185 lines
6.7 KiB
Rust
185 lines
6.7 KiB
Rust
//
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// Copyright (c) 2016 KAMADA Ken'ichi.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// 1. Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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// SUCH DAMAGE.
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//
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use std::io;
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use std::mem;
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// This is a module to select endianess by using generics
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// in order to avoid run-time dispatching penalty at the cost of
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// increased object size.
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pub trait Endian {
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fn loadu16(buf: &[u8], from: usize) -> u16;
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fn loadu32(buf: &[u8], from: usize) -> u32;
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fn loadu64(buf: &[u8], from: usize) -> u64;
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fn writeu16<W>(w: &mut W, num: u16) -> io::Result<()> where W: io::Write;
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fn writeu32<W>(w: &mut W, num: u32) -> io::Result<()> where W: io::Write;
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fn writeu64<W>(w: &mut W, num: u64) -> io::Result<()> where W: io::Write;
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}
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pub struct BigEndian;
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pub struct LittleEndian;
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macro_rules! generate_load {
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($name:ident, $int_type:ident, $from_func:ident) => (
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fn $name(buf: &[u8], offset: usize) -> $int_type {
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let mut num = [0u8; mem::size_of::<$int_type>()];
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num.copy_from_slice(
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&buf[offset .. offset + mem::size_of::<$int_type>()]);
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$int_type::$from_func(num)
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}
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)
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}
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macro_rules! generate_write {
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($name:ident, $int_type:ident, $to_func:ident) => (
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fn $name<W>(w: &mut W, num: $int_type)
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-> io::Result<()> where W: io::Write {
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let buf = num.$to_func();
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w.write_all(&buf)
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}
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)
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}
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impl Endian for BigEndian {
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generate_load!(loadu16, u16, from_be_bytes);
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generate_load!(loadu32, u32, from_be_bytes);
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generate_load!(loadu64, u64, from_be_bytes);
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generate_write!(writeu16, u16, to_be_bytes);
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generate_write!(writeu32, u32, to_be_bytes);
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generate_write!(writeu64, u64, to_be_bytes);
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}
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impl Endian for LittleEndian {
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generate_load!(loadu16, u16, from_le_bytes);
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generate_load!(loadu32, u32, from_le_bytes);
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generate_load!(loadu64, u64, from_le_bytes);
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generate_write!(writeu16, u16, to_le_bytes);
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generate_write!(writeu32, u32, to_le_bytes);
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generate_write!(writeu64, u64, to_le_bytes);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn loadu16() {
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assert_eq!(BigEndian::loadu16(&[0x01, 0x02], 0), 0x0102);
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assert_eq!(BigEndian::loadu16(&[0x01, 0x02, 0x03], 1), 0x0203);
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assert_eq!(LittleEndian::loadu16(&[0x01, 0x02], 0), 0x0201);
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assert_eq!(LittleEndian::loadu16(&[0x01, 0x02, 0x03], 1), 0x0302);
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}
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#[test]
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fn loadu32() {
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assert_eq!(BigEndian::loadu32(&[0x01, 0x02, 0x03, 0x04], 0),
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0x01020304);
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assert_eq!(BigEndian::loadu32(&[0x01, 0x02, 0x03, 0x04, 0x05], 1),
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0x02030405);
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assert_eq!(LittleEndian::loadu32(&[0x01, 0x02, 0x03, 0x04], 0),
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0x04030201);
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assert_eq!(LittleEndian::loadu32(&[0x01, 0x02, 0x03, 0x04, 0x05], 1),
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0x05040302);
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}
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#[test]
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fn loadu64() {
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assert_eq!(BigEndian::loadu64(&[0x01, 0x02, 0x03, 0x04,
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0x05, 0x06, 0x07, 0x08], 0),
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0x0102030405060708);
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assert_eq!(BigEndian::loadu64(&[0x01, 0x02, 0x03, 0x04, 0x05,
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0x06, 0x07, 0x08, 0x09], 1),
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0x0203040506070809);
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assert_eq!(LittleEndian::loadu64(&[0x01, 0x02, 0x03, 0x04,
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0x05, 0x06, 0x07, 0x08], 0),
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0x0807060504030201);
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assert_eq!(LittleEndian::loadu64(&[0x01, 0x02, 0x03, 0x04, 0x05,
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0x06, 0x07, 0x08, 0x09], 1),
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0x0908070605040302);
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}
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#[test]
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fn writeu16() {
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let mut buf = Vec::new();
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BigEndian::writeu16(&mut buf, 0x0102).unwrap();
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LittleEndian::writeu16(&mut buf, 0x0304).unwrap();
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assert_eq!(buf, b"\x01\x02\x04\x03");
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}
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#[test]
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fn writeu32() {
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let mut buf = Vec::new();
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BigEndian::writeu32(&mut buf, 0x01020304).unwrap();
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LittleEndian::writeu32(&mut buf, 0x05060708).unwrap();
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assert_eq!(buf, b"\x01\x02\x03\x04\x08\x07\x06\x05");
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}
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#[test]
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fn writeu64() {
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let mut buf = Vec::new();
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BigEndian::writeu64(&mut buf, 0x0102030405060708).unwrap();
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LittleEndian::writeu64(&mut buf, 0x090a0b0c0d0e0f10).unwrap();
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assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08\
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\x10\x0f\x0e\x0d\x0c\x0b\x0a\x09");
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}
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#[test]
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fn dispatch() {
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fn dispatch_sub<E>(data: &[u8]) -> u16 where E: Endian {
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E::loadu16(data, 0)
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}
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assert_eq!(dispatch_sub::<BigEndian>(&[0x01, 0x02]), 0x0102);
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assert_eq!(dispatch_sub::<LittleEndian>(&[0x01, 0x02]), 0x0201);
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}
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#[test]
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fn static_dispatch() {
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fn dispatch_sub<E>(data: &[u8]) -> u16 where E: Endian {
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E::loadu16(data, 0)
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}
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assert_eq!(dispatch_sub::<BigEndian> as *const (),
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dispatch_sub::<BigEndian> as *const ());
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assert_ne!(dispatch_sub::<BigEndian> as *const (),
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dispatch_sub::<LittleEndian> as *const ());
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}
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#[test]
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#[should_panic(expected = "index 3 out of range for slice of length 2")]
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fn out_of_range() {
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BigEndian::loadu16(&[0x01, 0x02], 1);
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}
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// "attempt to add with overflow" with the arithmetic overflow
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// check, and "slice index starts at 18446744073709551615 but ends
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// at 1" without it.
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#[test]
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#[should_panic(expected = "at")]
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fn wrap_around() {
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BigEndian::loadu16(&[0x01, 0x02], (-1isize) as usize);
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}
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}
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