chore(internal/format): support canon CR3 format

internal/format/cr3.go

@@ -0,0 +1,130 @@
+// Copyright (c) 2025 Stefano Scafiti
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+package format
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+var (
+	CR3Magic  = []byte{0x00, 0x00, 0x00, 0x18, 'f', 't', 'y', 'p', 'c', 'r', 'x'}
+	CR3Marker = []byte("CanonCR3")
+)
+
+var cr3FileHeader = FileHeader{
+	Ext:         "cr3",
+	Description: "Canon CR3 RAW image format",
+	Signatures:  [][]byte{CR3Magic},
+	ScanFile:    ScanCr3,
+}
+
+// CR3 files are composed of a series of atoms (chunks) with 32-bit or 64-bit sizes.
+// The scanner recognizes the CR3 magic header and the CanonCR3 marker to validate files.
+// This implementation is adapted from the Python project: https://github.com/WojciechMula/recovercr3/blob/master/recovercr3.py
+func ScanCr3(r *Reader) (*ScanResult, error) {
+	// Check CR3 header
+	magic := make([]byte, len(CR3Magic))
+	_, err := r.Read(magic)
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(magic, CR3Magic) {
+		return nil, errors.New("not a CR3 file: missing magic")
+	}
+
+	// Seek to marker position (offset 64)
+	if _, err := r.Discard(64 - len(CR3Magic)); err != nil {
+		return nil, err
+	}
+
+	marker := make([]byte, len(CR3Marker))
+	if _, err := io.ReadFull(r, marker); err != nil {
+		return nil, err
+	}
+	if !bytes.Equal(marker, CR3Marker) {
+		return nil, errors.New("not a CR3 file: missing CanonCR3 marker")
+	}
+
+	// Calculate total size by reading atoms
+	var totalSize uint64
+	for {
+		name, size, err := readAtom(r)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		// First atom must be 'ftyp'
+		if totalSize == 0 && string(name) != "ftyp" {
+			return nil, errors.New("first atom not 'ftyp'")
+		}
+
+		totalSize += size
+
+		// Stop at last chunk
+		if name == "mdat" {
+			break
+		}
+
+		// Seek to next atom, subtract header size
+		if _, err := r.Discard(int(size - 8)); err != nil {
+			return nil, err
+		}
+	}
+
+	return &ScanResult{
+		Name: "0001",
+		Ext:  "CR3",
+		Size: totalSize,
+	}, nil
+}
+
+func readAtom(r *Reader) (string, uint64, error) {
+	var sizeBytes [4]byte
+	if _, err := io.ReadFull(r, sizeBytes[:]); err != nil {
+		return "", 0, err
+	}
+
+	name := make([]byte, 4)
+	if _, err := io.ReadFull(r, name); err != nil {
+		return "", 0, err
+	}
+
+	var size uint64
+
+	size32 := binary.BigEndian.Uint32(sizeBytes[:])
+	if size32 == 1 {
+		// 64-bit size
+		sizeBytes8 := make([]byte, 8)
+		if _, err := io.ReadFull(r, sizeBytes8); err != nil {
+			return "", 0, err
+		}
+		size = binary.BigEndian.Uint64(sizeBytes8)
+	} else {
+		size = uint64(size32)
+	}
+	return string(name), size, nil
+}

internal/format/header.go

@@ -50,6 +50,7 @@ var fileHeaders = []FileHeader{
 	gifFileHeader,
 	pcxFileHeader,
 	tiffFileHeader,
+	cr3FileHeader,
 	// generic/documents formats
 	zipFileHeader,
 	rarFileHeader,