I've done it as a less generalised function, Yuri, based on what I need to achieve rather than an exact copy of strncasecmp:
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is_token:
ldy #0
istk_1:
lda (tok_ptr),y
beq istk_x ; while *tok_ptr != 0
lda (txt_ptr),y
ora #0x20
cmp (tok_ptr),y ; does it match?
bne istk_no ; nope
iny
bra istk_1 ; else back for next
istk_no:
ldy #0
istk_x
rts
is_token has two pointers initialised off-stage: txt_ptr points into a block of text which _may_ be the start of a token, and compares it against a particular zero-terminated string in tok_ptr. If it matches, it returns y with the length of the token text (not the zero) or if not, y = 0.
That's a helper function for match_token:
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match_token:
phx
ldx #LET ; token count
sta txt_ptr
sty txt_ptr+1 ; pointer to text to match
lda #lo tokens
sta tok_ptr
lda #hi tokens
sta tok_ptr+1 ; pointer to start of token table
matk_1:
jsr is_token ; a match yet?
cpy #0
bne matk_yes ; no
matk_2:
iny ; else
lda (tok_ptr),y
bne matk_2 ; scan for rest of token
sec ; <--- not a bug!
tya ; find the next token in list
adc tok_ptr
sta tok_ptr
bcc matk_3
inc tok_ptr+1
matk_3:
inx
cpx #LAST_KW
bcc matk_1 ; back for next token
ldy #0
bra matk_x ; we've tried them all
matk_yes: ; we found a match - y has the token length
txa ; how many tests?
ora #0x80 ; set high bit as token enum
matk_x:
plx
rts ; and back
which checks all the tokens in the token table against the text in txt_ptr, and again, if it finds one, returns the associated token value in A (0x80 upwards) or LAST_KW if not found, again with the length of the token, or zero, in Y. (And I've just noticed that the last ora #0x80 is no longer required since I fixed a bug earlier!)
And _that_ is another helper function for squish_buffer which
- Reads the line number and converts to int16_t
- Moves all the post-digit and post-whitespace text to start at buffer[3]
- Inserts the int16_t line number
- Scans the line, checking every character to see whether it might be the start of a keyword (unless it's in quoted text)
- Replaces every keyword with the token code, and shuffles the code down to fill the space if necessary (memmove)
- and finally goes and has a cup of tea because it's tired and thirsty after all that work!
So the (invalid code, but convenient to show) input line
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1234 for q = 1 to 10; print q; next
looks like this in the buffer (after the line number has been converted and inserted)
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d2 04 00 66 6f 72 20 71 20 3d 20 31 20 74 6f 20 31 30 3b 20 70 72 69 6e 74 20 71 3b 20 6e 65 78 74 0d
and is further converted to
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d2 04 1a 89 20 71 20 92 20 31 20 8a 20 31 30 3b 20 82 20 71 3b 20 8b 0d
| | | | |_ next
| | | |_ print
| | |_ to
| |_ =
|_ for
(In the final product there is only one keyword/token per line (except for 'for/to'))
Neil
)