1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277
//! Correct, fast, and configurable [base64][] decoding and encoding. Base64
//! transports binary data efficiently in contexts where only plain text is
//! allowed.
//!
//! [base64]: https://developer.mozilla.org/en-US/docs/Glossary/Base64
//!
//! # Usage
//!
//! Use an [`Engine`] to decode or encode base64, configured with the base64
//! alphabet and padding behavior best suited to your application.
//!
//! ## Engine setup
//!
//! There is more than one way to encode a stream of bytes as “base64”.
//! Different applications use different encoding
//! [alphabets][alphabet::Alphabet] and
//! [padding behaviors][engine::general_purpose::GeneralPurposeConfig].
//!
//! ### Encoding alphabet
//!
//! Almost all base64 [alphabets][alphabet::Alphabet] use `A-Z`, `a-z`, and
//! `0-9`, which gives nearly 64 characters (26 + 26 + 10 = 62), but they differ
//! in their choice of their final 2.
//!
//! Most applications use the [standard][alphabet::STANDARD] alphabet specified
//! in [RFC 4648][rfc-alphabet]. If that’s all you need, you can get started
//! quickly by using the pre-configured
//! [`STANDARD`][engine::general_purpose::STANDARD] engine, which is also available
//! in the [`prelude`] module as shown here, if you prefer a minimal `use`
//! footprint.
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! use base64::prelude::*;
//!
//! # fn main() -> Result<(), base64::DecodeError> {
//! assert_eq!(BASE64_STANDARD.decode(b"+uwgVQA=")?, b"\xFA\xEC\x20\x55\0");
//! assert_eq!(BASE64_STANDARD.encode(b"\xFF\xEC\x20\x55\0"), "/+wgVQA=");
//! # Ok(())
//! # }
//! ```
//!
//! [rfc-alphabet]: https://datatracker.ietf.org/doc/html/rfc4648#section-4
//!
//! Other common alphabets are available in the [`alphabet`] module.
//!
//! #### URL-safe alphabet
//!
//! The standard alphabet uses `+` and `/` as its two non-alphanumeric tokens,
//! which cannot be safely used in URL’s without encoding them as `%2B` and
//! `%2F`.
//!
//! To avoid that, some applications use a [“URL-safe” alphabet][alphabet::URL_SAFE],
//! which uses `-` and `_` instead. To use that alternative alphabet, use the
//! [`URL_SAFE`][engine::general_purpose::URL_SAFE] engine. This example doesn't
//! use [`prelude`] to show what a more explicit `use` would look like.
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! use base64::{engine::general_purpose::URL_SAFE, Engine as _};
//!
//! # fn main() -> Result<(), base64::DecodeError> {
//! assert_eq!(URL_SAFE.decode(b"-uwgVQA=")?, b"\xFA\xEC\x20\x55\0");
//! assert_eq!(URL_SAFE.encode(b"\xFF\xEC\x20\x55\0"), "_-wgVQA=");
//! # Ok(())
//! # }
//! ```
//!
//! ### Padding characters
//!
//! Each base64 character represents 6 bits (2⁶ = 64) of the original binary
//! data, and every 3 bytes of input binary data will encode to 4 base64
//! characters (8 bits × 3 = 6 bits × 4 = 24 bits).
//!
//! When the input is not an even multiple of 3 bytes in length, [canonical][]
//! base64 encoders insert padding characters at the end, so that the output
//! length is always a multiple of 4:
//!
//! [canonical]: https://datatracker.ietf.org/doc/html/rfc4648#section-3.5
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! use base64::{engine::general_purpose::STANDARD, Engine as _};
//!
//! assert_eq!(STANDARD.encode(b""), "");
//! assert_eq!(STANDARD.encode(b"f"), "Zg==");
//! assert_eq!(STANDARD.encode(b"fo"), "Zm8=");
//! assert_eq!(STANDARD.encode(b"foo"), "Zm9v");
//! ```
//!
//! Canonical encoding ensures that base64 encodings will be exactly the same,
//! byte-for-byte, regardless of input length. But the `=` padding characters
//! aren’t necessary for decoding, and they may be omitted by using a
//! [`NO_PAD`][engine::general_purpose::NO_PAD] configuration:
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! use base64::{engine::general_purpose::STANDARD_NO_PAD, Engine as _};
//!
//! assert_eq!(STANDARD_NO_PAD.encode(b""), "");
//! assert_eq!(STANDARD_NO_PAD.encode(b"f"), "Zg");
//! assert_eq!(STANDARD_NO_PAD.encode(b"fo"), "Zm8");
//! assert_eq!(STANDARD_NO_PAD.encode(b"foo"), "Zm9v");
//! ```
//!
//! The pre-configured `NO_PAD` engines will reject inputs containing padding
//! `=` characters. To encode without padding and still accept padding while
//! decoding, create an [engine][engine::general_purpose::GeneralPurpose] with
//! that [padding mode][engine::DecodePaddingMode].
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! # use base64::{engine::general_purpose::STANDARD_NO_PAD, Engine as _};
//! assert_eq!(STANDARD_NO_PAD.decode(b"Zm8="), Err(base64::DecodeError::InvalidPadding));
//! ```
//!
//! ### Further customization
//!
//! Decoding and encoding behavior can be customized by creating an
//! [engine][engine::GeneralPurpose] with an [alphabet][alphabet::Alphabet] and
//! [padding configuration][engine::GeneralPurposeConfig]:
//!
#![cfg_attr(feature = "alloc", doc = "```")]
#![cfg_attr(not(feature = "alloc"), doc = "```ignore")]
//! use base64::{engine, alphabet, Engine as _};
//!
