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我正在爲C語言開發postgreSQL的擴展。我創建了兩種新類型，一種是變量大小（vlen）。我不知道如何爲Geo_Polygon類型創建輸入和輸出函數。任何人都有一個例子？ 這是我迄今爲止所做的。用戶自定義Type C中的PostgreSQL
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);}