47 lines
1.4 KiB
Rust
47 lines
1.4 KiB
Rust
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const BASE38_CHARS: &str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-.";
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fn encode_base38(mut value: u32, char_count: u8) -> String {
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let mut result = String::new();
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for _ in 0..char_count {
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let mut chars = BASE38_CHARS.chars();
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let remainder = value % 38;
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result.push(chars.nth(remainder as usize).unwrap());
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value = (value - remainder) / 38;
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}
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result
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}
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pub fn encode(bytes: &[u8]) -> String {
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let length = bytes.len();
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let mut offset = 0;
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let mut result = String::new();
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while offset < length {
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let remaining = length - offset;
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match remaining.cmp(&2) {
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std::cmp::Ordering::Greater => {
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result.push_str(&encode_base38(
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((bytes[offset + 2] as u32) << 16)
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| ((bytes[offset + 1] as u32) << 8)
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| (bytes[offset] as u32),
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5,
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));
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offset += 3;
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}
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std::cmp::Ordering::Equal => {
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result.push_str(&encode_base38(
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((bytes[offset + 1] as u32) << 8) | (bytes[offset] as u32),
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4,
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));
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break;
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}
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std::cmp::Ordering::Less => {
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result.push_str(&encode_base38(bytes[offset] as u32, 2));
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break;
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}
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}
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}
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result
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}
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