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|
const SEPARATOR: char = '_';
/// Increment an integer.
///
/// Supported bases:
/// 2 with prefix 0b
/// 8 with prefix 0o
/// 10 with no prefix
/// 16 with prefix 0x
///
/// An integer can contain `_` as a separator but may not start or end with a separator.
/// Base 10 integers can go negative, but bases 2, 8, and 16 cannot.
/// All addition and subtraction is saturating.
pub fn increment(selected_text: &str, amount: i64) -> Option<String> {
if selected_text.is_empty()
|| selected_text.ends_with(SEPARATOR)
|| selected_text.starts_with(SEPARATOR)
{
return None;
}
let radix = if selected_text.starts_with("0x") {
16
} else if selected_text.starts_with("0o") {
8
} else if selected_text.starts_with("0b") {
2
} else {
10
};
// Get separator indexes from right to left.
let separator_rtl_indexes: Vec<usize> = selected_text
.chars()
.rev()
.enumerate()
.filter_map(|(i, c)| if c == SEPARATOR { Some(i) } else { None })
.collect();
let word: String = selected_text.chars().filter(|&c| c != SEPARATOR).collect();
let mut new_text = if radix == 10 {
let number = &word;
let value = i128::from_str_radix(number, radix).ok()?;
let new_value = value.saturating_add(amount as i128);
let format_length = match (value.is_negative(), new_value.is_negative()) {
(true, false) => number.len() - 1,
(false, true) => number.len() + 1,
_ => number.len(),
} - separator_rtl_indexes.len();
if number.starts_with('0') || number.starts_with("-0") {
format!("{:01$}", new_value, format_length)
} else {
format!("{}", new_value)
}
} else {
let number = &word[2..];
let value = u128::from_str_radix(number, radix).ok()?;
let new_value = (value as i128).saturating_add(amount as i128);
let new_value = if new_value < 0 { 0 } else { new_value };
let format_length = selected_text.len() - 2 - separator_rtl_indexes.len();
match radix {
2 => format!("0b{:01$b}", new_value, format_length),
8 => format!("0o{:01$o}", new_value, format_length),
16 => {
let (lower_count, upper_count): (usize, usize) =
number.chars().fold((0, 0), |(lower, upper), c| {
(
lower + c.is_ascii_lowercase() as usize,
upper + c.is_ascii_uppercase() as usize,
)
});
if upper_count > lower_count {
format!("0x{:01$X}", new_value, format_length)
} else {
format!("0x{:01$x}", new_value, format_length)
}
}
_ => unimplemented!("radix not supported: {}", radix),
}
};
// Add separators from original number.
for &rtl_index in &separator_rtl_indexes {
if rtl_index < new_text.len() {
let new_index = new_text.len().saturating_sub(rtl_index);
if new_index > 0 {
new_text.insert(new_index, SEPARATOR);
}
}
}
// Add in additional separators if necessary.
if new_text.len() > selected_text.len() && !separator_rtl_indexes.is_empty() {
let spacing = match separator_rtl_indexes.as_slice() {
[.., b, a] => a - b - 1,
_ => separator_rtl_indexes[0],
};
let prefix_length = if radix == 10 { 0 } else { 2 };
if let Some(mut index) = new_text.find(SEPARATOR) {
while index - prefix_length > spacing {
index -= spacing;
new_text.insert(index, SEPARATOR);
}
}
}
Some(new_text)
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_increment_basic_decimal_numbers() {
let tests = [
("100", 1, "101"),
("100", -1, "99"),
("99", 1, "100"),
("100", 1000, "1100"),
("100", -1000, "-900"),
("-1", 1, "0"),
("-1", 2, "1"),
("1", -1, "0"),
("1", -2, "-1"),
];
for (original, amount, expected) in tests {
assert_eq!(increment(original, amount).unwrap(), expected);
}
}
#[test]
fn test_increment_basic_hexadecimal_numbers() {
let tests = [
("0x0100", 1, "0x0101"),
("0x0100", -1, "0x00ff"),
("0x0001", -1, "0x0000"),
("0x0000", -1, "0x0000"),
("0xffffffffffffffff", 1, "0x10000000000000000"),
("0xffffffffffffffff", 2, "0x10000000000000001"),
("0xffffffffffffffff", -1, "0xfffffffffffffffe"),
("0xABCDEF1234567890", 1, "0xABCDEF1234567891"),
("0xabcdef1234567890", 1, "0xabcdef1234567891"),
];
for (original, amount, expected) in tests {
assert_eq!(increment(original, amount).unwrap(), expected);
}
}
#[test]
fn test_increment_basic_octal_numbers() {
let tests = [
("0o0107", 1, "0o0110"),
("0o0110", -1, "0o0107"),
("0o0001", -1, "0o0000"),
("0o7777", 1, "0o10000"),
("0o1000", -1, "0o0777"),
("0o0107", 10, "0o0121"),
("0o0000", -1, "0o0000"),
("0o1777777777777777777777", 1, "0o2000000000000000000000"),
("0o1777777777777777777777", 2, "0o2000000000000000000001"),
("0o1777777777777777777777", -1, "0o1777777777777777777776"),
];
for (original, amount, expected) in tests {
assert_eq!(increment(original, amount).unwrap(), expected);
}
}
#[test]
fn test_increment_basic_binary_numbers() {
let tests = [
("0b00000100", 1, "0b00000101"),
("0b00000100", -1, "0b00000011"),
("0b00000100", 2, "0b00000110"),
("0b00000100", -2, "0b00000010"),
("0b00000001", -1, "0b00000000"),
("0b00111111", 10, "0b01001001"),
("0b11111111", 1, "0b100000000"),
("0b10000000", -1, "0b01111111"),
("0b0000", -1, "0b0000"),
(
"0b1111111111111111111111111111111111111111111111111111111111111111",
1,
"0b10000000000000000000000000000000000000000000000000000000000000000",
),
(
"0b1111111111111111111111111111111111111111111111111111111111111111",
2,
"0b10000000000000000000000000000000000000000000000000000000000000001",
),
(
"0b1111111111111111111111111111111111111111111111111111111111111111",
-1,
"0b1111111111111111111111111111111111111111111111111111111111111110",
),
];
for (original, amount, expected) in tests {
assert_eq!(increment(original, amount).unwrap(), expected);
}
}
#[test]
fn test_increment_with_separators() {
let tests = [
("999_999", 1, "1_000_000"),
("1_000_000", -1, "999_999"),
("-999_999", -1, "-1_000_000"),
("0x0000_0000_0001", 0x1_ffff_0000, "0x0001_ffff_0001"),
("0x0000_0000", -1, "0x0000_0000"),
("0x0000_0000_0000", -1, "0x0000_0000_0000"),
("0b01111111_11111111", 1, "0b10000000_00000000"),
("0b11111111_11111111", 1, "0b1_00000000_00000000"),
];
for (original, amount, expected) in tests {
assert_eq!(increment(original, amount).unwrap(), expected);
}
}
#[test]
fn test_leading_and_trailing_separators_arent_a_match() {
assert_eq!(increment("9_", 1), None);
assert_eq!(increment("_9", 1), None);
assert_eq!(increment("_9_", 1), None);
}
}
|
