129 lines
2.7 KiB
Go
129 lines
2.7 KiB
Go
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package jpegstructure
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import (
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"bufio"
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"bytes"
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"io"
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"os"
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log "github.com/dsoprea/go-logging"
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riimage "github.com/dsoprea/go-utility/image"
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)
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// JpegMediaParser is a `riimage.MediaParser` that knows how to parse JPEG
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// images.
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type JpegMediaParser struct {
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}
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// NewJpegMediaParser returns a new JpegMediaParser.
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func NewJpegMediaParser() *JpegMediaParser {
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// TODO(dustin): Add test
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return new(JpegMediaParser)
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}
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// Parse parses a JPEG uses an `io.ReadSeeker`. Even if it fails, it will return
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// the list of segments encountered prior to the failure.
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func (jmp *JpegMediaParser) Parse(rs io.ReadSeeker, size int) (ec riimage.MediaContext, err error) {
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defer func() {
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if state := recover(); state != nil {
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err = log.Wrap(state.(error))
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}
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}()
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s := bufio.NewScanner(rs)
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// Since each segment can be any size, our buffer must allowed to grow as
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// large as the file.
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buffer := []byte{}
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s.Buffer(buffer, size)
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js := NewJpegSplitter(nil)
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s.Split(js.Split)
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for s.Scan() != false {
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}
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// Always return the segments that were parsed, at least until there was an
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// error.
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ec = js.Segments()
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log.PanicIf(s.Err())
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return ec, nil
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}
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// ParseFile parses a JPEG file. Even if it fails, it will return the list of
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// segments encountered prior to the failure.
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func (jmp *JpegMediaParser) ParseFile(filepath string) (ec riimage.MediaContext, err error) {
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defer func() {
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if state := recover(); state != nil {
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err = log.Wrap(state.(error))
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}
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}()
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// TODO(dustin): Add test
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f, err := os.Open(filepath)
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log.PanicIf(err)
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defer f.Close()
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stat, err := f.Stat()
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log.PanicIf(err)
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size := stat.Size()
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sl, err := jmp.Parse(f, int(size))
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// Always return the segments that were parsed, at least until there was an
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// error.
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ec = sl
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log.PanicIf(err)
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return ec, nil
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}
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// ParseBytes parses a JPEG byte-slice. Even if it fails, it will return the
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// list of segments encountered prior to the failure.
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func (jmp *JpegMediaParser) ParseBytes(data []byte) (ec riimage.MediaContext, err error) {
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defer func() {
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if state := recover(); state != nil {
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err = log.Wrap(state.(error))
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}
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}()
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br := bytes.NewReader(data)
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sl, err := jmp.Parse(br, len(data))
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// Always return the segments that were parsed, at least until there was an
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// error.
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ec = sl
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log.PanicIf(err)
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return ec, nil
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}
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// LooksLikeFormat indicates whether the data looks like a JPEG image.
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func (jmp *JpegMediaParser) LooksLikeFormat(data []byte) bool {
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if len(data) < 4 {
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return false
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}
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l := len(data)
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if data[0] != 0xff || data[1] != MARKER_SOI || data[l-2] != 0xff || data[l-1] != MARKER_EOI {
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return false
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}
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return true
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}
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var (
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// Enforce interface conformance.
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_ riimage.MediaParser = new(JpegMediaParser)
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)
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