Improve how changing the CCP at run-time is handled. (#204)

Much like recent changes this pull-request improves the handling
of changing the CCP at runtime:

* Show output in a way that is testable.
* Add the tests.
* Recognize a "no-change change".
* Remove needless quotes.

Author: skx

ccp/ccp.go

@@ -86,5 +86,5 @@ func Get(name string) (Flavour, error) {
 		valid = append(valid, ent.Name)
 	}
 
-	return Flavour{}, fmt.Errorf("ccp %s not found - valid choices are: %s", name, strings.Join(valid, ","))
+	return Flavour{}, fmt.Errorf("CCP %s not found - valid choices are: %s", name, strings.Join(valid, ","))
 }

cpm/cpm_bios.go

@@ -269,6 +269,8 @@ func BiosSysCallReserved1(cpm *CPM) error {
 	// Get/Set the CCP
 	case 0x0003:
 
+		// If DE is null then we're just being asked to return
+		// the current CCP name
 		if de == 0x0000 {
 			// Fill the DMA area with NULL bytes
 			addr := cpm.dma
@@ -290,10 +292,16 @@ func BiosSysCallReserved1(cpm *CPM) error {
 		// Get the string pointed to by DE
 		str := getStringFromMemory(de)
 
+		// If there is no change do nothing
+		if str == cpm.ccp {
+			cpm.output.WriteString("CCP is already set to " + str + ", doing nothing.\r\n")
+			return nil
+		}
+
 		// See if the CCP exists
 		entry, err := ccp.Get(str)
 		if err != nil {
-			fmt.Printf("Invalid CCP name %s\r\n", str)
+			cpm.output.WriteString("Error changing CCP to " + str + ", " + err.Error() + "\r\n")
 			return nil
 		}
 
@@ -302,8 +310,9 @@ func BiosSysCallReserved1(cpm *CPM) error {
 		cpm.ccp = str
 
 		if old != str {
-			fmt.Printf("CCP changed to %s [%s] Size:0x%04X Entry-Point:0x%04X\r\n", str, entry.Description, len(entry.Bytes), entry.Start)
+			cpm.output.WriteString(fmt.Sprintf("CCP changed to %s [%s] Size:0x%04X Entry-Point:0x%04X\r\n", str, entry.Description, len(entry.Bytes), entry.Start))
 		}
+		return nil
 
 	// Get/Set the quiet flag
 	case 0x0004:

static/A/!CCP.COM

@@ -93,9 +93,9 @@ not_cpmulator:
 ;; Text output strings.
 ;;
 CCP_PREFIX:
-        db "CCP is set to '$"
+        db "CCP is set to $"
 CCP_SUFFIX:
-        db "'", 0x0a, 0x0d, "$"
+        db ".", 0x0a, 0x0d, "$"
 
 WRONG_EMULATOR:
         db "This binary is not running under cpmulator, aborting.", 0x0a, 0x0d, "$"

static/ccp.z80

@@ -5,5 +5,8 @@
 A:!ctrlc
 !hostcmd
 !ccp ccp
+!ccp ccp
+!ccp ccpz
 !ccp ccpz
+!ccp Monday
 Exit

test/ccp2.in

@@ -1,5 +1,7 @@
 The Ctrl-C count is currently set to
 The prefix for executing commands on the host is unset.
 Running commands on the host is disabled.
-CCP changed to ccp
+CCP is already set to ccp, doing nothing.
 CCP changed to ccpz
+CCP is already set to ccpz, doing nothing.
+Error changing CCP to monday, CCP monday not found - valid choices are: ccp,ccpz