snarkvm_console_network_environment/helpers/
variable_length.rs

1// Copyright 2024-2025 Aleo Network Foundation
2// This file is part of the snarkVM library.
3
4// Licensed under the Apache License, Version 2.0 (the "License");
5// you may not use this file except in compliance with the License.
6// You may obtain a copy of the License at:
7
8// http://www.apache.org/licenses/LICENSE-2.0
9
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15
16use snarkvm_utilities::{
17    FromBytes,
18    error,
19    io::{Read, Result as IoResult},
20};
21
22/// Returns the variable length integer of the given value.
23/// https://en.bitcoin.it/wiki/Protocol_documentation#Variable_length_integer
24pub fn variable_length_integer(value: &u64) -> Vec<u8> {
25    match value {
26        // bounded by u8::max_value()
27        0..=252 => vec![*value as u8],
28        // bounded by u16::max_value()
29        253..=65535 => [vec![0xfd], (*value as u16).to_le_bytes().to_vec()].concat(),
30        // bounded by u32::max_value()
31        65536..=4_294_967_295 => [vec![0xfe], (*value as u32).to_le_bytes().to_vec()].concat(),
32        // bounded by u64::max_value()
33        _ => [vec![0xff], value.to_le_bytes().to_vec()].concat(),
34    }
35}
36
37/// Decode the value of a variable length integer.
38/// https://en.bitcoin.it/wiki/Protocol_documentation#Variable_length_integer
39pub fn read_variable_length_integer<R: Read>(mut reader: R) -> IoResult<u64> {
40    let flag = u8::read_le(&mut reader)?;
41
42    match flag {
43        0..=252 => Ok(flag as u64),
44        0xfd => match u16::read_le(&mut reader)? {
45            s if s < 253 => Err(error("Invalid variable size integer")),
46            s => Ok(s as u64),
47        },
48        0xfe => match u32::read_le(&mut reader)? {
49            s if s < 65536 => Err(error("Invalid variable size integer")),
50            s => Ok(s as u64),
51        },
52        _ => match u64::read_le(&mut reader)? {
53            s if s < 4_294_967_296 => Err(error("Invalid variable size integer")),
54            s => Ok(s),
55        },
56    }
57}
58
59#[cfg(test)]
60mod test {
61    use super::*;
62
63    const LENGTH_VALUES: [(u64, [u8; 9]); 14] = [
64        (20, [0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
65        (32, [0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
66        (200, [0xc8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
67        (252, [0xfc, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
68        (253, [0xfd, 0xfd, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
69        (40000, [0xfd, 0x40, 0x9c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
70        (65535, [0xfd, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]),
71        (65536, [0xfe, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00]),
72        (2000000000, [0xfe, 0x00, 0x94, 0x35, 0x77, 0x00, 0x00, 0x00, 0x00]),
73        (2000000000, [0xfe, 0x00, 0x94, 0x35, 0x77, 0x00, 0x00, 0x00, 0x00]),
74        (4294967295, [0xfe, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00]),
75        (4294967296, [0xff, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00]),
76        (500000000000000000, [0xff, 0x00, 0x00, 0xb2, 0xd3, 0x59, 0x5b, 0xf0, 0x06]),
77        (18446744073709551615, [0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
78    ];
79
80    #[test]
81    fn test_variable_length_integer() {
82        LENGTH_VALUES.iter().for_each(|(size, expected_output)| {
83            let variable_length_int = variable_length_integer(size);
84            let pruned_expected_output = &expected_output[..variable_length_int.len()];
85            assert_eq!(pruned_expected_output, &variable_length_int[..]);
86        });
87    }
88
89    #[test]
90    fn test_read_variable_length_integer() {
91        LENGTH_VALUES.iter().for_each(|(expected_size, _expected_output)| {
92            let variable_length_int = variable_length_integer(expected_size);
93            let size = read_variable_length_integer(&variable_length_int[..]).unwrap();
94            assert_eq!(*expected_size, size);
95        });
96    }
97}
snarkvm_console_network_environment/helpers/variable_length.rs

snarkvm_console_network_environment/helpers/
variable_length.rs
