src/libextra/crypto/cryptoutil.rs - third_party/rust - Git at Google

 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.

 use std::num::{One, Zero, CheckedAdd};
 use std::vec::bytes::{MutableByteVector, copy_memory};


 /// Write a u64 into a vector, which must be 8 bytes long. The value is written in big-endian
 /// format.
 pub fn write_u64_be(dst: &mut[u8], input: u64) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_be64;
     assert!(dst.len() == 8);
     unsafe {
         let x: *mut i64 = transmute(dst.unsafe_mut_ref(0));
         *x = to_be64(input as i64);
     }
 }

 /// Write a u32 into a vector, which must be 4 bytes long. The value is written in big-endian
 /// format.
 pub fn write_u32_be(dst: &mut[u8], input: u32) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_be32;
     assert!(dst.len() == 4);
     unsafe {
         let x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
         *x = to_be32(input as i32);
     }
 }

 /// Write a u32 into a vector, which must be 4 bytes long. The value is written in little-endian
 /// format.
 pub fn write_u32_le(dst: &mut[u8], input: u32) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_le32;
     assert!(dst.len() == 4);
     unsafe {
         let x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
         *x = to_le32(input as i32);
     }
 }

 /// Read a vector of bytes into a vector of u64s. The values are read in big-endian format.
 pub fn read_u64v_be(dst: &mut[u64], input: &[u8]) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_be64;
     assert!(dst.len() * 8 == input.len());
     unsafe {
         let mut x: *mut i64 = transmute(dst.unsafe_mut_ref(0));
         let mut y: *i64 = transmute(input.unsafe_ref(0));
         do dst.len().times() {
             *x = to_be64(*y);
             x = x.offset(1);
             y = y.offset(1);
         }
     }
 }

 /// Read a vector of bytes into a vector of u32s. The values are read in big-endian format.
 pub fn read_u32v_be(dst: &mut[u32], input: &[u8]) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_be32;
     assert!(dst.len() * 4 == input.len());
     unsafe {
         let mut x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
         let mut y: *i32 = transmute(input.unsafe_ref(0));
         do dst.len().times() {
             *x = to_be32(*y);
             x = x.offset(1);
             y = y.offset(1);
         }
     }
 }

 /// Read a vector of bytes into a vector of u32s. The values are read in little-endian format.
 pub fn read_u32v_le(dst: &mut[u32], input: &[u8]) {
     use std::cast::transmute;
     use std::unstable::intrinsics::to_le32;
     assert!(dst.len() * 4 == input.len());
     unsafe {
         let mut x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
         let mut y: *i32 = transmute(input.unsafe_ref(0));
         do dst.len().times() {
             *x = to_le32(*y);
             x = x.offset(1);
             y = y.offset(1);
         }
     }
 }


 trait ToBits {
     /// Convert the value in bytes to the number of bits, a tuple where the 1st item is the
     /// high-order value and the 2nd item is the low order value.
     fn to_bits(self) -> (Self, Self);
 }

 impl ToBits for u64 {
     fn to_bits(self) -> (u64, u64) {
         return (self >> 61, self << 3);
     }
 }

 /// Adds the specified number of bytes to the bit count. fail!() if this would cause numeric
 /// overflow.
 pub fn add_bytes_to_bits<T: Int + CheckedAdd + ToBits>(bits: T, bytes: T) -> T {
     let (new_high_bits, new_low_bits) = bytes.to_bits();

     if new_high_bits > Zero::zero() {
         fail!("Numeric overflow occured.")
     }

     match bits.checked_add(&new_low_bits) {
         Some(x) => return x,
         None => fail!("Numeric overflow occured.")
     }
 }

 /// Adds the specified number of bytes to the bit count, which is a tuple where the first element is
 /// the high order value. fail!() if this would cause numeric overflow.
 pub fn add_bytes_to_bits_tuple
         <T: Int + Unsigned + CheckedAdd + ToBits>
         (bits: (T, T), bytes: T) -> (T, T) {
     let (new_high_bits, new_low_bits) = bytes.to_bits();
     let (hi, low) = bits;

