shell: implement seek and peek
This introduces `core.asm` which includes routines used by other parts.
This commit is contained in:
Virgil Dupras
parent
9580cc3994
commit
21168f6c4e
193
parts/core.asm
Normal file
193
parts/core.asm
Normal file
@ -0,0 +1,193 @@
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; core
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;
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; Routines used by pretty much all parts. You will want to include it first
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; in your glue file.
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; *** CONSTS ***
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ASCII_CR .equ 0x0d
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ASCII_LF .equ 0x0a
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; *** CODE ***
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; add the value of A into DE
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addDE:
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add a, e
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jr nc, .end ; no carry? skip inc
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inc d
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.end:
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ld e, a
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ret
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; Format the lower nibble of A into a hex char and stores the result in A.
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fmtHex:
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and a, 0xf
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cp 10
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jr nc, .alpha ; if >= 10, we have alpha
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add a, '0'
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ret
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.alpha:
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add a, 'A'-10
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ret
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; Formats value in A into a string hex pair. Stores it in the memory location
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; that HL points to. Does *not* add a null char at the end.
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fmtHexPair:
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push af
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; let's start with the rightmost char
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inc hl
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call fmtHex
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ld (hl), a
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; and now with the leftmost
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dec hl
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pop af
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push af
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and a, 0xf0
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rra \ rra \ rra \ rra
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call fmtHex
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ld (hl), a
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pop af
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ret
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; jump to the location pointed to by HL. This allows us to call HL instead of
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; just jumping it.
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jumpHL:
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jp hl
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ret
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; Parse the hex char at A and extract it's 0-15 numerical value. Put the result
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; in A.
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;
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; On success, the carry flag is reset. On error, it is set.
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parseHex:
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; First, let's see if we have an easy 0-9 case
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cp '0'
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jr c, .error ; if < '0', we have a problem
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cp '9'+1
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jr nc, .alpha ; if >= '9'+1, we might have alpha
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; We are in the 0-9 range
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sub a, '0' ; C is clear
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ret
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.alpha:
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call upcase
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cp 'A'
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jr c, .error ; if < 'A', we have a problem
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cp 'F'+1
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jr nc, .error ; if >= 'F', we have a problem
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; We have alpha.
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sub a, 'A'-10 ; C is clear
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ret
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.error:
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scf
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ret
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; Parses 2 characters of the string pointed to by HL and returns the numerical
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; value in A. If the second character is a "special" character (<0x21) we don't
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; error out: the result will be the one from the first char only.
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;
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; On success, the carry flag is reset. On error, it is set.
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parseHexPair:
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push bc
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push hl
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ld a, (hl)
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call parseHex
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jr c, .end ; error? goto end, keeping the C flag on
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rla \ rla \ rla \ rla ; let's push this in MSB
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ld b, a
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inc hl
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ld a, (hl)
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;cp 0x21
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;jr c, .single ; special char? single digit
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call parseHex
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jr c, .end ; error?
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or b ; join left-shifted + new. we're done!
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; C flag was set on parseHex and is necessarily clear at this point
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jr .end
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.single:
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; If we have a single digit, our result is already stored in B, but
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; we have to right-shift it back.
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ld a, b
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and a, 0xf0
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rra \ rra \ rra \ rra
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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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; print null-terminated string pointed to by HL
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printstr:
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push af
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push hl
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.loop:
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ld a, (hl) ; load character to send
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or a ; is it zero?
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jr z, .end ; if yes, we're finished
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call aciaPutC
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inc hl
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jr .loop
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.end:
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pop hl
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pop af
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ret
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; print A characters from string that HL points to
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printnstr:
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push bc
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push hl
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ld b, a
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.loop:
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ld a, (hl) ; load character to send
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call aciaPutC
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inc hl
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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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ret
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; Compares strings pointed to by HL and DE up to A count of characters. If
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; equal, Z is set. If not equal, Z is reset.
