"git.curoverse.com/arvados.git/sdk/go/manifest"
)
+// ReadCloserWithLen extends io.ReadCloser with a Len() method that
+// returns the total number of bytes available to read.
+type ReadCloserWithLen interface {
+ io.ReadCloser
+ Len() uint64
+}
+
const (
// After reading a data block from Keep, cfReader slices it up
// and sends the slices to a buffered channel to be consumed
// parameter when retrieving the collection record).
var ErrNoManifest = errors.New("Collection has no manifest")
-// CollectionFileReader returns an io.Reader that reads file content
-// from a collection. The filename must be given relative to the root
-// of the collection, without a leading "./".
-func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, filename string) (*cfReader, error) {
+// CollectionFileReader returns a ReadCloserWithLen that reads file
+// content from a collection. The filename must be given relative to
+// the root of the collection, without a leading "./".
+func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, filename string) (ReadCloserWithLen, error) {
mText, ok := collection["manifest_text"].(string)
if !ok {
return nil, ErrNoManifest
}
m := manifest.Manifest{Text: mText}
+ return kc.ManifestFileReader(m, filename)
+}
+
+func (kc *KeepClient) ManifestFileReader(m manifest.Manifest, filename string) (ReadCloserWithLen, error) {
rdrChan := make(chan *cfReader)
- go func() {
- // q is a queue of FileSegments that we have received but
- // haven't yet been able to send to toGet.
- var q []*manifest.FileSegment
- var r *cfReader
- for seg := range m.FileSegmentIterByName(filename) {
- if r == nil {
- // We've just discovered that the
- // requested filename does appear in
- // the manifest, so we can return a
- // real reader (not nil) from
- // CollectionFileReader().
- r = newCFReader(kc)
- rdrChan <- r
- }
- q = append(q, seg)
- r.totalSize += uint64(seg.Len)
- // Send toGet as many segments as we can until
- // it blocks.
- Q:
- for len(q) > 0 {
- select {
- case r.toGet <- q[0]:
- q = q[1:]
- default:
- break Q
- }
- }
- }
+ go kc.queueSegmentsToGet(m, filename, rdrChan)
+ r, ok := <-rdrChan
+ if !ok {
+ return nil, os.ErrNotExist
+ }
+ return r, nil
+}
+
+// Send segments for the specified file to r.toGet. Send a *cfReader
+// to rdrChan if the specified file is found (even if it's empty).
+// Then, close rdrChan.
+func (kc *KeepClient) queueSegmentsToGet(m manifest.Manifest, filename string, rdrChan chan *cfReader) {
+ defer close(rdrChan)
+
+ // q is a queue of FileSegments that we have received but
+ // haven't yet been able to send to toGet.
+ var q []*manifest.FileSegment
+ var r *cfReader
+ for seg := range m.FileSegmentIterByName(filename) {
if r == nil {
- // File not found
- rdrChan <- nil
- return
+ // We've just discovered that the requested
+ // filename does appear in the manifest, so we
+ // can return a real reader (not nil) from
+ // CollectionFileReader().
+ r = newCFReader(kc)
+ rdrChan <- r
}
- close(r.countDone)
- for _, seg := range q {
- r.toGet <- seg
+ q = append(q, seg)
+ r.totalSize += uint64(seg.Len)
+ // Send toGet as many segments as we can until it
+ // blocks.
+ Q:
+ for len(q) > 0 {
+ select {
+ case r.toGet <- q[0]:
+ q = q[1:]
+ default:
+ break Q
+ }
}
- close(r.toGet)
- }()
- // Before returning a reader, wait until we know whether the
- // file exists here:
- r := <-rdrChan
+ }
if r == nil {
- return nil, os.ErrNotExist
+ // File not found.
+ return
}
- return r, nil
+ close(r.countDone)
+ for _, seg := range q {
+ r.toGet <- seg
+ }
+ close(r.toGet)
}
type cfReader struct {
keepClient *KeepClient
+
// doGet() reads FileSegments from toGet, gets the data from
// Keep, and sends byte slices to toRead to be consumed by
// Read().
toGet chan *manifest.FileSegment
+
// toRead is a buffered channel, sized to fit one full Keep
// block. This lets us verify checksums without having a
// store-and-forward delay between blocks: by the time the
// starting to fetch block N+1. A larger buffer would be
// useful for a caller whose read speed varies a lot.
toRead chan []byte
+
// bytes ready to send next time someone calls Read()
buf []byte
+
// Total size of the file being read. Not safe to read this
// until countDone is closed.
totalSize uint64
countDone chan struct{}
+
// First error encountered.
err error
+
// errNotNil is closed IFF err contains a non-nil error.
// Receiving from it will block until an error occurs.
errNotNil chan struct{}
+
// rdrClosed is closed IFF the reader's Close() method has
// been called. Any goroutines associated with the reader will
// stop and free up resources when they notice this channel is
func (r *cfReader) Read(outbuf []byte) (int, error) {
if r.Error() != nil {
+ // Short circuit: the caller might as well find out
+ // now that we hit an error, even if there's buffered
+ // data we could return.
return 0, r.Error()
}
- for r.buf == nil || len(r.buf) == 0 {
+ for len(r.buf) == 0 {
+ // Private buffer was emptied out by the last Read()
+ // (or this is the first Read() and r.buf is nil).
+ // Read from r.toRead until we get a non-empty slice
+ // or hit an error.
var ok bool
r.buf, ok = <-r.toRead
if r.Error() != nil {
+ // Error encountered while waiting for bytes
return 0, r.Error()
} else if !ok {
+ // No more bytes to read, no error encountered
return 0, io.EOF
}
}
+ // Copy as much as possible from our private buffer to the
+ // caller's buffer
n := len(r.buf)
if len(r.buf) > len(outbuf) {
n = len(outbuf)
}
copy(outbuf[:n], r.buf[:n])
+
+ // Next call to Read() will continue where we left off
r.buf = r.buf[n:]
+
return n, nil
}
+// Close releases resources. It returns a non-nil error if an error
+// was encountered by the reader.
func (r *cfReader) Close() error {
close(r.rdrClosed)
return r.Error()
}
+// Error returns an error if one has been encountered, otherwise
+// nil. It is safe to call from any goroutine.
func (r *cfReader) Error() error {
select {
case <-r.errNotNil:
}
}
+// Len returns the total number of bytes in the file being read. If
+// necessary, it waits for manifest parsing to finish.
func (r *cfReader) Len() uint64 {
// Wait for all segments to be counted
<-r.countDone
}
var buf = make([]byte, fs.Offset+fs.Len)
_, err = io.ReadFull(rdr, buf)
+ errClosing := rdr.Close()
+ if err == nil {
+ err = errClosing
+ }
if err != nil {
r.err = err
close(r.errNotNil)
return
}
- for bOff, bLen := fs.Offset, dataSliceSize; bOff <= fs.Offset+fs.Len && bLen > 0; bOff += bLen {
+ for bOff, bLen := fs.Offset, dataSliceSize; bOff < fs.Offset+fs.Len && bLen > 0; bOff += bLen {
if bOff+bLen > fs.Offset+fs.Len {
bLen = fs.Offset + fs.Len - bOff
}
projects / arvados.git / blobdiff