     // Add the low order value - if there is no overflow, then add the high order values
     // If the addition of the low order values causes overflow, add one to the high order values
     // before adding them.
     match low.checked_add(&new_low_bits) {
         Some(x) => {
             if new_high_bits == Zero::zero() {
                 // This is the fast path - every other alternative will rarely occur in practice
                 // considering how large an input would need to be for those paths to be used.
                 return (hi, x);
             } else {
                 match hi.checked_add(&new_high_bits) {
                     Some(y) => return (y, x),
                     None => fail!("Numeric overflow occured.")
                 }
             }
         },
         None => {
             let one: T = One::one();
             let z = match new_high_bits.checked_add(&one) {
                 Some(w) => w,
                 None => fail!("Numeric overflow occured.")
             };
             match hi.checked_add(&z) {
                 // This re-executes the addition that was already performed earlier when overflow
                 // occured, this time allowing the overflow to happen. Technically, this could be
                 // avoided by using the checked add intrinsic directly, but that involves using
                 // unsafe code and is not really worthwhile considering how infrequently code will
                 // run in practice. This is the reason that this function requires that the type T
                 // be Unsigned - overflow is not defined for Signed types. This function could be
                 // implemented for signed types as well if that were needed.
                 Some(y) => return (y, low + new_low_bits),
                 None => fail!("Numeric overflow occured.")
             }
         }
     }
 }


 /// A FixedBuffer, likes its name implies, is a fixed size buffer. When the buffer becomes full, it
 /// must be processed. The input() method takes care of processing and then clearing the buffer
 /// automatically. However, other methods do not and require the caller to process the buffer. Any
 /// method that modifies the buffer directory or provides the caller with bytes that can be modifies
 /// results in those bytes being marked as used by the buffer.
 pub trait FixedBuffer {
     /// Input a vector of bytes. If the buffer becomes full, process it with the provided
     /// function and then clear the buffer.
     fn input(&mut self, input: &[u8], func: &fn(&[u8]));

     /// Reset the buffer.
     fn reset(&mut self);

     /// Zero the buffer up until the specified index. The buffer position currently must not be
     /// greater than that index.
     fn zero_until(&mut self, idx: uint);

     /// Get a slice of the buffer of the specified size. There must be at least that many bytes
     /// remaining in the buffer.
     fn next<'s>(&'s mut self, len: uint) -> &'s mut [u8];

     /// Get the current buffer. The buffer must already be full. This clears the buffer as well.
     fn full_buffer<'s>(&'s mut self) -> &'s [u8];

     /// Get the current position of the buffer.
     fn position(&self) -> uint;

     /// Get the number of bytes remaining in the buffer until it is full.
     fn remaining(&self) -> uint;

     /// Get the size of the buffer
     fn size(&self) -> uint;
 }

 macro_rules! impl_fixed_buffer( ($name:ident, $size:expr) => (
     impl FixedBuffer for $name {
         fn input(&mut self, input: &[u8], func: &fn(&[u8])) {
             let mut i = 0;

             // FIXME: #6304 - This local variable shouldn't be necessary.
             let size = $size;

             // If there is already data in the buffer, copy as much as we can into it and process
             // the data if the buffer becomes full.
             if self.buffer_idx != 0 {
                 let buffer_remaining = size - self.buffer_idx;
                 if input.len() >= buffer_remaining {
                         copy_memory(
                             self.buffer.mut_slice(self.buffer_idx, size),
                             input.slice_to(buffer_remaining),
                             buffer_remaining);
                     self.buffer_idx = 0;
                     func(self.buffer);
                     i += buffer_remaining;
                 } else {
                     copy_memory(
                         self.buffer.mut_slice(self.buffer_idx, self.buffer_idx + input.len()),
                         input,
                         input.len());
                     self.buffer_idx += input.len();
                     return;
                 }
             }

             // While we have at least a full buffer size chunks's worth of data, process that data
             // without copying it into the buffer
             while input.len() - i >= size {
                 func(input.slice(i, i + size));
                 i += size;
             }

