1//! Utilities used in this crate which can also be generally useful downstream.
  2
  3use super::{utils::string::String, Word};
  4use core::fmt::{self, Display, Write};
  5
  6#[cfg(not(feature = "std"))]
  7pub use alloc::{format, vec};
  8
  9#[cfg(feature = "std")]
 10pub use std::{format, vec};
 11
 12mod kv_map;
 13
 14// RE-EXPORTS
 15// ================================================================================================
 16pub use winter_utils::{
 17    string, uninit_vector, Box, ByteReader, ByteWriter, Deserializable, DeserializationError,
 18    Serializable, SliceReader,
 19};
 20
 21pub mod collections {
 22    pub use super::kv_map::*;
 23    pub use winter_utils::collections::*;
 24}
 25
 26// UTILITY FUNCTIONS
 27// ================================================================================================
 28
 29/// Converts a [Word] into hex.
 30pub fn word_to_hex(w: &Word) -> Result<String, fmt::Error> {
 31    let mut s = String::new();
 32
 33    for byte in w.iter().flat_map(|e| e.to_bytes()) {
 34        write!(s, "{byte:02x}")?;
 35    }
 36
 37    Ok(s)
 38}
 39
 40/// Renders an array of bytes as hex into a String.
 41pub fn bytes_to_hex_string<const N: usize>(data: [u8; N]) -> String {
 42    let mut s = String::with_capacity(N + 2);
 43
 44    s.push_str("0x");
 45    for byte in data.iter() {
 46        write!(s, "{byte:02x}").expect("formatting hex failed");
 47    }
 48
 49    s
 50}
 51
 52/// Defines errors which can occur during parsing of hexadecimal strings.
 53#[derive(Debug)]
 54pub enum HexParseError {
 55    InvalidLength { expected: usize, actual: usize },
 56    MissingPrefix,
 57    InvalidChar,
 58    OutOfRange,
 59}
 60
 61impl Display for HexParseError {
 62    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
 63        match self {
 64            HexParseError::InvalidLength { expected, actual } => {
 65                write!(f, "Hex encoded RpoDigest must have length 66, including the 0x prefix. expected {expected} got {actual}")
 66            }
 67            HexParseError::MissingPrefix => {
 68                write!(f, "Hex encoded RpoDigest must start with 0x prefix")
 69            }
 70            HexParseError::InvalidChar => {
 71                write!(f, "Hex encoded RpoDigest must contain characters [a-zA-Z0-9]")
 72            }
 73            HexParseError::OutOfRange => {
 74                write!(f, "Hex encoded values of an RpoDigest must be inside the field modulus")
 75            }
 76        }
 77    }
 78}
 79
 80#[cfg(feature = "std")]
 81impl std::error::Error for HexParseError {}
 82
 83/// Parses a hex string into an array of bytes of known size.
 84pub fn hex_to_bytes<const N: usize>(value: &str) -> Result<[u8; N], HexParseError> {
 85    let expected: usize = (N * 2) + 2;
 86    if value.len() != expected {
 87        return Err(HexParseError::InvalidLength { expected, actual: value.len() });
 88    }
 89
 90    if !value.starts_with("0x") {
 91        return Err(HexParseError::MissingPrefix);
 92    }
 93
 94    let mut data = value.bytes().skip(2).map(|v| match v {
 95        b'0'..=b'9' => Ok(v - b'0'),
 96        b'a'..=b'f' => Ok(v - b'a' + 10),
 97        b'A'..=b'F' => Ok(v - b'A' + 10),
 98        _ => Err(HexParseError::InvalidChar),
 99    });
100
101    let mut decoded = [0u8; N];
102    #[allow(clippy::needless_range_loop)]
103    for pos in 0..N {
104        // These `unwrap` calls are okay because the length was checked above
105        let high: u8 = data.next().unwrap()?;
106        let low: u8 = data.next().unwrap()?;
107        decoded[pos] = (high << 4) + low;
108    }
109
110    Ok(decoded)
111}