c - 用户在 C 中定义类型 PostgreSQL

Question

我正在用 C 开发 postgreSQL 的扩展。我创建了两种新类型，一种是 var len size (vlen)。我不知道如何为 Geo_Polygon 类型创建输入和输出函数。有人有例子吗？这是我到目前为止所做的。

typedef struct Geo_Point{
   double x;
   double y;
}   Geo_Point;

typedef struct Geo_Polygon{
  int32 v_len;
  int32 n_points;
  Geo_Point point[FLEXIBLE_ARRAY_MEMBER];
} Geo_Polygon;


PG_FUNCTION_INFO_V1(geo_polygon_in);
Datum
geo_polygon_in(PG_FUNCTION_ARGS){


  char *str = PG_GETARG_CSTRING(0);
  char *new_position = NULL;
  char aux[1024];
  int i, dimension, len;
  Geo_Polygon *result;
  Geo_Point *point;
  double x, y;



point = (Geo_Point *) palloc(sizeof(Geo_Point));

  new_position = strchr(str, '(');

  for (dimension = 0; *new_position != '\0'; dimension++){

    memset(aux, 0, sizeof(aux));
    for (i  = 0; *new_position != ')'; i++, ++new_position) {
      aux[i] = *new_position;
    }
    aux[i] = *new_position;
    ++new_position;
    if (*new_position == ',') {
        ++new_position;
    }

    point = (Geo_Point *) repalloc(point, (dimension + 1) * sizeof(Geo_Point));
    if(sscanf(aux, " ( %lf , %lf )", &x, &y )!= 2)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("entrada errada para o tipo geo_point: \"%s\"",
                str)));

    point->x = x;
    point->y = y;

  }

  len = sizeof(Geo_Point) * (dimension + 1)+ VARHDRSZ;
  result = (Geo_Polygon *) palloc0(len);
  SET_VARSIZE(result, len);
  // copy the coordinates to the data area destino arqu e quantos bytes
  memcpy((void *) VARDATA(result),(void *) VARDATA (point),  (dimension) * sizeof(Geo_Point));

  result->n_points = dimension;

  PG_RETURN_POINTER(result);

}


Datum
geo_polygon_out(PG_FUNCTION_ARGS){
  Geo_Polygon *geo_polygon = (Geo_Polygon *) PG_GETARG_POINTER(0);
  StringInfoData buf;
  int           dim = geo_polygon->n_points;

  int           i;
  int           ndig = 2;

  initStringInfo(&buf);


  appendStringInfoChar(&buf, '(');
  for (i = 0; i < dim; i++){

    appendStringInfo(&buf, "%.*g", geo_polygon->point[i].x, "%.*g", geo_polygon->point[i].y);
    appendStringInfoChar(&buf, ')');

  }
  PG_FREE_IF_COPY(geo_polygon, 0);
  PG_RETURN_CSTRING(buf.data);}

Answer 1

您应该查看类型现有实现的来源，例如 contrib/ltree/ltree_io.c或者(也许更好，因为它听起来更接近你想要的)postgis/lwgeom_inout.c来自 PostGIS。