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Merged
rpuneet merged 1 commit into from
Dec 9, 2025
Merged

refactor(exif): reduce cyclomatic complexity and improve performance #5

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69 changes: 42 additions & 27 deletions internal/meta/exif/exif.go
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Original file line number Diff line number Diff line change
Expand Up @@ -47,14 +47,10 @@ func (p *Parser) parseTIFF(data []byte) ([]common.Directory, error) {
return nil, fmt.Errorf("TIFF header too short")
}

// Read byte order (first 2 bytes)
var byteOrder binary.ByteOrder
if data[0] == 'I' && data[1] == 'I' {
byteOrder = binary.LittleEndian // Intel
} else if data[0] == 'M' && data[1] == 'M' {
byteOrder = binary.BigEndian // Motorola
} else {
return nil, fmt.Errorf("invalid TIFF byte order: %02X %02X", data[0], data[1])
// Read byte order from TIFF header
byteOrder, err := parseByteOrder(data)
if err != nil {
return nil, err
}

// Verify TIFF magic number (should be 42)
Expand All @@ -78,24 +74,12 @@ func (p *Parser) parseTIFF(data []byte) ([]common.Directory, error) {
}
dirs = append(dirs, ifd0)

// Check for EXIF sub-IFD pointer
if exifOffset, ok := ifd0.Tags["EXIF:ExifOffset"]; ok {
if offset, ok := exifOffset.Value.(int); ok && offset > 0 && offset < len(data) {
exifIFD, _, err := p.parseIFD(data, offset, byteOrder, "ExifIFD")
if err == nil {
dirs = append(dirs, exifIFD)
}
}
// Parse EXIF and GPS sub-IFDs if present
if subIFD, ok := p.parseSubIFD(ifd0, "EXIF:ExifOffset", "ExifIFD", data, byteOrder); ok {
dirs = append(dirs, subIFD)
}

// Check for GPS sub-IFD pointer
if gpsOffset, ok := ifd0.Tags["EXIF:GPSInfo"]; ok {
if offset, ok := gpsOffset.Value.(int); ok && offset > 0 && offset < len(data) {
gpsIFD, _, err := p.parseIFD(data, offset, byteOrder, "GPS")
if err == nil {
dirs = append(dirs, gpsIFD)
}
}
if subIFD, ok := p.parseSubIFD(ifd0, "EXIF:GPSInfo", "GPS", data, byteOrder); ok {
dirs = append(dirs, subIFD)
}

// Parse IFD1 (thumbnail) if present
Expand All @@ -110,6 +94,37 @@ func (p *Parser) parseTIFF(data []byte) ([]common.Directory, error) {
return dirs, nil
}

// parseByteOrder reads and validates the TIFF byte order marker
func parseByteOrder(data []byte) (binary.ByteOrder, error) {
if data[0] == 'I' && data[1] == 'I' {
return binary.LittleEndian, nil // Intel
}
if data[0] == 'M' && data[1] == 'M' {
return binary.BigEndian, nil // Motorola
}
return nil, fmt.Errorf("invalid TIFF byte order: %02X %02X", data[0], data[1])
}

// parseSubIFD attempts to parse a sub-IFD referenced by a tag in the parent IFD
func (p *Parser) parseSubIFD(parentIFD common.Directory, tagID common.TagID, name string, data []byte, byteOrder binary.ByteOrder) (common.Directory, bool) {
tag, ok := parentIFD.Tags[tagID]
if !ok {
return common.Directory{}, false
}

offset, ok := tag.Value.(int)
if !ok || offset <= 0 || offset >= len(data) {
return common.Directory{}, false
}

subIFD, _, err := p.parseIFD(data, offset, byteOrder, name)
if err != nil {
return common.Directory{}, false
}

return subIFD, true
}

// parseIFD parses a single IFD (Image File Directory)
func (p *Parser) parseIFD(data []byte, offset int, byteOrder binary.ByteOrder, name string) (common.Directory, uint32, error) {
if offset+2 > len(data) {
Expand All @@ -124,7 +139,7 @@ func (p *Parser) parseIFD(data []byte, offset int, byteOrder binary.ByteOrder, n
dir := common.Directory{
Spec: common.SpecEXIF,
Name: name,
Tags: make(map[common.TagID]common.Tag),
Tags: make(map[common.TagID]common.Tag, entryCount),
}

// Parse each entry (12 bytes each)
Expand Down Expand Up @@ -179,7 +194,7 @@ func (p *Parser) parseEntry(data []byte, offset int, byteOrder binary.ByteOrder,
if !ok {
tagName = fmt.Sprintf("Tag%04X", tagID)
}
tag.ID = common.TagID(fmt.Sprintf("EXIF:%s", tagName))
tag.ID = common.TagID("EXIF:" + tagName)
tag.Name = tagName

// Parse value based on type
Expand Down
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