             // Copy any input data into the buffer. At this point in the method, the ammount of
             // data left in the input vector will be less than the buffer size and the buffer will
             // be empty.
             let input_remaining = input.len() - i;
             copy_memory(
                 self.buffer.mut_slice(0, input_remaining),
                 input.slice_from(i),
                 input.len() - i);
             self.buffer_idx += input_remaining;
         }

         fn reset(&mut self) {
             self.buffer_idx = 0;
         }

         fn zero_until(&mut self, idx: uint) {
             assert!(idx >= self.buffer_idx);
             self.buffer.mut_slice(self.buffer_idx, idx).set_memory(0);
             self.buffer_idx = idx;
         }

         fn next<'s>(&'s mut self, len: uint) -> &'s mut [u8] {
             self.buffer_idx += len;
             return self.buffer.mut_slice(self.buffer_idx - len, self.buffer_idx);
         }

         fn full_buffer<'s>(&'s mut self) -> &'s [u8] {
             assert!(self.buffer_idx == $size);
             self.buffer_idx = 0;
             return self.buffer.slice_to($size);
         }

         fn position(&self) -> uint { self.buffer_idx }

         fn remaining(&self) -> uint { $size - self.buffer_idx }

         fn size(&self) -> uint { $size }
     }
 ))


 /// A fixed size buffer of 64 bytes useful for cryptographic operations.
 pub struct FixedBuffer64 {
     priv buffer: [u8, ..64],
     priv buffer_idx: uint,
 }

 impl FixedBuffer64 {
     /// Create a new buffer
     pub fn new() -> FixedBuffer64 {
         return FixedBuffer64 {
             buffer: [0u8, ..64],
             buffer_idx: 0
         };
     }
 }

 impl_fixed_buffer!(FixedBuffer64, 64)

 /// A fixed size buffer of 128 bytes useful for cryptographic operations.
 pub struct FixedBuffer128 {
     priv buffer: [u8, ..128],
     priv buffer_idx: uint,
 }

 impl FixedBuffer128 {
     /// Create a new buffer
     pub fn new() -> FixedBuffer128 {
         return FixedBuffer128 {
             buffer: [0u8, ..128],
             buffer_idx: 0
         };
     }
 }

 impl_fixed_buffer!(FixedBuffer128, 128)


 /// The StandardPadding trait adds a method useful for various hash algorithms to a FixedBuffer
 /// struct.
 pub trait StandardPadding {
     /// Add standard padding to the buffer. The buffer must not be full when this method is called
     /// and is guaranteed to have exactly rem remaining bytes when it returns. If there are not at
     /// least rem bytes available, the buffer will be zero padded, processed, cleared, and then
     /// filled with zeros again until only rem bytes are remaining.
     fn standard_padding(&mut self, rem: uint, func: &fn(&[u8]));
 }

 impl <T: FixedBuffer> StandardPadding for T {
     fn standard_padding(&mut self, rem: uint, func: &fn(&[u8])) {
         let size = self.size();

         self.next(1)[0] = 128;

         if self.remaining() < rem {
             self.zero_until(size);
             func(self.full_buffer());
         }

         self.zero_until(size - rem);
     }
 }


 #[cfg(test)]
 mod test {
     use std::rand::{IsaacRng, Rng};
     use std::vec;

     use cryptoutil::{add_bytes_to_bits, add_bytes_to_bits_tuple};
     use digest::Digest;
     use hex::FromHex;

     /// Feed 1,000,000 'a's into the digest with varying input sizes and check that the result is
     /// correct.
     pub fn test_digest_1million_random<D: Digest>(digest: &mut D, blocksize: uint, expected: &str) {
         let total_size = 1000000;
         let buffer = vec::from_elem(blocksize * 2, 'a' as u8);
         let mut rng = IsaacRng::new_unseeded();
         let mut count = 0;

         digest.reset();

         while count < total_size {
             let next: uint = rng.gen_integer_range(0, 2 * blocksize + 1);
             let remaining = total_size - count;
             let size = if next > remaining { remaining } else { next };
             digest.input(buffer.slice_to(size));
             count += size;
         }

         let result_str = digest.result_str();
         let result_bytes = digest.result_bytes();

         assert_eq!(expected, result_str.as_slice());
         assert_eq!(expected.from_hex().unwrap(), result_bytes);
     }

