2411: Add copyright notices to everything.

[arvados.git] / sdk / go / keepclient / collectionreader.go

diff --git a/sdk/go/keepclient/collectionreader.go b/sdk/go/keepclient/collectionreader.go
index ca53ee52a26ea7930460d563d3a49e36feed0d06..57829aadebb0f3c4aff32c604db08e6e481a1a3b 100644 (file)
--- a/sdk/go/keepclient/collectionreader.go
+++ b/sdk/go/keepclient/collectionreader.go
@@ -1,3 +1,7 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package keepclient
 
 import (
@@ -6,19 +10,10 @@ import (
        "io"
        "os"
 
+       "git.curoverse.com/arvados.git/sdk/go/arvados"
        "git.curoverse.com/arvados.git/sdk/go/manifest"
 )
 
-// A Reader implements, io.Reader, io.Seeker, and io.Closer, and has a
-// Len() method that returns the total number of bytes available to
-// read.
-type Reader interface {
-       io.Reader
-       io.Seeker
-       io.Closer
-       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
@@ -35,10 +30,10 @@ const (
 // parameter when retrieving the collection record).
 var ErrNoManifest = errors.New("Collection has no manifest")
 
-// CollectionFileReader returns a 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) (Reader, error) {
+// CollectionFileReader returns a Reader that reads content from a single file
+// in the collection. The filename must be relative to the root of the
+// collection.  A leading prefix of "/" or "./" in the filename is ignored.
+func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, filename string) (arvados.File, error) {
        mText, ok := collection["manifest_text"].(string)
        if !ok {
                return nil, ErrNoManifest
@@ -47,11 +42,15 @@ func (kc *KeepClient) CollectionFileReader(collection map[string]interface{}, fi
        return kc.ManifestFileReader(m, filename)
 }
 
-func (kc *KeepClient) ManifestFileReader(m manifest.Manifest, filename string) (Reader, error) {
+func (kc *KeepClient) ManifestFileReader(m manifest.Manifest, filename string) (arvados.File, error) {
        f := &file{
                kc: kc,
        }
-       return f, f.load(m, filename)
+       err := f.load(m, filename)
+       if err != nil {
+               return nil, err
+       }
+       return f, nil
 }
 
 type file struct {
@@ -68,6 +67,7 @@ type file struct {
        readaheadDone bool
 }
 
+// Close implements io.Closer.
 func (f *file) Close() error {
        f.kc = nil
        f.segments = nil
@@ -75,6 +75,7 @@ func (f *file) Close() error {
        return nil
 }
 
+// Read implements io.Reader.
 func (f *file) Read(buf []byte) (int, error) {
        if f.seg == nil || f.offset < f.segStart || f.offset >= f.segStart+int64(f.seg.Len) {
                // f.seg does not cover the current read offset
@@ -109,16 +110,19 @@ func (f *file) Read(buf []byte) (int, error) {
                }
                f.segData = data[f.seg.Offset : f.seg.Offset+f.seg.Len]
        }
+       // dataOff and dataLen denote a portion of f.segData
+       // corresponding to a portion of the file at f.offset.
        dataOff := int(f.offset - f.segStart)
        dataLen := f.seg.Len - dataOff
 
-       if !f.readaheadDone && len(f.segNext) > 0 && f.offset >= 1048576 && dataOff+dataLen >= 1048576 {
+       if !f.readaheadDone && len(f.segNext) > 0 && f.offset >= 1048576 && dataOff+dataLen > len(f.segData)/16 {
                // If we have already read more than just the first
-               // few bytes of this file, and more than just a few
-               // bytes of this block, and there's more data for this
-               // file in the next segment/block ... then there's a
-               // good chance we are going to want the next block
-               // soon. Start getting it into the cache now.
+               // few bytes of this file, and we have already
+               // consumed a noticeable portion of this segment, and
+               // there's more data for this file in the next segment
+               // ... then there's a good chance we are going to need
+               // the data for that next segment soon. Start getting
+               // it into the cache now.
                go f.kc.cache().Get(f.kc, f.segNext[0].Locator)
                f.readaheadDone = true
        }
@@ -132,6 +136,7 @@ func (f *file) Read(buf []byte) (int, error) {
        return n, nil
 }
 
+// Seek implements io.Seeker.
 func (f *file) Seek(offset int64, whence int) (int64, error) {
        var want int64
        switch whence {
@@ -154,8 +159,9 @@ func (f *file) Seek(offset int64, whence int) (int64, error) {
        return f.offset, nil
 }
 
-func (f *file) Len() uint64 {
-       return uint64(f.size)
+// Size returns the file size in bytes.
+func (f *file) Size() int64 {
+       return f.size
 }
 
 func (f *file) load(m manifest.Manifest, path string) error {