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/* * BSD 3-Clause License * * Copyright (c) 2020, InterlockLedger Network * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * * Neither the name of the copyright holder nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ //! This crate provides a **no_std** implementation of the **InterlockLedger ILInt** //! format. This format allows the encoding of 64 bit integer values in a compact //! format that uses 1 to 9 bytes of space depending on the actual value. See //! [ILInt Specification](https://github.com/interlockledger/specification/tree/master/ILInt) //! for further details about the format. #![no_std] #[cfg(test)] mod tests; /// LInt base value. All values smaller than this value are encoded as /// a single byte. pub const ILINT_BASE:u8 = 0xF8; /// Value of ILINT_BASE as U64. pub const ILINT_BASE_U64:u64 = ILINT_BASE as u64; /// Types of errors generated by this library. pub enum ErrorKind { /// The provided buffer is too small. InsufficientBuffer, /// The encoded value is larger than 26^4 - 1 (18446744073709551615). Overflow, } /// Alias to the Result used by this library. pub type Result<T> = core::result::Result<T, ErrorKind>; /// Returns the size of the given value encoded as an ILInt. /// /// Arguments: /// /// * `value` : The value to be encoded; /// /// Returns: /// /// * The number of bytes required to encode the value; /// pub fn encoded_size(value: u64) -> usize { if value < ILINT_BASE_U64 { 1 } else if value <= (0xFF + ILINT_BASE_U64) { 2 } else if value <= (0xFFFF + ILINT_BASE_U64) { 3 } else if value <= (0x00FF_FFFF + ILINT_BASE_U64){ 4 } else if value <= (0xFFFF_FFFF + ILINT_BASE_U64){ 5 } else if value <= (0x00FF_FFFF_FFFF + ILINT_BASE_U64){ 6 } else if value <= (0xFFFF_FFFF_FFFF + ILINT_BASE_U64){ 7 } else if value <= (0x00FF_FFFF_FFFF_FFFF + ILINT_BASE_U64){ 8 } else { 9 } } /// Encodes the given value into a ILInt value. /// /// Arguments: /// /// * `value`: The value to be encoded; /// * `enc`: The slice that will receive the encoded value. /// It must have at least encoded_size(value) bytes; /// /// Returns: /// /// * `Ok(size)`: The number of bytes used. /// * `Err(ErrorKind::InsufficientBuffer)`: If the buffer is too small /// to hold the encoded value. /// pub fn encode(value: u64, enc: &mut[u8]) -> Result<usize> { let size = encoded_size(value); if size > enc.len() { Err(ErrorKind::InsufficientBuffer) } else { if size == 1 { enc[0] = value as u8 } else { enc[0] = (ILINT_BASE + ((size - 2) as u8)) as u8; let v = value - ILINT_BASE_U64; let mut shift = 8 * (size - 1); for i in enc.iter_mut().take(size).skip(1) { shift -= 8; *i = ((v >> shift) & 0xFF) as u8; } } Ok(size) } } /// Determines the size of the ILInt based on its header (the /// first byte of the encoded value). /// /// Arguments: /// /// * `header`: The header of the ILInt. It is always the first byte of /// the ILInt value; /// /// Returns: /// /// * The size of the ILInt in bytes, including the header. /// pub fn decoded_size(header : u8) -> usize { if header < ILINT_BASE { 1 } else { (header - ILINT_BASE + 2) as usize } } /// Decodes an **ILInt** value. /// /// Arguments: /// /// * `value`: The **ILInt** value; /// /// Returns: /// /// * Ok(value,size): The decoded value and the number of bytes used. /// * `Err(ErrorKind::InsufficientBuffer)`: If the buffer is too small /// to hold the encoded value. /// * `Err(ErrorKind::Overflow)`: If the encoded value is larger than /// the maximum allowed value. /// pub fn decode(value: &[u8]) -> Result<(u64, usize)> { if value.is_empty() { return Err(ErrorKind::InsufficientBuffer); } let size = decoded_size(value[0]); if size > value.len() { return Err(ErrorKind::InsufficientBuffer); } if size == 1 { Ok((value[0] as u64, 1)) } else { let mut v:u64 = 0; for i in value.iter().take(size).skip(1) { v = (v << 8) + (*i as u64); } if v > 0xFFFF_FFFF_FFFF_FF07 { Err(ErrorKind::Overflow) } else { Ok((v + ILINT_BASE_U64, size)) } } }