shell: add shellParseArgs

Replaces individual command parsing. Quite a big and complex chunk of
code, but makes each command much simpler.
This commit is contained in:
Virgil Dupras 2019-04-14 23:14:07 -04:00
parent 83f63c7146
commit 26b125b337
2 changed files with 170 additions and 164 deletions

View File

@ -18,6 +18,15 @@ addDE:
ld e, a
ret
; add the value of A into HL
addHL:
add a, l
jr nc, .end ; no carry? skip inc
inc h
.end:
ld l, a
ret
; jump to the location pointed to by IX. This allows us to call IX instead of
; just jumping it. We use IX because we never use this for arguments.
callIX:
@ -108,11 +117,11 @@ parseHex:
; Parses 2 characters of the string pointed to by HL and returns the numerical
; value in A. If the second character is a "special" character (<0x21) we don't
; error out: the result will be the one from the first char only.
; HL is set to point to the last char of the pair.
;
; On success, the carry flag is reset. On error, it is set.
parseHexPair:
push bc
push hl
ld a, (hl)
call parseHex
@ -135,36 +144,12 @@ parseHexPair:
ld a, b
and a, 0xf0
rra \ rra \ rra \ rra
dec hl
.end:
pop hl
pop bc
ret
; Parse a series of A hex pairs from (HL) and put the result in (DE)
parseHexChain:
push af
push bc
push de
push hl
ld b, a
.loop:
call parseHexPair
jr c, .end ; error?
ld (de), a
inc hl
inc hl
inc de
djnz .loop
.end:
pop hl
pop de
pop bc
pop af
ret
; print null-terminated string pointed to by HL
printstr:
push af
@ -232,21 +217,6 @@ strncmp:
; early, set otherwise)
ret
; Swap the two bytes at (HL)
swapBytes:
push af
ld a, (hl)
ex af, af'
inc hl
ld a, (hl)
ex af, af'
ld (hl), a
dec hl
ex af, af'
ld (hl), a
pop af
ret
; Transforms the character in A, if it's in the a-z range, into its upcase
; version.
upcase:

