test_parser.c

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/*-------------------------------------------------------------------------
 *
 * test_parser.c
 *    Simple example of a text search parser
 *
 * Copyright (c) 2007-2013, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    contrib/test_parser/test_parser.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "fmgr.h"

PG_MODULE_MAGIC;


/*
 * types
 */

/* self-defined type */
typedef struct
{
    char       *buffer;         /* text to parse */
    int         len;            /* length of the text in buffer */
    int         pos;            /* position of the parser */
} ParserState;

/* copy-paste from wparser.h of tsearch2 */
typedef struct
{
    int         lexid;
    char       *alias;
    char       *descr;
} LexDescr;

/*
 * prototypes
 */
PG_FUNCTION_INFO_V1(testprs_start);
Datum       testprs_start(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_getlexeme);
Datum       testprs_getlexeme(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_end);
Datum       testprs_end(PG_FUNCTION_ARGS);

PG_FUNCTION_INFO_V1(testprs_lextype);
Datum       testprs_lextype(PG_FUNCTION_ARGS);

/*
 * functions
 */
Datum
testprs_start(PG_FUNCTION_ARGS)
{
    ParserState *pst = (ParserState *) palloc0(sizeof(ParserState));

    pst->buffer = (char *) PG_GETARG_POINTER(0);
    pst->len = PG_GETARG_INT32(1);
    pst->pos = 0;

    PG_RETURN_POINTER(pst);
}

Datum
testprs_getlexeme(PG_FUNCTION_ARGS)
{
    ParserState *pst = (ParserState *) PG_GETARG_POINTER(0);
    char      **t = (char **) PG_GETARG_POINTER(1);
    int        *tlen = (int *) PG_GETARG_POINTER(2);
    int         startpos = pst->pos;
    int         type;

    *t = pst->buffer + pst->pos;

    if (pst->pos < pst->len &&
        (pst->buffer)[pst->pos] == ' ')
    {
        /* blank type */
        type = 12;
        /* go to the next non-space character */
        while (pst->pos < pst->len &&
               (pst->buffer)[pst->pos] == ' ')
            (pst->pos)++;
    }
    else
    {
        /* word type */
        type = 3;
        /* go to the next space character */
        while (pst->pos < pst->len &&
               (pst->buffer)[pst->pos] != ' ')
            (pst->pos)++;
    }

    *tlen = pst->pos - startpos;

    /* we are finished if (*tlen == 0) */
    if (*tlen == 0)
        type = 0;

    PG_RETURN_INT32(type);
}

Datum
testprs_end(PG_FUNCTION_ARGS)
{
    ParserState *pst = (ParserState *) PG_GETARG_POINTER(0);

    pfree(pst);
    PG_RETURN_VOID();
}

Datum
testprs_lextype(PG_FUNCTION_ARGS)
{
    /*
     * Remarks: - we have to return the blanks for headline reason - we use
     * the same lexids like Teodor in the default word parser; in this way we
     * can reuse the headline function of the default word parser.
     */
    LexDescr   *descr = (LexDescr *) palloc(sizeof(LexDescr) * (2 + 1));

    /* there are only two types in this parser */
    descr[0].lexid = 3;
    descr[0].alias = pstrdup("word");
    descr[0].descr = pstrdup("Word");
    descr[1].lexid = 12;
    descr[1].alias = pstrdup("blank");
    descr[1].descr = pstrdup("Space symbols");
    descr[2].lexid = 0;

    PG_RETURN_POINTER(descr);
}