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strncmp:
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push bc
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push hl
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push de
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ld b, a
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.loop:
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ld a, (de)
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cp (hl)
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jr nz, .end ; not equal? break early
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inc hl
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inc de
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djnz .loop
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.end:
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pop de
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pop hl
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pop bc
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; Because we don't call anything else than CP that modify the Z flag,
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; our Z value will be that of the last cp (reset if we broke the loop
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; early, set otherwise)
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ret
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; Transforms the character in A, if it's in the a-z range, into its upcase
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; version.
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upcase:
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cp 'a'
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ret c ; A < 'a'. nothing to do
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cp 'z'+1
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ret nc ; A >= 'z'+1. nothing to do
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; 'a' - 'A' == 0x20
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sub 0x20
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ret
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177
parts/shell.asm
177
parts/shell.asm
@ -13,8 +13,6 @@
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; See constants below for error codes.
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; *** CONSTS ***
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CR .equ 0x0d
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LF .equ 0x0a
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; number of entries in shellCmdTbl
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SHELL_CMD_COUNT .equ 2
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@ -25,8 +23,19 @@ SHELL_ERR_UNKNOWN_CMD .equ 0x01
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; Arguments for the command weren't properly formatted
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SHELL_ERR_BAD_ARGS .equ 0x02
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; *** VARIABLES ***
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; Memory address that the shell is currently "pointing at" for peek and deek
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; operations. Set with seek.
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SHELL_MEM_PTR .equ SHELL_RAMSTART
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; Used to store formatted hex values just before printing it.
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SHELL_HEX_FMT .equ SHELL_MEM_PTR+2
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SHELL_RAMEND .equ SHELL_HEX_FMT+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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; print prompt
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ld hl, .prompt
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call printstr
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@ -40,32 +49,14 @@ shellLoop:
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call chkbuf
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jr shellLoop
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; print null-terminated string pointed to by HL
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printstr:
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push af
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push hl
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.loop:
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ld a, (hl) ; load character to send
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or a ; is it zero?
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jr z, .end ; if yes, we're finished
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call aciaPutC
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inc hl
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jr .loop
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.end:
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pop hl
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pop af
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ret
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printcrlf:
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ld a, CR
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ld a, ASCII_CR
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call aciaPutC
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ld a, LF
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ld a, ASCII_LF
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call aciaPutC
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ret
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; check if the input buffer is full or ends in CR or LF. If it does, prints it
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; back and empty it.
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chkbuf:
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@ -81,9 +72,9 @@ chkbuf:
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ld a, (hl) ; now, that's our char we have in A
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inc hl ; put HL back where it was
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cp CR
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cp ASCII_CR
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jr z, .do ; char is CR? do!
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cp LF
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cp ASCII_LF
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jr z, .do ; char is LF? do!
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; nothing matched? don't do anything
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@ -101,51 +92,12 @@ chkbuf:
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call shellParse
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ret
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; Compares strings pointed to by HL and DE up to A count of characters. If
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; equal, Z is set. If not equal, Z is reset.
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strncmp:
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push bc
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push hl
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push de
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ld b, a
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.loop:
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ld a, (de)
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cp (hl)
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jr nz, .end ; not equal? break early
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inc hl
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inc de
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djnz .loop
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.end:
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pop de
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pop hl
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pop bc
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; Because we don't call anything else than CP that modify the Z flag,
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; our Z value will be that of the last cp (reset if we broke the loop
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; early, set otherwise)
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ret
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; add the value of A into DE
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addDE:
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add a, e
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jr nc, .end ; no carry? skip inc
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inc d
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.end:
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ld e, a
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ret
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; jump to the location pointed to by HL. This allows us to call HL instead of
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; just jumping it.
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jumpHL:
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jp hl
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ret
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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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ld de, shellCmdTbl
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ld a, SHELL_CMD_COUNT
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@ -165,19 +117,34 @@ shellParse:
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jr .end
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.found:
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; all right, we're almost ready to call the cmd. Let's just have DE
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; point to the cmd jump line.