     // A normal addition - no overflow occurs
     #[test]
     fn test_add_bytes_to_bits_ok() {
         assert!(add_bytes_to_bits::<u64>(100, 10) == 180);
     }

     // A simple failure case - adding 1 to the max value
     #[test]
     #[should_fail]
     fn test_add_bytes_to_bits_overflow() {
         add_bytes_to_bits::<u64>(Bounded::max_value(), 1);
     }

     // A normal addition - no overflow occurs (fast path)
     #[test]
     fn test_add_bytes_to_bits_tuple_ok() {
         assert!(add_bytes_to_bits_tuple::<u64>((5, 100), 10) == (5, 180));
     }

     // The low order value overflows into the high order value
     #[test]
     fn test_add_bytes_to_bits_tuple_ok2() {
         assert!(add_bytes_to_bits_tuple::<u64>((5, Bounded::max_value()), 1) == (6, 7));
     }

     // The value to add is too large to be converted into bits without overflowing its type
     #[test]
     fn test_add_bytes_to_bits_tuple_ok3() {
         assert!(add_bytes_to_bits_tuple::<u64>((5, 0), 0x4000000000000001) == (7, 8));
     }

     // A simple failure case - adding 1 to the max value
     #[test]
     #[should_fail]
     fn test_add_bytes_to_bits_tuple_overflow() {
         add_bytes_to_bits_tuple::<u64>((Bounded::max_value(), Bounded::max_value()), 1);
     }

     // The value to add is too large to convert to bytes without overflowing its type, but the high
     // order value from this conversion overflows when added to the existing high order value
     #[test]
     #[should_fail]
     fn test_add_bytes_to_bits_tuple_overflow2() {
         let value: u64 = Bounded::max_value();
         add_bytes_to_bits_tuple::<u64>((value - 1, 0), 0x8000000000000000);
     }
 }
	// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
	// file at the top-level directory of this distribution and at
	// http://rust-lang.org/COPYRIGHT.
	//
	// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
	// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
	// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
	// option. This file may not be copied, modified, or distributed
	// except according to those terms.

	use std::num::{One, Zero, CheckedAdd};
	use std::vec::bytes::{MutableByteVector, copy_memory};


	/// Write a u64 into a vector, which must be 8 bytes long. The value is written in big-endian
	/// format.
	pub fn write_u64_be(dst: &mut[u8], input: u64) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_be64;
	assert!(dst.len() == 8);
	unsafe {
	let x: *mut i64 = transmute(dst.unsafe_mut_ref(0));
	*x = to_be64(input as i64);
	}
	}

	/// Write a u32 into a vector, which must be 4 bytes long. The value is written in big-endian
	/// format.
	pub fn write_u32_be(dst: &mut[u8], input: u32) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_be32;
	assert!(dst.len() == 4);
	unsafe {
	let x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
	*x = to_be32(input as i32);
	}
	}

	/// Write a u32 into a vector, which must be 4 bytes long. The value is written in little-endian
	/// format.
	pub fn write_u32_le(dst: &mut[u8], input: u32) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_le32;
	assert!(dst.len() == 4);
	unsafe {
	let x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
	*x = to_le32(input as i32);
	}
	}

	/// Read a vector of bytes into a vector of u64s. The values are read in big-endian format.
	pub fn read_u64v_be(dst: &mut[u64], input: &[u8]) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_be64;
	assert!(dst.len() * 8 == input.len());
	unsafe {
	let mut x: *mut i64 = transmute(dst.unsafe_mut_ref(0));
	let mut y: *i64 = transmute(input.unsafe_ref(0));
	do dst.len().times() {
	x = to_be64(y);
	x = x.offset(1);
	y = y.offset(1);
	}
	}
	}

