Use non-compressed DSK images with http links. Valid also with ROMs

README.md

@@ -39,9 +39,9 @@ casa@servidor:~$ ./apple2sdl
 ![DOS 3.3 started](doc/dos33.png)
 
 ### Play games
-Download an DSK file ([Asimov](https://mirrors.apple2.org.za/ftp.apple.asimov.net/images/) is an excellent source) and use the `-disk` parameter.
+Download an DSK file locally or use the a link ([Asimov](https://www.apple.asimov.net/images/) is an excellent source) with the `-disk` parameter:
 ```
-casa@servidor:~$ ./apple2sdl -disk ~/Downloads/karateka.dsk
+casa@servidor:~$ ./apple2sdl -disk "https://www.apple.asimov.net/images/games/action/karateka/karateka (includes intro).dsk"
 ```
 ![Karateka](doc/karateka.png)
 

resources.go

@@ -3,6 +3,7 @@ package apple2
 import (
 	"io"
 	"io/ioutil"
+	"net/http"
 	"os"
 	"strings"
 
@@ -11,12 +12,19 @@ import (
 
 const (
 	internalPrefix = "<internal>/"
+	httpPrefix     = "http://"
+	httpsPrefix    = "https://"
 )
 
 func isInternalResource(filename string) bool {
 	return strings.HasPrefix(filename, internalPrefix)
 }
 
+func isHTTPResource(filename string) bool {
+	return strings.HasPrefix(filename, httpPrefix) ||
+		strings.HasPrefix(filename, httpsPrefix)
+}
+
 func loadResource(filename string) []uint8 {
 	var file io.Reader
 	if isInternalResource(filename) {
@@ -28,6 +36,15 @@ func loadResource(filename string) []uint8 {
 		}
 		defer resourceFile.Close()
 		file = resourceFile
+
+	} else if isHTTPResource(filename) {
+		response, err := http.Get(filename)
+		if err != nil {
+			panic(err)
+		}
+		defer response.Body.Close()
+		file = response.Body
+
 	} else {
 		diskFile, err := os.Open(filename)
 		if err != nil {