cursor.rs

#![allow(unstable)]

use std::io;
use std::iter::repeat;
use std::slice;

pub struct Cursor<T> {
    pos: u64,
    inner: T,
}

impl<T> Cursor<T> {
    pub fn new(inner: T) -> Cursor<T> {
        Cursor { pos: 0, inner: inner }
    }
    pub fn into_inner(self) -> T { self.inner }
    pub fn get_ref(&self) -> &T { &self.inner }
}

macro_rules! seek {
    () => {
        fn tell(&self) -> io::IoResult<u64> { Ok(self.pos) }

        fn seek(&mut self, offset: i64, style: io::SeekStyle) -> io::IoResult<()> {
            let pos = match style {
                io::SeekSet => 0,
                io::SeekEnd => self.inner.len() as u64,
                io::SeekCur => self.pos,
            } as i64;

            if offset + pos < 0 {
                Err(io::IoError {
                    kind: io::InvalidInput,
                    desc: "invalid seek to a negative offset",
                    detail: None
                })
            } else {
                self.pos = (offset + pos) as u64;
                Ok(())
            }
        }
    }
}

impl io::Seek for Cursor<Vec<u8>> { seek!(); }
impl<'a> io::Seek for Cursor<&'a [u8]> { seek!(); }
impl<'a> io::Seek for Cursor<&'a mut [u8]> { seek!(); }

macro_rules! read {
    () => {
        fn read(&mut self, buf: &mut [u8]) -> io::IoResult<usize> {
            if self.pos > self.inner.len() as u64 {
                return Err(io::standard_error(io::EndOfFile))
            }
            let mut slice = &self.inner[(self.pos as usize)..];
            match slice.read(buf) {
                Ok(amt) => {
                    self.pos += amt as u64;
                    Ok(amt)
                }
                Err(e) => Err(e)
            }
        }
    }
}

impl io::Reader for Cursor<Vec<u8>> { read!(); }
impl<'a> io::Reader for Cursor<&'a [u8]> { read!(); }
impl<'a> io::Reader for Cursor<&'a mut [u8]> { read!(); }

macro_rules! buffer {
    () => {
        fn fill_buf(&mut self) -> io::IoResult<&[u8]> {
            if self.pos < (self.inner.len() as u64) {
                Ok(&self.inner[(self.pos as usize)..])
            } else {
                Err(io::standard_error(io::EndOfFile))
            }
        }
        fn consume(&mut self, amt: usize) { self.pos += amt as u64; }
    }
}

impl io::Buffer for Cursor<Vec<u8>> { buffer!(); }
impl<'a> io::Buffer for Cursor<&'a [u8]> { buffer!(); }
impl<'a> io::Buffer for Cursor<&'a mut [u8]> { buffer!(); }

impl io::Writer for Cursor<Vec<u8>> {
    fn write(&mut self, buf: &[u8]) -> io::IoResult<()> {
        if self.pos == self.inner.len() as u64 {
            self.inner.push_all(buf)
        } else {
            // Make sure the internal buffer is as least as big as where we
            // currently are
            let difference = self.pos as i64 - self.inner.len() as i64;
            if difference > 0 {
                self.inner.extend(repeat(0).take(difference as usize));
            }

            // Figure out what bytes will be used to overwrite what's currently
            // there (left), and what will be appended on the end (right)
            let cap = self.inner.len() - (self.pos as usize);
            let (left, right) = if cap <= buf.len() {
                (&buf[..cap], &buf[cap..])
            } else {
                let result: (_, &[_]) = (buf, &[]);
                result
            };

            // Do the necessary writes
            if left.len() > 0 {
                let dst = &mut self.inner[(self.pos as usize)..];
                slice::bytes::copy_memory(dst, left);
            }
            if right.len() > 0 {
                self.inner.push_all(right);
            }
        }