	/// Read a vector of bytes into a vector of u32s. The values are read in big-endian format.
	pub fn read_u32v_be(dst: &mut[u32], input: &[u8]) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_be32;
	assert!(dst.len() * 4 == input.len());
	unsafe {
	let mut x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
	let mut y: *i32 = transmute(input.unsafe_ref(0));
	do dst.len().times() {
	x = to_be32(y);
	x = x.offset(1);
	y = y.offset(1);
	}
	}
	}

	/// Read a vector of bytes into a vector of u32s. The values are read in little-endian format.
	pub fn read_u32v_le(dst: &mut[u32], input: &[u8]) {
	use std::cast::transmute;
	use std::unstable::intrinsics::to_le32;
	assert!(dst.len() * 4 == input.len());
	unsafe {
	let mut x: *mut i32 = transmute(dst.unsafe_mut_ref(0));
	let mut y: *i32 = transmute(input.unsafe_ref(0));
	do dst.len().times() {
	x = to_le32(y);
	x = x.offset(1);
	y = y.offset(1);
	}
	}
	}


	trait ToBits {
	/// Convert the value in bytes to the number of bits, a tuple where the 1st item is the
	/// high-order value and the 2nd item is the low order value.
	fn to_bits(self) -> (Self, Self);
	}

	impl ToBits for u64 {
	fn to_bits(self) -> (u64, u64) {
	return (self >> 61, self << 3);
	}
	}

	/// Adds the specified number of bytes to the bit count. fail!() if this would cause numeric
	/// overflow.
	pub fn add_bytes_to_bits<T: Int + CheckedAdd + ToBits>(bits: T, bytes: T) -> T {
	let (new_high_bits, new_low_bits) = bytes.to_bits();

	if new_high_bits > Zero::zero() {
	fail!("Numeric overflow occured.")
	}

	match bits.checked_add(&new_low_bits) {
	Some(x) => return x,
	None => fail!("Numeric overflow occured.")
	}
	}

	/// Adds the specified number of bytes to the bit count, which is a tuple where the first element is
	/// the high order value. fail!() if this would cause numeric overflow.
	pub fn add_bytes_to_bits_tuple
	<T: Int + Unsigned + CheckedAdd + ToBits>
	(bits: (T, T), bytes: T) -> (T, T) {
	let (new_high_bits, new_low_bits) = bytes.to_bits();
	let (hi, low) = bits;

	// Add the low order value - if there is no overflow, then add the high order values
	// If the addition of the low order values causes overflow, add one to the high order values
	// before adding them.
	match low.checked_add(&new_low_bits) {
	Some(x) => {
	if new_high_bits == Zero::zero() {
	// This is the fast path - every other alternative will rarely occur in practice
	// considering how large an input would need to be for those paths to be used.
	return (hi, x);
	} else {
	match hi.checked_add(&new_high_bits) {
	Some(y) => return (y, x),
	None => fail!("Numeric overflow occured.")
	}
	}
	},
	None => {
	let one: T = One::one();
	let z = match new_high_bits.checked_add(&one) {
	Some(w) => w,
	None => fail!("Numeric overflow occured.")
	};
	match hi.checked_add(&z) {
	// This re-executes the addition that was already performed earlier when overflow
	// occured, this time allowing the overflow to happen. Technically, this could be
	// avoided by using the checked add intrinsic directly, but that involves using
	// unsafe code and is not really worthwhile considering how infrequently code will
	// run in practice. This is the reason that this function requires that the type T
	// be Unsigned - overflow is not defined for Signed types. This function could be
	// implemented for signed types as well if that were needed.
	Some(y) => return (y, low + new_low_bits),
	None => fail!("Numeric overflow occured.")
	}
	}
	}
	}


	/// A FixedBuffer, likes its name implies, is a fixed size buffer. When the buffer becomes full, it
	/// must be processed. The input() method takes care of processing and then clearing the buffer
	/// automatically. However, other methods do not and require the caller to process the buffer. Any
	/// method that modifies the buffer directory or provides the caller with bytes that can be modifies
	/// results in those bytes being marked as used by the buffer.
	pub trait FixedBuffer {
	/// Input a vector of bytes. If the buffer becomes full, process it with the provided
	/// function and then clear the buffer.
	fn input(&mut self, input: &[u8], func: &fn(&[u8]));

