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use std::io::{Read, Seek, SeekFrom};
use Result;
pub trait Tape: Read + Seek + Sized {
#[doc(hidden)]
#[inline]
fn jump(&mut self, position: u64) -> Result<u64> {
self.seek(SeekFrom::Start(position))
}
#[doc(hidden)]
#[inline]
fn peek<T: Value>(&mut self) -> Result<T> {
self.stay(|tape| Value::read(tape))
}
#[doc(hidden)]
#[inline]
fn position(&mut self) -> Result<u64> {
self.seek(SeekFrom::Current(0))
}
#[doc(hidden)]
#[inline(always)]
fn take<T: Value>(&mut self) -> Result<T> {
Value::read(self)
}
#[doc(hidden)]
fn stay<F, T>(&mut self, mut body: F) -> Result<T> where F: FnMut(&mut Self) -> Result<T> {
let position = try!(self.position());
let result = body(self);
try!(self.jump(position));
result
}
}
pub trait Value: Sized {
fn read<T: Tape>(&mut T) -> Result<Self>;
}
pub trait Walue<P>: Sized {
fn read<T: Tape>(&mut T, P) -> Result<Self>;
}
impl<T: Read + Seek> Tape for T {}
macro_rules! read(
($tape:ident, $count:expr, $buffer:ident) => (
if try!(::std::io::Read::read($tape, &mut $buffer)) != $count {
return raise!("failed to read as much as needed");
}
);
($tape:ident, $size:expr) => (unsafe {
let mut buffer: [u8; $size] = ::std::mem::uninitialized();
read!($tape, $size, buffer);
::std::mem::transmute(buffer)
});
);
macro_rules! value {
($kind:ident, 1) => (impl Value for $kind {
#[inline]
fn read<T: Tape>(tape: &mut T) -> Result<Self> {
Ok(read!(tape, 1))
}
});
($kind:ident, $size:expr) => (impl Value for $kind {
#[inline]
fn read<T: Tape>(tape: &mut T) -> Result<Self> {
Ok($kind::from_be(read!(tape, $size)))
}
});
}
value!(i8, 1);
value!(u8, 1);
value!(i16, 2);
value!(u16, 2);
value!(u32, 4);
value!(i64, 8);
macro_rules! value(
([i8; $count:expr]) => (impl Value for [i8; $count] {
fn read<T: Tape>(tape: &mut T) -> Result<Self> {
let mut array: [u8; $count] = unsafe { ::std::mem::uninitialized() };
if try!(::std::io::Read::read(tape, &mut array)) != $count {
raise!("failed to read as much as needed")
}
Ok(unsafe { ::std::mem::transmute(array) })
}
});
([u8; $count:expr]) => (impl Value for [u8; $count] {
fn read<T: Tape>(tape: &mut T) -> Result<Self> {
let mut array: [u8; $count] = unsafe { ::std::mem::uninitialized() };
if try!(::std::io::Read::read(tape, &mut array)) != $count {
raise!("failed to read as much as needed")
}
Ok(array)
}
});
);
value!([i8; 4]);
value!([u8; 10]);
impl<V> Walue<usize> for Vec<V> where V: Value {
fn read<T: Tape>(tape: &mut T, count: usize) -> Result<Self> {
let mut values = Vec::with_capacity(count);
for _ in 0..count {
values.push(try!(Value::read(tape)));
}
Ok(values)
}
}