pub fn base64_encode(bytes: &[u8]) -> String {
const ALPHA: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
let mut out = String::with_capacity(bytes.len().div_ceil(3) * 4);
let mut chunks = bytes.chunks_exact(3);
for chunk in &mut chunks {
let b = (chunk[0] as u32) << 16 | (chunk[1] as u32) << 8 | (chunk[2] as u32);
out.push(ALPHA[((b >> 18) & 0x3f) as usize] as char);
out.push(ALPHA[((b >> 12) & 0x3f) as usize] as char);
out.push(ALPHA[((b >> 6) & 0x3f) as usize] as char);
out.push(ALPHA[(b & 0x3f) as usize] as char);
}
let rem = chunks.remainder();
match rem.len() {
1 => {
let b = (rem[0] as u32) << 16;
out.push(ALPHA[((b >> 18) & 0x3f) as usize] as char);
out.push(ALPHA[((b >> 12) & 0x3f) as usize] as char);
out.push('=');
out.push('=');
}
2 => {
let b = (rem[0] as u32) << 16 | (rem[1] as u32) << 8;
out.push(ALPHA[((b >> 18) & 0x3f) as usize] as char);
out.push(ALPHA[((b >> 12) & 0x3f) as usize] as char);
out.push(ALPHA[((b >> 6) & 0x3f) as usize] as char);
out.push('=');
}
_ => {}
}
out
}
#[cfg(test)]
mod tests {
use super::base64_encode;
#[test]
fn base64_vectors() {
assert_eq!(base64_encode(b""), "");
assert_eq!(base64_encode(b"f"), "Zg==");
assert_eq!(base64_encode(b"fo"), "Zm8=");
assert_eq!(base64_encode(b"foo"), "Zm9v");
assert_eq!(base64_encode(b"foob"), "Zm9vYg==");
assert_eq!(base64_encode(b"fooba"), "Zm9vYmE=");
assert_eq!(base64_encode(b"foobar"), "Zm9vYmFy");
}
}