dusk_cdf/
preamble.rs

1use std::{io, mem};
2
3use crate::{
4    Config, Constraint, DecodableElement, DecoderContext, Element, EncodableElement,
5    EncoderContext, Witness,
6};
7
8/// Metadata information of the CDF file
9#[derive(Debug, Clone, Copy, PartialEq, Eq)]
10pub struct Preamble {
11    /// Witnesses count
12    pub witnesses: usize,
13    /// Constraints count
14    pub constraints: usize,
15    /// Configuration parameters for encoding and decoding
16    pub config: Config,
17}
18
19impl Preamble {
20    /// Serialized length
21    pub const LEN: usize = 2 * mem::size_of::<usize>() + Config::LEN;
22
23    /// Create a new preamble instance
24    pub const fn new(witnesses: usize, constraints: usize, config: Config) -> Self {
25        Self {
26            witnesses,
27            constraints,
28            config,
29        }
30    }
31
32    /// Witness offset in CDF, from an index
33    pub fn witness_offset(&self, idx: usize) -> Option<usize> {
34        (idx < self.witnesses).then(|| Self::LEN + idx * Witness::len(&self.config))
35    }
36
37    /// Constraint offset in CDF, from an index
38    pub fn constraint_offset(&self, idx: usize) -> Option<usize> {
39        (idx < self.constraints).then(|| {
40            Self::LEN
41                + self.witnesses * Witness::len(&self.config)
42                + idx * Constraint::len(&self.config)
43        })
44    }
45
46    /// Cache starting position
47    pub fn source_cache_offset(&self) -> usize {
48        Self::LEN
49            + self.witnesses * Witness::len(&self.config)
50            + self.constraints * Constraint::len(&self.config)
51    }
52}
53
54impl Default for Preamble {
55    fn default() -> Self {
56        Self {
57            witnesses: 1,
58            constraints: 0,
59            config: Default::default(),
60        }
61    }
62}
63
64impl Element for Preamble {
65    fn len(ctx: &Config) -> usize {
66        2 * usize::len(ctx) + Config::len(ctx)
67    }
68
69    fn validate(&self, preamble: &Preamble) -> io::Result<()> {
70        self.witnesses.validate(preamble)?;
71        self.constraints.validate(preamble)?;
72        self.config.validate(preamble)?;
73
74        Ok(())
75    }
76}
77
78impl EncodableElement for Preamble {
79    fn to_buffer(&self, ctx: &mut EncoderContext, buf: &mut [u8]) {
80        let buf = self.witnesses.encode(ctx, buf);
81        let buf = self.constraints.encode(ctx, buf);
82        let _ = self.config.encode(ctx, buf);
83    }
84}
85
86impl DecodableElement for Preamble {
87    fn try_from_buffer_in_place<'a, 'b>(
88        &'a mut self,
89        ctx: &DecoderContext<'a>,
90        buf: &'b [u8],
91    ) -> io::Result<()> {
92        Self::validate_buffer(ctx.config(), buf)?;
93
94        let buf = self.witnesses.try_decode_in_place(ctx, buf)?;
95        let buf = self.constraints.try_decode_in_place(ctx, buf)?;
96        let _ = self.config.try_decode_in_place(ctx, buf)?;
97
98        Ok(())
99    }
100}
dusk_cdf/preamble.rs

dusk_cdf/
preamble.rs