        // Bump us forward
        self.pos += buf.len() as u64;
        Ok(())
    }
}

impl<'a> io::Writer for Cursor<&'a mut [u8]> {
    fn write(&mut self, data: &[u8]) -> io::IoResult<()> {
        if self.pos > self.inner.len() as u64 {
            return Err(io::standard_error(io::EndOfFile));
        }
        let dst = &mut self.inner[(self.pos as usize)..];
        let dst_len = dst.len();
        if dst_len == 0 {
            return Err(io::standard_error(io::EndOfFile));
        }

        let src_len = data.len();
        if dst_len >= src_len {
            slice::bytes::copy_memory(dst, data);
            self.pos += src_len as u64;
            Ok(())
        } else {
            slice::bytes::copy_memory(dst, &data[..dst_len]);
            self.pos += dst_len as u64;
            Err(io::standard_error(io::ShortWrite(dst_len)))
        }
    }
}

#[cfg(test)]
mod test {
    use std::io::{self, SeekSet, SeekCur, SeekEnd};
    use super::Cursor;

    #[test]
    fn test_vec_writer() {
        let mut writer = Vec::new();
        writer.write(&[0]).unwrap();
        writer.write(&[1, 2, 3]).unwrap();
        writer.write(&[4, 5, 6, 7]).unwrap();
        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
        assert_eq!(writer.as_slice(), b);
    }

    #[test]
    fn test_mem_writer() {
        let mut writer = Cursor::new(Vec::new());
        writer.write(&[0]).unwrap();
        writer.write(&[1, 2, 3]).unwrap();
        writer.write(&[4, 5, 6, 7]).unwrap();
        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
        assert_eq!(&writer.get_ref()[], b);
    }

    #[test]
    fn test_buf_writer() {
        let mut buf = [0 as u8; 9];
        {
            let mut writer = Cursor::new(&mut buf[]);
            assert_eq!(writer.tell(), Ok(0));
            writer.write(&[0]).unwrap();
            assert_eq!(writer.tell(), Ok(1));
            writer.write(&[1, 2, 3]).unwrap();
            writer.write(&[4, 5, 6, 7]).unwrap();
            assert_eq!(writer.tell(), Ok(8));
            writer.write(&[]).unwrap();
            assert_eq!(writer.tell(), Ok(8));

            assert_eq!(writer.write(&[8, 9]).err().unwrap().kind, io::ShortWrite(1));
            assert_eq!(writer.write(&[10]).err().unwrap().kind, io::EndOfFile);
        }
        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
        assert_eq!(buf, b);
    }

    #[test]
    fn test_buf_writer_seek() {
        let mut buf = [0 as u8; 8];
        {
            let mut writer = Cursor::new(&mut buf[]);
            assert_eq!(writer.tell(), Ok(0));
            writer.write(&[1]).unwrap();
            assert_eq!(writer.tell(), Ok(1));

            writer.seek(2, SeekSet).unwrap();
            assert_eq!(writer.tell(), Ok(2));
            writer.write(&[2]).unwrap();
            assert_eq!(writer.tell(), Ok(3));

            writer.seek(-2, SeekCur).unwrap();
            assert_eq!(writer.tell(), Ok(1));
            writer.write(&[3]).unwrap();
            assert_eq!(writer.tell(), Ok(2));

            writer.seek(-1, SeekEnd).unwrap();
            assert_eq!(writer.tell(), Ok(7));
            writer.write(&[4]).unwrap();
            assert_eq!(writer.tell(), Ok(8));

        }
        let b: &[_] = &[1, 3, 2, 0, 0, 0, 0, 4];
        assert_eq!(buf, b);
    }

    #[test]
    fn test_buf_writer_error() {
        let mut buf = [0 as u8; 2];
        let mut writer = Cursor::new(&mut buf[]);
        writer.write(&[0]).unwrap();

        match writer.write(&[0, 0]) {
            Ok(..) => panic!(),
            Err(e) => assert_eq!(e.kind, io::ShortWrite(1)),
        }
    }

