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// Copyright 2016 Google Inc.
//
// 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.
//
////////////////////////////////////////////////////////////////////////////////
#ifndef COMPACT_ENC_DET_COMPACT_ENC_DET_H_
#define COMPACT_ENC_DET_COMPACT_ENC_DET_H_
#include "util/encodings/encodings.h" // for Encoding
#include "util/languages/languages.h" // for Language
#include <string.h>
namespace CompactEncDet {
// We may want different statistics, depending on whether the text being
// identfied is from the web, from email, etc. This is currently ignored,
// except WEB_CORPUS enables ignoring chars inside tags.
enum TextCorpusType {
WEB_CORPUS,
XML_CORPUS,
QUERY_CORPUS, // Use this for vanilla plaintext
EMAIL_CORPUS,
NUM_CORPA, // always last
};
// Scan raw bytes and detect most likely encoding
// Design goals:
// Skip over big initial stretches of seven-bit ASCII bytes very quickly
// Thread safe
// Works equally well on
// 50-byte queries,
// 5000-byte email and
// 50000-byte web pages
// Length 0 input returns ASCII (aka ISO-8859-1 or Latin1)
//
// Inputs: text and text_length
// web page's url (preferred) or just
// top-level domain name (e.g. "com") or NULL as a hint
// web page's HTTPheader charset= string (e.g. "Latin1") or NULL as a hint
// web page's <meta> tag charset= string (e.g. "utf-8") or NULL as a hint
// an Encoding or UNKNOWN_ENCODING as a hint
// a Language or UNKNOWN_LANGUAGE as a hint
// corpus type from the list above. Currently ignored; may select
// different probability tables in the future
// ignore_7bit if true says to NOT return the pure seven-bit encodings
// ISO-2022-JP (aka JIS), ISO-2022-CN, ISO-2022-KR, HZ, and UTF-7.
// This may save a little scoring time on pure printable ASCII input text
// Outputs: bytes_consumed says how much of text_length was actually examined
// is_reliable set true if the returned encoding is at least 2**10 time more
// probable then the second-best encoding
// Return value: the most likely encoding for the input text
//
// Setting ignore_7bit_mail_encodings effectively turns off detection of
// UTF-7, HZ, and ISO-2022-xx. It is recommended that this flag be true
// when corpus_type is QUERY_CORPUS.
Encoding DetectEncoding(
const char* text, int text_length, const char* url_hint,
const char* http_charset_hint, const char* meta_charset_hint,
const int encoding_hint,
const Language language_hint, // User interface lang
const TextCorpusType corpus_type, bool ignore_7bit_mail_encodings,
int* bytes_consumed, bool* is_reliable);
// Support functions for unit test program
int BackmapEncodingToRankedEncoding(Encoding enc);
Encoding TopEncodingOfLangHint(const char* name);
Encoding TopEncodingOfTLDHint(const char* name);
Encoding TopEncodingOfCharsetHint(const char* name);
const char* Version(void);
} // End namespace CompactEncDet
#endif // COMPACT_ENC_DET_COMPACT_ENC_DET_H_
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