forest_cid 0.3.0

A Cid library used in Forest for the Filecoin protocol
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61

// Copyright 2020 ChainSafe Systems
// SPDX-License-Identifier: Apache-2.0, MIT

use super::{Cid, Error, Version};
use integer_encoding::{VarIntReader, VarIntWriter};
use std::convert::TryFrom;
use std::io::Cursor;

/// Prefix represents all metadata of a CID, without the actual content.
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct Prefix {
    pub version: Version,
    pub codec: u64,
    pub mh_type: u64,
    pub mh_len: usize,
}

impl Prefix {
    /// Generate new prefix from encoded bytes
    pub fn new_from_bytes(data: &[u8]) -> Result<Prefix, Error> {
        let mut cur = Cursor::new(data);

        let raw_version: u64 = cur.read_varint()?;
        let codec = cur.read_varint()?;
        let mh_type: u64 = cur.read_varint()?;
        let mh_len: usize = cur.read_varint()?;

        let version = Version::try_from(raw_version)?;

        Ok(Prefix {
            version,
            codec,
            mh_type,
            mh_len,
        })
    }

    /// Encodes prefix to bytes
    pub fn to_bytes(&self) -> Vec<u8> {
        let mut res = Vec::with_capacity(4);

        // io can't fail on Vec
        res.write_varint(u64::from(self.version)).unwrap();
        res.write_varint(self.codec).unwrap();
        res.write_varint(self.mh_type).unwrap();
        res.write_varint(self.mh_len).unwrap();

        res
    }
}

impl From<Cid> for Prefix {
    fn from(cid: Cid) -> Self {
        Self {
            version: cid.version(),
            codec: cid.codec(),
            mh_type: cid.hash().code(),
            mh_len: cid.hash().size().into(),
        }
    }
}