	/// Reset the buffer.
	fn reset(&mut self);

	/// Zero the buffer up until the specified index. The buffer position currently must not be
	/// greater than that index.
	fn zero_until(&mut self, idx: uint);

	/// Get a slice of the buffer of the specified size. There must be at least that many bytes
	/// remaining in the buffer.
	fn next<'s>(&'s mut self, len: uint) -> &'s mut [u8];

	/// Get the current buffer. The buffer must already be full. This clears the buffer as well.
	fn full_buffer<'s>(&'s mut self) -> &'s [u8];

	/// Get the current position of the buffer.
	fn position(&self) -> uint;

	/// Get the number of bytes remaining in the buffer until it is full.
	fn remaining(&self) -> uint;

	/// Get the size of the buffer
	fn size(&self) -> uint;
	}

	macro_rules! impl_fixed_buffer( ($name:ident, $size:expr) => (
	impl FixedBuffer for $name {
	fn input(&mut self, input: &[u8], func: &fn(&[u8])) {
	let mut i = 0;

	// FIXME: #6304 - This local variable shouldn't be necessary.
	let size = $size;

	// If there is already data in the buffer, copy as much as we can into it and process
	// the data if the buffer becomes full.
	if self.buffer_idx != 0 {
	let buffer_remaining = size - self.buffer_idx;
	if input.len() >= buffer_remaining {
	copy_memory(
	self.buffer.mut_slice(self.buffer_idx, size),
	input.slice_to(buffer_remaining),
	buffer_remaining);
	self.buffer_idx = 0;
	func(self.buffer);
	i += buffer_remaining;
	} else {
	copy_memory(
	self.buffer.mut_slice(self.buffer_idx, self.buffer_idx + input.len()),
	input,
	input.len());
	self.buffer_idx += input.len();
	return;
	}
	}

	// While we have at least a full buffer size chunks's worth of data, process that data
	// without copying it into the buffer
	while input.len() - i >= size {
	func(input.slice(i, i + size));
	i += size;
	}

	// Copy any input data into the buffer. At this point in the method, the ammount of
	// data left in the input vector will be less than the buffer size and the buffer will
	// be empty.
	let input_remaining = input.len() - i;
	copy_memory(
	self.buffer.mut_slice(0, input_remaining),
	input.slice_from(i),
	input.len() - i);
	self.buffer_idx += input_remaining;
	}

	fn reset(&mut self) {
	self.buffer_idx = 0;
	}

	fn zero_until(&mut self, idx: uint) {
	assert!(idx >= self.buffer_idx);
	self.buffer.mut_slice(self.buffer_idx, idx).set_memory(0);
	self.buffer_idx = idx;
	}

	fn next<'s>(&'s mut self, len: uint) -> &'s mut [u8] {
	self.buffer_idx += len;
	return self.buffer.mut_slice(self.buffer_idx - len, self.buffer_idx);
	}

	fn full_buffer<'s>(&'s mut self) -> &'s [u8] {
	assert!(self.buffer_idx == $size);
	self.buffer_idx = 0;
	return self.buffer.slice_to($size);
	}

	fn position(&self) -> uint { self.buffer_idx }

	fn remaining(&self) -> uint { $size - self.buffer_idx }

	fn size(&self) -> uint { $size }
	}
	))


	/// A fixed size buffer of 64 bytes useful for cryptographic operations.
	pub struct FixedBuffer64 {
	priv buffer: [u8, ..64],
	priv buffer_idx: uint,
	}

	impl FixedBuffer64 {
	/// Create a new buffer
	pub fn new() -> FixedBuffer64 {
	return FixedBuffer64 {
	buffer: [0u8, ..64],
	buffer_idx: 0
	};
	}
	}

	impl_fixed_buffer!(FixedBuffer64, 64)

	/// A fixed size buffer of 128 bytes useful for cryptographic operations.
	pub struct FixedBuffer128 {
	priv buffer: [u8, ..128],
	priv buffer_idx: uint,
	}

	impl FixedBuffer128 {
	/// Create a new buffer
	pub fn new() -> FixedBuffer128 {
	return FixedBuffer128 {
	buffer: [0u8, ..128],
	buffer_idx: 0
	};
	}
	}

	impl_fixed_buffer!(FixedBuffer128, 128)


