Initial CLD2 source upload.
git-svn-id: https://cld2.googlecode.com/svn/trunk@3 b252ecd4-b096-bf77-eb8e-91563289f87e
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dsites@google.com
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internal/lang_script.h
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internal/lang_script.h
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// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// File: lang_script.h
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// ================
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//
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// Author: dsites@google.com (Dick Sites)
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//
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// This file declares language and script numbers and names for CLD2,
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// plus routines that access side tables based on these
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//
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#ifndef I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__
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#define I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__
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#include "generated_language.h"
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#include "generated_ulscript.h"
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#include "integral_types.h"
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// NOTE: The script numbers and language numbers here are not guaranteed to be
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// stable. If you want to record a result for posterity, save the
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// ULScriptCode(ULScript ulscript) result as character strings.
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//
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// The Unicode scripts recognized by CLD2 are numbered almost arbitrarily,
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// specified in an enum. Each script has human-readable script name and a
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// 4-letter ISO 15924 script code. Each has a C name (largely for use by
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// programs that generate declarations in cld2_generated_scripts.h). Each
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// also has a recognition type
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// r_type: 0 script-only, 1 nilgrams, 2 quadgrams, 3 CJK
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//
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// The declarations for a particular version of Unicode are machine-generated in
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// generated_scripts.h
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//
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// This file includes that one and declares the access routines. The type
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// involved is called "ULScript" to signify Unicode Letters-Marks Scripts,
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// which are not quite Unicode Scripts. In particular, the CJK scripts are
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// merged into a single number because CLD2 recognizes the CJK languages from
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// four scripts intermixed: Hani (both Hans and Hant), Hangul, Hiragana, and
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// Katakana.
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// Each script has one of these four recognition types.
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// RTypeNone: There is no language associated with this script. In extended
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// language recognition calls, return a fake language number that maps to
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// xx-Cham, with literally "xx" for the language code,and with the script
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// code instead of "Cham". In non-extended calls, return UNKNOWN_LANGUAGE.
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// RTypeOne: The script maps 1:1 to a single language. No letters are examined
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// during recognition and no lookups done.
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// RTypeMany: The usual quadgram + delta-octagram + distinctive-words scoring
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// is done to determine the languages involved.
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// RTypeCJK: The CJK unigram + delta-bigram scoring is done to determine the
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// languages involved.
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//
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// Note that the choice of recognition type is a function of script, not
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// language. In particular, some languges are recognized in multiple scripts
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// and those have different recognition types (Mongolian mn-Latn vs. mn-Mong
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// for example).
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namespace CLD2 {
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//----------------------------------------------------------------------------//
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// Functions of ULScript //
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//----------------------------------------------------------------------------//
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// If the input is out of range or otherwise unrecognized, it is treated
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// as ULScript_Common (which never participates in language recognition)
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const char* ULScriptName(ULScript ulscript);
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const char* ULScriptCode(ULScript ulscript);
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const char* ULScriptDeclaredName(ULScript ulscript);
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ULScriptRType ULScriptRecognitionType(ULScript ulscript);
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// Name can be either full name or ISO code, or can be ISO code embedded in
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// a language-script combination such as "en-Latn-GB"
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ULScript GetULScriptFromName(const char* src);
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// Map script into Latin, Cyrillic, Arabic, Other
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int LScript4(ULScript ulscript);
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//----------------------------------------------------------------------------//
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// Functions of Language //
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//----------------------------------------------------------------------------//
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// The languages recognized by CLD2 are numbered almost arbitrarily,
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// specified in an enum. Each language has human-readable language name and a
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// 2- or 3-letter ISO 639 language code. Each has a C name (largely for use by
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// programs that generate declarations in cld2_generated_languagess.h).
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// Each has a list of up to four scripts in which it is currently recognized.
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//
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// The declarations for a particular set of recognized languages are
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// machine-generated in
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// generated_languages.h
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//
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// The Language enum is intended to match the internal Google Language enum
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// in i18n/languages/proto/languages.proto up to NUM_LANGUAGES, with additional
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// languages assigned above that. Over time, some languages may be renumbered
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// if they are moved into the Language enum.
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//
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// The Language enum includes the fake language numbers for RTypeNone above.
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//
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// In an open-source environment, the Google-specific Language enum is not
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// available. Language decouples the two environments while maintaining
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// internal compatibility.
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// If the input is out of range or otherwise unrecognized, it is treated
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// as UNKNOWN_LANGUAGE
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//
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// LanguageCode
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// ------------
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// Given the Language, return the language code, e.g. "ko"
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// This is determined by
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// the following (in order of preference):
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// - ISO-639-1 two-letter language code
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// (all except those mentioned below)
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// - ISO-639-2 three-letter bibliographic language code
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// (Tibetan, Dhivehi, Cherokee, Syriac)
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// - Google-specific language code
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// (ChineseT ("zh-TW"), Teragram Unknown, Unknown,
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// Portuguese-Portugal, Portuguese-Brazil, Limbu)
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// - Fake RTypeNone names.
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const char* LanguageName(Language lang);
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const char* LanguageCode(Language lang);
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const char* LanguageShortCode(Language lang);
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const char* LanguageDeclaredName(Language lang);
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// n is in 0..3. Trailing entries are filled with
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// ULScript_Common (which never participates in language recognition)
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ULScript LanguageRecognizedScript(Language lang, int n);
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// Name can be either full name or ISO code, or can be ISO code embedded in
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// a language-script combination such as "en-Latn-GB"
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Language GetLanguageFromName(const char* src);
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// Returns which set of statistically-close languages lang is in. 0 means none.
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int LanguageCloseSet(Language lang);
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//----------------------------------------------------------------------------//
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// Functions of ULScript and Language //
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//----------------------------------------------------------------------------//
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// Most common language in each script
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Language DefaultLanguage(ULScript ulscript);
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// For RTypeMany recognition,
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// the CLD2 lookup tables are kept small by encoding a language into one byte.
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// To avoid limiting CLD2 to at most 256 languages, a larger range of external
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// Language numbers is mapped to a smaller range of per-script numbers. At
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// the moment (January 2013) the Latin script has about 90 languages to be
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// recognized, while all the other scripts total about 50 more languages. In
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// addition, the RTypeNone scripts map to about 100 fake languages.
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// So we map all Latin-script languages to one range of 1..255 per-script
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// numbers and map all the other RTypeMany languages to an overlapping range
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// 1..255 of per-script numbers.
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uint8 PerScriptNumber(ULScript ulscript, Language lang);
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Language FromPerScriptNumber(ULScript ulscript, uint8 perscript_number);
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//----------------------------------------------------------------------------//
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// Other //
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//----------------------------------------------------------------------------//
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// Utility routine to search alphabetical tables
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int BinarySearch(const char* key, int lo, int hi, const CharIntPair* cipair);
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} // namespace CLD2
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#endif // I18N_ENCODINGS_CLD2_LANG_SCRIPT_H__
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