advent-of-code-2022/day-01/gforth/examples-read-files.fth

\ Print lines from a text file.

\ This prints lines from a file, but does not put them on
\ the stack.

256 Constant max-bytes-line
\ Create a buffer of appropriate size for lines. Add 2 bytes
\ to the buffer size for CR LF bytes.
Create line-buffer max-bytes-line 2 + allot
s" input" r/o open-file throw Value puzzle-input-handle

: print-line ( line-buffer --  )
  dup max-bytes-line puzzle-input-handle read-line throw
  if
    line-buffer swap
  then ;

\ given a line-buffer, print-line will print one line per call

line-buffer

print-line
print-line
print-line

\ Finally close the file.
puzzle-input-handle close-file

\ ================
\ Interpret a file
\ ================

\ This can be useful, if the file contains only words which
\ are valid Forth words and the input file is
\ trusted. However, this discards any whitespace. If
\ whitespace of the input file is significant, this method
\ will fail.

s" my-trusted-file" included
.s

\ ======================
\ Read numbers from file
\ ======================
256 Constant max-bytes-line
Create line-buffer max-bytes-line 2 + allot
s" input" r/o open-file throw Value puzzle-input-handle

: add-nums-from-file ( c-addr length -- ??? )
  begin
    \ Read the next line from the puzzle input.
    line-buffer max-bytes-line puzzle-input-handle read-line throw
    \ stack: length eof-flag
    swap
    \ stack: eof-flag length
    \ Check if more than 0 characters were read as a number.
    dup 0 >
    \ stack: eof-flag length more-than-0-chars-flag
    rot
    \ stack: length more-than-0-chars-flag eof-flag
    \ Check that both true.
    and
    \ stack: length flag
  while
    \ stack: length
    \ Put a float at the bottom for >number which requires a
    \ double to be at specific position.
    0.
    \ stack: length 0. 0
    rot
    \ stack: 0. 0 length
    line-buffer swap
    \ stack: 0. 0 length c-addr
    >number
    2swap
    \ convert double to one integer number (?)
    d>s
    \ Use the numbers here. For now only dropping them.
    . drop drop
  repeat ;

puzzle-input-handle close-file