758 lines
17 KiB
C
758 lines
17 KiB
C
/* $NetBSD: custom_apropos_tokenizer.c,v 1.2 2017/10/31 10:14:27 abhinav Exp $ */
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/*
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** 2006 September 30
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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*************************************************************************
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** Implementation of the full-text-search tokenizer that implements
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** a Porter stemmer.
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*/
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/*
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** The code in this file is only compiled if:
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**
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** * The FTS3 module is being built as an extension
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** (in which case SQLITE_CORE is not defined), or
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**
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** * The FTS3 module is being built into the core of
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** SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
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*/
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#include <assert.h>
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#include <ctype.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "custom_apropos_tokenizer.h"
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#include "fts3_tokenizer.h"
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#include "nostem.c"
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/*
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* Class derived from sqlite3_tokenizer
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*/
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typedef struct custom_apropos_tokenizer {
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sqlite3_tokenizer base; /* Base class */
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} custom_apropos_tokenizer;
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/*
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* Class derived from sqlite3_tokenizer_cursor
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*/
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typedef struct custom_apropos_tokenizer_cursor {
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sqlite3_tokenizer_cursor base;
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const char *zInput; /* input we are tokenizing */
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size_t nInput; /* size of the input */
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size_t iOffset; /* current position in zInput */
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size_t iToken; /* index of next token to be returned */
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char *zToken; /* storage for current token */
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size_t nAllocated; /* space allocated to zToken buffer */
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} custom_apropos_tokenizer_cursor;
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/*
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* Create a new tokenizer instance.
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*/
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static int
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aproposPorterCreate(int argc, const char *const * argv,
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sqlite3_tokenizer ** ppTokenizer)
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{
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custom_apropos_tokenizer *t;
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t = calloc(1, sizeof(*t));
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if (t == NULL)
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return SQLITE_NOMEM;
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*ppTokenizer = &t->base;
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return SQLITE_OK;
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}
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/*
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* Destroy a tokenizer
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*/
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static int
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aproposPorterDestroy(sqlite3_tokenizer * pTokenizer)
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{
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free(pTokenizer);
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return SQLITE_OK;
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}
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/*
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* Prepare to begin tokenizing a particular string. The input
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* string to be tokenized is zInput[0..nInput-1]. A cursor
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* used to incrementally tokenize this string is returned in
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* *ppCursor.
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*/
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static int
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aproposPorterOpen(
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sqlite3_tokenizer * pTokenizer, /* The tokenizer */
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const char *zInput, int nInput, /* String to be tokenized */
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sqlite3_tokenizer_cursor ** ppCursor /* OUT: Tokenization cursor */
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)
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{
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custom_apropos_tokenizer_cursor *c;
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c = calloc(1, sizeof(*c));
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if (c == NULL)
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return SQLITE_NOMEM;
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c->zInput = zInput;
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if (zInput != 0) {
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if (nInput < 0)
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c->nInput = strlen(zInput);
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else
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c->nInput = nInput;
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}
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*ppCursor = &c->base;
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return SQLITE_OK;
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}
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/*
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* Close a tokenization cursor previously opened by a call to
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* aproposPorterOpen() above.
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*/
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static int
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aproposPorterClose(sqlite3_tokenizer_cursor *pCursor)
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{
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custom_apropos_tokenizer_cursor *c = (custom_apropos_tokenizer_cursor *) pCursor;
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free(c->zToken);
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free(c);
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return SQLITE_OK;
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}
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/*
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* Vowel or consonant
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*/
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static const char cType[] = {
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0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0,
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1, 1, 1, 2, 1
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};
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/*
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* isConsonant() and isVowel() determine if their first character in
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* the string they point to is a consonant or a vowel, according
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* to Porter ruls.
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*
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* A consonate is any letter other than 'a', 'e', 'i', 'o', or 'u'.
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* 'Y' is a consonant unless it follows another consonant,
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* in which case it is a vowel.
