Crate encoding [] [src]

Encoding 0.2.33

Character encoding support for Rust. (also known as rust-encoding) It is based on WHATWG Encoding Standard, and also provides an advanced interface for error detection and recovery.


Put this in your Cargo.toml:

encoding = "0.2"

Then put this in your crate root:

extern crate encoding;


To encode a string:

use encoding::{Encoding, EncoderTrap};
use encoding::all::ISO_8859_1;

assert_eq!(ISO_8859_1.encode("caf\u{e9}", EncoderTrap::Strict),

To encode a string with unrepresentable characters:

use encoding::{Encoding, EncoderTrap};
use encoding::all::ISO_8859_2;

assert!(ISO_8859_2.encode("Acme\u{a9}", EncoderTrap::Strict).is_err());
assert_eq!(ISO_8859_2.encode("Acme\u{a9}", EncoderTrap::Replace),
assert_eq!(ISO_8859_2.encode("Acme\u{a9}", EncoderTrap::Ignore),
assert_eq!(ISO_8859_2.encode("Acme\u{a9}", EncoderTrap::NcrEscape),

To decode a byte sequence:

use encoding::{Encoding, DecoderTrap};
use encoding::all::ISO_8859_1;

assert_eq!(ISO_8859_1.decode(&[99,97,102,233], DecoderTrap::Strict),

To decode a byte sequence with invalid sequences:

use encoding::{Encoding, DecoderTrap};
use encoding::all::ISO_8859_6;

assert!(ISO_8859_6.decode(&[65,99,109,101,169], DecoderTrap::Strict).is_err());
assert_eq!(ISO_8859_6.decode(&[65,99,109,101,169], DecoderTrap::Replace),
assert_eq!(ISO_8859_6.decode(&[65,99,109,101,169], DecoderTrap::Ignore),

To encode or decode the input into the already allocated buffer:

use encoding::{Encoding, EncoderTrap, DecoderTrap};
use encoding::all::{ISO_8859_2, ISO_8859_6};

let mut bytes = Vec::new();
let mut chars = String::new();

assert!(ISO_8859_2.encode_to("Acme\u{a9}", EncoderTrap::Ignore, &mut bytes).is_ok());
assert!(ISO_8859_6.decode_to(&[65,99,109,101,169], DecoderTrap::Replace, &mut chars).is_ok());

assert_eq!(bytes, [65,99,109,101]);
assert_eq!(chars, "Acme\u{fffd}");

A practical example of custom encoder traps:

use encoding::{Encoding, ByteWriter, EncoderTrap, DecoderTrap};
use encoding::types::RawEncoder;
use encoding::all::ASCII;

// hexadecimal numeric character reference replacement
fn hex_ncr_escape(_encoder: &mut RawEncoder, input: &str, output: &mut ByteWriter) -> bool {
    let escapes: Vec<String> =
        input.chars().map(|ch| format!("&#x{:x};", ch as isize)).collect();
    let escapes = escapes.concat();
static HEX_NCR_ESCAPE: EncoderTrap = EncoderTrap::Call(hex_ncr_escape);

let orig = "Hello, 世界!".to_string();
let encoded = ASCII.encode(&orig, HEX_NCR_ESCAPE).unwrap();
assert_eq!(ASCII.decode(&encoded, DecoderTrap::Strict),
           Ok("Hello, &#x4e16;&#x754c;!".to_string()));

Getting the encoding from the string label, as specified in WHATWG Encoding standard:

use encoding::{Encoding, DecoderTrap};
use encoding::label::encoding_from_whatwg_label;
use encoding::all::WINDOWS_949;

let euckr = encoding_from_whatwg_label("euc-kr").unwrap();
assert_eq!(, "windows-949");
assert_eq!(euckr.whatwg_name(), Some("euc-kr")); // for the sake of compatibility
let broken = &[0xbf, 0xec, 0xbf, 0xcd, 0xff, 0xbe, 0xd3];
assert_eq!(euckr.decode(broken, DecoderTrap::Replace),

// corresponding Encoding native API:
assert_eq!(WINDOWS_949.decode(broken, DecoderTrap::Replace),

Types and Stuffs

There are three main entry points to Encoding.

Encoding is a single character encoding. It contains encode and decode methods for converting String to Vec<u8> and vice versa. For the error handling, they receive traps (EncoderTrap and DecoderTrap respectively) which replace any error with some string (e.g. U+FFFD) or sequence (e.g. ?). You can also use EncoderTrap::Strict and DecoderTrap::Strict traps to stop on an error.

There are two ways to get Encoding:

RawEncoder is an experimental incremental encoder. At each step of raw_feed, it receives a slice of string and emits any encoded bytes to a generic ByteWriter (normally Vec<u8>). It will stop at the first error if any, and would return a CodecError struct in that case. The caller is responsible for calling raw_finish at the end of encoding process.

RawDecoder is an experimental incremental decoder. At each step of raw_feed, it receives a slice of byte sequence and emits any decoded characters to a generic StringWriter (normally String). Otherwise it is identical to RawEncoders.

One should prefer Encoding::{encode,decode} as a primary interface. RawEncoder and RawDecoder is experimental and can change substantially. See the additional documents on encoding::types module for more information on them.

Supported Encodings

Encoding covers all encodings specified by WHATWG Encoding Standard and some more:

Parenthesized names refer to the encoding's primary name assigned by WHATWG Encoding Standard.

Many legacy character encodings lack the proper specification, and even those that have a specification are highly dependent of the actual implementation. Consequently one should be careful when picking a desired character encoding. The only standards reliable in this regard are WHATWG Encoding Standard and vendor-provided mappings from the Unicode consortium. Whenever in doubt, look at the source code and specifications for detailed explanations.


pub use self::types::{CodecError, ByteWriter, StringWriter, RawEncoder, RawDecoder, EncodingRef, Encoding, EncoderTrapFunc, DecoderTrapFunc, DecoderTrap, EncoderTrap, decode};



A list of all supported encodings. Useful for encodings fixed in the compile time.


Codec implementations.


An interface for retrieving an encoding (or a set of encodings) from a string/numeric label.


Interface to the character encoding.