mirror of
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d2c6e21c64
When I zasm-ified the shell a couple of dozens of commits ago, I inverted push and pops...
520 lines
12 KiB
NASM
520 lines
12 KiB
NASM
; shell
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;
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; Runs a shell over a block device interface.
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; Status: incomplete. As it is now, it spits a welcome prompt, wait for input
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; and compare the first 4 chars of the input with a command table and call the
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; appropriate routine if it's found, an error if it's not.
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;
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; Commands, for now, are partially implemented.
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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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; parse
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; stdio
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; blkdev
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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 7+SHELL_EXTRA_CMD_COUNT
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; maximum number of bytes to receive as args in all commands. Determines the
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; size of the args variable.
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.equ SHELL_CMD_ARGS_MAXSIZE 3
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; The command that was type isn't known to the shell
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.equ SHELL_ERR_UNKNOWN_CMD 0x01
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; Arguments for the command weren't properly formatted
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.equ SHELL_ERR_BAD_ARGS 0x02
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; IO routines (GetC, PutC) returned an error in a load/save command
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.equ SHELL_ERR_IO_ERROR 0x05
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; Size of the shell command buffer. If a typed command reaches this size, the
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; command is flushed immediately (same as pressing return).
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.equ SHELL_BUFSIZE 0x20
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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 SHELL_MEM_PTR+2
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; Command buffer. We read types chars into this buffer until return is pressed
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; This buffer is null-terminated and we don't keep an index around: we look
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; for the null-termination every time we write to it. Simpler that way.
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.equ SHELL_BUF SHELL_CMD_ARGS+SHELL_CMD_ARGS_MAXSIZE
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.equ SHELL_RAMEND SHELL_BUF+SHELL_BUFSIZE
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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 (SHELL_BUF), a
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; print welcome
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ld hl, .welcome
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call printstr
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ret
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.welcome:
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.db "Collapse OS", ASCII_CR, ASCII_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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; First, let's wait until something is typed.
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call stdioGetC
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jr nz, shellLoop ; nothing typed? loop
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; got it. Now, is it a CR or LF?
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cp ASCII_CR
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jr z, .do ; char is CR? do!
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cp ASCII_LF
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jr z, .do ; char is LF? do!
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; Echo the received character right away so that we see what we type
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call stdioPutC
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; Ok, gotta add it do the buffer
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; save char for later
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ex af, af'
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ld hl, SHELL_BUF
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xor a ; look for null
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call findchar ; HL points to where we need to write
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; A is the number of chars in the buf
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cp SHELL_BUFSIZE
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jr z, .do ; A == bufsize? then our buffer is full. do!
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; bring the char back in A
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ex af, af'
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; Buffer not full, not CR or LF. Let's put that char in our buffer and
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; read again.
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ld (hl), a
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; Now, write a zero to the next byte to properly terminate our string.
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inc hl
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xor a
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ld (hl), a
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jr shellLoop
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.do:
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call printcrlf
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ld hl, SHELL_BUF
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call shellParse
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; empty our buffer by writing a zero to its first char
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xor a
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ld (hl), a
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ld hl, .prompt
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call printstr
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jr shellLoop
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; no ret because we never return
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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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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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ld de, shellCmdTbl
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ld a, SHELL_CMD_COUNT
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ld b, a
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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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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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ld a, ' '
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call findchar
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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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call shellParseArgs
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cp 0
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jr nz, .parseerror
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ld hl, SHELL_CMD_ARGS
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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 a, SHELL_CMD_ARGS_MAXSIZE
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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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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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; Parse arguments at (HL) with specifiers at (DE) into (SHELL_CMD_ARGS).
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; (HL) should point to the character *just* after the name of the command
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; because we verify, in the case that we have args, that we have a space there.
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;
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; Args specifiers are a series of flag for each arg:
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; Bit 0 - arg present: if unset, we stop parsing there
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; Bit 1 - is word: this arg is a word rather than a byte. Because our
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; destination are bytes anyway, this doesn't change much except
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; for whether we expect a space between the hex pairs. If set,
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; you still need to have a specifier for the second part of
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; the multibyte.