View File

@ -23,6 +23,10 @@
; number of entries in shellCmdTbl
SHELL_CMD_COUNT .equ 4
; maximum number of bytes to receive as args in all commands. Determines the
; size of the args variable.
SHELL_CMD_ARGS_MAXSIZE .equ 3
; The command that was type isn't known to the shell
SHELL_ERR_UNKNOWN_CMD .equ 0x01
@ -34,16 +38,20 @@ SHELL_ERR_BAD_ARGS .equ 0x02
SHELL_BUFSIZE .equ 0x20
; *** VARIABLES ***
; Memory address that the shell is currently "pointing at" for peek and deek
; Memory address that the shell is currently "pointing at" for peek, load, call
; operations. Set with seek.
SHELL_MEM_PTR .equ SHELL_RAMSTART
; Used to store formatted hex values just before printing it.
SHELL_HEX_FMT .equ SHELL_MEM_PTR+2
; Places where we store arguments specifiers and where resulting values are
; written to after parsing.
SHELL_CMD_ARGS .equ SHELL_HEX_FMT+2
; Command buffer. We read types chars into this buffer until return is pressed
; This buffer is null-terminated and we don't keep an index around: we look
; for the null-termination every time we write to it. Simpler that way.
SHELL_BUF .equ SHELL_HEX_FMT+2
SHELL_BUF .equ SHELL_CMD_ARGS+SHELL_CMD_ARGS_MAXSIZE
SHELL_RAMEND .equ SHELL_BUF+SHELL_BUFSIZE
@ -132,7 +140,7 @@ shellParse:
ld a, 4 ; 4 chars to compare
call strncmp
jr z, .found
ld a, 7
ld a, 7 + SHELL_CMD_ARGS_MAXSIZE
call addDE
djnz .loop
@ -142,28 +150,31 @@ shellParse:
jr .end
.found:
; all right, we're almost ready to call the cmd. Let's just have DE
; point to the cmd jump line.
; we found our command. Now, let's parse our args.
ld a, 4
call addHL
; Now, let's have DE point to the argspecs
ld a, 4
call addDE
; We're ready to parse args
call shellParseArgs
cp 0
jr nz, .parseerror
ld hl, SHELL_CMD_ARGS
; Args parsed, now we can load the routine address and call it.
; let's have DE point to the jump line
ld a, SHELL_CMD_ARGS_MAXSIZE
call addDE
ld ixh, d
ld ixl, e
; Now, let's swap HL and DE because, well because that's how we're set.
ex hl, de ; DE = cmd str pointer
; Before we call our command, we want to set up the pointer to the arg
; list. Normally, it's DE+5 (DE+4 is the space) unless DE+4 is null,
; which means no arg.
ld a, 4
call addDE
ld a, (DE)
cp 0
jr z, .noarg ; char is null? we have no arg
inc de
.noarg:
; DE points to args, IX points to jump line. Ready to roll!
; Ready to roll!
call callIX
jr .end
.parseerror:
ld a, SHELL_ERR_BAD_ARGS
call shellPrintErr
.end:
pop ix
pop hl
@ -193,9 +204,99 @@ shellPrintErr:
.str:
.db "ERR ", 0
; Parse arguments at (HL) with specifiers at (DE) into (SHELL_CMD_ARGS).
; (HL) should point to the character *just* after the name of the command
; because we verify, in the case that we have args, that we have a space there.
;
; Args specifiers are a series of flag for each arg:
; Bit 0 - arg present: if unset, we stop parsing there
; Bit 1 - is word: this arg is a word rather than a byte. Because our
; destination are bytes anyway, this doesn't change much except
; for whether we expect a space between the hex pairs. If set,
; you still need to have a specifier for the second part of
; the multibyte.
; Bit 2 - optional: If set and not present during parsing, we don't error out
; and write zero
;
; Sets A to nonzero if there was an error during parsing, zero otherwise.
; If there was an error during parsing, carry is set.
shellParseArgs:
push bc
push de
push hl
push ix
ld ix, SHELL_CMD_ARGS
ld a, SHELL_CMD_ARGS_MAXSIZE
ld b, a
xor c
.loop:
; init the arg value to a default 0
xor a
ld (ix), a
ld a, (hl)
; is this the end of the line?
cp 0
jr z, .endofargs
; do we have a proper space char?
cp ' '
jr z, .hasspace ; We're fine
; is our previous arg a multibyte? (argspec still in C)
bit 1, c
jr z, .error ; bit not set? error
dec hl ; offset the "inc hl" below
.hasspace:
; Get the specs
ld a, (de)
bit 0, a ; do we have an arg?
jr z, .error ; not set? then we have too many args
ld c, a ; save the specs for the next loop
inc hl ; (hl) points to a space, go next
call parseHexPair
jr c, .error
; we have a good arg and we need to write A in (IX).
ld (ix), a
; Good! increase counters
inc de
inc ix