    #[test]
    fn test_mem_reader() {
        let mut reader = Cursor::new(vec!(0u8, 1, 2, 3, 4, 5, 6, 7));
        let mut buf = [];
        assert_eq!(reader.read(&mut buf), Ok(0));
        assert_eq!(reader.tell(), Ok(0));
        let mut buf = [0];
        assert_eq!(reader.read(&mut buf), Ok(1));
        assert_eq!(reader.tell(), Ok(1));
        let b: &[_] = &[0];
        assert_eq!(buf, b);
        let mut buf = [0; 4];
        assert_eq!(reader.read(&mut buf), Ok(4));
        assert_eq!(reader.tell(), Ok(5));
        let b: &[_] = &[1, 2, 3, 4];
        assert_eq!(buf, b);
        assert_eq!(reader.read(&mut buf), Ok(3));
        let b: &[_] = &[5, 6, 7];
        assert_eq!(&buf[..3], b);
        assert!(reader.read(&mut buf).is_err());
        let mut reader = Cursor::new(vec!(0u8, 1, 2, 3, 4, 5, 6, 7));
        assert_eq!(reader.read_until(3).unwrap(), vec!(0, 1, 2, 3));
        assert_eq!(reader.read_until(3).unwrap(), vec!(4, 5, 6, 7));
        assert!(reader.read(&mut buf).is_err());
    }

    #[test]
    fn test_slice_reader() {
        let in_buf = vec![0u8, 1, 2, 3, 4, 5, 6, 7];
        let mut reader = &mut in_buf.as_slice();
        let mut buf = [];
        assert_eq!(reader.read(&mut buf), Ok(0));
        let mut buf = [0];
        assert_eq!(reader.read(&mut buf), Ok(1));
        assert_eq!(reader.len(), 7);
        let b: &[_] = &[0];
        assert_eq!(buf.as_slice(), b);
        let mut buf = [0; 4];
        assert_eq!(reader.read(&mut buf), Ok(4));
        assert_eq!(reader.len(), 3);
        let b: &[_] = &[1, 2, 3, 4];
        assert_eq!(buf.as_slice(), b);
        assert_eq!(reader.read(&mut buf), Ok(3));
        let b: &[_] = &[5, 6, 7];
        assert_eq!(&buf[..3], b);
        assert!(reader.read(&mut buf).is_err());
        let mut reader = &mut in_buf.as_slice();
        assert_eq!(reader.read_until(3).unwrap(), vec!(0, 1, 2, 3));
        assert_eq!(reader.read_until(3).unwrap(), vec!(4, 5, 6, 7));
        assert!(reader.read(&mut buf).is_err());
    }

    #[test]
    fn test_buf_reader() {
        let in_buf = vec![0u8, 1, 2, 3, 4, 5, 6, 7];
        let mut reader = Cursor::new(in_buf.as_slice());
        let mut buf = [];
        assert_eq!(reader.read(&mut buf), Ok(0));
        assert_eq!(reader.tell(), Ok(0));
        let mut buf = [0];
        assert_eq!(reader.read(&mut buf), Ok(1));
        assert_eq!(reader.tell(), Ok(1));
        let b: &[_] = &[0];
        assert_eq!(buf, b);
        let mut buf = [0; 4];
        assert_eq!(reader.read(&mut buf), Ok(4));
        assert_eq!(reader.tell(), Ok(5));
        let b: &[_] = &[1, 2, 3, 4];
        assert_eq!(buf, b);
        assert_eq!(reader.read(&mut buf), Ok(3));
        let b: &[_] = &[5, 6, 7];
        assert_eq!(&buf[..3], b);
        assert!(reader.read(&mut buf).is_err());
        let mut reader = Cursor::new(in_buf.as_slice());
        assert_eq!(reader.read_until(3).unwrap(), vec!(0, 1, 2, 3));
        assert_eq!(reader.read_until(3).unwrap(), vec!(4, 5, 6, 7));
        assert!(reader.read(&mut buf).is_err());
    }

    #[test]
    fn test_read_char() {
        let b = b"Vi\xE1\xBB\x87t";
        let mut r = Cursor::new(b);
        assert_eq!(r.read_char(), Ok('V'));
        assert_eq!(r.read_char(), Ok('i'));
        assert_eq!(r.read_char(), Ok('ệ'));
        assert_eq!(r.read_char(), Ok('t'));
        assert!(r.read_char().is_err());
    }

    #[test]
    fn test_read_bad_char() {
        let b = b"\x80";
        let mut r = Cursor::new(b);
        assert!(r.read_char().is_err());
    }

    #[test]
    fn test_write_strings() {
        let mut writer = Cursor::new(Vec::new());
        writer.write_str("testing").unwrap();
        writer.write_line("testing").unwrap();
        writer.write_str("testing").unwrap();
        let mut r = Cursor::new(&writer.get_ref()[]);
        assert_eq!(r.read_to_string().unwrap(), "testingtesting\ntesting");
    }

