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|
package pngstructure
import (
"bufio"
"bytes"
"io"
"os"
"github.com/dsoprea/go-logging"
"github.com/dsoprea/go-utility/image"
)
// PngMediaParser knows how to parse a PNG stream.
type PngMediaParser struct {
}
// NewPngMediaParser returns a new `PngMediaParser` struct.
func NewPngMediaParser() *PngMediaParser {
// TODO(dustin): Add test
return new(PngMediaParser)
}
// Parse parses a PNG stream given a `io.ReadSeeker`.
func (pmp *PngMediaParser) Parse(rs io.ReadSeeker, size int) (mc riimage.MediaContext, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
ps := NewPngSplitter()
err = ps.readHeader(rs)
log.PanicIf(err)
s := bufio.NewScanner(rs)
// Since each segment can be any size, our buffer must be allowed to grow
// as large as the file.
buffer := []byte{}
s.Buffer(buffer, size)
s.Split(ps.Split)
for s.Scan() != false {
}
log.PanicIf(s.Err())
return ps.Chunks(), nil
}
// ParseFile parses a PNG stream given a file-path.
func (pmp *PngMediaParser) ParseFile(filepath string) (mc riimage.MediaContext, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
f, err := os.Open(filepath)
log.PanicIf(err)
defer f.Close()
stat, err := f.Stat()
log.PanicIf(err)
size := stat.Size()
chunks, err := pmp.Parse(f, int(size))
log.PanicIf(err)
return chunks, nil
}
// ParseBytes parses a PNG stream given a byte-slice.
func (pmp *PngMediaParser) ParseBytes(data []byte) (mc riimage.MediaContext, err error) {
defer func() {
if state := recover(); state != nil {
err = log.Wrap(state.(error))
}
}()
// TODO(dustin): Add test
br := bytes.NewReader(data)
chunks, err := pmp.Parse(br, len(data))
log.PanicIf(err)
return chunks, nil
}
// LooksLikeFormat returns a boolean indicating whether the stream looks like a
// PNG image.
func (pmp *PngMediaParser) LooksLikeFormat(data []byte) bool {
return bytes.Compare(data[:len(PngSignature)], PngSignature[:]) == 0
}
var (
// Enforce interface conformance.
_ riimage.MediaParser = new(PngMediaParser)
)
|
