362 lines
7.7 KiB
NASM
362 lines
7.7 KiB
NASM
; shell
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;
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; Runs a shell over a block device interface.
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; The shell spits a welcome prompt, wait for input and compare the first 4 chars
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; of the input with a command table and call the appropriate routine if it's
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; found, an error if it's not.
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;
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; To determine the correct routine to call we first go through cmds in
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; shellCmdTbl. This means that we first go through internal cmds, then cmds
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; "grafted" by glue code.
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;
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; If the command isn't found, SHELL_CMDHOOK is called, which should set A to
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; zero if it executes something. Otherwise, SHELL_ERR_UNKNOWN_CMD will be
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; returned.
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;
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; See constants below for error codes.
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;
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; All numerical values in the Collapse OS shell are represented and parsed in
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; hexadecimal form, without prefix or suffix.
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; *** REQUIREMENTS ***
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; err
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; core
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; parse
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; stdio
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; *** DEFINES ***
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; SHELL_EXTRA_CMD_COUNT: Number of extra cmds to be expected after the regular
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; ones. See comment in COMMANDS section for details.
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; SHELL_RAMSTART
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; *** CONSTS ***
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; number of entries in shellCmdTbl
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.equ SHELL_CMD_COUNT 6+SHELL_EXTRA_CMD_COUNT
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; maximum length for shell commands. Should be confortably below stdio's
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; readline buffer length.
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.equ SHELL_MAX_CMD_LEN 0x10
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; *** VARIABLES ***
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; Memory address that the shell is currently "pointing at" for peek, load, call
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; operations. Set with mptr.
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.equ SHELL_MEM_PTR SHELL_RAMSTART
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; Places where we store arguments specifiers and where resulting values are
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; written to after parsing.
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.equ SHELL_CMD_ARGS @+2
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; Pointer to a hook to call when a cmd name isn't found
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.equ SHELL_CMDHOOK @+PARSE_ARG_MAXCOUNT
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.equ SHELL_RAMEND @+2
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; *** CODE ***
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shellInit:
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xor a
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ld (SHELL_MEM_PTR), a
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ld (SHELL_MEM_PTR+1), a
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ld hl, noop
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ld (SHELL_CMDHOOK), hl
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; print welcome
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ld hl, .welcome
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jp printstr
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.welcome:
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.db "Collapse OS", CR, LF, "> ", 0
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; Inifite loop that processes input. Because it's infinite, you should jump
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; to it rather than call it. Saves two precious bytes in the stack.
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shellLoop:
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call stdioReadLine
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call printcrlf
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call shellParse
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ld hl, .prompt
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call printstr
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jr shellLoop
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.prompt:
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.db "> ", 0
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; Parse command (null terminated) at HL and calls it
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shellParse:
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; first thing: is command empty?
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ld a, (hl)
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or a
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ret z ; empty, nothing to do
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push af
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push bc
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push de
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push hl
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push ix
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; Before looking for a suitable command, let's make the cmd line more
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; usable by replacing the first ' ' with a null char. This way, cmp is
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; easy to make.
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push hl ; --> lvl 1
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ld a, ' '
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call findchar
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jr z, .hasArgs
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; no arg, (HL) is zero to facilitate processing later, add a second
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; null next to that one to indicate unambiguously that we have no args.
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inc hl
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; Oh wait, before we proceed, is our cmd length within limits? cmd len
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; is currently in A from findchar
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cp SHELL_MAX_CMD_LEN
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jr c, .hasArgs ; within limits
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; outside limits
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ld a, SHELL_ERR_UNKNOWN_CMD
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jr .error
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.hasArgs:
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xor a
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ld (hl), a
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pop hl ; <-- lvl 1, beginning of cmd
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ld de, shellCmdTbl
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ld b, SHELL_CMD_COUNT
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.loop:
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push de ; we need to keep that table entry around...
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call intoDE ; Jump from the table entry to the cmd addr.
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ld a, 4 ; 4 chars to compare
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call strncmp
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pop de
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jr z, .found
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inc de
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inc de
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djnz .loop
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; exhausted loop? not found
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ld a, SHELL_ERR_UNKNOWN_CMD
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; Before erroring out, let's try SHELL_HOOK.
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ld ix, (SHELL_CMDHOOK)
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call callIX
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jr z, .end ; oh, not an error!
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; still an error. Might be different than SHELL_ERR_UNKNOWN_CMD though.
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; maybe a routine was called, but errored out.
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jr .error
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.found:
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; we found our command. DE points to its table entry. Now, let's parse
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; our args.
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call intoDE ; Jump from the table entry to the cmd addr.
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; advance the HL pointer to the beginning of the args.
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xor a
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call findchar
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inc hl ; beginning of args
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; Now, let's have DE point to the argspecs
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ld a, 4
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call addDE
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; We're ready to parse args
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ld ix, SHELL_CMD_ARGS
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call parseArgs
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or a ; cp 0
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jr nz, .parseerror
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; Args parsed, now we can load the routine address and call it.
