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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <syserr.h>
include <chars.h>
include "tty.h"
.help index caplist
.nf _________________________________________________________________________
TTY_INDEX_CAPS -- Prepare an index into the caplist string, stored in
the tty descriptor. Each two character capability name maps into a unique
integer code, called the capcode. We prepare a list of capcodes, keeping
only the first such code encountered in the case of multiple entries.
The offset of the capability in the caplist string is associated with each
capcode. When these lists have been prepared, they are sorted to permit
a binary search for capabilities at runtime.
.endhelp ____________________________________________________________________
procedure tty_index_caps (tty, t_capcode, t_capindex, ncaps)
pointer tty
int t_capcode[ARB], t_capindex[ARB]
int ncaps
pointer ip, caplist
int i, swap, capcode, temp
int tty_encode_capability()
pointer coerce()
errchk syserr
begin
caplist = coerce (tty + T_OFFCAP, TY_STRUCT, TY_CHAR)
ip = caplist
# Scan the caplist and prepare the capcode and capindex lists.
for (ncaps=0; ncaps <= MAX_CAPS; ) {
# Advance to the next capability field. Normal exit occurs
# when ':' is followed immediately by EOS.
while (Memc[ip] != ':' && Memc[ip] != EOS)
ip = ip + 1
if (Memc[ip+1] == EOS || Memc[ip] == EOS)
break
ip = ip + 1 # skip the ':'
capcode = tty_encode_capability (Memc[ip])
# Is the capcode already in the list? If not found, add it to
# the list.
for (i=1; i <= ncaps && t_capcode[i] != capcode; i=i+1)
;
if (i > ncaps) { # not found
ncaps = ncaps + 1
t_capcode[ncaps] = capcode
t_capindex[ncaps] = ip - caplist + 1
}
}
if (ncaps > MAX_CAPS)
call syserr (SYS_TTYOVFL)
# A simple interchange sort is sufficient here, even though it would
# not be hard to interface to qsort. The longest termcap entries are
# about 50 caps, and the time req'd to sort such a short list is
# negligible compared to the time spent searching the termcap file.
if (ncaps > 1)
repeat {
swap = 0
do i = 1, ncaps-1
if (t_capcode[i] > t_capcode[i+1]) {
temp = t_capcode[i]
t_capcode[i] = t_capcode[i+1]
t_capcode[i+1] = temp
temp = t_capindex[i]
t_capindex[i] = t_capindex[i+1]
t_capindex[i+1] = temp
swap = 1
}
} until (swap == 0)
end
# TTY_FIND_CAPABILITY -- Search the caplist for the named capability.
# If found, return the char pointer IP to the first char of the value field,
# and YES as the function value. If the first char in the capability string
# is '@', the capability "is not present".
int procedure tty_find_capability (tty, cap, ip)
pointer tty # tty descriptor
char cap[ARB] # two character name of capability
pointer ip # pointer to capability string
int capcode, capnum
int tty_binsearch(), tty_encode_capability()
pointer coerce()
errchk syserr
begin
if (tty == NULL)
call syserr (SYS_TTYINVDES)
capcode = tty_encode_capability (cap)
capnum = tty_binsearch (capcode, T_CAPCODE(tty), T_NCAPS(tty))
if (capnum > 0) {
# Add 2 to skip the two capname chars.
ip = coerce (tty + T_OFFCAP, TY_STRUCT, TY_CHAR) +
T_CAPINDEX(tty+capnum-1) - 1 + 2
if (Memc[ip] != '@')
return (YES)
}
return (NO)
end
# TTY_BINSEARCH -- Perform a binary search of the capcode array for the
# indicated capability. Return the array index of the capability if found,
# else zero.
int procedure tty_binsearch (capcode, t_capcode, ncaps)
int capcode
int t_capcode[ARB], ncaps
int low, high, pos, ntrips
begin
low = 1
high = ncaps
pos = 0
# Cut range of search in half until code is found, or until range
# vanishes (high - low <= 1). If neither high or low is the one,
# code is not found in the list.
do ntrips = 1, ncaps {
pos = (high - low) / 2 + low
if (t_capcode[low] == capcode)
return (low)
else if (t_capcode[high] == capcode)
return (high)
else if (pos == low) # (high-low)/2 == 0
return (0) # not found
else if (t_capcode[pos] < capcode)
low = pos
else
high = pos
}
# Search cannot fail to converge unless there is a bug in the software
# somewhere.
call syserr (SYS_TTYBINSRCH)
end
# TTY_ENCODE_CAPABILITY -- Encode the two character capability string
# as a unique integer value.
int procedure tty_encode_capability (cap)
char cap[ARB]
begin
return (ENCODE(cap))
end
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