glium 0.17.1

Elegant and safe OpenGL wrapper. Glium is an intermediate layer between OpenGL and your application. You still need to manually handle the graphics pipeline, but without having to use OpenGL's old and error-prone API. Its objectives: - Be safe to use. Many aspects of OpenGL that can trigger a crash if misused are automatically handled by glium. - Provide an API that enforces good pratices such as RAII or stateless function calls. - Be compatible with all OpenGL versions that support shaders, providing unified API when things diverge. - Avoid all OpenGL errors beforehand. - Produce optimized OpenGL function calls, and allow the user to easily use modern OpenGL techniques.
Documentation 
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const NUM_DWORDS: usize = 8;

/// 64-bits bitsfield
pub struct Bitsfield {
    data: [u32; NUM_DWORDS],
}

impl Bitsfield {
    #[inline]
    pub fn new() -> Bitsfield {
        Bitsfield {
            data: [0xffffffff; NUM_DWORDS],
        }
    }

    #[inline]
    pub fn set_used(&mut self, mut bit: u16) {
        let mut offset = 0;

        loop {
            if offset >= NUM_DWORDS {
                unimplemented!();
            }

            if bit < 32 {
                let mask: u32 = 1 << bit;
                let mask = !mask;
                self.data[offset] &= mask;
                return;
            }

            bit -= 32;
            offset += 1;
        }
    }

    #[inline]
    pub fn set_unused(&mut self, mut bit: u16) {
        let mut offset = 0;

        loop {
            if offset >= NUM_DWORDS {
                unimplemented!();
            }

            if bit < 32 {
                let mask: u32 = 1 << bit;
                self.data[offset] |= mask;
                return;
            }

            bit -= 32;
            offset += 1;
        }
    }

    #[inline]
    pub fn is_used(&self, mut bit: u16) -> bool {
        let mut offset = 0;

        loop {
            if offset >= NUM_DWORDS {
                unimplemented!();
            }

            if bit < 32 {
                let mask: u32 = 1 << bit;
                return self.data[offset] & mask == 0;
            }

            bit -= 32;
            offset += 1;
        }
    }

    #[inline]
    pub fn get_unused(&self) -> Option<u16> {
        let mut offset = 0;

        loop {
            if offset >= NUM_DWORDS {
                return None;
            }

            let v = self.data[offset].trailing_zeros() as u16;
            if v < 32 {
                return Some(v + offset as u16 * 32);
            }

            offset += 1;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::Bitsfield;

    #[test]
    fn get_unused() {
        let mut bitsfield = Bitsfield::new();
        bitsfield.set_used(0);
        bitsfield.set_used(1);
        assert_eq!(bitsfield.get_unused(), Some(2))
    }

    #[test]
    fn get_unused2() {
        let mut bitsfield = Bitsfield::new();
        for i in 0 .. 34 {
            bitsfield.set_used(i);
        }
        assert_eq!(bitsfield.get_unused(), Some(34))
    }

    #[test]
    fn is_used() {
        let mut bitsfield = Bitsfield::new();
        bitsfield.set_used(5);
        bitsfield.set_used(6);
        bitsfield.set_used(37);
        assert!(!bitsfield.is_used(4));
        assert!(bitsfield.is_used(5));
        assert!(bitsfield.is_used(6));
        assert!(!bitsfield.is_used(7));
        assert!(!bitsfield.is_used(36));
        assert!(bitsfield.is_used(37));
        assert!(!bitsfield.is_used(38));
    }
}