File: bitdump.go 1 /* 2 The MIT License (MIT) 3 4 Copyright © 2026 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, -help show this help message 55 -no-offset, -no-offsets don't start lines with current byte offsets 56 -tab, -tabs separate items with tabs instead of spaces 57 ` 58 59 const itemsPerLine = 8 60 61 // errNoMoreOutput is a dummy error whose message is ignored, and which 62 // causes the app to quit immediately and successfully 63 var errNoMoreOutput = errors.New(`no more output`) 64 65 func main() { 66 emitOffsets := true 67 separator := byte(' ') 68 args := os.Args[1:] 69 70 out: 71 for len(args) > 0 { 72 switch args[0] { 73 case `-h`, `--h`, `-help`, `--help`: 74 os.Stdout.WriteString(info[1:]) 75 return 76 case `-no-offset`, `--no-offset`, `-no-offsets`, `--no-offsets`: 77 emitOffsets = false 78 args = args[1:] 79 case `-tab`, `--tab`, `-tabs`, `--tabs`: 80 separator = '\t' 81 args = args[1:] 82 default: 83 break out 84 } 85 } 86 87 if len(args) > 0 && args[0] == `--` { 88 args = args[1:] 89 } 90 91 var p params 92 p.emitOffset = emitNoOffset 93 if emitOffsets { 94 p.emitOffset = emitDecimalOffset 95 } 96 p.separator = separator 97 98 if err := run(os.Stdout, p, args); isActualError(err) { 99 os.Stderr.WriteString(err.Error()) 100 os.Stderr.WriteString("\n") 101 os.Exit(1) 102 } 103 } 104 105 type params struct { 106 offset *int64 107 emitOffset func(w *bufio.Writer, offset int64, sep byte) 108 separator byte 109 } 110 111 func run(w io.Writer, p params, args []string) error { 112 offset := int64(0) 113 p.offset = &offset 114 bw := bufio.NewWriter(w) 115 defer func() { 116 if offset%itemsPerLine == 0 && offset > 0 { 117 bw.WriteByte('\n') 118 } 119 bw.Flush() 120 }() 121 122 if len(args) == 0 { 123 return bitdump(bw, os.Stdin, p) 124 } 125 126 for _, name := range args { 127 if err := handleFile(bw, name, p); err != nil { 128 return err 129 } 130 } 131 return nil 132 } 133 134 func handleFile(w *bufio.Writer, name string, p params) error { 135 if name == `` || name == `-` { 136 return bitdump(w, os.Stdin, p) 137 } 138 139 f, err := os.Open(name) 140 if err != nil { 141 return errors.New(`can't read from file named "` + name + `"`) 142 } 143 defer f.Close() 144 145 return bitdump(w, f, p) 146 } 147 148 // isActualError is to figure out whether not to ignore an error, and thus 149 // show it as an error message 150 func isActualError(err error) bool { 151 return err != nil && err != io.EOF && err != errNoMoreOutput 152 } 153 154 func bitdump(w *bufio.Writer, r io.Reader, p params) error { 155 var buf [32 * 1024]byte 156 defer w.Flush() 157 158 for { 159 n, err := r.Read(buf[:]) 160 if n < 1 && err == io.EOF { 161 return nil 162 } 163 164 if err != nil && err != io.EOF { 165 return err 166 } 167 168 chunk := buf[:n] 169 170 for len(chunk) >= itemsPerLine { 171 if err := emitChunk(w, chunk[:itemsPerLine], p); err != nil { 172 return err 173 } 174 175 chunk = chunk[itemsPerLine:] 176 *p.offset += itemsPerLine 177 } 178 179 if len(chunk) > 0 { 180 if err := emitChunk(w, chunk, p); err != nil { 181 return err 182 } 183 184 *p.offset += int64(len(chunk)) 185 } 186 } 187 } 188 189 func emitDecimalOffset(w *bufio.Writer, offset int64, sep byte) { 190 const pad = `00000000` 191 var str [24]byte 192 193 s := strconv.AppendInt(str[:0], offset, 10) 194 // pad small offsets with leading zeros 195 if len(s) < len(pad) { 196 w.WriteString(pad[len(s):]) 197 } 198 w.Write(s) 199 w.WriteByte(sep) 200 } 201 202 func emitNoOffset(w *bufio.Writer, offset int64, sep byte) { 203 // deliberately does nothing 204 } 205 206 func emitChunk(w *bufio.Writer, chunk []byte, p params) error { 207 p.emitOffset(w, *p.offset, p.separator) 208 for i, b := range