"Could not deserialize bitmap for key #0: error in roaringArray.readFrom: did not find expected serialCookie in header" on v1.8.0 when reading a bitmap written by roaring64

[wjohnson-aurora]

Per the io.Reader documentation, it is acceptable for an implementation to read 0 <= n <= len(p) bytes on each call to Read. I've found that roaring64.Bitmap.ReadFrom returns the following error when passed an io.Reader that reads less than len(p) bytes on calls to Read:

Could not deserialize bitmap for key #0: error in roaringArray.readFrom: did not find expected serialCookie in header

To replicate:

1. Create main.go with the following contents:

package main

import (
	"bytes"
	"io"

	"github.com/RoaringBitmap/roaring/roaring64"
)

func main() {
	bitmap := roaring64.NewBitmap()
	bitmap.Add(1234)

	var bitmapBuf bytes.Buffer
	if _, err := bitmap.WriteTo(&bitmapBuf); err != nil {
		panic(err)
	}

	bitmapMinusOneReader := minusOneReader{
		reader: &bitmapBuf,
	}
	readBitmap := roaring64.NewBitmap()
	if _, err := readBitmap.ReadFrom(&bitmapMinusOneReader); err != nil {
		panic(err)
	}
}

type minusOneReader struct {
	reader io.Reader
}

func (r minusOneReader) Read(p []byte) (int, error) {
	if len(p) > 1 {
		p = p[:len(p)-1]
	}
	return r.reader.Read(p)
}

2. Create go.mod with the following contents:

module roaring-replication

go 1.20

require github.com/RoaringBitmap/roaring v1.8.0

require (
	github.com/bits-and-blooms/bitset v1.12.0 // indirect
	github.com/mschoch/smat v0.2.0 // indirect
)

3. Run go mod tidy
4. Run go run main.go
5. Observe error from ReadFrom:

panic: Could not deserialize bitmap for key #0: error in roaringArray.readFrom: did not find expected serialCookie in header

goroutine 1 [running]:
main.main()
	main.go:24 +0x12d
exit status 2

[lemire]

A pull request fixing this issue is invited.