| // Copyright 2023 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //go:build ignore |
| // +build ignore |
| |
| package main |
| |
| // print-jpeg-markers.go prints a JPEG's markers' position and type. |
| // |
| // Usage: go run print-jpeg-markers.go foo.jpeg |
| |
| import ( |
| "fmt" |
| "os" |
| ) |
| |
| func main() { |
| if err := main1(); err != nil { |
| os.Stderr.WriteString(err.Error() + "\n") |
| os.Exit(1) |
| } |
| } |
| |
| func main1() error { |
| if len(os.Args) < 2 { |
| return fmt.Errorf("usage: progname filename.jpeg") |
| } |
| src, err := os.ReadFile(os.Args[1]) |
| if err != nil { |
| return err |
| } |
| |
| pos := 0 |
| if len(src) < 2 { |
| return posError(pos) |
| } |
| for pos <= (len(src) - 2) { |
| if src[pos] != 0xFF { |
| return posError(pos) |
| } |
| marker := src[pos+1] |
| fmt.Printf("pos = 0x%08X = %10d marker = 0xFF 0x%02X %s\n", pos, pos, marker, names[marker]) |
| pos += 2 |
| switch { |
| case (0xD0 <= marker) && (marker < 0xD9): |
| // RSTn (Restart) and SOI (Start Of Image) markers have no payload. |
| continue |
| case marker == 0xD9: |
| // EOI (End Of Image) marker. |
| return nil |
| } |
| |
| if pos >= (len(src) - 2) { |
| return posError(pos) |
| } |
| payloadLength := (int(src[pos]) << 8) | int(src[pos+1]) |
| pos += payloadLength |
| if (payloadLength < 2) || (pos < 0) || (pos > len(src)) { |
| return posError(pos) |
| } |
| |
| if marker != 0xDA { // SOS (Start Of Scan) marker. |
| continue |
| } |
| for pos < len(src) { |
| if src[pos] != 0xFF { |
| pos += 1 |
| } else if pos >= (len(src) - 1) { |
| return posError(pos) |
| } else if m := src[pos+1]; (m != 0x00) && ((m < 0xD0) || (0xD7 < m)) { |
| break |
| } else { |
| pos += 2 |
| } |
| } |
| } |
| return posError(pos) |
| } |
| |
| func posError(pos int) error { |
| return fmt.Errorf("invalid JPEG at pos = 0x%08X = %10d", pos, pos) |
| } |
| |
| var names = [256]string{ |
| 0xC0: "SOF0 (Sequential/Baseline)", |
| 0xC1: "SOF1 (Sequential/Extended)", |
| 0xC2: "SOF2 (Progressive)", |
| 0xC3: "SOF3", |
| 0xC4: "DHT", |
| 0xC5: "SOF5", |
| 0xC6: "SOF6", |
| 0xC7: "SOF7", |
| |
| 0xC8: "JPG", |
| 0xC9: "SOF9", |
| 0xCA: "SOF10", |
| 0xCB: "SOF11", |
| 0xCC: "DAC", |
| 0xCD: "SOF13", |
| 0xCE: "SOF14", |
| 0xCF: "SOF15", |
| |
| 0xD0: "RST0", |
| 0xD1: "RST1", |
| 0xD2: "RST2", |
| 0xD3: "RST3", |
| 0xD4: "RST4", |
| 0xD5: "RST5", |
| 0xD6: "RST6", |
| 0xD7: "RST7", |
| |
| 0xD8: "SOI", |
| 0xD9: "EOI", |
| 0xDA: "SOS", |
| 0xDB: "DQT", |
| 0xDC: "DNL", |
| 0xDD: "DRI", |
| 0xDE: "DHP", |
| 0xDF: "EXP", |
| |
| 0xE0: "APP0", |
| 0xE1: "APP1", |
| 0xE2: "APP2", |
| 0xE3: "APP3", |
| 0xE4: "APP4", |
| 0xE5: "APP5", |
| 0xE6: "APP6", |
| 0xE7: "APP7", |
| |
| 0xE8: "APP8", |
| 0xE9: "APP9", |
| 0xEA: "APP10", |
| 0xEB: "APP11", |
| 0xEC: "APP12", |
| 0xED: "APP13", |
| 0xEE: "APP14", |
| 0xEF: "APP15", |
| |
| 0xFE: "COM", |
| } |