chunk { 209 if i > 0 { 210 w.WriteByte(p.separator) 211 } 212 w.WriteString(bits[b]) 213 } 214 215 if err := w.WriteByte('\n'); err != nil { 216 // assume a write error is the consequence of stdout 217 // being closed, perhaps by another app along a pipe 218 return errNoMoreOutput 219 } 220 return nil 221 } 222 223 /* 224 tlp = '(f"{bin(v)[2:]:>08}" for v in range(256))' | lineup 6 | 225 gsub '\t' '`, `' | tlp 'f"\t`{l}`,"' 226 */ 227 var bits = [256]string{ 228 `00000000`, `00000001`, `00000010`, `00000011`, `00000100`, `00000101`, 229 `00000110`, `00000111`, `00001000`, `00001001`, `00001010`, `00001011`, 230 `00001100`, `00001101`, `00001110`, `00001111`, `00010000`, `00010001`, 231 `00010010`, `00010011`, `00010100`, `00010101`, `00010110`, `00010111`, 232 `00011000`, `00011001`, `00011010`, `00011011`, `00011100`, `00011101`, 233 `00011110`, `00011111`, `00100000`, `00100001`, `00100010`, `00100011`, 234 `00100100`, `00100101`, `00100110`, `00100111`, `00101000`, `00101001`, 235 `00101010`, `00101011`, `00101100`, `00101101`, `00101110`, `00101111`, 236 `00110000`, `00110001`, `00110010`, `00110011`, `00110100`, `00110101`, 237 `00110110`, `00110111`, `00111000`, `00111001`, `00111010`, `00111011`, 238 `00111100`, `00111101`, `00111110`, `00111111`, `01000000`, `01000001`, 239 `01000010`, `01000011`, `01000100`, `01000101`, `01000110`, `01000111`, 240 `01001000`, `01001001`, `01001010`, `01001011`, `01001100`, `01001101`, 241 `01001110`, `01001111`, `01010000`, `01010001`, `01010010`, `01010011`, 242 `01010100`, `01010101`, `01010110`, `01010111`, `01011000`, `01011001`, 243 `01011010`, `01011011`, `01011100`, `01011101`, `01011110`, `01011111`, 244 `01100000`, `01100001`, `01100010`, `01100011`, `01100100`, `01100101`, 245 `01100110`, `01100111`, `01101000`, `01101001`, `01101010`, `01101011`, 246 `01101100`, `01101101`, `01101110`, `01101111`, `01110000`, `01110001`, 247 `01110010`, `01110011`, `01110100`, `01110101`, `01110110`, `01110111`, 248 `01111000`, `01111001`, `01111010`, `01111011`, `01111100`, `01111101`, 249 `01111110`, `01111111`, `10000000`, `10000001`, `10000010`, `10000011`, 250 `10000100`, `10000101`, `10000110`, `10000111`, `10001000`, `10001001`, 251 `10001010`, `10001011`, `10001100`, `10001101`, `10001110`, `10001111`, 252 `10010000`, `10010001`, `10010010`, `10010011`, `10010100`, `10010101`, 253 `10010110`, `10010111`, `10011000`, `10011001`, `10011010`, `10011011`, 254 `10011100`, `10011101`, `10011110`, `10011111`, `10100000`, `10100001`, 255 `10100010`, `10100011`, `10100100`, `10100101`, `10100110`, `10100111`, 256 `10101000`, `10101001`, `10101010`, `10101011`, `10101100`, `10101101`, 257 `10101110`, `10101111`, `10110000`, `10110001`, `10110010`, `10110011`, 258 `10110100`, `10110101`, `10110110`, `10110111`, `10111000`, `10111001`, 259 `10111010`, `10111011`, `10111100`, `10111101`, `10111110`, `10111111`, 260 `11000000`, `11000001`, `11000010`, `11000011`, `11000100`, `11000101`, 261 `11000110`, `11000111`, `11001000`, `11001001`, `11001010`, `11001011`, 262 `11001100`, `11001101`, `11001110`, `11001111`, `11010000`, `11010001`, 263 `11010010`, `11010011`, `11010100`, `11010101`, `11010110`, `11010111`, 264 `11011000`, `11011001`, `11011010`, `11011011`, `11011100`, `11011101`, 265 `11011110`, `11011111`, `11100000`, `11100001`, `11100010`, `11100011`, 266 `11100100`, `11100101`, `11100110`, `11100111`, `11101000`, `11101001`, 267 `11101010`, `11101011`, `11101100`, `11101101`, `11101110`, `11101111`, 268 `11110000`, `11110001`, `11110010`, `11110011`, `11110100`, `11110101`, 269 `11110110`, `11110111`, `11111000`, `11111001`, `11111010`, `11111011`, 270 `11111100`, `11111101`, `11111110`, `11111111`, 271 }