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GODRIVER-2311 Improve the BSON unmarshal buffer reuse fix to reduce memory allocations. #891

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Merged
merged 1 commit into from
Mar 31, 2022
Merged

GODRIVER-2311 Improve the BSON unmarshal buffer reuse fix to reduce memory allocations. #891

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14 changes: 9 additions & 5 deletions bson/bsonrw/value_reader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -384,9 +384,13 @@ func (vr *valueReader) ReadBinary() (b []byte, btype byte, err error) {
if err != nil {
return nil, 0, err
}
// Make a copy of the returned byte slice because it's just a subslice from the valueReader's
// buffer and is not safe to return in the unmarshaled value.
cp := make([]byte, len(b))
copy(cp, b)

vr.pop()
return b, btype, nil
return cp, btype, nil
}

func (vr *valueReader) ReadBoolean() (bool, error) {
Expand Down Expand Up @@ -737,6 +741,9 @@ func (vr *valueReader) ReadValue() (ValueReader, error) {
return vr, nil
}

// readBytes reads length bytes from the valueReader starting at the current offset. Note that the
// returned byte slice is a subslice from the valueReader buffer and must be converted or copied
// before returning in an unmarshaled value.
func (vr *valueReader) readBytes(length int32) ([]byte, error) {
if length < 0 {
return nil, fmt.Errorf("invalid length: %d", length)
Expand All @@ -749,10 +756,7 @@ func (vr *valueReader) readBytes(length int32) ([]byte, error) {
start := vr.offset
vr.offset += int64(length)

b := make([]byte, length)
copy(b, vr.d[start:start+int64(length)])

return b, nil
return vr.d[start : start+int64(length)], nil
}

func (vr *valueReader) appendBytes(dst []byte, length int32) ([]byte, error) {
Expand Down