011100`, `00011101`, 195 `00011110`, `00011111`, `00100000`, `00100001`, `00100010`, `00100011`, 196 `00100100`, `00100101`, `00100110`, `00100111`, `00101000`, `00101001`, 197 `00101010`, `00101011`, `00101100`, `00101101`, `00101110`, `00101111`, 198 `00110000`, `00110001`, `00110010`, `00110011`, `00110100`, `00110101`, 199 `00110110`, `00110111`, `00111000`, `00111001`, `00111010`, `00111011`, 200 `00111100`, `00111101`, `00111110`, `00111111`, `01000000`, `01000001`, 201 `01000010`, `01000011`, `01000100`, `01000101`, `01000110`, `01000111`, 202 `01001000`, `01001001`, `01001010`, `01001011`, `01001100`, `01001101`, 203 `01001110`, `01001111`, `01010000`, `01010001`, `01010010`, `01010011`, 204 `01010100`, `01010101`, `01010110`, `01010111`, `01011000`, `01011001`, 205 `01011010`, `01011011`, `01011100`, `01011101`, `01011110`, `01011111`, 206 `01100000`, `01100001`, `01100010`, `01100011`, `01100100`, `01100101`, 207 `01100110`, `01100111`, `01101000`, `01101001`, `01101010`, `01101011`, 208 `01101100`, `01101101`, `01101110`, `01101111`, `01110000`, `01110001`, 209 `01110010`, `01110011`, `01110100`, `01110101`, `01110110`, `01110111`, 210 `01111000`, `01111001`, `01111010`, `01111011`, `01111100`, `01111101`, 211 `01111110`, `01111111`, `10000000`, `10000001`, `10000010`, `10000011`, 212 `10000100`, `10000101`, `10000110`, `10000111`, `10001000`, `10001001`, 213 `10001010`, `10001011`, `10001100`, `10001101`, `10001110`, `10001111`, 214 `10010000`, `10010001`, `10010010`, `10010011`, `10010100`, `10010101`, 215 `10010110`, `10010111`, `10011000`, `10011001`, `10011010`, `10011011`, 216 `10011100`, `10011101`, `10011110`, `10011111`, `10100000`, `10100001`, 217 `10100010`, `10100011`, `10100100`, `10100101`, `10100110`, `10100111`, 218 `10101000`, `10101001`, `10101010`, `10101011`, `10101100`, `10101101`, 219 `10101110`, `10101111`, `10110000`, `10110001`, `10110010`, `10110011`, 220 `10110100`, `10110101`, `10110110`, `10110111`, `10111000`, `10111001`, 221 `10111010`, `10111011`, `10111100`, `10111101`, `10111110`, `10111111`, 222 `11000000`, `11000001`, `11000010`, `11000011`, `11000100`, `11000101`, 223 `11000110`, `11000111`, `11001000`, `11001001`, `11001010`, `11001011`, 224 `11001100`, `11001101`, `11001110`, `11001111`, `11010000`, `11010001`, 225 `11010010`, `11010011`, `11010100`, `11010101`, `11010110`, `11010111`, 226 `11011000`, `11011001`, `11011010`, `11011011`, `11011100`, `11011101`, 227 `11011110`, `11011111`, `11100000`, `11100001`, `11100010`, `11100011`, 228 `11100100`, `11100101`, `11100110`, `11100111`, `11101000`, `11101001`, 229 `11101010`, `11101011`, `11101100`, `11101101`, `11101110`, `11101111`, 230 `11110000`, `11110001`, `11110010`, `11110011`, `11110100`, `11110101`, 231 `11110110`, `11110111`, `11111000`, `11111001`, `11111010`, `11111011`, 232 `11111100`, `11111101`, `11111110`, `11111111`, 233 }