identifier.go (3385B)
1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 //go:generate go run gen.go 6 7 // Package identifier defines the contract between implementations of Encoding 8 // and Index by defining identifiers that uniquely identify standardized coded 9 // character sets (CCS) and character encoding schemes (CES), which we will 10 // together refer to as encodings, for which Encoding implementations provide 11 // converters to and from UTF-8. This package is typically only of concern to 12 // implementers of Indexes and Encodings. 13 // 14 // One part of the identifier is the MIB code, which is defined by IANA and 15 // uniquely identifies a CCS or CES. Each code is associated with data that 16 // references authorities, official documentation as well as aliases and MIME 17 // names. 18 // 19 // Not all CESs are covered by the IANA registry. The "other" string that is 20 // returned by ID can be used to identify other character sets or versions of 21 // existing ones. 22 // 23 // It is recommended that each package that provides a set of Encodings provide 24 // the All and Common variables to reference all supported encodings and 25 // commonly used subset. This allows Index implementations to include all 26 // available encodings without explicitly referencing or knowing about them. 27 package identifier 28 29 // Note: this package is internal, but could be made public if there is a need 30 // for writing third-party Indexes and Encodings. 31 32 // References: 33 // - http://source.icu-project.org/repos/icu/icu/trunk/source/data/mappings/convrtrs.txt 34 // - http://www.iana.org/assignments/character-sets/character-sets.xhtml 35 // - http://www.iana.org/assignments/ianacharset-mib/ianacharset-mib 36 // - http://www.ietf.org/rfc/rfc2978.txt 37 // - https://www.unicode.org/reports/tr22/ 38 // - http://www.w3.org/TR/encoding/ 39 // - https://encoding.spec.whatwg.org/ 40 // - https://encoding.spec.whatwg.org/encodings.json 41 // - https://tools.ietf.org/html/rfc6657#section-5 42 43 // Interface can be implemented by Encodings to define the CCS or CES for which 44 // it implements conversions. 45 type Interface interface { 46 // ID returns an encoding identifier. Exactly one of the mib and other 47 // values should be non-zero. 48 // 49 // In the usual case it is only necessary to indicate the MIB code. The 50 // other string can be used to specify encodings for which there is no MIB, 51 // such as "x-mac-dingbat". 52 // 53 // The other string may only contain the characters a-z, A-Z, 0-9, - and _. 54 ID() (mib MIB, other string) 55 56 // NOTE: the restrictions on the encoding are to allow extending the syntax 57 // with additional information such as versions, vendors and other variants. 58 } 59 60 // A MIB identifies an encoding. It is derived from the IANA MIB codes and adds 61 // some identifiers for some encodings that are not covered by the IANA 62 // standard. 63 // 64 // See http://www.iana.org/assignments/ianacharset-mib. 65 type MIB uint16 66 67 // These additional MIB types are not defined in IANA. They are added because 68 // they are common and defined within the text repo. 69 const ( 70 // Unofficial marks the start of encodings not registered by IANA. 71 Unofficial MIB = 10000 + iota 72 73 // Replacement is the WhatWG replacement encoding. 74 Replacement 75 76 // XUserDefined is the code for x-user-defined. 77 XUserDefined 78 79 // MacintoshCyrillic is the code for x-mac-cyrillic. 80 MacintoshCyrillic 81 )