1//! Utilities used in this crate which can also be generally useful downstream.
  2
  3use alloc::string::String;
  4use core::fmt::{self, Display, Write};
  5
  6use super::Word;
  7
  8mod kv_map;
  9
 10// RE-EXPORTS
 11// ================================================================================================
 12
 13pub use winter_utils::{
 14    uninit_vector, ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable,
 15    SliceReader,
 16};
 17
 18pub mod collections {
 19    pub use super::kv_map::*;
 20}
 21
 22// UTILITY FUNCTIONS
 23// ================================================================================================
 24
 25/// Converts a [Word] into hex.
 26pub fn word_to_hex(w: &Word) -> Result<String, fmt::Error> {
 27    let mut s = String::new();
 28
 29    for byte in w.iter().flat_map(|e| e.to_bytes()) {
 30        write!(s, "{byte:02x}")?;
 31    }
 32
 33    Ok(s)
 34}
 35
 36/// Renders an array of bytes as hex into a String.
 37pub fn bytes_to_hex_string<const N: usize>(data: [u8; N]) -> String {
 38    let mut s = String::with_capacity(N + 2);
 39
 40    s.push_str("0x");
 41    for byte in data.iter() {
 42        write!(s, "{byte:02x}").expect("formatting hex failed");
 43    }
 44
 45    s
 46}
 47
 48/// Defines errors which can occur during parsing of hexadecimal strings.
 49#[derive(Debug)]
 50pub enum HexParseError {
 51    InvalidLength { expected: usize, actual: usize },
 52    MissingPrefix,
 53    InvalidChar,
 54    OutOfRange,
 55}
 56
 57impl Display for HexParseError {
 58    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
 59        match self {
 60            HexParseError::InvalidLength { expected, actual } => {
 61                write!(f, "Hex encoded RpoDigest must have length 66, including the 0x prefix. expected {expected} got {actual}")
 62            }
 63            HexParseError::MissingPrefix => {
 64                write!(f, "Hex encoded RpoDigest must start with 0x prefix")
 65            }
 66            HexParseError::InvalidChar => {
 67                write!(f, "Hex encoded RpoDigest must contain characters [a-zA-Z0-9]")
 68            }
 69            HexParseError::OutOfRange => {
 70                write!(f, "Hex encoded values of an RpoDigest must be inside the field modulus")
 71            }
 72        }
 73    }
 74}
 75
 76#[cfg(feature = "std")]
 77impl std::error::Error for HexParseError {}
 78
 79/// Parses a hex string into an array of bytes of known size.
 80pub fn hex_to_bytes<const N: usize>(value: &str) -> Result<[u8; N], HexParseError> {
 81    let expected: usize = (N * 2) + 2;
 82    if value.len() != expected {
 83        return Err(HexParseError::InvalidLength { expected, actual: value.len() });
 84    }
 85
 86    if !value.starts_with("0x") {
 87        return Err(HexParseError::MissingPrefix);
 88    }
 89
 90    let mut data = value.bytes().skip(2).map(|v| match v {
 91        b'0'..=b'9' => Ok(v - b'0'),
 92        b'a'..=b'f' => Ok(v - b'a' + 10),
 93        b'A'..=b'F' => Ok(v - b'A' + 10),
 94        _ => Err(HexParseError::InvalidChar),
 95    });
 96
 97    let mut decoded = [0u8; N];
 98    for byte in decoded.iter_mut() {
 99        // These `unwrap` calls are okay because the length was checked above
100        let high: u8 = data.next().unwrap()?;
101        let low: u8 = data.next().unwrap()?;
102        *byte = (high << 4) + low;
103    }
104
105    Ok(decoded)
106}