diff options
Diffstat (limited to 'vendor/google.golang.org/appengine/blobstore/read.go')
-rw-r--r-- | vendor/google.golang.org/appengine/blobstore/read.go | 160 |
1 files changed, 0 insertions, 160 deletions
diff --git a/vendor/google.golang.org/appengine/blobstore/read.go b/vendor/google.golang.org/appengine/blobstore/read.go deleted file mode 100644 index 578b1f550..000000000 --- a/vendor/google.golang.org/appengine/blobstore/read.go +++ /dev/null @@ -1,160 +0,0 @@ -// Copyright 2012 Google Inc. All rights reserved. -// Use of this source code is governed by the Apache 2.0 -// license that can be found in the LICENSE file. - -package blobstore - -import ( - "errors" - "fmt" - "io" - "os" - "sync" - - "github.com/golang/protobuf/proto" - "golang.org/x/net/context" - - "google.golang.org/appengine" - "google.golang.org/appengine/internal" - - blobpb "google.golang.org/appengine/internal/blobstore" -) - -// openBlob returns a reader for a blob. It always succeeds; if the blob does -// not exist then an error will be reported upon first read. -func openBlob(c context.Context, blobKey appengine.BlobKey) Reader { - return &reader{ - c: c, - blobKey: blobKey, - } -} - -const readBufferSize = 256 * 1024 - -// reader is a blob reader. It implements the Reader interface. -type reader struct { - c context.Context - - // Either blobKey or filename is set: - blobKey appengine.BlobKey - filename string - - closeFunc func() // is nil if unavailable or already closed. - - // buf is the read buffer. r is how much of buf has been read. - // off is the offset of buf[0] relative to the start of the blob. - // An invariant is 0 <= r && r <= len(buf). - // Reads that don't require an RPC call will increment r but not off. - // Seeks may modify r without discarding the buffer, but only if the - // invariant can be maintained. - mu sync.Mutex - buf []byte - r int - off int64 -} - -func (r *reader) Close() error { - if f := r.closeFunc; f != nil { - f() - } - r.closeFunc = nil - return nil -} - -func (r *reader) Read(p []byte) (int, error) { - if len(p) == 0 { - return 0, nil - } - r.mu.Lock() - defer r.mu.Unlock() - if r.r == len(r.buf) { - if err := r.fetch(r.off + int64(r.r)); err != nil { - return 0, err - } - } - n := copy(p, r.buf[r.r:]) - r.r += n - return n, nil -} - -func (r *reader) ReadAt(p []byte, off int64) (int, error) { - if len(p) == 0 { - return 0, nil - } - r.mu.Lock() - defer r.mu.Unlock() - // Convert relative offsets to absolute offsets. - ab0 := r.off + int64(r.r) - ab1 := r.off + int64(len(r.buf)) - ap0 := off - ap1 := off + int64(len(p)) - // Check if we can satisfy the read entirely out of the existing buffer. - if r.off <= ap0 && ap1 <= ab1 { - // Convert off from an absolute offset to a relative offset. - rp0 := int(ap0 - r.off) - return copy(p, r.buf[rp0:]), nil - } - // Restore the original Read/Seek offset after ReadAt completes. - defer r.seek(ab0) - // Repeatedly fetch and copy until we have filled p. - n := 0 - for len(p) > 0 { - if err := r.fetch(off + int64(n)); err != nil { - return n, err - } - r.r = copy(p, r.buf) - n += r.r - p = p[r.r:] - } - return n, nil -} - -func (r *reader) Seek(offset int64, whence int) (ret int64, err error) { - r.mu.Lock() - defer r.mu.Unlock() - switch whence { - case os.SEEK_SET: - ret = offset - case os.SEEK_CUR: - ret = r.off + int64(r.r) + offset - case os.SEEK_END: - return 0, errors.New("seeking relative to the end of a blob isn't supported") - default: - return 0, fmt.Errorf("invalid Seek whence value: %d", whence) - } - if ret < 0 { - return 0, errors.New("negative Seek offset") - } - return r.seek(ret) -} - -// fetch fetches readBufferSize bytes starting at the given offset. On success, -// the data is saved as r.buf. -func (r *reader) fetch(off int64) error { - req := &blobpb.FetchDataRequest{ - BlobKey: proto.String(string(r.blobKey)), - StartIndex: proto.Int64(off), - EndIndex: proto.Int64(off + readBufferSize - 1), // EndIndex is inclusive. - } - res := &blobpb.FetchDataResponse{} - if err := internal.Call(r.c, "blobstore", "FetchData", req, res); err != nil { - return err - } - if len(res.Data) == 0 { - return io.EOF - } - r.buf, r.r, r.off = res.Data, 0, off - return nil -} - -// seek seeks to the given offset with an effective whence equal to SEEK_SET. -// It discards the read buffer if the invariant cannot be maintained. -func (r *reader) seek(off int64) (int64, error) { - delta := off - r.off - if delta >= 0 && delta < int64(len(r.buf)) { - r.r = int(delta) - return off, nil - } - r.buf, r.r, r.off = nil, 0, off - return off, nil -} |