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postgresql/contrib/fuzzystrmatch/fuzzystrmatch.c

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/*
* fuzzystrmatch.c
*
* Functions for "fuzzy" comparison of strings
*
* Joe Conway <mail@joeconway.com>
*
* Copyright (c) 2001, 2002, 2003 by PostgreSQL Global Development Group
* ALL RIGHTS RESERVED;
*
* levenshtein()
* -------------
* Written based on a description of the algorithm by Michael Gilleland
* found at http://www.merriampark.com/ld.htm
* Also looked at levenshtein.c in the PHP 4.0.6 distribution for
* inspiration.
*
* metaphone()
* -----------
* Modified for PostgreSQL by Joe Conway.
* Based on CPAN's "Text-Metaphone-1.96" by Michael G Schwern <schwern@pobox.com>
* Code slightly modified for use as PostgreSQL function (palloc, elog, etc).
* Metaphone was originally created by Lawrence Philips and presented in article
* in "Computer Language" December 1990 issue.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose, without fee, and without a written agreement
* is hereby granted, provided that the above copyright notice and this
* paragraph and the following two paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
*/
#include "fuzzystrmatch.h"
/*
* Calculates Levenshtein Distance between two strings.
* Uses simplest and fastest cost model only, i.e. assumes a cost of 1 for
* each deletion, substitution, or insertion.
*/
PG_FUNCTION_INFO_V1(levenshtein);
Datum
levenshtein(PG_FUNCTION_ARGS)
{
char *str_s;
char *str_s0;
char *str_t;
int cols = 0;
int rows = 0;
int *u_cells;
int *l_cells;
int *tmp;
int i;
int j;
/*
* Fetch the arguments. str_s is referred to as the "source" cols =
* length of source + 1 to allow for the initialization column str_t
* is referred to as the "target", rows = length of target + 1 rows =
* length of target + 1 to allow for the initialization row
*/
str_s = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
str_t = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1))));
cols = strlen(str_s) + 1;
rows = strlen(str_t) + 1;
/*
* Restrict the length of the strings being compared to something
* reasonable because we will have to perform rows * cols
* calculations. If longer strings need to be compared, increase
* MAX_LEVENSHTEIN_STRLEN to suit (but within your tolerance for speed
* and memory usage).
*/
if ((cols > MAX_LEVENSHTEIN_STRLEN + 1) || (rows > MAX_LEVENSHTEIN_STRLEN + 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds max length: %d",
MAX_LEVENSHTEIN_STRLEN)));
/*
* If either rows or cols is 0, the answer is the other value. This
* makes sense since it would take that many insertions the build a
* matching string
*/
if (cols == 0)
PG_RETURN_INT32(rows);
if (rows == 0)
PG_RETURN_INT32(cols);
/*
* Allocate two vectors of integers. One will be used for the "upper"
* row, the other for the "lower" row. Initialize the "upper" row to
* 0..cols
*/
u_cells = palloc(sizeof(int) * cols);
for (i = 0; i < cols; i++)
u_cells[i] = i;
l_cells = palloc(sizeof(int) * cols);
/*
* Use str_s0 to "rewind" the pointer to str_s in the nested for loop
* below
*/
str_s0 = str_s;
/*
* Loop throught the rows, starting at row 1. Row 0 is used for the
* initial "upper" row.
*/
for (j = 1; j < rows; j++)
{
/*
* We'll always start with col 1, and initialize lower row col 0
* to j
*/
l_cells[0] = j;
for (i = 1; i < cols; i++)
{
int c = 0;
int c1 = 0;
int c2 = 0;
int c3 = 0;
/*
* The "cost" value is 0 if the character at the current col
* position in the source string, matches the character at the
* current row position in the target string; cost is 1
* otherwise.
*/
c = ((CHAREQ(str_s, str_t)) ? 0 : 1);
/*
* c1 is upper right cell plus 1
*/
c1 = u_cells[i] + 1;
/*
* c2 is lower left cell plus 1
*/
c2 = l_cells[i - 1] + 1;
/*
* c3 is cell diagonally above to the left plus "cost"
*/
c3 = u_cells[i - 1] + c;
/*
* The lower right cell is set to the minimum of c1, c2, c3
*/
l_cells[i] = (c1 < c2 ? c1 : c2) < c3 ? (c1 < c2 ? c1 : c2) : c3;
/*
* Increment the pointer to str_s
*/
NextChar(str_s);
}
/*
* Lower row now becomes the upper row, and the upper row gets
* reused as the new lower row.