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*
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* In these routine, the letters are in reverse order. So the 'y' rule
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* is that 'y' is a consonant unless it is followed by another
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* consonent.
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*/
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static int isVowel(const char*);
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static int
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isConsonant(const char *z)
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{
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int j;
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char x = *z;
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if (x == 0)
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return 0;
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assert(x >= 'a' && x <= 'z');
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j = cType[x - 'a'];
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if (j < 2)
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return j;
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return z[1] == 0 || isVowel(z + 1);
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}
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static int
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isVowel(const char *z)
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{
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int j;
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char x = *z;
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if (x == 0)
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return 0;
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assert(x >= 'a' && x <= 'z');
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j = cType[x - 'a'];
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if (j < 2)
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return 1 - j;
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return isConsonant(z + 1);
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}
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/*
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* Let any sequence of one or more vowels be represented by V and let
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* C be sequence of one or more consonants. Then every word can be
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* represented as:
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*
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* [C] (VC){m} [V]
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*
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* In prose: A word is an optional consonant followed by zero or
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* vowel-consonant pairs followed by an optional vowel. "m" is the
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* number of vowel consonant pairs. This routine computes the value
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* of m for the first i bytes of a word.
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*
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* Return true if the m-value for z is 1 or more. In other words,
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* return true if z contains at least one vowel that is followed
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* by a consonant.
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*
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* In this routine z[] is in reverse order. So we are really looking
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* for an instance of a consonant followed by a vowel.
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*/
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static int
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m_gt_0(const char *z)
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{
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while (isVowel(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isConsonant(z)) {
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z++;
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}
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return *z != 0;
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}
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/* Like mgt0 above except we are looking for a value of m which is
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* exactly 1
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*/
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static int
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m_eq_1(const char *z)
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{
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while (isVowel(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isConsonant(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isVowel(z)) {
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z++;
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}
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if (*z == 0)
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return 1;
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while (isConsonant(z)) {
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z++;
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}
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return *z == 0;
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}
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/* Like mgt0 above except we are looking for a value of m>1 instead
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* or m>0
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*/
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static int
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m_gt_1(const char *z)
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{
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while (isVowel(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isConsonant(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isVowel(z)) {
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z++;
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}
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if (*z == 0)
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return 0;
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while (isConsonant(z)) {
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z++;
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}
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return *z != 0;
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}
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/*
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* Return TRUE if there is a vowel anywhere within z[0..n-1]
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*/
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static int
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hasVowel(const char *z)
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{
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while (isConsonant(z)) {
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z++;
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}
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return *z != 0;
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}
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/*
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* Return TRUE if the word ends in a double consonant.
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*
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* The text is reversed here. So we are really looking at
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* the first two characters of z[].
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*/
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static int
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doubleConsonant(const char *z)
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{
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return isConsonant(z) && z[0] == z[1];
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}
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/*
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* Return TRUE if the word ends with three letters which
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* are consonant-vowel-consonent and where the final consonant
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* is not 'w', 'x', or 'y'.
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*
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* The word is reversed here. So we are really checking the
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* first three letters and the first one cannot be in [wxy].
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*/
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static int
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star_oh(const char *z)
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{
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return isConsonant(z) &&
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z[0] != 'w' && z[0] != 'x' && z[0] != 'y' &&
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isVowel(z + 1) &&
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isConsonant(z + 2);
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}
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/*
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* If the word ends with zFrom and xCond() is true for the stem
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* of the word that preceeds the zFrom ending, then change the
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* ending to zTo.
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*
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* The input word *pz and zFrom are both in reverse order. zTo
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* is in normal order.
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*
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* Return TRUE if zFrom matches. Return FALSE if zFrom does not
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* match. Not that TRUE is returned even if xCond() fails and
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* no substitution occurs.
