Use io::Write::write_all

[nox]

It's incorrect to use io::Write::write and ignore how many bytes were actually written in the underlying writer.

[marshallpierce]

This snippet demonstrates the issue, extracted from me tinkering in base64 to see what was going on:

#[test]
fn png() {
    let mut rng = rand::thread_rng();
    let mut input_bytes = Vec::<u8>::new();
    let mut png_data = Vec::<u8>::new();

    // A really ugly 200x200 rgba
    for _ in 0..(200 * 200 * 4) {
        input_bytes.push(rng.gen());
    }

    // encode into a Vec
    self::image::png::PNGEncoder::new(&mut png_data)
        .encode(&input_bytes, 200, 200, self::image::ColorType::RGBA(8))
        .unwrap();

    // and b64 the vec
    let simple_b64 = encode_config(&png_data, ::STANDARD);

    // encode into a b64 streaming encoder
    let mut stream_png_b64 = Vec::new();

    {
        let mut b64_encoder = EncoderWriter::new(&mut stream_png_b64, ::STANDARD);

        self::image::png::PNGEncoder::new(&mut b64_encoder)
            .encode(&input_bytes, 200, 200, self::image::ColorType::RGBA(8))
            .unwrap();

        b64_encoder.finish().unwrap();
    }

    assert_eq!(simple_b64, ::std::str::from_utf8(&stream_png_b64).unwrap());
}

With debug logging in base64 added to show when the streaming encoder can't write the full input it's given, I get this:

input = 160236, consumed = 768

I'm working on getting a failing test case and possibly a fix.

[marshallpierce]

I changed the roundtrip test to use all available test images, which worked fine but only for images whose line_size was 32, so the test skips all other images. For the affected images, encoding fails with errors like "wrong data size, expected 65536 got 196608". What's up with that? Just a guess, but perhaps the decode buffer is sized conservatively, but since next_frame doesn't return the number of bytes decoded, there's no way to only encode the relevant portion of the decode buffer?

[nox]

I added your commit, this is now ready to be reviewed.

[nox]

@bvssvni?

[bvssvni]

Merging.

[nox]

@bvssvni Can you make a new png release, please?