    #[test]
    fn test_write_char() {
        let mut writer = Cursor::new(Vec::new());
        writer.write_char('a').unwrap();
        writer.write_char('\n').unwrap();
        writer.write_char('ệ').unwrap();
        let mut r = Cursor::new(&writer.get_ref()[]);
        assert_eq!(r.read_to_string().unwrap(), "a\nệ");
    }

    #[test]
    fn test_read_whole_string_bad() {
        let buf = [0xff_u8];
        let mut r = Cursor::new(&buf[]);
        match r.read_to_string() {
            Ok(..) => panic!(),
            Err(..) => {}
        }
    }

    #[test]
    fn seek_past_end() {
        let buf = [0xff];
        let mut r = Cursor::new(&buf[]);
        r.seek(10, SeekSet).unwrap();
        assert!(r.read(&mut []).is_err());

        let mut r = Cursor::new(vec!(10u8));
        r.seek(10, SeekSet).unwrap();
        assert!(r.read(&mut []).is_err());

        let mut buf = [0];
        let mut r = Cursor::new(&mut buf[]);
        r.seek(10, SeekSet).unwrap();
        assert!(r.write(&[3]).is_err());
    }

    #[test]
    fn seek_before_0() {
        let buf = [0xff_u8];
        let mut r = Cursor::new(&buf[]);
        assert!(r.seek(-1, SeekSet).is_err());

        let mut r = Cursor::new(vec!(10u8));
        assert!(r.seek(-1, SeekSet).is_err());

        let mut buf = [0];
        let mut r = Cursor::new(&mut buf[]);
        assert!(r.seek(-1, SeekSet).is_err());
    }

    #[test]
    fn io_read_at_least() {
        let mut r = Cursor::new(vec![1u8, 2, 3, 4, 5, 6, 7, 8]);
        let mut buf = [0; 3];
        assert!(r.read_at_least(buf.len(), &mut buf).is_ok());
        let b: &[_] = &[1, 2, 3];
        assert_eq!(buf, b);
        assert!(r.read_at_least(0, buf.slice_to_mut(0)).is_ok());
        assert_eq!(buf, b);
        assert!(r.read_at_least(buf.len(), &mut buf).is_ok());
        let b: &[_] = &[4, 5, 6];
        assert_eq!(buf, b);
        assert!(r.read_at_least(buf.len(), &mut buf).is_err());
        let b: &[_] = &[7, 8, 6];
        assert_eq!(buf, b);
    }
}

#[cfg(test)]
mod tests {
    use super::Cursor;
    use std::io;

    #[test]
    fn test_seekable_mem_writer() {
        let mut writer = Cursor::new(Vec::<u8>::new());
        assert_eq!(writer.tell(), Ok(0));
        writer.write(&[0]).unwrap();
        assert_eq!(writer.tell(), Ok(1));
        writer.write(&[1, 2, 3]).unwrap();
        writer.write(&[4, 5, 6, 7]).unwrap();
        assert_eq!(writer.tell(), Ok(8));
        let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
        assert_eq!(&writer.get_ref()[], b);

        writer.seek(0, io::SeekSet).unwrap();
        assert_eq!(writer.tell(), Ok(0));
        writer.write(&[3, 4]).unwrap();
        let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
        assert_eq!(&writer.get_ref()[], b);

        writer.seek(1, io::SeekCur).unwrap();
        writer.write(&[0, 1]).unwrap();
        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
        assert_eq!(&writer.get_ref()[], b);

        writer.seek(-1, io::SeekEnd).unwrap();
        writer.write(&[1, 2]).unwrap();
        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
        assert_eq!(&writer.get_ref()[], b);

        writer.seek(1, io::SeekEnd).unwrap();
        writer.write(&[1]).unwrap();
        let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
        assert_eq!(&writer.get_ref()[], b);
    }

    #[test]
    fn seek_past_end() {
        let mut r = Cursor::new(Vec::new());
        r.seek(10, io::SeekSet).unwrap();
        assert!(r.write(&[3]).is_ok());
    }

    #[test]
    fn seek_before_0() {
        let mut r = Cursor::new(Vec::new());
        assert!(r.seek(-1, io::SeekSet).is_err());
    }
}