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Diffstat (limited to 'browser/components/translation/cld2/internal/lang_script.h')
| -rw-r--r-- | browser/components/translation/cld2/internal/lang_script.h | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/browser/components/translation/cld2/internal/lang_script.h b/browser/components/translation/cld2/internal/lang_script.h new file mode 100644 index 000000000..9311707e4 --- /dev/null +++ b/browser/components/translation/cld2/internal/lang_script.h @@ -0,0 +1,187 @@ +// Copyright 2013 Google Inc. All Rights Reserved. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// +// File: lang_script.h +// ================ +// +// Author: dsites@google.com (Dick Sites) +// +// This file declares language and script numbers and names for CLD2, +// plus routines that access side tables based on these +// + +#ifndef I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__ +#define I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__ + +#include "generated_language.h" +#include "generated_ulscript.h" +#include "integral_types.h" + + +// NOTE: The script numbers and language numbers here are not guaranteed to be +// stable. If you want to record a result for posterity, save the +// ULScriptCode(ULScript ulscript) result as character strings. +// +// The Unicode scripts recognized by CLD2 are numbered almost arbitrarily, +// specified in an enum. Each script has human-readable script name and a +// 4-letter ISO 15924 script code. Each has a C name (largely for use by +// programs that generate declarations in cld2_generated_scripts.h). Each +// also has a recognition type +// r_type: 0 script-only, 1 nilgrams, 2 quadgrams, 3 CJK +// +// The declarations for a particular version of Unicode are machine-generated in +// generated_scripts.h +// +// This file includes that one and declares the access routines. The type +// involved is called "ULScript" to signify Unicode Letters-Marks Scripts, +// which are not quite Unicode Scripts. In particular, the CJK scripts are +// merged into a single number because CLD2 recognizes the CJK languages from +// four scripts intermixed: Hani (both Hans and Hant), Hangul, Hiragana, and +// Katakana. + +// Each script has one of these four recognition types. +// RTypeNone: There is no language associated with this script. In extended +// language recognition calls, return a fake language number that maps to +// xx-Cham, with literally "xx" for the language code,and with the script +// code instead of "Cham". In non-extended calls, return UNKNOWN_LANGUAGE. +// RTypeOne: The script maps 1:1 to a single language. No letters are examined +// during recognition and no lookups done. +// RTypeMany: The usual quadgram + delta-octagram + distinctive-words scoring +// is done to determine the languages involved. +// RTypeCJK: The CJK unigram + delta-bigram scoring is done to determine the +// languages involved. +// +// Note that the choice of recognition type is a function of script, not +// language. In particular, some languges are recognized in multiple scripts +// and those have different recognition types (Mongolian mn-Latn vs. mn-Mong +// for example). + +namespace CLD2 { + +//----------------------------------------------------------------------------// +// Functions of ULScript // +//----------------------------------------------------------------------------// + +// If the input is out of range or otherwise unrecognized, it is treated +// as ULScript_Common (which never participates in language recognition) +const char* ULScriptName(ULScript ulscript); +const char* ULScriptCode(ULScript ulscript); +const char* ULScriptDeclaredName(ULScript ulscript); +ULScriptRType ULScriptRecognitionType(ULScript ulscript); + +// Name can be either full name or ISO code, or can be ISO code embedded in +// a language-script combination such as "en-Latn-GB" +ULScript GetULScriptFromName(const char* src); + +// Map script into Latin, Cyrillic, Arabic, Other +int LScript4(ULScript ulscript); + +//----------------------------------------------------------------------------// +// Functions of Language // +//----------------------------------------------------------------------------// + +// The languages recognized by CLD2 are numbered almost arbitrarily, +// specified in an enum. Each language has human-readable language name and a +// 2- or 3-letter ISO 639 language code. Each has a C name (largely for use by +// programs that generate declarations in cld2_generated_languagess.h). +// Each has a list of up to four scripts in which it is currently recognized. +// +// The declarations for a particular set of recognized languages are +// machine-generated in +// generated_languages.h +// +// The Language enum is intended to match the internal Google Language enum +// in i18n/languages/proto/languages.proto up to NUM_LANGUAGES, with additional +// languages assigned above that. Over time, some languages may be renumbered +// if they are moved into the Language enum. +// +// The Language enum includes the fake language numbers for RTypeNone above. +// + + +// If the input is out of range or otherwise unrecognized, it is treated +// as UNKNOWN_LANGUAGE +// +// LanguageCode +// ------------ +// Given the Language, return the language code, e.g. "ko" +// This is determined by +// the following (in order of preference): +// - ISO-639-1 two-letter language code +// (all except those mentioned below) +// - ISO-639-2 three-letter bibliographic language code +// (Tibetan, Dhivehi, Cherokee, Syriac) +// - Google-specific language code +// (ChineseT ("zh-TW"), Teragram Unknown, Unknown, +// Portuguese-Portugal, Portuguese-Brazil, Limbu) +// - Fake RTypeNone names. + +const char* LanguageName(Language lang); +const char* LanguageCode(Language lang); +const char* LanguageShortCode(Language lang); +const char* LanguageDeclaredName(Language lang); + +// n is in 0..3. Trailing entries are filled with +// ULScript_Common (which never participates in language recognition) +ULScript LanguageRecognizedScript(Language lang, int n); + +// Name can be either full name or ISO code, or can be ISO code embedded in +// a language-script combination such as "en-Latn-GB" +Language GetLanguageFromName(const char* src); + +// Returns which set of statistically-close languages lang is in. 0 means none. +int LanguageCloseSet(Language lang); + +//----------------------------------------------------------------------------// +// Functions of ULScript and Language // +//----------------------------------------------------------------------------// + +// Most common language in each script +Language DefaultLanguage(ULScript ulscript); + +// For RTypeMany recognition, +// the CLD2 lookup tables are kept small by encoding a language into one byte. +// To avoid limiting CLD2 to at most 256 languages, a larger range of external +// Language numbers is mapped to a smaller range of per-script numbers. At +// the moment (January 2013) the Latin script has about 90 languages to be +// recognized, while all the other scripts total about 50 more languages. In +// addition, the RTypeNone scripts map to about 100 fake languages. +// So we map all Latin-script languages to one range of 1..255 per-script +// numbers and map all the other RTypeMany languages to an overlapping range +// 1..255 of per-script numbers. + +uint8 PerScriptNumber(ULScript ulscript, Language lang); +Language FromPerScriptNumber(ULScript ulscript, uint8 perscript_number); + +// While the speed-sensitive processing deals with per-script language numbers, +// there is a need for low-performance dealing with original language numbers +// and unknown scripts, mostly for processing language hints. +// These routines let one derive a script class from a bare language. +// For languages written in multiple scripts, both of these can return true. + +bool IsLatnLanguage(Language lang); +bool IsOthrLanguage(Language lang); + + +//----------------------------------------------------------------------------// +// Other // +//----------------------------------------------------------------------------// + +// Utility routine to search alphabetical tables +int BinarySearch(const char* key, int lo, int hi, const CharIntPair* cipair); + +} // namespace CLD2 + +#endif // I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__ |