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ld a, 4
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call addDE
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ex hl, de
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; Now, let's swap HL and DE because, welll because that's how we're set.
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ex hl, de ; HL = jump line, DE = cmd str pointer
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; Before we call our command, we want to set up the pointer to the arg
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; list. Normally, it's DE+5 (DE+4 is the space) unless DE+4 is null,
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; which means no arg.
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ld a, 4
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call addDE
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ld a, (DE)
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cp 0
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jr z, .noarg ; char is null? we have no arg
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inc de
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.noarg:
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; DE points to args, HL points to jump line. Ready to roll!
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call jumpHL
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ex hl, de
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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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pop af
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ret
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; Print the error code set in A (doesn't work for codes > 9 yet...)
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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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@ -185,9 +152,10 @@ shellPrintErr:
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ld hl, .str
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call printstr
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; ascii for '0' is 0x30
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add a, 0x30
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call aciaPutC
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ld hl, SHELL_HEX_FMT
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call fmtHexPair
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ld a, 2
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call printnstr
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call printcrlf
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pop hl
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@ -198,19 +166,66 @@ shellPrintErr:
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.db "ERR ", 0
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; *** COMMANDS ***
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shellSeek:
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ld hl, .str
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call printstr
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ret
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.str:
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.db "seek called", CR, LF, 0
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; When these commands are called, DE points to the first character of the
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; command args.
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shellPeek:
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ld hl, .str
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call printstr
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; Set memory pointer to the specified address.
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; Example: seek 01fe
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shellSeek:
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push de
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push hl
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ex de, hl
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call parseHexPair
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jr c, .error
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ld (SHELL_MEM_PTR), a
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inc hl
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inc hl
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call parseHexPair
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jr c, .error
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ld (SHELL_MEM_PTR+1), a
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jr .success
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.error:
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ld a, SHELL_ERR_BAD_ARGS
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call shellPrintErr
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jr .end
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.success:
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ld a, (SHELL_MEM_PTR)
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ld hl, SHELL_HEX_FMT
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call fmtHexPair
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ld a, 2
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call printnstr
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ld a, (SHELL_MEM_PTR+1)
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call fmtHexPair
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ld a, 2
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call printnstr
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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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ret
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; peek byte where memory pointer points to aby display its value
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shellPeek:
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push af
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push hl
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ld hl, (SHELL_MEM_PTR)
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ld a, (hl)
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ld hl, SHELL_HEX_FMT
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call fmtHexPair
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ld a, 2
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call printnstr
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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 "peek called", CR, LF, 0
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; Format: 4 bytes name followed by 2 bytes jump. fill names with zeroes
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shellCmdTbl:
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@ -47,7 +47,7 @@ This is what your glue code would look like:
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jr init
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.fill 0x38-$
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jr aciaInt
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jp aciaInt
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init:
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di
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@ -63,8 +63,10 @@ init:
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ei
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call shellLoop
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#include "core.asm"
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ACIA_RAMSTART .equ RAMSTART
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#include "acia.asm"
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SHELL_RAMSTART .equ ACIA_RAMEND
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#include "shell.asm"
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```
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@ -83,11 +85,9 @@ We set interrupt mode to 1 because that's what `acia.asm` is written around.
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Then, we init ACIA, shell, enable interrupt and give control of the main loop
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to `shell.asm`.
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What comes below is actual code include from the acia and shell modules. As you
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can see, we need to tell each module where to put their variables. `shell.asm`
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doesn't have variables, but if it did, we would have a `SHELL_RAMSTART .equ
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ACIA_RAMEND` just below the `acia.asm` include. `ACIA_RAMEND` is defined in
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`acia.asm`.
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What comes below is actual code include from parts we want to include in our
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OS. As you can see, we need to tell each module where to put their variables.
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See `parts/README.md` for details.
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### Build the image
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