( Managing variables in a core module is tricky. Sure, we
have (sysv), but here we need to allocate a big buffer, and
that cannot be done through (sysv). What we do is that we
allocate that buffer at runtime and use (sysv) to point to
it, a pointer that is set during the initialization
routine. )
64 CONSTANT INBUFSZ
( points to INBUF )
(sysv) IN(
( points to INBUF's end )
(sysv) IN)
( current position in INBUF )
(sysv) IN>
( flush input buffer )
( set IN> to IN( and set IN> @ to null )
: (infl) 0 IN( @ DUP IN> ! ! ;
( Initializes the readln subsystem )
: (c<$)
H@ IN( !
INBUFSZ ALLOT
H@ IN) !
( We need two extra bytes. 1 for the last typed 0x0a and
one for the following NULL. )
2 ALLOT
(infl)
;
( handle backspace: go back one char in IN>, if possible, then
emit SPC + BS )
: (inbs)
( already at IN( ? )
IN> @ IN( @ = IF EXIT THEN
IN> @ 1 - IN> !
SPC BS
;
( read one char into input buffer and returns whether we
should continue, that is, whether newline was not met. )
: (rdlnc) ( -- f )
( buffer overflow? same as if we typed a newline )
IN> @ IN) @ = IF 0x0a ELSE KEY THEN ( c )
( del? same as backspace )
DUP 0x7f = IF DROP 0x8 THEN
( echo back )
DUP EMIT ( c )
( bacspace? handle and exit )
DUP 0x8 = IF (inbs) EXIT THEN
( write and advance )
DUP ( keep as result ) ( c c )
( Here, we take advantage of the fact that c's MSB is
always zero and thus ! automatically null-terminates
our string )
IN> @ ! 1 IN> +! ( c )
( if newline, replace with zero to indicate EOL )
DUP 0xa = IF DROP 0 THEN
;
( Read one line in input buffer and make IN> point to it )
: (rdln)
( Should we prompt? if we're executing a word, FLAGS bit
0, then we shouldn't. )
FLAGS @ 0x1 AND NOT IF LF '>' EMIT SPC THEN
(infl)
BEGIN (rdlnc) NOT UNTIL
IN( @ IN> !
;
( And finally, implement a replacement for the (c<) routine )
: (c<)
IN> @ C@ ( c )
( not EOL? good, inc and return )
DUP IF 1 IN> +! EXIT THEN ( c )
( EOL ? readline. we still return typed char though )
(rdln) (<c) ( c )
;