//! // bizarro-world base64: +/ as the first symbols instead of the last
//! let alphabet =
//! alphabet::Alphabet::new("+/ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")
//! .unwrap();
//!
//! // a very weird config that encodes with padding but requires no padding when decoding...?
//! let crazy_config = engine::GeneralPurposeConfig::new()
//! .with_decode_allow_trailing_bits(true)
//! .with_encode_padding(true)
//! .with_decode_padding_mode(engine::DecodePaddingMode::RequireNone);
//!
//! let crazy_engine = engine::GeneralPurpose::new(&alphabet, crazy_config);
//!
//! let encoded = crazy_engine.encode(b"abc 123");
//!
//! ```
//!
//! ## Memory allocation
//!
//! The [decode][Engine::decode()] and [encode][Engine::encode()] engine methods
//! allocate memory for their results – `decode` returns a `Vec<u8>` and
//! `encode` returns a `String`. To instead decode or encode into a buffer that
//! you allocated, use one of the alternative methods:
//!
//! #### Decoding
//!
//! | Method | Output | Allocates memory |
//! | -------------------------- | ----------------------------- | ----------------------------- |
//! | [`Engine::decode`] | returns a new `Vec<u8>` | always |
//! | [`Engine::decode_vec`] | appends to provided `Vec<u8>` | if `Vec` lacks capacity |
//! | [`Engine::decode_slice`] | writes to provided `&[u8]` | never
//!
//! #### Encoding
//!
//! | Method | Output | Allocates memory |
//! | -------------------------- | ---------------------------- | ------------------------------ |
//! | [`Engine::encode`] | returns a new `String` | always |
//! | [`Engine::encode_string`] | appends to provided `String` | if `String` lacks capacity |
//! | [`Engine::encode_slice`] | writes to provided `&[u8]` | never |
//!
//! ## Input and output
//!
//! The `base64` crate can [decode][Engine::decode()] and
//! [encode][Engine::encode()] values in memory, or
//! [`DecoderReader`][read::DecoderReader] and
//! [`EncoderWriter`][write::EncoderWriter] provide streaming decoding and
//! encoding for any [readable][std::io::Read] or [writable][std::io::Write]
//! byte stream.
//!
//! #### Decoding
//!
#![cfg_attr(feature = "std", doc = "```")]
#![cfg_attr(not(feature = "std"), doc = "```ignore")]
//! # use std::io;
//! use base64::{engine::general_purpose::STANDARD, read::DecoderReader};
//!
//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
//! let mut input = io::stdin();
//! let mut decoder = DecoderReader::new(&mut input, &STANDARD);
//! io::copy(&mut decoder, &mut io::stdout())?;
//! # Ok(())
//! # }
//! ```
//!
//! #### Encoding
//!
#![cfg_attr(feature = "std", doc = "```")]
#![cfg_attr(not(feature = "std"), doc = "```ignore")]
//! # use std::io;
//! use base64::{engine::general_purpose::STANDARD, write::EncoderWriter};
//!
//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
//! let mut output = io::stdout();
//! let mut encoder = EncoderWriter::new(&mut output, &STANDARD);
//! io::copy(&mut io::stdin(), &mut encoder)?;
//! # Ok(())
//! # }
//! ```
//!
//! #### Display
//!
//! If you only need a base64 representation for implementing the
//! [`Display`][std::fmt::Display] trait, use
//! [`Base64Display`][display::Base64Display]:
//!
//! ```
//! use base64::{display::Base64Display, engine::general_purpose::STANDARD};
//!
//! let value = Base64Display::new(b"\0\x01\x02\x03", &STANDARD);
//! assert_eq!("base64: AAECAw==", format!("base64: {}", value));
//! ```
//!
//! # Panics
//!
//! If length calculations result in overflowing `usize`, a panic will result.
#![cfg_attr(feature = "cargo-clippy", allow(clippy::cast_lossless))]
#![deny(
missing_docs,
trivial_casts,
trivial_numeric_casts,
unused_extern_crates,
unused_import_braces,
unused_results,
variant_size_differences
)]
#![forbid(unsafe_code)]
// Allow globally until https://github.com/rust-lang/rust-clippy/issues/8768 is resolved.
// The desired state is to allow it only for the rstest_reuse import.
#![allow(clippy::single_component_path_imports)]
#![cfg_attr(not(any(feature = "std", test)), no_std)]
#[cfg(any(feature = "alloc", test))]
extern crate alloc;
// has to be included at top level because of the way rstest_reuse defines its macros
#[cfg(test)]
use rstest_reuse;
mod chunked_encoder;
pub mod display;
#[cfg(any(feature = "std", test))]
pub mod read;
#[cfg(any(feature = "std", test))]
pub mod write;
pub mod engine;
pub use engine::Engine;
pub mod alphabet;
mod encode;
#[allow(deprecated)]
#[cfg(any(feature = "alloc", test))]
pub use crate::encode::{encode, encode_engine, encode_engine_string};
#[allow(deprecated)]
pub use crate::encode::{encode_engine_slice, encoded_len, EncodeSliceError};
mod decode;
#[allow(deprecated)]
#[cfg(any(feature = "alloc", test))]
pub use crate::decode::{decode, decode_engine, decode_engine_vec};
#[allow(deprecated)]
pub use crate::decode::{decode_engine_slice, decoded_len_estimate, DecodeError, DecodeSliceError};
pub mod prelude;
#[cfg(test)]
mod tests;
const PAD_BYTE: u8 = b'=';