B.1. Parser sources

Parser sources was adapted to 8.3 release from original tutorial by Valli parser HOWTO.

To compile an example just do

make 
make install
psql regression < test_parser.sql

This is a test_parser.c

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

/*
 * 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 *) palloc(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         type;

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

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

  *tlen = pst->pos - *tlen;

  /* 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);
}

This is a Makefile

override CPPFLAGS := -I. $(CPPFLAGS)

MODULE_big = test_parser
OBJS = test_parser.o

DATA_built = test_parser.sql
DATA =
DOCS = README.test_parser
REGRESS = test_parser


ifdef USE_PGXS
PGXS := $(shell pg_config --pgxs)
include $(PGXS)
else
subdir = contrib/test_parser
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif

This is a test_parser.sql.in

SET search_path = public;

BEGIN;

CREATE FUNCTION testprs_start(internal,int4)
RETURNS internal
AS 'MODULE_PATHNAME'
LANGUAGE 'C' with (isstrict);

CREATE FUNCTION testprs_getlexeme(internal,internal,internal)
RETURNS internal
AS 'MODULE_PATHNAME'
LANGUAGE 'C' with (isstrict);

CREATE FUNCTION testprs_end(internal)
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE 'C' with (isstrict);

CREATE FUNCTION testprs_lextype(internal)
RETURNS internal
AS 'MODULE_PATHNAME'
LANGUAGE 'C' with (isstrict);


CREATE FULLTEXT PARSER testparser 
        START     'testprs_start'
        GETTOKEN  'testprs_getlexeme'
        END       'testprs_end'
        LEXTYPES  'testprs_lextype'
;

CREATE FULLTEXT CONFIGURATION  testcfg  PARSER  'testparser' LOCALE  NULL;
CREATE FULLTEXT MAPPING ON testcfg FOR word WITH simple;

END;