ethjson 0.1.0

Parity Ethereum JSON Deserialization
Documentation 
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// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.

// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Ethereum.  If not, see <http://www.gnu.org/licenses/>.

//! Lenient uint json deserialization for test json files.

use std::fmt;
use std::str::FromStr;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
use serde::de::{Error, Visitor, Unexpected};
use ethereum_types::U256;

/// Lenient uint json deserialization for test json files.
#[derive(Default, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Copy)]
pub struct Uint(pub U256);

impl Into<U256> for Uint {
	fn into(self) -> U256 {
		self.0
	}
}

impl Into<u64> for Uint {
	fn into(self) -> u64 {
		self.0.low_u64()
	}
}

impl Into<usize> for Uint {
	fn into(self) -> usize {
		self.0.low_u64() as usize
	}
}


impl Serialize for Uint {
	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
		where S: Serializer {
		self.0.to_string().serialize(serializer)
	}
}

impl<'a> Deserialize<'a> for Uint {
	fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
		where D: Deserializer<'a> {
		deserializer.deserialize_any(UintVisitor)
	}
}

struct UintVisitor;

impl<'a> Visitor<'a> for UintVisitor {
	type Value = Uint;

	fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
		write!(formatter, "a hex encoded or decimal uint")
	}

	fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E> where E: Error {
		Ok(Uint(U256::from(value)))
	}

	fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> where E: Error {
		let value = match value.len() {
			0 => U256::from(0),
			2 if value.starts_with("0x") => U256::from(0),
			_ if value.starts_with("0x") => {
				if value.len() > 66 {
					return Err(Error::custom(format!("Invalid hex value {}: value too big", value).as_str()));
				}
				U256::from_str(&value[2..]).map_err(|e| {
					Error::custom(format!("Invalid hex value {}: {}", value, e).as_str())
				})?
			},
			_ => U256::from_dec_str(value).map_err(|e| {
				Error::custom(format!("Invalid decimal value {}: {:?}", value, e).as_str())
			})?
		};

		Ok(Uint(value))
	}

	fn visit_string<E>(self, value: String) -> Result<Self::Value, E> where E: Error {
		self.visit_str(value.as_ref())
	}
}

/// Deserialize and validate that the value is non-zero
pub fn validate_non_zero<'de, D>(d: D) -> Result<Uint, D::Error> where D: Deserializer<'de> {
	let value = Uint::deserialize(d)?;

	if value == Uint(U256::from(0)) {
		return Err(Error::invalid_value(Unexpected::Unsigned(0), &"a non-zero value"))
	}

	Ok(value)
}

/// Deserialize and validate that the value is non-zero
pub fn validate_optional_non_zero<'de, D>(d: D) -> Result<Option<Uint>, D::Error> where D: Deserializer<'de> {
	let value: Option<Uint> = Option::deserialize(d)?;

	if let Some(value) = value {
		if value == Uint(U256::from(0)) {
			return Err(Error::invalid_value(Unexpected::Unsigned(0), &"a non-zero value"))
		}
	}

	Ok(value)
}

#[cfg(test)]
mod test {
	use super::Uint;
	use ethereum_types::U256;

	#[test]
	fn uint_deserialization() {
		let s = r#"["0xa", "10", "", "0x", 0]"#;
		let deserialized: Vec<Uint> = serde_json::from_str(s).unwrap();
		assert_eq!(deserialized, vec![
				   Uint(U256::from(10)),
				   Uint(U256::from(10)),
				   Uint(U256::from(0)),
				   Uint(U256::from(0)),
				   Uint(U256::from(0))
		]);
	}

	#[test]
	fn uint_deserialization_error_for_hex_too_large() {
		let hex = format!("0x{}", "1".repeat(65));
		let result: Result<Uint, _> = serde_json::from_str(&format!(r#""{}""#, hex));
		let err = result.unwrap_err();
		assert!(err.is_data());
		assert_eq!(
			err.to_string(),
			format!("Invalid hex value {}: value too big at line 1 column 69", hex)
		);
	}

	#[test]
	fn uint_into() {
		assert_eq!(U256::from(10), Uint(U256::from(10)).into());
	}
}