*/
tmp = u_cells;
u_cells = l_cells;
l_cells = tmp;
/*
* Increment the pointer to str_t
*/
NextChar(str_t);
/*
* Rewind the pointer to str_s
*/
str_s = str_s0;
}
/*
* Because the final value (at position row, col) was swapped from the
* lower row to the upper row, that's where we'll find it.
*/
PG_RETURN_INT32(u_cells[cols - 1]);
}
/*
* Calculates the metaphone of an input string.
* Returns number of characters requested
* (suggested value is 4)
*/
PG_FUNCTION_INFO_V1(metaphone);
Datum
metaphone(PG_FUNCTION_ARGS)
{
int reqlen;
char *str_i;
size_t str_i_len;
char *metaph;
text *result_text;
int retval;
str_i = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
str_i_len = strlen(str_i);
if (str_i_len > MAX_METAPHONE_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("argument exceeds max length: %d",
MAX_METAPHONE_STRLEN)));
if (!(str_i_len > 0))
ereport(ERROR,
(errcode(ERRCODE_ZERO_LENGTH_CHARACTER_STRING),
errmsg("argument is empty string")));
reqlen = PG_GETARG_INT32(1);
if (reqlen > MAX_METAPHONE_STRLEN)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("output length exceeds max length: %d",
MAX_METAPHONE_STRLEN)));
if (!(reqlen > 0))
ereport(ERROR,
(errcode(ERRCODE_ZERO_LENGTH_CHARACTER_STRING),
errmsg("output cannot be empty string")));
retval = _metaphone(str_i, reqlen, &metaph);
if (retval == META_SUCCESS)
{
result_text = DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(metaph)));
PG_RETURN_TEXT_P(result_text);
}
else
{
/* internal error */
elog(ERROR, "metaphone: failure");
/*
* Keep the compiler quiet
*/
PG_RETURN_NULL();
}
}
/*
* Original code by Michael G Schwern starts here.
* Code slightly modified for use as PostgreSQL
* function (palloc, etc). Original includes
* are rolled into fuzzystrmatch.h
*------------------------------------------------------------------*/
/* I suppose I could have been using a character pointer instead of
* accessing the array directly... */
/* Look at the next letter in the word */
#define Next_Letter (toupper((unsigned char) word[w_idx+1]))
/* Look at the current letter in the word */
#define Curr_Letter (toupper((unsigned char) word[w_idx]))
/* Go N letters back. */
#define Look_Back_Letter(n) \
(w_idx >= (n) ? toupper((unsigned char) word[w_idx-(n)]) : '\0')
/* Previous letter. I dunno, should this return null on failure? */
#define Prev_Letter (Look_Back_Letter(1))
/* Look two letters down. It makes sure you don't walk off the string. */
#define After_Next_Letter \
(Next_Letter != '\0' ? toupper((unsigned char) word[w_idx+2]) : '\0')
#define Look_Ahead_Letter(n) toupper((unsigned char) Lookahead(word+w_idx, n))
/* Allows us to safely look ahead an arbitrary # of letters */
/* I probably could have just used strlen... */
char
Lookahead(char *word, int how_far)
{
char letter_ahead = '\0'; /* null by default */
int idx;
for (idx = 0; word[idx] != '\0' && idx < how_far; idx++);
/* Edge forward in the string... */
letter_ahead = word[idx]; /* idx will be either == to how_far or at
* the end of the string */
return letter_ahead;
}
/* phonize one letter */
#define Phonize(c) do {(*phoned_word)[p_idx++] = c;} while (0)
/* Slap a null character on the end of the phoned word */
#define End_Phoned_Word do {(*phoned_word)[p_idx] = '\0';} while (0)
/* How long is the phoned word? */
#define Phone_Len (p_idx)
/* Note is a letter is a 'break' in the word */
#define Isbreak(c) (!isalpha((unsigned char) (c)))
int
_metaphone(