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*/
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static int
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stem(
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char **pz, /* The word being stemmed (Reversed) */
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const char *zFrom, /* If the ending matches this... (Reversed) */
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const char *zTo, /* ... change the ending to this (not reversed) */
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int (*xCond) (const char *) /* Condition that must be true */
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)
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{
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char *z = *pz;
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while (*zFrom && *zFrom == *z) {
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z++;
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zFrom++;
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}
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if (*zFrom != 0)
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return 0;
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if (xCond && !xCond(z))
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return 1;
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while (*zTo) {
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*(--z) = *(zTo++);
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}
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*pz = z;
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return 1;
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}
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/*
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* This is the fallback stemmer used when the porter stemmer is
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* inappropriate. The input word is copied into the output with
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* US-ASCII case folding. If the input word is too long (more
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* than 20 bytes if it contains no digits or more than 6 bytes if
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* it contains digits) then word is truncated to 20 or 6 bytes
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* by taking 10 or 3 bytes from the beginning and end.
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*/
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static void
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copy_stemmer(const char *zIn, size_t nIn, char *zOut, size_t *pnOut)
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{
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size_t i, mx, j;
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int hasDigit = 0;
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for (i = 0; i < nIn; i++) {
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char c = zIn[i];
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if (c >= 'A' && c <= 'Z') {
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zOut[i] = c - 'A' + 'a';
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} else {
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if (c >= '0' && c <= '9')
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hasDigit = 1;
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zOut[i] = c;
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}
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}
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mx = hasDigit ? 3 : 10;
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if (nIn > mx * 2) {
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for (j = mx, i = nIn - mx; i < nIn; i++, j++) {
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zOut[j] = zOut[i];
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}
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i = j;
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}
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zOut[i] = 0;
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*pnOut = i;
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}
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/*
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* Stem the input word zIn[0..nIn-1]. Store the output in zOut.
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* zOut is at least big enough to hold nIn bytes. Write the actual
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* size of the output word (exclusive of the '\0' terminator) into *pnOut.
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*
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* Any upper-case characters in the US-ASCII character set ([A-Z])
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* are converted to lower case. Upper-case UTF characters are
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* unchanged.
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*
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* Words that are longer than about 20 bytes are stemmed by retaining
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* a few bytes from the beginning and the end of the word. If the
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* word contains digits, 3 bytes are taken from the beginning and
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* 3 bytes from the end. For long words without digits, 10 bytes
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* are taken from each end. US-ASCII case folding still applies.
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*
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* If the input word contains not digits but does characters not
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* in [a-zA-Z] then no stemming is attempted and this routine just
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* copies the input into the input into the output with US-ASCII
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* case folding.
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*
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* Stemming never increases the length of the word. So there is
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* no chance of overflowing the zOut buffer.
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*/
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static void
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porter_stemmer(const char *zIn, size_t nIn, char *zOut, size_t *pnOut)
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{
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size_t i, j;
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char zReverse[28];
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char *z, *z2;
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if (nIn < 3 || nIn >= sizeof(zReverse) - 7) {
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/* The word is too big or too small for the porter stemmer.
