//! Copy-pasted from the internet /// Available encoding character sets #[derive(Clone, Copy, Debug)] enum _CharacterSet { /// The standard character set (uses `+` and `/`) _Standard, /// The URL safe character set (uses `-` and `_`) _UrlSafe, } static STANDARD_CHARS: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\ abcdefghijklmnopqrstuvwxyz\ 0123456789+/"; static _URLSAFE_CHARS: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\ abcdefghijklmnopqrstuvwxyz\ 0123456789-_"; pub fn encode(input: &[u8]) -> String { let bytes = STANDARD_CHARS; let len = input.len(); // Preallocate memory. let prealloc_len = (len + 2) / 3 * 4; let mut out_bytes = vec![b'='; prealloc_len]; // Deal with padding bytes let mod_len = len % 3; // Use iterators to reduce branching { let mut s_in = input[..len - mod_len].iter().map(|&x| x as u32); let mut s_out = out_bytes.iter_mut(); // Convenient shorthand let enc = |val| bytes[val as usize]; let mut write = |val| *s_out.next().unwrap() = val; // Iterate though blocks of 4 while let (Some(first), Some(second), Some(third)) = (s_in.next(), s_in.next(), s_in.next()) { let n = first << 16 | second << 8 | third; // This 24-bit number gets separated into four 6-bit numbers. write(enc((n >> 18) & 63)); write(enc((n >> 12) & 63)); write(enc((n >> 6) & 63)); write(enc((n >> 0) & 63)); } // Heh, would be cool if we knew this was exhaustive // (the dream of bounded integer types) match mod_len { 0 => (), 1 => { let n = (input[len - 1] as u32) << 16; write(enc((n >> 18) & 63)); write(enc((n >> 12) & 63)); } 2 => { let n = (input[len - 2] as u32) << 16 | (input[len - 1] as u32) << 8; write(enc((n >> 18) & 63)); write(enc((n >> 12) & 63)); write(enc((n >> 6) & 63)); } _ => panic!("Algebra is broken, please alert the math police"), } } // `out_bytes` vec is prepopulated with `=` symbols and then only updated // with base64 chars, so this unsafe is safe. unsafe { String::from_utf8_unchecked(out_bytes) } } /// Errors that can occur when decoding a base64 encoded string #[derive(Clone, Copy, Debug, thiserror::Error)] pub enum FromBase64Error { /// The input contained a character not part of the base64 format #[error("Invalid base64 byte")] InvalidBase64Byte(u8, usize), /// The input had an invalid length #[error("Invalid base64 length")] InvalidBase64Length, } pub fn decode(input: &str) -> Result, FromBase64Error> { let mut r = Vec::with_capacity(input.len()); let mut buf: u32 = 0; let mut modulus = 0; let mut it = input.as_bytes().iter(); for byte in it.by_ref() { let code = DECODE_TABLE[*byte as usize]; if code >= SPECIAL_CODES_START { match code { NEWLINE_CODE => continue, EQUALS_CODE => break, INVALID_CODE => { return Err(FromBase64Error::InvalidBase64Byte( *byte, (byte as *const _ as usize) - input.as_ptr() as usize, )) } _ => unreachable!(), } } buf = (buf | code as u32) << 6; modulus += 1; if modulus == 4 { modulus = 0; r.push((buf >> 22) as u8); r.push((buf >> 14) as u8); r.push((buf >> 6) as u8); } } for byte in it { match *byte { b'=' | b'\r' | b'\n' => continue, _ => { return Err(FromBase64Error::InvalidBase64Byte( *byte, (byte as *const _ as usize) - input.as_ptr() as usize, )) } } } match modulus { 2 => { r.push((buf >> 10) as u8); } 3 => { r.push((buf >> 16) as u8); r.push((buf >> 8) as u8); } 0 => (), _ => return Err(FromBase64Error::InvalidBase64Length), } Ok(r) } const DECODE_TABLE: [u8; 256] = [ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFD, 0xFF, 0xFF, 0xFD, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0x3E, 0xFF, 0x3F, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0xFF, 0xFF, 0xFF, 0xFE, 0xFF, 0xFF, 0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0x3F, 0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, ]; const INVALID_CODE: u8 = 0xFF; const EQUALS_CODE: u8 = 0xFE; const NEWLINE_CODE: u8 = 0xFD; const SPECIAL_CODES_START: u8 = NEWLINE_CODE; #[cfg(test)] mod tests { use super::*; #[test] fn test_encode_basic() { assert_eq!(encode(b""), ""); assert_eq!(encode(b"f"), "Zg=="); assert_eq!(encode(b"fo"), "Zm8="); assert_eq!(encode(b"foo"), "Zm9v"); assert_eq!(encode(b"foob"), "Zm9vYg=="); assert_eq!(encode(b"fooba"), "Zm9vYmE="); assert_eq!(encode(b"foobar"), "Zm9vYmFy"); } #[test] fn test_encode_standard_safe() { assert_eq!(encode(&[251, 255]), "+/8="); } #[test] fn test_decode_basic() { assert_eq!(decode("").unwrap(), b""); assert_eq!(decode("Zg==").unwrap(), b"f"); assert_eq!(decode("Zm8=").unwrap(), b"fo"); assert_eq!(decode("Zm9v").unwrap(), b"foo"); assert_eq!(decode("Zm9vYg==").unwrap(), b"foob"); assert_eq!(decode("Zm9vYmE=").unwrap(), b"fooba"); assert_eq!(decode("Zm9vYmFy").unwrap(), b"foobar"); } #[test] fn test_decode() { assert_eq!(decode("Zm9vYmFy").unwrap(), b"foobar"); } #[test] fn test_decode_newlines() { assert_eq!(decode("Zm9v\r\nYmFy").unwrap(), b"foobar"); assert_eq!(decode("Zm9vYg==\r\n").unwrap(), b"foob"); assert_eq!(decode("Zm9v\nYmFy").unwrap(), b"foobar"); assert_eq!(decode("Zm9vYg==\n").unwrap(), b"foob"); } #[test] fn test_decode_urlsafe() { assert_eq!(decode("-_8").unwrap(), decode("+/8=").unwrap()); } #[test] fn test_from_base64_invalid_char() { assert!(decode("Zm$=").is_err()); assert!(decode("Zg==$").is_err()); } #[test] fn test_decode_invalid_padding() { assert!(decode("Z===").is_err()); } }