	/// The StandardPadding trait adds a method useful for various hash algorithms to a FixedBuffer
	/// struct.
	pub trait StandardPadding {
	/// Add standard padding to the buffer. The buffer must not be full when this method is called
	/// and is guaranteed to have exactly rem remaining bytes when it returns. If there are not at
	/// least rem bytes available, the buffer will be zero padded, processed, cleared, and then
	/// filled with zeros again until only rem bytes are remaining.
	fn standard_padding(&mut self, rem: uint, func: &fn(&[u8]));
	}

	impl <T: FixedBuffer> StandardPadding for T {
	fn standard_padding(&mut self, rem: uint, func: &fn(&[u8])) {
	let size = self.size();

	self.next(1)[0] = 128;

	if self.remaining() < rem {
	self.zero_until(size);
	func(self.full_buffer());
	}

	self.zero_until(size - rem);
	}
	}


	#[cfg(test)]
	mod test {
	use std::rand::{IsaacRng, Rng};
	use std::vec;

	use cryptoutil::{add_bytes_to_bits, add_bytes_to_bits_tuple};
	use digest::Digest;
	use hex::FromHex;

	/// Feed 1,000,000 'a's into the digest with varying input sizes and check that the result is
	/// correct.
	pub fn test_digest_1million_random<D: Digest>(digest: &mut D, blocksize: uint, expected: &str) {
	let total_size = 1000000;
	let buffer = vec::from_elem(blocksize * 2, 'a' as u8);
	let mut rng = IsaacRng::new_unseeded();
	let mut count = 0;

	digest.reset();

	while count < total_size {
	let next: uint = rng.gen_integer_range(0, 2 * blocksize + 1);
	let remaining = total_size - count;
	let size = if next > remaining { remaining } else { next };
	digest.input(buffer.slice_to(size));
	count += size;
	}

	let result_str = digest.result_str();
	let result_bytes = digest.result_bytes();

	assert_eq!(expected, result_str.as_slice());
	assert_eq!(expected.from_hex().unwrap(), result_bytes);
	}

	// A normal addition - no overflow occurs
	#[test]
	fn test_add_bytes_to_bits_ok() {
	assert!(add_bytes_to_bits::<u64>(100, 10) == 180);
	}

	// A simple failure case - adding 1 to the max value
	#[test]
	#[should_fail]
	fn test_add_bytes_to_bits_overflow() {
	add_bytes_to_bits::<u64>(Bounded::max_value(), 1);
	}

	// A normal addition - no overflow occurs (fast path)
	#[test]
	fn test_add_bytes_to_bits_tuple_ok() {
	assert!(add_bytes_to_bits_tuple::<u64>((5, 100), 10) == (5, 180));
	}

	// The low order value overflows into the high order value
	#[test]
	fn test_add_bytes_to_bits_tuple_ok2() {
	assert!(add_bytes_to_bits_tuple::<u64>((5, Bounded::max_value()), 1) == (6, 7));
	}

	// The value to add is too large to be converted into bits without overflowing its type
	#[test]
	fn test_add_bytes_to_bits_tuple_ok3() {
	assert!(add_bytes_to_bits_tuple::<u64>((5, 0), 0x4000000000000001) == (7, 8));
	}

	// A simple failure case - adding 1 to the max value
	#[test]
	#[should_fail]
	fn test_add_bytes_to_bits_tuple_overflow() {
	add_bytes_to_bits_tuple::<u64>((Bounded::max_value(), Bounded::max_value()), 1);
	}

	// The value to add is too large to convert to bytes without overflowing its type, but the high
	// order value from this conversion overflows when added to the existing high order value
	#[test]
	#[should_fail]
	fn test_add_bytes_to_bits_tuple_overflow2() {
	let value: u64 = Bounded::max_value();
	add_bytes_to_bits_tuple::<u64>((value - 1, 0), 0x8000000000000000);
	}
	}