GODRIVER-3291 Refactor bson.valueReader with bufio.
#1732
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bson/value_reader.go
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| if err == nil { | ||
| err = io.EOF | ||
| } | ||
| buf := make([]byte, length) |
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Optional: The length is frequently static, which allows using static-size arrays or slices. To take advantage of that, consider changing the readBytes API to accept a []byte instead of a length.
E.g.
func (vr *valueReader) read(buf []byte) (int, error) { ... }Then an example call from readi32 would look like:
func (vr *valueReader) readi32() (int32, error) {
var buf [4]byte
_, err := vr.read(buf[:])
// ...
bson/value_reader.go
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| @@ -700,7 +687,7 @@ func (vr *valueReader) ReadElement() (string, ValueReader, error) { | |||
| return "", nil, vr.invalidDocumentLengthError() | |||
| } | |||
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| vr.pop() | |||
| _ = vr.pop() | |||
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We should handle this error.
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This line is inside an error-handling block. We don't need to overwrite the original error even when pop() returns an error.
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ErrEOD is a sentinel error, similar to io.EOF, so it's not an error handling block in the sense that "something has gone wrong". However, it does seem like the pop call here will never read from the underlying reader, so it should be safe to discard. Consider adding a comment that says the pop call here will never read from the underlying reader, so it's safe to discard the error.
bson/value_reader.go
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| @@ -730,11 +717,11 @@ func (vr *valueReader) ReadValue() (ValueReader, error) { | |||
| return nil, vr.invalidDocumentLengthError() | |||
| } | |||
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| vr.pop() | |||
| _ = vr.pop() | |||
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We should handle this error.
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This line is inside an error-handling block. We don't need to overwrite the original error even when pop() returns an error.
API Change ReportNo changes found! |
bson/value_reader.go
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| func (vr *valueReader) read(p []byte) error { | ||
| n, err := io.ReadFull(vr.r, p) | ||
| if errors.Is(err, io.ErrUnexpectedEOF) { | ||
| return io.EOF |
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Why do we convert an io.UnexpectedEOF to io.EOF here? io.UnexpectedEOF actually seems more appropriate considering this note from the io.EOF documentation:
Functions should return EOF only to signal a graceful end of input. If the EOF occurs unexpectedly in a structured data stream, the appropriate error is either ErrUnexpectedEOF or some other error giving more detail.
Some other valueReader methods should also be updated to return io.UnexpectedEOF if the end of the input was reached before
bson/value_reader.go
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| buf := make([]byte, length) | ||
| _, err = io.ReadFull(vr.r, buf) | ||
| if errors.Is(err, io.ErrUnexpectedEOF) { | ||
| return nil, io.EOF |
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Same question as in read: Why do we convert an io.UnexpectedEOF to io.EOF here?
blink1073
added
priority-2-medium
GODRIVER-3291
Summary
Refactor
bson.valueReaderwith bufio.Background & Motivation