bin_encode_decode/decode/
func.rs

1use crate::*;
2
3/// decodes a given encoded string based on a specified charset, using 4-character
4/// groups to restore the original bytes. Each character in the `decode_str` string
5/// is mapped to an index in `charset` to form the decoded bytes.
6///
7/// # Parameters
8/// - `charset`: A string representing the character set used to encode and decode
9///   the data. Each character should have a unique position in `charset`.
10/// - `decode_str`: The string to be decoded, which was originally encoded with
11///   the provided `charset`.
12///
13/// # Returns
14/// Returns a `Result` containing the decoded `String` if successful, or a `DecodeError` if the charset is invalid.
15///
16/// # Example
17/// ```
18/// use bin_encode_decode::*;
19///
20/// let charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_=";
21/// let encoded_str = "aab0aabLaabZaab0";
22/// let decoded_str = decode(charset, encoded_str);
23/// assert_eq!(decoded_str.unwrap(), "test");
24/// ```
25pub fn decode(charset: &str, decode_str: &str) -> Result<String, DecodeError> {
26    if !Endecode::judge_charset_safe(charset) {
27        return Err(DecodeError::CharsetError);
28    }
29    let mut buffer: Vec<u8> = Vec::new();
30    let mut decoded: Vec<u8> = Vec::new();
31    for ch in decode_str.chars() {
32        if let Some(idx) = charset.chars().position(|c| c == ch) {
33            buffer.push(idx as u8);
34        }
35        if buffer.len() == 4 {
36            let combined: usize = ((buffer[0] as usize) << 18)
37                | ((buffer[1] as usize) << 12)
38                | ((buffer[2] as usize) << 6)
39                | (buffer[3] as usize);
40            decoded.push((combined >> 16) as u8);
41            decoded.push((combined >> 8) as u8);
42            decoded.push(combined as u8);
43            buffer.clear();
44        }
45    }
46    let decode_res: String =
47        String::from_utf8(decoded.into_iter().filter(|&x| x != 0).collect()).unwrap_or_default();
48    Ok(decode_res)
49}
bin_encode_decode/decode/func.rs

bin_encode_decode/decode/
func.rs
