init

.gitignore

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+/target

Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "hex"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "hex"
+version = "0.1.0"
+authors = ["phyto <phyto@disroot.org>"]
+edition = "2021"
+description = "A hexadecimal (de)serialiser"
+license = "AGPL-3.0-or-later"
+

src/lib.rs

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+#![warn(clippy::nursery)]
+#![warn(clippy::panic_in_result_fn)]
+
+fn unsigned_to_hex(mut x: u128) -> Option<String> {
+	let mut r = String::new();
+
+	while x > 0 {
+		let digit = x % 0x10;
+
+		r.push(int_to_char(digit as u8)?);
+		x /= 0x10;
+	}
+
+	Some(r.chars().rev().collect())
+}
+
+fn unsigned_from_hex(strn: &str) -> Option<u128> {
+	let mut r = 0;
+
+	let mut inp_str = strn.chars().rev().collect::<String>();
+
+	while !inp_str.is_empty() {
+		let digit = char_to_int(inp_str.pop().expect("we just checked it's not empty"))?;
+		r <<= 4;
+		r += u128::from(digit);
+	}
+
+	Some(r)
+}
+
+pub fn to_hex(x: i128) -> Option<String> {
+	let mut r = unsigned_to_hex(x.unsigned_abs())?;
+
+	if x < 0 {
+		r.insert(0, '-');
+	}
+
+	Some(r)
+}
+
+/// Convert a hexadecimal string into a signed integer.
+/// A `-` for a negative can be before or after the optional `0x`.
+/// # Example
+/// ```
+/// use hex::from_hex;
+/// assert_eq!( from_hex("e"), Some(14) );
+/// assert_eq!( from_hex("0xA3"), Some(163) );
+/// assert_eq!( from_hex("-0xabCdef"), Some(-11259375) );
+/// assert_eq!( from_hex("-abcdef"), Some(-11259375) );
+/// assert_eq!( from_hex("0x-ABCDEF"), from_hex("-0xabcdef") );
+///
+/// assert_eq!( from_hex("abcdefG"), None );
+/// assert_eq!( from_hex("ab cd ef"), None );
+/// assert_eq!( from_hex(" 0011"), None );
+///
+/// ```
+pub fn from_hex(mut strn: &str) -> Option<i128> {
+	let mut is_positive = true;
+	{
+		if let Some(s) = strn.strip_prefix('-') {
+			strn = s;
+			is_positive = false;
+		}
+
+		if let Some(s) = strn.strip_prefix("0x-") {
+			strn = s;
+			is_positive = false;
+		}
+	}
+
+	let mut r = unsigned_from_hex(strn)? as i128;
+
+	if !is_positive {
+		r = -r;
+	}
+
+	Some(r)
+}
+
+#[cfg(test)]
+mod _test {
+	#[test]
+	fn to_hex() {
+		use super::*;
+		let pairs = [("3039", 12345), ("4", 4), ("cffee", 851_950), ("-ae", -174)];
+
+		for (lhs, rhs) in pairs {
+			println!("{lhs} == {rhs} ?");
+			assert_eq!(lhs.to_string(), to_hex(rhs).unwrap());
+		}
+	}
+
+	#[test]
+	fn from_hex() {
+		use super::*;
+		let pairs = [("3039", 12345), ("4", 4), ("cffee", 851_950), ("-ae", -174)];
+
+		println!("Hex == Deniary ?");
+		for (lhs, rhs) in pairs {
+			println!("{lhs} == {rhs} ?");
+			assert_eq!(from_hex(lhs).unwrap(), rhs);
+		}
+	}
+}
+
+const fn char_to_int(chr: char) -> Option<u8> {
+	const UNCONVERTABLE: u8 = core::u8::MAX;
+
+	let r = match chr.to_ascii_lowercase() {
+		'0' => 0,
+		'1' => 1,
+		'2' => 2,
+		'3' => 3,
+		'4' => 4,
+		'5' => 5,
+		'6' => 6,
+		'7' => 7,
+		'8' => 8,
+		'9' => 9,
+		'a' => 10,
+		'b' => 11,
+		'c' => 12,
+		'd' => 13,
+		'e' => 14,
+		'f' => 15,
+		_ => UNCONVERTABLE,
+	};
+
+	if r == UNCONVERTABLE {
+		return None;
+	}
+
+	Some(r)
+}
+
+const fn int_to_char(i: u8) -> Option<char> {
+	const UNCONVERTABLE: char = '\0';
+
+	let r = match i {
+		0 => '0',
+		1 => '1',
+		2 => '2',
+		3 => '3',
+		4 => '4',
+		5 => '5',
+		6 => '6',
+		7 => '7',
+		8 => '8',
+		9 => '9',
+		10 => 'a',
+		11 => 'b',
+		12 => 'c',
+		13 => 'd',
+		14 => 'e',
+		15 => 'f',
+		_ => UNCONVERTABLE,
+	};
+
+	if r == UNCONVERTABLE {
+		return None;
+	}
+
+	Some(r)
+}