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; Bit 2 - optional: If set and not present during parsing, we don't error out
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; and write zero
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;
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; Bit 3 - String argument: If set, this argument is a string. A pointer to the
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; read string, null terminated (max 0x20 chars) will
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; be placed in the next two bytes. This has to be the
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; last argument of the list and it stops parsing.
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; Sets A to nonzero if there was an error during parsing, zero otherwise.
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; If there was an error during parsing, carry is set.
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shellParseArgs:
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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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ld ix, SHELL_CMD_ARGS
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ld a, SHELL_CMD_ARGS_MAXSIZE
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ld b, a
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xor c
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.loop:
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; init the arg value to a default 0
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xor a
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ld (ix), a
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ld a, (hl)
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; is this the end of the line?
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cp 0
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jr z, .endofargs
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; do we have a proper space char?
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cp ' '
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jr z, .hasspace ; We're fine
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; is our previous arg a multibyte? (argspec still in C)
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bit 1, c
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jr z, .error ; bit not set? error
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dec hl ; offset the "inc hl" below
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.hasspace:
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; Get the specs
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ld a, (de)
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bit 0, a ; do we have an arg?
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jr z, .error ; not set? then we have too many args
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ld c, a ; save the specs for the next loop
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inc hl ; (hl) points to a space, go next
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bit 3, a ; is our arg a string?
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jr z, .notAString
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; our arg is a string. Let's place HL in our next two bytes and call
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; it a day. Little endian, remember
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ld (ix), l
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ld (ix+1), h
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jr .success ; directly to success: skip endofargs checks
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.notAString:
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call parseHexPair
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jr c, .error
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; we have a good arg and we need to write A in (IX).
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ld (ix), a
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; Good! increase counters
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inc de
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inc ix
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inc hl ; get to following char (generally a space)
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djnz .loop
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; If we get here, it means that our next char *has* to be a null char
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ld a, (hl)
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cp 0
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jr z, .success ; zero? great!
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jr .error
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.endofargs:
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; We encountered our null char. Let's verify that we either have no
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; more args or that they are optional
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ld a, (de)
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cp 0
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jr z, .success ; no arg? success
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bit 2, a
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jr nz, .success ; if set, arg is optional. success
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jr .error
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.success:
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xor a
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jr .end
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.error:
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inc a
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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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ret
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; *** COMMANDS ***
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; A command is a 4 char names, followed by a SHELL_CMD_ARGS_MAXSIZE 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 SHELL_CMD_ARGS_MAXSIZE 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 '#include "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 byte where memory pointer points to any display its value. If the
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; optional numerical byte arg is supplied, this number of bytes will be printed
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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", 0b101, 0, 0
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shellPeek:
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push bc
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push de
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push hl
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ld a, (hl)
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cp 0
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jr nz, .arg1isset ; if arg1 is set, no need for a default
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ld a, 1 ; default for arg1
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.arg1isset:
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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 de
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pop bc
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xor a
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ret
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; Load the specified number of bytes (max 0xff) from IO and write them in the
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; current memory pointer (which doesn't change). This gets chars from
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; blkGetCW.
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; Control is returned to the shell only after all bytes are read.
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;
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; Example: load 42
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shellLoadCmd:
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.db "load", 0b001, 0, 0
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shellLoad:
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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 blkGetCW
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jr nz, .ioError
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ld (hl), a
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inc hl
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djnz .loop
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; success
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xor a
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jr .end
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.ioError:
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ld a, SHELL_ERR_IO_ERROR
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.end:
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pop hl
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pop bc
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ret
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; Load the specified number of bytes (max 0xff) from the current memory pointer
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; and write them to I/O. Memory pointer doesn't move. This puts chars to
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; blkPutC.
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; Control is returned to the shell only after all bytes are written.
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;
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; Example: save 42
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shellSaveCmd:
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.db "save", 0b001, 0, 0
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shellSave:
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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:
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ld a, (hl)
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inc hl
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call blkPutC
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djnz .loop
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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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; 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, shellLoadCmd, shellSaveCmd, shellCallCmd
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.dw shellIORDCmd, shellIOWRCmd
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