101 lines
3.4 KiB
Java
101 lines
3.4 KiB
Java
/* GENERATED SOURCE. DO NOT MODIFY. */
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// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/**
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*******************************************************************************
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* Copyright (C) 2005 - 2014, International Business Machines Corporation and *
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* others. All Rights Reserved. *
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*******************************************************************************
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*/
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package android.icu.text;
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/**
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* Charset recognizer for UTF-8
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*/
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class CharsetRecog_UTF8 extends CharsetRecognizer {
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@Override
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String getName() {
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return "UTF-8";
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}
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/* (non-Javadoc)
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* @see android.icu.text.CharsetRecognizer#match(android.icu.text.CharsetDetector)
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*/
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@Override
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CharsetMatch match(CharsetDetector det) {
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boolean hasBOM = false;
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int numValid = 0;
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int numInvalid = 0;
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byte input[] = det.fRawInput;
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int i;
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int trailBytes = 0;
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int confidence;
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if (det.fRawLength >= 3 &&
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(input[0] & 0xFF) == 0xef && (input[1] & 0xFF) == 0xbb && (input[2] & 0xFF) == 0xbf) {
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hasBOM = true;
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}
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// Scan for multi-byte sequences
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for (i=0; i<det.fRawLength; i++) {
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int b = input[i];
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if ((b & 0x80) == 0) {
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continue; // ASCII
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}
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// Hi bit on char found. Figure out how long the sequence should be
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if ((b & 0x0e0) == 0x0c0) {
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trailBytes = 1;
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} else if ((b & 0x0f0) == 0x0e0) {
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trailBytes = 2;
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} else if ((b & 0x0f8) == 0xf0) {
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trailBytes = 3;
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} else {
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numInvalid++;
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continue;
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}
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// Verify that we've got the right number of trail bytes in the sequence
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for (;;) {
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i++;
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if (i>=det.fRawLength) {
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break;
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}
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b = input[i];
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if ((b & 0xc0) != 0x080) {
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numInvalid++;
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break;
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}
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if (--trailBytes == 0) {
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numValid++;
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break;
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}
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}
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}
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// Cook up some sort of confidence score, based on presence of a BOM
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// and the existence of valid and/or invalid multi-byte sequences.
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confidence = 0;
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if (hasBOM && numInvalid==0) {
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confidence = 100;
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} else if (hasBOM && numValid > numInvalid*10) {
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confidence = 80;
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} else if (numValid > 3 && numInvalid == 0) {
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confidence = 100;
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} else if (numValid > 0 && numInvalid == 0) {
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confidence = 80;
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} else if (numValid == 0 && numInvalid == 0) {
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// Plain ASCII. Confidence must be > 10, it's more likely than UTF-16, which
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// accepts ASCII with confidence = 10.
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// TODO: add plain ASCII as an explicitly detected type.
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confidence = 15;
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} else if (numValid > numInvalid*10) {
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// Probably corrupt utf-8 data. Valid sequences aren't likely by chance.
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confidence = 25;
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}
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return confidence == 0 ? null : new CharsetMatch(det, this, confidence);
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}
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}
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