/* IN */
char *word,
int max_phonemes,
/* OUT */
char **phoned_word
)
{
int w_idx = 0; /* point in the phonization we're at. */
int p_idx = 0; /* end of the phoned phrase */
/*-- Parameter checks --*/
/*
* Shouldn't be necessary, but left these here anyway jec Aug 3, 2001
*/
/* Negative phoneme length is meaningless */
if (!(max_phonemes > 0))
/* internal error */
elog(ERROR, "metaphone: Requested output length must be > 0");
/* Empty/null string is meaningless */
if ((word == NULL) || !(strlen(word) > 0))
/* internal error */
elog(ERROR, "metaphone: Input string length must be > 0");
/*-- Allocate memory for our phoned_phrase --*/
if (max_phonemes == 0)
{ /* Assume largest possible */
*phoned_word = palloc(sizeof(char) * strlen(word) +1);
if (!*phoned_word)
return META_ERROR;
}
else
{
*phoned_word = palloc(sizeof(char) * max_phonemes + 1);
if (!*phoned_word)
return META_ERROR;
}
/*-- The first phoneme has to be processed specially. --*/
/* Find our first letter */
for (; !isalpha((unsigned char) (Curr_Letter)); w_idx++)
{
/* On the off chance we were given nothing but crap... */
if (Curr_Letter == '\0')
{
End_Phoned_Word;
return META_SUCCESS; /* For testing */
}
}
switch (Curr_Letter)
{
/* AE becomes E */
case 'A':
if (Next_Letter == 'E')
{
Phonize('E');
w_idx += 2;
}
/* Remember, preserve vowels at the beginning */
else
{
Phonize('A');
w_idx++;
}
break;
/* [GKP]N becomes N */
case 'G':
case 'K':
case 'P':
if (Next_Letter == 'N')
{
Phonize('N');
w_idx += 2;
}
break;
/*
* WH becomes H, WR becomes R W if followed by a vowel
*/
case 'W':
if (Next_Letter == 'H' ||
Next_Letter == 'R')
{
Phonize(Next_Letter);
w_idx += 2;
}
else if (isvowel(Next_Letter))
{
Phonize('W');
w_idx += 2;
}
/* else ignore */
break;
/* X becomes S */
case 'X':
Phonize('S');
w_idx++;
break;
/* Vowels are kept */
/*
* We did A already case 'A': case 'a':
*/
case 'E':
case 'I':
case 'O':
case 'U':
Phonize(Curr_Letter);
w_idx++;
break;
default:
/* do nothing */
break;
}
/* On to the metaphoning */
for (; Curr_Letter != '\0' &&
(max_phonemes == 0 || Phone_Len < max_phonemes);
w_idx++)
{
/*
* How many letters to skip because an earlier encoding handled
* multiple letters
*/
unsigned short int skip_letter = 0;
/*
* THOUGHT: It would be nice if, rather than having things
* like... well, SCI. For SCI you encode the S, then have to
* remember to skip the C. So the phonome SCI invades both S and
* C. It would be better, IMHO, to skip the C from the S part of
* the encoding. Hell, I'm trying it.
*/
/* Ignore non-alphas */
if (!isalpha((unsigned char) (Curr_Letter)))
continue;
/* Drop duplicates, except CC */
if (Curr_Letter == Prev_Letter &&
Curr_Letter != 'C')
continue;
switch (Curr_Letter)
{
/* B -> B unless in MB */
case 'B':
if (Prev_Letter != 'M')
Phonize('B');
break;
/*
* 'sh' if -CIA- or -CH, but not SCH, except SCHW. (SCHW
* is handled in S) S if -CI-, -CE- or -CY- dropped if
* -SCI-, SCE-, -SCY- (handed in S) else K
*/
case 'C':
if (MAKESOFT(Next_Letter))
{ /* C[IEY] */
if (After_Next_Letter == 'A' &&
Next_Letter == 'I')
{ /* CIA */
Phonize(SH);
}
/* SC[IEY] */
else if (Prev_Letter == 'S')
{
/* Dropped */
}
else
Phonize('S');
}
else if (Next_Letter == 'H')
{
#ifndef USE_TRADITIONAL_METAPHONE
if (After_Next_Letter == 'R' ||
Prev_Letter == 'S')
{ /* Christ, School */
Phonize('K');
}
else
Phonize(SH);
#else
Phonize(SH);
#endif
skip_letter++;
}
else
Phonize('K');
break;
/*
* J if in -DGE-, -DGI- or -DGY- else T