inc hl ; get to following char (generally a space)
djnz .loop
; If we get here, it means that our next char *has* to be a null char
ld a, (hl)
cp 0
jr z, .success ; zero? great!
jr .error
.endofargs:
; We encountered our null char. Let's verify that we either have no
; more args or that they are optional
ld a, (de)
cp 0
jr z, .success ; no arg? success
bit 2, a
jr nz, .success ; if set, arg is optional. success
jr .error
.success:
xor a
jr .end
.error:
inc a
.end:
pop ix
pop hl
pop de
pop bc
ret
; *** COMMANDS ***
; When these commands are called, DE points to the first character of the
; command args.
; When these commands are called, HL points to the first byte of the
; parsed command args.
; Set memory pointer to the specified address (word).
; Example: seek 01fe
@ -205,35 +306,26 @@ shellSeek:
push de
push hl
ex de, hl
ld de, SHELL_MEM_PTR
ld a, 2
call parseHexChain
jr c, .error
; z80 is little endian. in a "ld hl, (nn)" op, L is loaded from the
; first byte, H is loaded from the second. We have to swap our result.
ld hl, SHELL_MEM_PTR
call swapBytes
jr .success
; first byte, H is loaded from the second.
ld a, (hl)
ld (SHELL_MEM_PTR+1), a
inc hl
ld a, (hl)
ld (SHELL_MEM_PTR), a
.error:
ld a, SHELL_ERR_BAD_ARGS
call shellPrintErr
jr .end
.success:
ld a, (SHELL_MEM_PTR+1)
ld de, (SHELL_MEM_PTR)
ld hl, SHELL_HEX_FMT
ld a, d
call fmtHexPair
ld a, 2
call printnstr
ld a, (SHELL_MEM_PTR)
ld a, e
call fmtHexPair
ld a, 2
call printnstr
call printcrlf
.end:
pop hl
pop de
pop af
@ -250,25 +342,12 @@ shellPeek:
push de
push hl
ld b, 1 ; by default, we run the loop once
ld a, (de)
ld a, (hl)
cp 0
jr z, .success ; no arg? don't try to parse
ex de, hl
call parseHexPair
jr c, .error
cp 0
jr z, .error ; zero isn't a good arg, error
ld b, a ; loop the number of times specified in arg
jr .success
.error:
ld a, SHELL_ERR_BAD_ARGS
call shellPrintErr
jr .end
.success:
jr nz, .arg1isset ; if arg1 is set, no need for a default
ld a, 1 ; default for arg1
.arg1isset:
ld b, a
ld hl, (SHELL_MEM_PTR)
.loop: ld a, (hl)
ex hl, de
@ -300,17 +379,7 @@ shellLoad:
push bc
push hl
ld a, (de)
call parseHex
jr c, .error
jr .success
.error:
ld a, SHELL_ERR_BAD_ARGS
call shellPrintErr
jr .end
.success:
ld a, (hl)
ld b, a
ld hl, (SHELL_MEM_PTR)
.loop: SHELL_GETC
@ -330,80 +399,47 @@ shellLoad:
; Example: run 42 cafe
shellCall:
push af
push de
push hl
push ix
ld a, (de)
cp 0
jr z, .defA ; no arg? don't try to parse
call parseHex
jr c, .error
; We have a proper A arg, in A. We push it for later use, just before
; the actual call.
push af
; Let's try DE parsing now
inc de
inc de
ld a, (de)
cp 0
jr z, .defDE ; no arg? don't try to parse
inc de ; we're on a space (maybe...) we parse the
; next char
ex hl, de ; we need HL to point to our hex str for
; parseHexChain
; We need a tmp 2 bytes space for our result. Let's use SHELL_HEX_FMT.
ld de, SHELL_HEX_FMT
ld a, 2
call parseHexChain
jr c, .error
ex hl, de ; result is in DE, we need it in HL
call swapBytes
; Alright, we have a proper address in (SHELL_HEX_FMT), let's push it
; to the stack
ld hl, (SHELL_HEX_FMT)
push hl
jr .success
.error:
ld a, SHELL_ERR_BAD_ARGS
call shellPrintErr
jr .end
.defA:
xor a
push af
.defDE:
ld hl, 0
push hl
.success:
; Let's recap here. At this point, we have:
; 1. The address we want to execute in (SHELL_MEM_PTR)
; 2. our HL arg on top of the stack
; 3. our A arg underneath.
; 2. our A arg as the first byte of (HL)
; 2. our HL arg as (HL+1) and (HL+2)
; Ready, set, go!
ld a, (SHELL_MEM_PTR)
ld ixl, a
ld a, (SHELL_MEM_PTR+1)
ld ixh, a
pop hl
pop af
ld a, (hl)
ex af, af'
inc hl
ld a, (hl)
exx
ld h, a
exx
inc hl
ld a, (hl)
exx
ld l, a
ex af, af'
call callIX
.end:
pop ix
pop hl
pop de
pop af
ret
; Format: 4 bytes name followed by 3 bytes jump. fill names with zeroes
; Format: 4 bytes name followed by SHELL_CMD_ARGS_MAXSIZE bytes specifiers,
; followed by 3 bytes jump. fill names with zeroes
shellCmdTbl:
.db "seek"
.db "seek", 0b011, 0b001, 0
jp shellSeek
.db "peek"
.db "peek", 0b101, 0, 0
jp shellPeek
.db "load"
.db "load", 0b001, 0, 0
jp shellLoad
.db "call"
.db "call", 0b101, 0b111, 0b001
jp shellCall