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Change readstring() to use buffered input.

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Change from `uread(0, c, 1)` to `read(c)`, so input goes through
libpc's buffer.  If input is a tty in Unix, this reduces the number of
read(2) system calls from one per character to one per line.

This change will become necessary in CP/M when I enable the line
editor.
This commit is contained in:
George Koehler 2018-05-04 18:06:51 -04:00
parent 4a3b7be795
commit b4be612832
1 changed files with 9 additions and 32 deletions
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41
examples/hilo.p
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@ -9,7 +9,6 @@ program hilo(input, output);
type
string = packed array [0..255] of char;
charstar = packed array [0..0] of char;
var
playing : Boolean;
@ -30,47 +29,25 @@ function random(range : integer) : integer;
random := seed mod range;
end;
{ Pascal doesn't provide string input, so we interface to the read() syscall
and do it manually. But... we can't interface to read() directly because
that conflicts with a Pascal keyword. Luckily there's a private function
uread() in the ACK Pascal library that we can use instead. }
function uread(fd : integer; var buffer : charstar; count : integer) : integer;
extern;
{ Pascal doesn't provide string input, so we read characters until the
end of line and put them in a string. }
function readchar : char;
var
c : charstar;
dummy : integer;
begin
c[0] := chr(0);
dummy := uread(0, c, 1);
readchar := c[0];
end;
procedure readstring(var buffer : string; var length : integer);
var
finished : Boolean;
c : char;
begin
write('> ');
length := 0;
finished := FALSE;
seed := 0;
while not finished do
repeat
begin
c := readchar;
if (ord(c) = 10) then
finished := true
else
begin
buffer[length] := c;
length := length + 1;
end
end;
read(c);
buffer[length] := c;
length := length + 1;
end
until eoln;
readln; { discard end of line }
end;
procedure getname;