*/
case 'D':
if (Next_Letter == 'G' &&
MAKESOFT(After_Next_Letter))
{
Phonize('J');
skip_letter++;
}
else
Phonize('T');
break;
/*
* F if in -GH and not B--GH, D--GH, -H--GH, -H---GH else
* dropped if -GNED, -GN, else dropped if -DGE-, -DGI- or
* -DGY- (handled in D) else J if in -GE-, -GI, -GY and
* not GG else K
*/
case 'G':
if (Next_Letter == 'H')
{
if (!(NOGHTOF(Look_Back_Letter(3)) ||
Look_Back_Letter(4) == 'H'))
{
Phonize('F');
skip_letter++;
}
else
{
/* silent */
}
}
else if (Next_Letter == 'N')
{
if (Isbreak(After_Next_Letter) ||
(After_Next_Letter == 'E' &&
Look_Ahead_Letter(3) == 'D'))
{
/* dropped */
}
else
Phonize('K');
}
else if (MAKESOFT(Next_Letter) &&
Prev_Letter != 'G')
Phonize('J');
else
Phonize('K');
break;
/* H if before a vowel and not after C,G,P,S,T */
case 'H':
if (isvowel(Next_Letter) &&
!AFFECTH(Prev_Letter))
Phonize('H');
break;
/*
* dropped if after C else K
*/
case 'K':
if (Prev_Letter != 'C')
Phonize('K');
break;
/*
* F if before H else P
*/
case 'P':
if (Next_Letter == 'H')
Phonize('F');
else
Phonize('P');
break;
/*
* K
*/
case 'Q':
Phonize('K');
break;
/*
* 'sh' in -SH-, -SIO- or -SIA- or -SCHW- else S
*/
case 'S':
if (Next_Letter == 'I' &&
(After_Next_Letter == 'O' ||
After_Next_Letter == 'A'))
Phonize(SH);
else if (Next_Letter == 'H')
{
Phonize(SH);
skip_letter++;
}
#ifndef USE_TRADITIONAL_METAPHONE
else if (Next_Letter == 'C' &&
Look_Ahead_Letter(2) == 'H' &&
Look_Ahead_Letter(3) == 'W')
{
Phonize(SH);
skip_letter += 2;
}
#endif
else
Phonize('S');
break;
/*
* 'sh' in -TIA- or -TIO- else 'th' before H else T
*/
case 'T':
if (Next_Letter == 'I' &&
(After_Next_Letter == 'O' ||
After_Next_Letter == 'A'))
Phonize(SH);
else if (Next_Letter == 'H')
{
Phonize(TH);
skip_letter++;
}
else
Phonize('T');
break;
/* F */
case 'V':
Phonize('F');
break;
/* W before a vowel, else dropped */
case 'W':
if (isvowel(Next_Letter))
Phonize('W');
break;
/* KS */
case 'X':
Phonize('K');
if (max_phonemes == 0 || Phone_Len < max_phonemes)
Phonize('S');
break;
/* Y if followed by a vowel */
case 'Y':
if (isvowel(Next_Letter))
Phonize('Y');
break;
/* S */
case 'Z':
Phonize('S');
break;
/* No transformation */
case 'F':
case 'J':
case 'L':
case 'M':
case 'N':
case 'R':
Phonize(Curr_Letter);
break;
default:
/* nothing */
break;
} /* END SWITCH */
w_idx += skip_letter;
} /* END FOR */
End_Phoned_Word;
return (META_SUCCESS);
} /* END metaphone */
/*
* SQL function: soundex(text) returns text
*/
PG_FUNCTION_INFO_V1(soundex);
Datum
soundex(PG_FUNCTION_ARGS)
{
char outstr[SOUNDEX_LEN + 1];
char *arg;
arg = _textout(PG_GETARG_TEXT_P(0));
_soundex(arg, outstr);
PG_RETURN_TEXT_P(_textin(outstr));
}
static void
_soundex(const char *instr, char *outstr)
{
int count;
AssertArg(instr);
AssertArg(outstr);
outstr[SOUNDEX_LEN] = '\0';
/* Skip leading non-alphabetic characters */
while (!isalpha((unsigned char) instr[0]) && instr[0])
++instr;
/* No string left */
if (!instr[0])
{
outstr[0] = (char) 0;
return;
}
/* Take the first letter as is */
*outstr++ = (char) toupper((unsigned char) *instr++);
count = 1;
while (*instr && count < SOUNDEX_LEN)
{
if (isalpha((unsigned char) *instr) &&
soundex_code(*instr) != soundex_code(*(instr - 1)))
{
*outstr = soundex_code(instr[0]);
if (*outstr != '0')
{
++outstr;
++count;
}
}
++instr;
}
/* Fill with 0's */
while (count < SOUNDEX_LEN)
{
*outstr = '0';
++outstr;
++count;
}
}
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