diff --git a/parts/core.asm b/parts/core.asm index 59fbe29..0a0ea9a 100644 --- a/parts/core.asm +++ b/parts/core.asm @@ -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 @@ -135,34 +144,10 @@ 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 @@ -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: diff --git a/parts/shell.asm b/parts/shell.asm index 1497105..a1aa1e4 100644 --- a/parts/shell.asm +++ b/parts/shell.asm @@ -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 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. + call addHL + ; Now, let's have DE point to the argspecs ld a, 4 call addDE - ld a, (DE) + ; We're ready to parse args + call shellParseArgs 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! + 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 + ; 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 - -.error: - ld a, SHELL_ERR_BAD_ARGS - call shellPrintErr - jr .end + ; 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 -.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