Encoders and decoders for converting between different data representations,including JSON and UTF-8.

In addition to converters for common data representations, this libraryprovides support for implementing converters in a way which makes them easyto chain and to use with streams.

To use this library in your code:

import 'dart:convert';

Two commonly used converters are the top-level instances ofJsonCodec andUtf8Codec, namedjson andutf8, respectively.

JSON

JSON is a simple text format for representing structured objects andcollections.

AJsonCodec encodes JSON objects to strings and decodes strings toJSON objects. Thejson encoder/decoder transforms between strings andobject structures, such as lists and maps, using the JSON format.

Thejson is the default implementation ofJsonCodec.

Examples

var encoded = json.encode([1, 2, { "a": null }]);var decoded = json.decode('["foo", { "bar": 499 }]');

For more information, see alsoJsonEncoder andJsonDecoder.

UTF-8

AUtf8Codec encodes strings to UTF-8 code units (bytes) and decodesUTF-8 code units to strings.

Theutf8 is the default implementation ofUtf8Codec.

Example:

var encoded = utf8.encode('Îñţérñåţîöñåļîžåţîờñ');var decoded = utf8.decode([  195, 142, 195, 177, 197, 163, 195, 169, 114, 195, 177, 195, 165, 197,  163, 195, 174, 195, 182, 195, 177, 195, 165, 196, 188, 195, 174, 197,  190, 195, 165, 197, 163, 195, 174, 225, 187, 157, 195, 177]);

For more information, see alsoUtf8Encoder andUtf8Decoder.

ASCII

AnAsciiCodec encodes strings as ASCII codes stored as bytes and decodesASCII bytes to strings. Not all characters can be represented as ASCII, sonot all strings can be successfully converted.

Theascii is the default implementation ofAsciiCodec.

Example:

var encoded = ascii.encode('This is ASCII!');var decoded = ascii.decode([0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73,                            0x20, 0x41, 0x53, 0x43, 0x49, 0x49, 0x21]);

For more information, see alsoAsciiEncoder andAsciiDecoder.

Latin-1

ALatin1Codec encodes strings to ISO Latin-1 (aka ISO-8859-1) bytesand decodes Latin-1 bytes to strings. Not all characters can be representedas Latin-1, so not all strings can be successfully converted.

Thelatin1 is the default implementation ofLatin1Codec.

Example:

var encoded = latin1.encode('blåbærgrød');var decoded = latin1.decode([0x62, 0x6c, 0xe5, 0x62, 0xe6,                             0x72, 0x67, 0x72, 0xf8, 0x64]);

For more information, see alsoLatin1Encoder andLatin1Decoder.

Base64

ABase64Codec encodes bytes using the default base64 alphabet,decodes using both the base64 and base64url alphabets,does not allow invalid characters and requires padding.

Thebase64 is the default implementation ofBase64Codec.

Example:

var encoded = base64.encode([0x62, 0x6c, 0xc3, 0xa5, 0x62, 0xc3, 0xa6,                             0x72, 0x67, 0x72, 0xc3, 0xb8, 0x64]);var decoded = base64.decode('YmzDpWLDpnJncsO4ZAo=');

For more information, see alsoBase64Encoder andBase64Decoder.

Converters

Converters are often used with streamsto transform the data that comes through the streamas it becomes available.The following code uses two converters.The first is a UTF-8 decoder, which converts the data from bytes to UTF-8as it is read from a file,The second is an instance ofLineSplitter,which splits the data on newline boundaries.

const showLineNumbers = true;var lineNumber = 1;var stream = File('quotes.txt').openRead();stream.transform(utf8.decoder)      .transform(const LineSplitter())      .forEach((line) {        if (showLineNumbers) {          stdout.write('${lineNumber++} ');        }        stdout.writeln(line);      });

See the documentation for theCodec andConverter classesfor information about creating your own converters.

HTML Escape

HtmlEscape converter escapes characters with special meaning in HTML.The converter finds characters that are significant in HTML source andreplaces them with corresponding HTML entities.

Custom escape modes can be created using theHtmlEscapeMode.newconstructor.

