// FileTime returns the best guess of the file's creation time (or modtime).
// If the file doesn't have its own metadata indication the creation time (such as in EXIF),
// FileTime uses the modification time from the file system.
// It there was a valid EXIF but an error while trying to get a date from it,
// it logs the error and tries the other methods.
func FileTime(f io.ReaderAt) (time.Time, error) {
var ct time.Time
defaultTime := func() (time.Time, error) {
if osf, ok := f.(*os.File); ok {
fi, err := osf.Stat()
if err != nil {
return ct, fmt.Errorf("Failed to find a modtime: stat: %v", err)
}
return fi.ModTime(), nil
}
return ct, errors.New("All methods failed to find a creation time or modtime.")
}
size, ok := findSize(f)
if !ok {
size = 256 << 10 // enough to get the EXIF
}
r := io.NewSectionReader(f, 0, size)
var tiffErr error
ex, err := exif.Decode(r)
if err != nil {
tiffErr = err
if exif.IsShortReadTagValueError(err) {
return ct, io.ErrUnexpectedEOF
}
if exif.IsCriticalError(err) || exif.IsExifError(err) {
return defaultTime()
}
}
ct, err = ex.DateTime()
if err != nil {
return defaultTime()
}
// If the EXIF file only had local timezone, but it did have
// GPS, then lookup the timezone and correct the time.
if ct.Location() == time.Local {
if exif.IsGPSError(tiffErr) {
log.Printf("Invalid EXIF GPS data: %v", tiffErr)
return ct, nil
}
if lat, long, err := ex.LatLong(); err == nil {
if loc := lookupLocation(latlong.LookupZoneName(lat, long)); loc != nil {
if t, err := exifDateTimeInLocation(ex, loc); err == nil {
return t, nil
}
}
} else if !exif.IsTagNotPresentError(err) {
log.Printf("Invalid EXIF GPS data: %v", err)
}
}
return ct, nil
}
func indexEXIF(wholeRef blob.Ref, r io.Reader, mm *mutationMap) (err error) {
var tiffErr error
ex, err := exif.Decode(r)
if err != nil {
tiffErr = err
if exif.IsCriticalError(err) {
if exif.IsShortReadTagValueError(err) {
return io.ErrUnexpectedEOF // trigger a retry with whole file
}
return
}
log.Printf("Non critical TIFF decoding error: %v", err)
}
defer func() {
// The EXIF library panics if you access a field past
// what the file contains. Be paranoid and just
// recover here, instead of crashing on an invalid
// EXIF file.
if e := recover(); e != nil {
err = errEXIFPanic
}
}()
err = ex.Walk(exifWalkFunc(func(name exif.FieldName, tag *tiff.Tag) error {
tagFmt := tagFormatString(tag)
if tagFmt == "" {
return nil
}
key := keyEXIFTag.Key(wholeRef, fmt.Sprintf("%04x", tag.Id))
numComp := int(tag.Count)
if tag.Format() == tiff.StringVal {
numComp = 1
}
var val bytes.Buffer
val.WriteString(keyEXIFTag.Val(tagFmt, numComp, ""))
if tag.Format() == tiff.StringVal {
str, err := tag.StringVal()
if err != nil {
log.Printf("Invalid EXIF string data: %v", err)
return nil
}
if containsUnsafeRawStrByte(str) {
val.WriteString(urle(str))
} else {
val.WriteString(str)
}
} else {
for i := 0; i < int(tag.Count); i++ {
if i > 0 {
val.WriteByte('|')
}
switch tagFmt {
case "int":
v, err := tag.Int(i)
if err != nil {
log.Printf("Invalid EXIF int data: %v", err)
return nil
}
fmt.Fprintf(&val, "%d", v)
case "rat":
n, d, err := tag.Rat2(i)
if err != nil {
log.Printf("Invalid EXIF rat data: %v", err)
return nil
}
fmt.Fprintf(&val, "%d/%d", n, d)
case "float":
v, err := tag.Float(i)
if err != nil {
log.Printf("Invalid EXIF float data: %v", err)
return nil
}
fmt.Fprintf(&val, "%v", v)
default:
panic("shouldn't get here")
}
}
}
valStr := val.String()
mm.Set(key, valStr)
return nil
}))
if err != nil {
return
}
if exif.IsGPSError(tiffErr) {
log.Printf("Invalid EXIF GPS data: %v", tiffErr)
return nil
}
if lat, long, err := ex.LatLong(); err == nil {
if math.Abs(long) > 180.0 || math.Abs(lat) > 90.0 {
log.Printf("Long, lat outside allowed range: %v, %v", long, lat)
return nil
}
// index 7 places fixed precision (~10mm worst case at equator)
// http://stackoverflow.com/a/1947615/114581
mm.Set(keyEXIFGPS.Key(wholeRef), keyEXIFGPS.Val(fmt.Sprintf("%.7f", lat), fmt.Sprintf("%.7f", long)))
} else if !exif.IsTagNotPresentError(err) {
log.Printf("Invalid EXIF GPS data: %v", err)
}
return nil
}