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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,89 @@ | ||
| package seeker | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "io" | ||
| ) | ||
|
|
||
| type readSeekCloser struct { | ||
| getReader func(start int64) (io.ReadCloser, error) | ||
| size int64 | ||
| offset int64 | ||
| current io.ReadCloser | ||
| } | ||
|
|
||
| func NewReadSeekCloser(getReadCloser func(int64) (io.ReadCloser, error), size int64) io.ReadSeekCloser { | ||
| return &readSeekCloser{ | ||
| getReader: getReadCloser, | ||
| size: size, | ||
| offset: 0, | ||
| current: nil, | ||
| } | ||
| } | ||
|
|
||
| func (rs *readSeekCloser) Read(p []byte) (int, error) { | ||
| if rs.offset >= rs.size { | ||
| return 0, io.EOF | ||
| } | ||
|
|
||
| if rs.current == nil { | ||
| reader, err := rs.getReader(rs.offset) | ||
| if err != nil { | ||
| return 0, err | ||
| } | ||
| rs.current = reader | ||
| } | ||
|
|
||
| n, err := rs.current.Read(p) | ||
| rs.offset += int64(n) | ||
|
|
||
| if err == io.EOF { | ||
| rs.current.Close() | ||
| rs.current = nil | ||
| if rs.offset >= rs.size { | ||
| err = io.EOF | ||
| } else { | ||
| err = nil | ||
| } | ||
| } | ||
|
|
||
| return n, err | ||
| } | ||
|
|
||
| func (rs *readSeekCloser) Seek(offset int64, whence int) (int64, error) { | ||
| var newOffset int64 | ||
| switch whence { | ||
| case io.SeekStart: | ||
| newOffset = offset | ||
| case io.SeekCurrent: | ||
| newOffset = rs.offset + offset | ||
| case io.SeekEnd: | ||
| newOffset = rs.size + offset | ||
| default: | ||
| return 0, fmt.Errorf("seek: invalid whence") | ||
| } | ||
|
|
||
| if newOffset < 0 { | ||
| return 0, fmt.Errorf("seek: negative position") | ||
| } | ||
| if newOffset > rs.size { | ||
| newOffset = rs.size | ||
| } | ||
|
|
||
| if rs.current != nil && newOffset != rs.offset { | ||
| rs.current.Close() | ||
| rs.current = nil | ||
| } | ||
|
|
||
| rs.offset = newOffset | ||
| return newOffset, nil | ||
| } | ||
|
|
||
| func (rs *readSeekCloser) Close() error { | ||
| if rs.current != nil { | ||
| err := rs.current.Close() | ||
| rs.current = nil | ||
| return err | ||
| } | ||
| return nil | ||
| } |