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* Fallback to the copy stemmer
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*/
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copy_stemmer(zIn, nIn, zOut, pnOut);
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return;
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}
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for (i = 0, j = sizeof(zReverse) - 6; i < nIn; i++, j--) {
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char c = zIn[i];
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if (c >= 'A' && c <= 'Z') {
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zReverse[j] = c + 'a' - 'A';
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} else if (c >= 'a' && c <= 'z') {
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zReverse[j] = c;
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} else {
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/* The use of a character not in [a-zA-Z] means that
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* we fallback * to the copy stemmer
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*/
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copy_stemmer(zIn, nIn, zOut, pnOut);
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return;
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}
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}
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memset(&zReverse[sizeof(zReverse) - 5], 0, 5);
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z = &zReverse[j + 1];
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/* Step 1a */
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if (z[0] == 's') {
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if (
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!stem(&z, "sess", "ss", 0) &&
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!stem(&z, "sei", "i", 0) &&
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!stem(&z, "ss", "ss", 0)
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) {
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z++;
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}
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}
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/* Step 1b */
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z2 = z;
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if (stem(&z, "dee", "ee", m_gt_0)) {
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/* Do nothing. The work was all in the test */
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} else if (
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(stem(&z, "gni", "", hasVowel) || stem(&z, "de", "", hasVowel))
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&& z != z2
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) {
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if (stem(&z, "ta", "ate", 0) ||
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stem(&z, "lb", "ble", 0) ||
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stem(&z, "zi", "ize", 0)) {
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/* Do nothing. The work was all in the test */
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} else if (doubleConsonant(z) && (*z != 'l' && *z != 's' && *z != 'z')) {
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z++;
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} else if (m_eq_1(z) && star_oh(z)) {
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*(--z) = 'e';
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}
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}
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/* Step 1c */
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if (z[0] == 'y' && hasVowel(z + 1)) {
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z[0] = 'i';
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}
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/* Step 2 */
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switch (z[1]) {
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case 'a':
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if (!stem(&z, "lanoita", "ate", m_gt_0)) {
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stem(&z, "lanoit", "tion", m_gt_0);
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}
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break;
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case 'c':
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if (!stem(&z, "icne", "ence", m_gt_0)) {
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stem(&z, "icna", "ance", m_gt_0);
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}
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break;
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case 'e':
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stem(&z, "rezi", "ize", m_gt_0);
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break;
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case 'g':
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stem(&z, "igol", "log", m_gt_0);
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break;
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case 'l':
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if (!stem(&z, "ilb", "ble", m_gt_0)
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&& !stem(&z, "illa", "al", m_gt_0)
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&& !stem(&z, "iltne", "ent", m_gt_0)
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&& !stem(&z, "ile", "e", m_gt_0)
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) {
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stem(&z, "ilsuo", "ous", m_gt_0);
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}
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break;
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case 'o':
