Implement random reading and C_RAWIO

README.md

@@ -1,19 +1,17 @@
 # cpmulator - A CP/M emulator written in golang
 
-A couple of years ago I wrote [a text-based adventure game](https://github.com/skx/lighthouse-of-doom/) in Z80 assembly for CP/M, to amuse my child.  As the game is written in Z80 assembly and only uses a couple of the CP/M BIOS functions I reasoned it should be possible to emulate just a few functions to get the game playable via golang - which would make it portable to Windows, MacOS, and other systems.
+A couple of years ago I wrote [a text-based adventure game](https://github.com/skx/lighthouse-of-doom/) in Z80 assembly for CP/M, to amuse my child.  As only a handful of CP/M BIOS functions were used I reasoned it should be possible to emulate those BIOS calls alongside a basic Z80 emulator, and play my game on a modern computer.
 
-* **NOTE**: My game was later ported to the ZX Spectrum.
-
-This repository is the result, a minimal/portable emulator for CP/M that supports just enough of the CP/M BIOS functions to run my game.
+This repository is the result, a minimal/portable emulator for CP/M that supports _just enough_ CP/M-functionality to run my game, as well as the ZORK games from Infocom!
 
-My intention is to implement sufficient functionality to run ZORK and HITCHHIKERS, and then stop active work upon it.
+* **NOTE**: My game was later ported to the ZX Spectrum.
 
 
 
 
 # Credits
 
-95% of the functionality of this repository comes from the Z80 emulator library I'm using:
+90% of the functionality of this repository comes from the Z80 emulator library I'm using:
 
 * https://github.com/koron-go/z80
 
@@ -22,18 +20,29 @@ My intention is to implement sufficient functionality to run ZORK and HITCHHIKER
 
 # Limitations
 
-This CP/M emulator is extremely basic:
+This CP/M emulator is extremely basic, I initially implemented just those primitives required to play _my_ game.
+
+Later I added more BIOS functions such that it is now possible to run the Z-machine from Infocom:
+
+* This means you can play Zork 1
+* This means you can play Zork 2
+* This means you can play Zork 3
+* This means you can play The Hitchhikers guide to the galacy
+
+**NOTE**: At the point I can successfully run Zork I will slow down the updates to this repository, but pull-requests to add functionality will always be welcome!
+
 
-* It loads a binary at 0x0100, which is the starting address for CP/M binaries.
-* Initially I implements only the four syscalls (i.e. BIOS functions) I needed:
-  * Read a single character from the console.
-  * Read a line of input from the console.
-  * Output a character to the console.
-  * Output a $-terminated string to the console.
-* I've since started to add more, and there are open issues you can use to track progress of the obvious missing calls (primarily file I/O related functinality):
-  * [Open issues](https://github.com/skx/cpmulator/issues)
 
-**NOTE**: At the point I can successfully run Zork I will slow down the updates to this repository, but pull-requests to add functionality will be welcome regardless.
+## Notes On Filesystem Functions
+
+Traditionally CP/M would upper-case the command-line arguments it received, which means that you will ALWAYS need to work with filenames in upper-case.
+
+I don't handle different drive-letters, or user-areas.  If you were to run the file-creation code each of these functions would create "./FOO.TXT":
+
+* `cpmulater samples/create.com foo.txt`
+* `cpmulater samples/create.com B:foo.txt`
+* `cpmulater samples/create.com C:foo.txt`
+* `cpmulater samples/create.com D:foo.txt`
 
 
 
@@ -42,13 +51,13 @@ This CP/M emulator is extremely basic:
 When the emulator is asked to execute an unimplemented BIOS call it will abort with a fatal error, for example:
 
 ```
-$ ./cpmulator ZORK1.COM
+$ ./cpmulator FOO.COM
 {"time":"2024-04-14T15:39:34.560609302+03:00",
   "level":"ERROR",
   "msg":"Unimplemented syscall",
   "syscall":15,
   "syscallHex":"0x0F"}
-Error running ZORK1.COM: UNIMPLEMENTED
+Error running FOO.COM: UNIMPLEMENTED
 ```
 
 You can see a lot of the functions it did successfully emulate and handle by setting the environmental variable DEBUG to a non-empty value, this will generate a log to STDERR where you can save it:
@@ -91,10 +100,26 @@ Or:
 go install github.com/skx/cpmulator@latest
 ```
 
-After that you may launch the binary you wish to run under the emulator - in my case that would be `lihouse.com` from [the release page](https://github.com/skx/lighthouse-of-doom/releases):
+If you wish to play ZORK, or a similar game you'll want to have the two files:
+
+* ZORK1.COM
+  * The filename of this doesn't matter.
+* ZORK1.DAT
+  * This **must** be named ZORK1.DAT, in upper-case, and be in the current directory.
 
 ```
-$ cpmulator lihouse.com
+$ cpmulator ZORK1.COM
+ZORK I: The Great Underground Empire
+Copyright (c) 1981, 1982, 1983 Infocom, Inc. All rights
+reserved.
+ZORK is a registered trademark of Infocom, Inc.
+Revision 88 / Serial number 840726
+
+West of House
+You are standing in an open field west of a white house, with
+a boarded front door.
+There is a small mailbox here.
+..
 ```
 
 
@@ -103,6 +128,8 @@ $ cpmulator lihouse.com
 
 You'll see some Z80 assembly programs beneath [samples](samples/) which are used to check my understanding.  If you have the `pasmo` compiler enabled you can build them all by running "make".
 
+In case you don't I've added the compiled versions.
+
 
 
 ## Bugs?

cpm/cpm.go

@@ -1,4 +1,4 @@
-// Package CPM is the main package for our emulator, it uses memory to
+// Package cpm is the main package for our emulator, it uses memory to
 // emulate execution of things at the bios level
 package cpm
 
@@ -64,6 +64,12 @@ type CPM struct {
 	// Valid values are 00-15
 	userNumber uint8
 
+	// fileIsOpen records whether we have an open file.
+	fileIsOpen bool
+
+	// file has the handle to the open file, if fileIsOpen is true.
+	file *os.File
+
 	// findFirstResults is a sneaky cache of files that match a glob.
 	//
 	// For finding files CP/M uses "find first" to find the first result
@@ -103,6 +109,10 @@ func New(filename string, logger *slog.Logger) *CPM {
 		Desc:    "C_WRITE",
 		Handler: SysCallWriteChar,
 	}
+	sys[6] = CPMHandler{
+		Desc:    "C_RAWIO",
+		Handler: SysCallRawIO,
+	}
 	sys[9] = CPMHandler{
 		Desc:    "C_WRITESTRING",
 		Handler: SysCallWriteString,
@@ -115,6 +125,14 @@ func New(filename string, logger *slog.Logger) *CPM {
 		Desc:    "DRV_SET",
 		Handler: SysCallDriveSet,
 	}
+	sys[15] = CPMHandler{
+		Desc:    "F_OPEN",
+		Handler: SysCallFileOpen,
+	}
+	sys[16] = CPMHandler{
+		Desc:    "F_CLOSE",
+		Handler: SysCallFileClose,
+	}
 	sys[17] = CPMHandler{
 		Desc:    "F_SFIRST",
 		Handler: SysCallFindFirst,
@@ -143,6 +161,10 @@ func New(filename string, logger *slog.Logger) *CPM {
 		Desc:    "F_USERNUM",
 		Handler: SysCallUserNumber,
 	}
+	sys[33] = CPMHandler{
+		Desc:    "F_READRAND",
+		Handler: SysCallReadRand,
+	}
 
 	// Create the object
 	tmp := &CPM{