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; let's have DE point to the jump line
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ld hl, SHELL_CMD_ARGS
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ld a, PARSE_ARG_MAXCOUNT
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call addDE
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push de \ pop ix
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; Ready to roll!
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call callIX
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or a ; cp 0
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jr nz, .error ; if A is non-zero, we have an error
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jr .end
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.parseerror:
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ld a, SHELL_ERR_BAD_ARGS
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.error:
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call shellPrintErr
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.end:
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pop ix
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pop hl
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pop de
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pop bc
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pop af
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ret
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; Print the error code set in A (in hex)
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shellPrintErr:
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push af
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push hl
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ld hl, .str
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call printstr
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call printHex
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call printcrlf
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pop hl
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pop af
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ret
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.str:
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.db "ERR ", 0
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; *** COMMANDS ***
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; A command is a 4 char names, followed by a PARSE_ARG_MAXCOUNT bytes of
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; argument specs, followed by the routine. Then, a simple table of addresses
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; is compiled in a block and this is what is iterated upon when we want all
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; available commands.
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;
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; Format: 4 bytes name followed by PARSE_ARG_MAXCOUNT bytes specifiers,
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; followed by 3 bytes jump. fill names with zeroes
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;
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; When these commands are called, HL points to the first byte of the
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; parsed command args.
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;
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; If the command is a success, it should set A to zero. If the command results
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; in an error, it should set an error code in A.
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;
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; Extra commands: Other parts might define new commands. You can add these
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; commands to your shell. First, set SHELL_EXTRA_CMD_COUNT to
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; the number of extra commands to add, then add a ".dw"
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; directive *just* after your '.inc "shell.asm"'. Voila!
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;
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; Set memory pointer to the specified address (word).
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; Example: mptr 01fe
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shellMptrCmd:
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.db "mptr", 0b011, 0b001, 0
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shellMptr:
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push hl
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; reminder: z80 is little-endian
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ld a, (hl)
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ld (SHELL_MEM_PTR+1), a
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inc hl
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ld a, (hl)
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ld (SHELL_MEM_PTR), a
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ld hl, (SHELL_MEM_PTR)
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ld a, h
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call printHex
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ld a, l
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call printHex
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call printcrlf
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pop hl
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xor a
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ret
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; peek the number of bytes specified by argument where memory pointer points to
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; and display their value. If 0 is specified, 0x100 bytes are peeked.
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;
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; Example: peek 2 (will print 2 bytes)
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shellPeekCmd:
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.db "peek", 0b001, 0, 0
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shellPeek:
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push bc
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push hl
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ld a, (hl)
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ld b, a
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ld hl, (SHELL_MEM_PTR)
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.loop: ld a, (hl)
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call printHex
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inc hl
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djnz .loop
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call printcrlf
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.end:
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pop hl
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pop bc
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xor a
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ret
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; poke specified number of bytes where memory pointer points and set them to
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; bytes typed through stdioGetC. Blocks until all bytes have been fetched.
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shellPokeCmd:
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.db "poke", 0b001, 0, 0
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shellPoke:
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push bc
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push hl
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ld a, (hl)
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ld b, a
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ld hl, (SHELL_MEM_PTR)
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.loop: call stdioGetC
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jr nz, .loop ; nothing typed? loop
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ld (hl), a
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inc hl
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djnz .loop
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pop hl
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pop bc
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xor a
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ret
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; Calls the routine where the memory pointer currently points. This can take two
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; parameters, A and HL. The first one is a byte, the second, a word. These are
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; the values that A and HL are going to be set to just before calling.
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; Example: run 42 cafe
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shellCallCmd:
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.db "call", 0b101, 0b111, 0b001
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shellCall:
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push hl
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push ix
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; Let's recap here. At this point, we have:
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; 1. The address we want to execute in (SHELL_MEM_PTR)
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; 2. our A arg as the first byte of (HL)
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; 2. our HL arg as (HL+1) and (HL+2)
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; Ready, set, go!
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ld ix, (SHELL_MEM_PTR)
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ld a, (hl)
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ex af, af'
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inc hl
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ld a, (hl)
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exx
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ld h, a
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exx
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inc hl
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ld a, (hl)
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exx
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ld l, a
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ex af, af'
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call callIX
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.end:
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pop ix
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pop hl
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xor a
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ret
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shellIORDCmd:
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.db "iord", 0b001, 0, 0
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push bc
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ld a, (hl)
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ld c, a
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in a, (c)
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call printHex
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xor a
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pop bc
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ret
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shellIOWRCmd:
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.db "iowr", 0b001, 0b001, 0
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push bc
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ld a, (hl)
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ld c, a
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inc hl
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ld a, (hl)
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out (c), a
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xor a
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pop bc
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ret
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; This table is at the very end of the file on purpose. The idea is to be able
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; to graft extra commands easily after an include in the glue file.
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shellCmdTbl:
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.dw shellMptrCmd, shellPeekCmd, shellPokeCmd, shellCallCmd
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.dw shellIORDCmd, shellIOWRCmd
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