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if (!stem(&z, "noitazi", "ize", m_gt_0)
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&& !stem(&z, "noita", "ate", m_gt_0)
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) {
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stem(&z, "rota", "ate", m_gt_0);
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}
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break;
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case 's':
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if (!stem(&z, "msila", "al", m_gt_0)
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&& !stem(&z, "ssenevi", "ive", m_gt_0)
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&& !stem(&z, "ssenluf", "ful", m_gt_0)
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) {
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stem(&z, "ssensuo", "ous", m_gt_0);
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}
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break;
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case 't':
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if (!stem(&z, "itila", "al", m_gt_0)
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&& !stem(&z, "itivi", "ive", m_gt_0)
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) {
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stem(&z, "itilib", "ble", m_gt_0);
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}
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break;
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}
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/* Step 3 */
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switch (z[0]) {
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case 'e':
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if (!stem(&z, "etaci", "ic", m_gt_0)
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&& !stem(&z, "evita", "", m_gt_0)
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) {
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stem(&z, "ezila", "al", m_gt_0);
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}
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break;
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case 'i':
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stem(&z, "itici", "ic", m_gt_0);
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break;
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case 'l':
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if (!stem(&z, "laci", "ic", m_gt_0)) {
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stem(&z, "luf", "", m_gt_0);
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}
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break;
|
|
case 's':
|
|
stem(&z, "ssen", "", m_gt_0);
|
|
break;
|
|
}
|
|
|
|
/* Step 4 */
|
|
switch (z[1]) {
|
|
case 'a':
|
|
if (z[0] == 'l' && m_gt_1(z + 2)) {
|
|
z += 2;
|
|
}
|
|
break;
|
|
case 'c':
|
|
if (z[0] == 'e' && z[2] == 'n' && (z[3] == 'a' || z[3] == 'e') && m_gt_1(z + 4)) {
|
|
z += 4;
|
|
}
|
|
break;
|
|
case 'e':
|
|
if (z[0] == 'r' && m_gt_1(z + 2)) {
|
|
z += 2;
|
|
}
|
|
break;
|
|
case 'i':
|
|
if (z[0] == 'c' && m_gt_1(z + 2)) {
|
|
z += 2;
|
|
}
|
|
break;
|
|
case 'l':
|
|
if (z[0] == 'e' && z[2] == 'b' && (z[3] == 'a' || z[3] == 'i') && m_gt_1(z + 4)) {
|
|
z += 4;
|
|
}
|
|
break;
|
|
case 'n':
|
|
if (z[0] == 't') {
|
|
if (z[2] == 'a') {
|
|
if (m_gt_1(z + 3)) {
|
|
z += 3;
|
|
}
|
|
} else if (z[2] == 'e') {
|
|
if (!stem(&z, "tneme", "", m_gt_1)
|
|
&& !stem(&z, "tnem", "", m_gt_1)
|
|
) {
|
|
stem(&z, "tne", "", m_gt_1);
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
case 'o':
|
|
if (z[0] == 'u') {
|
|
if (m_gt_1(z + 2)) {
|
|
z += 2;
|
|
}
|
|
} else if (z[3] == 's' || z[3] == 't') {
|
|
stem(&z, "noi", "", m_gt_1);
|
|
}
|
|
break;
|
|
case 's':
|
|
if (z[0] == 'm' && z[2] == 'i' && m_gt_1(z + 3)) {
|
|
z += 3;
|
|
}
|
|
break;
|
|
case 't':
|
|
if (!stem(&z, "eta", "", m_gt_1)) {
|
|
stem(&z, "iti", "", m_gt_1);
|
|
}
|
|
break;
|
|
case 'u':
|
|
if (z[0] == 's' && z[2] == 'o' && m_gt_1(z + 3)) {
|
|
z += 3;
|
|
}
|
|
break;
|
|
case 'v':
|
|
case 'z':
|
|
if (z[0] == 'e' && z[2] == 'i' && m_gt_1(z + 3)) {
|
|
z += 3;
|
|
}
|
|
break;
|
|
}
|
|
|
|
/* Step 5a */
|
|
if (z[0] == 'e') {
|
|
if (m_gt_1(z + 1)) {
|
|
z++;
|
|
} else if (m_eq_1(z + 1) && !star_oh(z + 1)) {
|
|
z++;
|
|
}
|
|
}
|
|
/* Step 5b */
|
|
if (m_gt_1(z) && z[0] == 'l' && z[1] == 'l') {
|
|
z++;
|
|
}
|
|
/* z[] is now the stemmed word in reverse order. Flip it back
|
|
* around into forward order and return.
|
|
*/
|
|
*pnOut = i = strlen(z);
|
|
zOut[i] = 0;
|
|
while (*z) {
|
|
zOut[--i] = *(z++);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Based on whether the input word is in the nostem list or not
|
|
* call porter stemmer to stem it, or call copy_stemmer to keep it
|
|
* as it is (copy_stemmer converts simply converts it to lower case)
|
|
* Returns SQLITE_OK if stemming is successful, an error code for
|
|
* any errors
|
|
*/
|
|
static int
|
|
do_stem(const char *zIn, size_t nIn, char *zOut, size_t *pnOut)
|
|
{
|
|
/* Before looking up the word in the hash table, convert it to lower-case */
|
|
char *dupword = malloc(nIn);
|
|
if (dupword == NULL)
|
|
return SQLITE_NOMEM;
|
|
|
|
for (size_t i = 0; i < nIn; i++)
|
|
dupword[i] = tolower((unsigned char) zIn[i]);
|
|
|
|
size_t idx = nostem_hash(dupword, nIn);
|
|
if (strncmp(nostem[idx], dupword, nIn) == 0 && nostem[idx][nIn] == 0)
|
|
copy_stemmer(zIn, nIn, zOut, pnOut);
|
|
else
|
|
porter_stemmer(zIn, nIn, zOut, pnOut);
|
|
|
|
free(dupword);
|
|
return SQLITE_OK;
|
|
}
|
|
|
|
|
|
/*
|
|
* Characters that can be part of a token. We assume any character
|
|
* whose value is greater than 0x80 (any UTF character) can be
|
|
* part of a token. In other words, delimiters all must have
|
|
* values of 0x7f or lower.
