stl 0.2.0

Stereo Lithography file input and output.
Documentation 
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extern crate byteorder;

use std::io::{Result, Write, ErrorKind, Error};
use byteorder::{ReadBytesExt, LittleEndian, WriteBytesExt};

pub struct Triangle {
    normal: [f32; 3],
    v1: [f32; 3],
    v2: [f32; 3],
    v3: [f32; 3],
    attr_byte_count: u16
}

fn point_eq(lhs: [f32; 3], rhs: [f32; 3]) -> bool {
    lhs[0] == rhs[0] && lhs[1] == rhs[1] && lhs[2] == rhs[2]
}

impl PartialEq for Triangle {
    fn eq(&self, rhs: &Triangle) -> bool {
        point_eq(self.normal, rhs.normal)
            && point_eq(self.v1, rhs.v1)
            && point_eq(self.v2, rhs.v2)
            && point_eq(self.v3, rhs.v3)
            && self.attr_byte_count == rhs.attr_byte_count
    }
}

impl Eq for Triangle {}

pub struct BinaryStlHeader {
    pub header: [u8; 80],
    pub num_triangles: u32
}

pub struct BinaryStlFile {
    pub header: BinaryStlHeader,
    pub triangles: Vec<Triangle>
}

fn read_point<T: ReadBytesExt>(input: &mut T) -> Result<[f32; 3]> {
    let x1 = try!(input.read_f32::<LittleEndian>());
    let x2 = try!(input.read_f32::<LittleEndian>());
    let x3 = try!(input.read_f32::<LittleEndian>());
    
    Ok([x1, x2, x3])
}

fn read_triangle<T: ReadBytesExt>(input: &mut T) -> Result<Triangle> {
    let normal = try!(read_point(input));
    let v1 = try!(read_point(input));
    let v2 = try!(read_point(input));
    let v3 = try!(read_point(input));
    let attr_count = try!(input.read_u16::<LittleEndian>());

    Ok(Triangle { normal: normal,
                  v1: v1, v2: v2, v3: v3,
                  attr_byte_count: attr_count })
}

fn read_header<T: ReadBytesExt>(input: &mut T) -> Result<BinaryStlHeader> {
    let mut header = [0u8; 80];

    match input.read(&mut header) {
        Ok(n) => if n == header.len() {
            ()
        }
        else {
            return Err(Error::new(ErrorKind::Other,
                                  "Couldn't read STL header"));
        },
        Err(e) => return Err(e)
    };

    let num_triangles = try!(input.read_u32::<LittleEndian>());

    Ok(BinaryStlHeader{ header: header, num_triangles: num_triangles })
}

pub fn read_stl<T: ReadBytesExt>(input: &mut T) -> Result<BinaryStlFile> {

    // read the header
    let header = try!(read_header(input));

    let mut triangles = Vec::new();
    for _ in 0 .. header.num_triangles {
        triangles.push(try!(read_triangle(input)));
    }

    Ok(BinaryStlFile {
        header: header,
        triangles: triangles
    })
}

fn write_point<T: WriteBytesExt>(out: &mut T, p: [f32; 3]) -> Result<()> {
    for x in p.iter() {
        try!(out.write_f32::<LittleEndian>(*x));
    }
    Ok(())
}

pub fn write_stl<T: WriteBytesExt>(out: &mut T,
                                   stl: &BinaryStlFile) -> Result<()> {
    assert!(stl.header.num_triangles as usize == stl.triangles.len());

    //write the header.
    try!(out.write(&stl.header.header));
    try!(out.write_u32::<LittleEndian>(stl.header.num_triangles));
    
    // write all the triangles
    for t in stl.triangles.iter() {
        try!(write_point(out, t.normal));
        try!(write_point(out, t.v1));
        try!(write_point(out, t.v2));
        try!(write_point(out, t.v3));
        try!(out.write_u16::<LittleEndian>(t.attr_byte_count));
    }

    Ok(())
}

#[cfg(test)]
mod test {
    use super::{BinaryStlFile, BinaryStlHeader, write_stl, read_stl, Triangle};
    use std::io::Cursor;
    #[test]
    fn write_read() {
        // Make sure we can write and read a simple file.
        let file = BinaryStlFile {
            header: BinaryStlHeader { header: [0u8; 80],
                                      num_triangles: 1 },
            triangles: vec![Triangle { normal: [0f32, 1f32, 0f32],
                                       v1: [0f32, 0f32, 0f32],
                                       v2: [0f32, 0f32, 1f32],
                                       v3: [1f32, 0f32, 1f32],
                                       attr_byte_count: 0 }]
        };

        let mut buffer = Vec::new();

        match write_stl(&mut buffer, &file) {
            Ok(_) => (),
            Err(_) => panic!()
        }

        match read_stl(&mut Cursor::new(buffer)) {
            Ok(stl) => {
                assert!(stl.header.num_triangles == file.header.num_triangles);
                assert!(stl.triangles.len() == 1);
                assert!(stl.triangles[0] == file.triangles[0])
            },
            Err(_) => panic!()
        }
    }
}