Function base64::encoded_len

pub fn encoded_len(bytes_len: usize, padding: bool) -> Option<usize>

Calculate the base64 encoded length for a given input length, optionally including any appropriate padding bytes.

Returns None if the encoded length can’t be represented in usize. This will happen for input lengths in approximately the top quarter of the range of usize.

Examples found in repository

src/engine/mod.rs (line 127)

    fn encode<T: AsRef<[u8]>>(&self, input: T) -> String {
        let encoded_size = encoded_len(input.as_ref().len(), self.config().encode_padding())
            .expect("integer overflow when calculating buffer size");
        let mut buf = vec![0; encoded_size];

        encode_with_padding(input.as_ref(), &mut buf[..], self, encoded_size);

        String::from_utf8(buf).expect("Invalid UTF8")
    }

    /// Encode arbitrary octets as base64 into a supplied `String`.
    /// Writes into the supplied `String`, which may allocate if its internal buffer isn't big enough.
    ///
    /// # Example
    ///
    /// ```rust
    /// use base64::Engine as _;
    /// const URL_SAFE_ENGINE: base64::engine::GeneralPurpose =
    ///     base64::engine::GeneralPurpose::new(
    ///         &base64::alphabet::URL_SAFE,
    ///         base64::engine::general_purpose::NO_PAD);
    /// fn main() {
    ///     let mut buf = String::new();
    ///     base64::engine::STANDARD.encode_string(b"hello world~", &mut buf);
    ///     println!("{}", buf);
    ///
    ///     buf.clear();
    ///     URL_SAFE_ENGINE.encode_string(b"hello internet~", &mut buf);
    ///     println!("{}", buf);
    /// }
    /// ```
    #[cfg(any(feature = "alloc", feature = "std", test))]
    fn encode_string<T: AsRef<[u8]>>(&self, input: T, output_buf: &mut String) {
        let input_bytes = input.as_ref();

        {
            let mut sink = chunked_encoder::StringSink::new(output_buf);

            chunked_encoder::ChunkedEncoder::new(self)
                .encode(input_bytes, &mut sink)
                .expect("Writing to a String shouldn't fail");
        }
    }

    /// Encode arbitrary octets as base64 into a supplied slice.
    /// Writes into the supplied output buffer.
    ///
    /// This is useful if you wish to avoid allocation entirely (e.g. encoding into a stack-resident
    /// or statically-allocated buffer).
    ///
    /// # Example
    ///
    /// ```rust
    /// use base64::{engine, Engine as _};
    /// let s = b"hello internet!";
    /// let mut buf = Vec::new();
    /// // make sure we'll have a slice big enough for base64 + padding
    /// buf.resize(s.len() * 4 / 3 + 4, 0);
    ///
    /// let bytes_written = engine::STANDARD.encode_slice(s, &mut buf).unwrap();
    ///
    /// // shorten our vec down to just what was written
    /// buf.truncate(bytes_written);
    ///
    /// assert_eq!(s, engine::STANDARD.decode(&buf).unwrap().as_slice());
    /// ```
    fn encode_slice<T: AsRef<[u8]>>(
        &self,
        input: T,
        output_buf: &mut [u8],
    ) -> Result<usize, EncodeSliceError> {
        let input_bytes = input.as_ref();

        let encoded_size = encoded_len(input_bytes.len(), self.config().encode_padding())
            .expect("usize overflow when calculating buffer size");

        if output_buf.len() < encoded_size {
            return Err(EncodeSliceError::OutputSliceTooSmall);
        }

        let b64_output = &mut output_buf[0..encoded_size];

        encode_with_padding(input_bytes, b64_output, self, encoded_size);

        Ok(encoded_size)
    }