Example:

const htmlEscapeMode = HtmlEscapeMode(  name: 'custom',  escapeLtGt: true,  escapeQuot: false,  escapeApos: false,  escapeSlash: false, );const HtmlEscape htmlEscape = HtmlEscape(htmlEscapeMode);String unescaped = 'Text & subject';String escaped = htmlEscape.convert(unescaped);print(escaped); // Text &amp; subjectunescaped = '10 > 1 and 1 < 10';escaped = htmlEscape.convert(unescaped);print(escaped); // 10 &gt; 1 and 1 &lt; 10unescaped = "Single-quoted: 'text'";escaped = htmlEscape.convert(unescaped);print(escaped); // Single-quoted: 'text'unescaped = 'Double-quoted: "text"';escaped = htmlEscape.convert(unescaped);print(escaped); // Double-quoted: "text"unescaped = 'Path: /system/';escaped = htmlEscape.convert(unescaped);print(escaped); // Path: /system/

Classes

AsciiCodec

AnAsciiCodec allows encoding strings as ASCII bytesand decoding ASCII bytes to strings.

AsciiDecoder

Converts ASCII bytes to string.

AsciiEncoder

Converts strings of only ASCII characters to bytes.

Base64Codec

Abase64 encoder and decoder.

Base64Decoder

Decoder for base64 encoded data.

Base64Encoder

Base64 and base64url encoding converter.

ByteConversionSink

TheByteConversionSink provides an interface for converters toefficiently transmit byte data.

ChunkedConversionSink<T>

AChunkedConversionSink is used to transmit data more efficiently betweentwo converters during chunked conversions.

ClosableStringSink

AClosableStringSink extends theStringSink interface by adding aclose method.

Codec<S,T>

ACodec encodes and (if supported) decodes data.

Converter<S,T>

AConverter converts data from one representation into another.

Encoding

Open-ended set of encodings.

HtmlEscape

Converter which escapes characters with special meaning in HTML.

HtmlEscapeMode

HTML escape modes.

JsonCodec

AJsonCodec encodes JSON objects to strings and decodes strings toJSON objects.

JsonDecoder

This class parses JSON strings and builds the corresponding objects.

JsonEncoder

This class converts JSON objects to strings.

JsonUtf8Encoder

Encoder that encodes a single object as a UTF-8 encoded JSON string.

Latin1Codec

ALatin1Codec encodes strings to ISO Latin-1 (aka ISO-8859-1) bytesand decodes Latin-1 bytes to strings.

Latin1Decoder

This class converts Latin-1 bytes (lists of unsigned 8-bit integers)to a string.

Latin1Encoder

This class converts strings of only ISO Latin-1 characters to bytes.

LineSplitter

AStreamTransformer that splits aString into individual lines.

StringConversionSink

A sink for converters to efficiently transmit String data.

Utf8Codec

AUtf8Codec encodes strings to utf-8 code units (bytes) and decodesUTF-8 code units to strings.

Utf8Decoder

This class converts UTF-8 code units (lists of unsigned 8-bit integers)to a string.

Utf8Encoder

This class converts strings to their UTF-8 code units (a list ofunsigned 8-bit integers).

Constants

ascii→ constAsciiCodec

An instance of the default implementation of theAsciiCodec.

base64→ constBase64Codec

Abase64 encoder and decoder.

base64Url→ constBase64Codec

Abase64url encoder and decoder.

htmlEscape→ constHtmlEscape

AString converter that converts characters to HTML entities.

json→ constJsonCodec

An instance of the default implementation of theJsonCodec.

latin1→ constLatin1Codec

An instance of the default implementation of theLatin1Codec.

unicodeBomCharacterRune→ constint

The Unicode Byte Order Marker (BOM) characterU+FEFF.

unicodeReplacementCharacterRune→ constint

The Unicode Replacement characterU+FFFD (�).

utf8→ constUtf8Codec

An instance of the default implementation of theUtf8Codec.

Functions

base64Decode(Stringsource)→Uint8List

Decodesbase64 orbase64url encoded bytes.

base64Encode(List<int>bytes)→String

Encodesbytes usingbase64 encoding.

base64UrlEncode(List<int>bytes)→String

Encodesbytes usingbase64url encoding.

jsonDecode(Stringsource, {Object?reviver(Object?key,Object?value)?})→ dynamic

Parses the string and returns the resulting Json object.

jsonEncode(Object?object, {Object?toEncodable(Object?nonEncodable)?})→String

Convertsobject to a JSON string.

Typedefs

ByteConversionSinkBase =ByteConversionSink

This class provides a base-class for converters that need to accept byteinputs.

StringConversionSinkBase =StringConversionSink

This class provides a base-class for converters that need to accept Stringinputs.

StringConversionSinkMixin =StringConversionSink

This class provides a mixin for converters that need to accept Stringinputs.

Exceptions / Errors

JsonCyclicError

Reports that an object could not be stringified due to cyclic references.

JsonUnsupportedObjectError

Error thrown by JSON serialization if an object cannot be serialized.