70 lines
2.3 KiB
Rust
70 lines
2.3 KiB
Rust
use super::bencode::BencodeValue;
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/// Decodes a 40-character hexadecimal string into a fixed-width 20-byte array.
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pub(super) fn decode_hex_20_array(input: &str) -> Result<[u8; 20], String> {
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if input.len() != 40 {
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return Err(format!(
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"expected 40 hex characters for 20-byte info-hash, got {}",
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input.len()
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));
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}
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let mut out = [0_u8; 20];
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for (index, chunk) in input.as_bytes().chunks_exact(2).enumerate() {
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let hi = decode_hex_nibble(chunk[0])
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.ok_or_else(|| "info-hash contains non-hex characters".to_owned())?;
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let lo = decode_hex_nibble(chunk[1])
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.ok_or_else(|| "info-hash contains non-hex characters".to_owned())?;
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out[index] = (hi << 4) | lo;
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}
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Ok(out)
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}
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/// Decodes one ASCII hexadecimal nibble.
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const fn decode_hex_nibble(byte: u8) -> Option<u8> {
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match byte {
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b'0'..=b'9' => Some(byte - b'0'),
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b'a'..=b'f' => Some(byte - b'a' + 10),
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b'A'..=b'F' => Some(byte - b'A' + 10),
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_ => None,
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}
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}
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/// Decodes torrent byte strings into owned lossy UTF-8 text.
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pub(super) fn bytes_to_string(bytes: &[u8]) -> String {
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String::from_utf8_lossy(bytes).into_owned()
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}
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/// Converts one torrent bencode value into human-readable string form.
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pub(super) fn value_to_string(value: &BencodeValue) -> String {
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match value {
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BencodeValue::Bytes(bytes) => bytes_to_string(bytes),
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BencodeValue::Int(value) => value.to_string(),
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BencodeValue::List(values) => values
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.iter()
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.map(value_to_string)
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.collect::<Vec<_>>()
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.join(","),
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BencodeValue::Dict(map) => map
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.iter()
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.map(|(key, value)| format!("{key}={}", value_to_string(value)))
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.collect::<Vec<_>>()
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.join("&"),
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}
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}
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/// Hex-encodes raw torrent bytes using lowercase hexadecimal.
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pub(super) fn hex_encode(bytes: &[u8]) -> String {
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const HEX: &[u8; 16] = b"0123456789abcdef";
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let mut out = String::with_capacity(bytes.len() * 2);
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for &byte in bytes {
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out.push(char::from(HEX[usize::from(byte >> 4)]));
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out.push(char::from(HEX[usize::from(byte & 0x0f)]));
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}
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out
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}
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/// Saturates an integer-like torrent length field into `u64`.
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pub(super) fn i64_to_u64(value: i64) -> u64 {
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u64::try_from(value.max(0)).unwrap_or(u64::MAX)
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}
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