Tolerate (incorrect) folding whitespace used in base64 encoded body content.

[Spiral90210]

Fixes #151

[Spiral90210]

Any thoughts on accepting this PR? Fixes a problem we see with real world mail, yes it technically shouldn't be happening, but as with most things email there's always something writing mail that does so badly. Always.

[emersion]

Can we maybe replace ' ' and '\t' with '\n' which already gets ignored by encoding/base64? That way no need to deal with count/offset changes etc.

[Spiral90210]

It's actually based on the code from base64.go, just extended to account for these extra characters - I figured extending that would make more sense than wrapping/filtering twice.

Here's the original code from the standard library:

type newlineFilteringReader struct {
    wrapped io.Reader
}

func (r *newlineFilteringReader) Read(p []byte) (int, error) {
    n, err := r.wrapped.Read(p)
    for n > 0 {
        offset := 0
        for i, b := range p[:n] {
            if b != '\r' && b != '\n' {
                if i != offset {
                    p[offset] = b
                }
                offset++
            }
        }
        if offset > 0 {
            return offset, err
        }
        // Previous buffer entirely whitespace, read again
        n, err = r.wrapped.Read(p)
    }
    return n, err
}

[Spiral90210]

Can we maybe replace ' ' and '\t' with '\n' which already gets ignored by encoding/base64? That way no need to deal with count/offset changes etc.

Done - yes it is a lot more simple, thanks for the suggestion!

[emersion]

I figured extending that would make more sense than wrapping/filtering twice.

Hm but the wrapping is done internally by the standard library anyways right?

[emersion]

Thanks!

[Spiral90210]

I figured extending that would make more sense than wrapping/filtering twice.

Hm but the wrapping is done internally by the standard library anyways right?

Yup 🙄 clearly I was just satisfied with it working and then just went to live in fantasy land for a while!