|
|
*/
|
|
static const char porterIdChar[] = {
|
|
/* x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF */
|
|
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, /* 3x */
|
|
0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 4x */
|
|
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, /* 5x */
|
|
0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 6x */
|
|
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, /* 7x */
|
|
};
|
|
|
|
#define isDelim(C) (((ch=C)&0x80)==0 && (ch<0x30 || !porterIdChar[ch-0x30]))
|
|
|
|
/*
|
|
* Extract the next token from a tokenization cursor. The cursor must
|
|
* have been opened by a prior call to aproposPorterOpen().
|
|
*/
|
|
static int
|
|
aproposPorterNext(
|
|
sqlite3_tokenizer_cursor *pCursor, /* Cursor returned by aproposPorterOpen */
|
|
const char **pzToken, /* OUT: *pzToken is the token text */
|
|
int *pnBytes, /* OUT: Number of bytes in token */
|
|
int *piStartOffset, /* OUT: Starting offset of token */
|
|
int *piEndOffset, /* OUT: Ending offset of token */
|
|
int *piPosition /* OUT: Position integer of token */
|
|
)
|
|
{
|
|
custom_apropos_tokenizer_cursor *c = (custom_apropos_tokenizer_cursor *) pCursor;
|
|
const char *z = c->zInput;
|
|
|
|
while (c->iOffset < c->nInput) {
|
|
size_t iStartOffset, ch;
|
|
|
|
/* Scan past delimiter characters */
|
|
while (c->iOffset < c->nInput && isDelim(z[c->iOffset])) {
|
|
c->iOffset++;
|
|
}
|
|
|
|
/* Count non-delimiter characters. */
|
|
iStartOffset = c->iOffset;
|
|
while (c->iOffset < c->nInput && !isDelim(z[c->iOffset])) {
|
|
c->iOffset++;
|
|
}
|
|
|
|
if (c->iOffset > iStartOffset) {
|
|
size_t n = c->iOffset - iStartOffset;
|
|
if (n > c->nAllocated) {
|
|
char *pNew;
|
|
c->nAllocated = n + 20;
|
|
pNew = realloc(c->zToken, c->nAllocated);
|
|
if (!pNew)
|
|
return SQLITE_NOMEM;
|
|
c->zToken = pNew;
|
|
}
|
|
|
|
size_t temp;
|
|
int stemStatus = do_stem(&z[iStartOffset], n, c->zToken, &temp);
|
|
*pnBytes = temp;
|
|
if (stemStatus != SQLITE_OK)
|
|
return stemStatus;
|
|
|
|
*pzToken = c->zToken;
|
|
*piStartOffset = iStartOffset;
|
|
*piEndOffset = c->iOffset;
|
|
*piPosition = c->iToken++;
|
|
return SQLITE_OK;
|
|
}
|
|
}
|
|
return SQLITE_DONE;
|
|
}
|
|
|
|
/*
|
|
* The set of routines that implement the porter-stemmer tokenizer
|
|
*/
|
|
static const sqlite3_tokenizer_module aproposPorterTokenizerModule = {
|
|
0,
|
|
aproposPorterCreate,
|
|
aproposPorterDestroy,
|
|
aproposPorterOpen,
|
|
aproposPorterClose,
|
|
aproposPorterNext,
|
|
0
|
|
};
|
|
|
|
/*
|
|
* Allocate a new porter tokenizer. Return a pointer to the new
|
|
* tokenizer in *ppModule
|
|
*/
|
|
void
|
|
get_custom_apropos_tokenizer(sqlite3_tokenizer_module const ** ppModule)
|
|
{
|
|
*ppModule = &aproposPorterTokenizerModule;
|
|
}
|