1 files changed, 126 insertions, 0 deletions
diff --git a/src/tutorial/funcs.c b/src/tutorial/funcs.c
new file mode 100644
index 0000000..cdd155e
--- /dev/null
+++ b/src/tutorial/funcs.c
@@ -0,0 +1,126 @@
+/* src/tutorial/funcs.c */
+
+/******************************************************************************
+  These are user-defined functions that can be bound to a Postgres backend
+  and called by Postgres to execute SQL functions of the same name.
+
+  The calling format for these functions is defined by the CREATE FUNCTION
+  SQL statement that binds them to the backend.
+*****************************************************************************/
+
+#include "postgres.h"			/* general Postgres declarations */
+
+#include "executor/executor.h"	/* for GetAttributeByName() */
+#include "utils/geo_decls.h"	/* for point type */
+
+PG_MODULE_MAGIC;
+
+
+/* By Value */
+
+PG_FUNCTION_INFO_V1(add_one);
+
+Datum
+add_one(PG_FUNCTION_ARGS)
+{
+	int32		arg = PG_GETARG_INT32(0);
+
+	PG_RETURN_INT32(arg + 1);
+}
+
+/* By Reference, Fixed Length */
+
+PG_FUNCTION_INFO_V1(add_one_float8);
+
+Datum
+add_one_float8(PG_FUNCTION_ARGS)
+{
+	/* The macros for FLOAT8 hide its pass-by-reference nature */
+	float8		arg = PG_GETARG_FLOAT8(0);
+
+	PG_RETURN_FLOAT8(arg + 1.0);
+}
+
+PG_FUNCTION_INFO_V1(makepoint);
+
+Datum
+makepoint(PG_FUNCTION_ARGS)
+{
+	Point	   *pointx = PG_GETARG_POINT_P(0);
+	Point	   *pointy = PG_GETARG_POINT_P(1);
+	Point	   *new_point = (Point *) palloc(sizeof(Point));
+
+	new_point->x = pointx->x;
+	new_point->y = pointy->y;
+
+	PG_RETURN_POINT_P(new_point);
+}
+
+/* By Reference, Variable Length */
+
+PG_FUNCTION_INFO_V1(copytext);
+
+Datum
+copytext(PG_FUNCTION_ARGS)
+{
+	text	   *t = PG_GETARG_TEXT_PP(0);
+
+	/*
+	 * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the
+	 * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a
+	 * full-length header.
+	 */
+	text	   *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
+
+	SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
+
+	/*
+	 * VARDATA is a pointer to the data region of the new struct.  The source
+	 * could be a short datum, so retrieve its data through VARDATA_ANY.
+	 */
+	memcpy((void *) VARDATA(new_t), /* destination */
+		   (void *) VARDATA_ANY(t), /* source */
+		   VARSIZE_ANY_EXHDR(t));	/* how many bytes */
+	PG_RETURN_TEXT_P(new_t);
+}
+
+PG_FUNCTION_INFO_V1(concat_text);
+
+Datum
+concat_text(PG_FUNCTION_ARGS)
+{
+	text	   *arg1 = PG_GETARG_TEXT_PP(0);
+	text	   *arg2 = PG_GETARG_TEXT_PP(1);
+	int32		arg1_size = VARSIZE_ANY_EXHDR(arg1);
+	int32		arg2_size = VARSIZE_ANY_EXHDR(arg2);
+	int32		new_text_size = arg1_size + arg2_size + VARHDRSZ;
+	text	   *new_text = (text *) palloc(new_text_size);
+
+	SET_VARSIZE(new_text, new_text_size);
+	memcpy(VARDATA(new_text), VARDATA_ANY(arg1), arg1_size);
+	memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(arg2), arg2_size);
+	PG_RETURN_TEXT_P(new_text);
+}
+
+/* Composite types */
+
+PG_FUNCTION_INFO_V1(c_overpaid);
+
+Datum
+c_overpaid(PG_FUNCTION_ARGS)
+{
+	HeapTupleHeader t = PG_GETARG_HEAPTUPLEHEADER(0);
+	int32		limit = PG_GETARG_INT32(1);
+	bool		isnull;
+	int32		salary;
+
+	salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
+	if (isnull)
+		PG_RETURN_BOOL(false);
+
+	/*
+	 * Alternatively, we might prefer to do PG_RETURN_NULL() for null salary
+	 */
+
+	PG_RETURN_BOOL(salary > limit);
+}