Add examples/rwops/memory.go example

Signed-off-by: Lilis Iskandar <lilis@veand.co>

examples/rwops/memory.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+var rwops *sdl.RWops
+var writer io.Writer
+var reader io.Reader
+var seeker io.Seeker
+var closer io.Closer
+var data = []byte{0, 10, 20, 30}
+var err error
+
+func size() {
+	if n, err := rwops.Size(); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Println("size:", n)
+	}
+}
+
+func read() {
+	buf := make([]byte, 4)
+	reader.Read(buf[:])
+	fmt.Println("read:", buf[0], buf[1], buf[2], buf[3])
+}
+
+func tell() {
+	if n, err := rwops.Tell(); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Println("tell:", n)
+	}
+}
+
+func seek() {
+	// Seek
+	if n, err := seeker.Seek(0, io.SeekStart); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Println("seek: offset is", n)
+	}
+}
+
+func write() {
+	if n, err := writer.Write([]byte{40, 50, 60, 70}); err != nil {
+		log.Fatal(err)
+	} else {
+		fmt.Println("write:", n, "bytes")
+	}
+}
+
+func main() {
+	rwops, err = sdl.RWFromMem(data)
+	if err != nil {
+		log.Println(err)
+	}
+
+	writer = rwops
+	reader = rwops
+	seeker = rwops
+	closer = rwops
+
+	defer closer.Close()
+
+	size()  // Print RWops data size
+	tell()  // Print current data offset
+	read()  // Read data via RWops
+	tell()  // Print current data offset
+	seek()  // Seek to start of the data
+	write() // Write some data via RWops
+	tell()  // Print current data offset
+	seek()  // Seek to start of the data
+	tell()  // Print current data offset
+	read()  // Read data via RWops again
+}