165 lines
3.4 KiB
Forth
165 lines
3.4 KiB
Forth
# File I/O
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The file device (device type 4) adds support for generic file I/O
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that is similar to the C standard library on Unix. On a Unix host
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these are very thin wrappers over fopen(), fclose(), etc. For non
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Unix hosts, implementing these may take much more work, and it may
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be preferable to design a file I/O device that models the host
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expectations.
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~~~
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:file:operation
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#4 io:scan-for
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dup n:negative? [ drop 'Error:_device_(0004)_not_found s:put nl ] if;
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io:invoke ;
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~~~
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First up, constants for the file modes.
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| # | Used For |
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| -- | ---------------------------- |
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| R | Mode for READING |
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| W | Mode for WRITING |
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| A | Mode for APPENDING |
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| R+ | Mode for READING and WRITING |
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~~~
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#0 'file:R const
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#1 'file:W const
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#2 'file:A const
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#3 'file:R+ const
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~~~
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For opening a file, provide the file name and mode. This will return
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a number identifying the file handle.
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~~~
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:file:open (sm-h) #0 file:operation ;
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~~~
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Given a file handle, close the file.
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~~~
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:file:close (h-) #1 file:operation ;
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~~~
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Given a file handle, read a character.
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~~~
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:file:read (h-c) #2 file:operation ;
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~~~
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Write a character to an open file.
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~~~
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:file:write (ch-) #3 file:operation ;
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~~~
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Return the current pointer within a file.
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~~~
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:file:tell (h-n) #4 file:operation ;
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~~~
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Move the file pointer to the specified location.
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~~~
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:file:seek (nh-) #5 file:operation ;
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~~~
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Return the size of the opened file.
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~~~
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:file:size (h-n) #6 file:operation ;
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~~~
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Given a file name, delete the file.
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~~~
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:file:delete (s-) #7 file:operation ;
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~~~
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Flush pending writes to disk.
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~~~
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:file:flush (f-) #8 file:operation ;
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~~~
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Given a file name, return `TRUE` if it exists or `FALSE` otherwise.
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~~~
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:file:exists? (s-f)
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file:R file:open dup n:-zero?
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[ file:close TRUE ]
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[ drop FALSE ] choose ;
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~~~
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~~~
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:file:open-for-reading (s-nn)
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file:R file:open dup file:size swap ;
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:file:open-for-append (s-nn)
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file:A file:open dup file:size swap ;
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:file:open-for-writing (s-n)
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file:W file:open ;
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~~~
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With that out of the way, we can begin building higher level functionality.
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The first of these reads a line from the file. This is read to `here`; move
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it somewhere safe if you need to keep it around.
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The second goes with it. The `for-each-line` word will invoke a combinator
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once for each line in a file. This makes some things trivial. E.g., a simple
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'cat' implementation could be as simple as:
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'filename [ s:put nl ] file:for-each-line
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~~~
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{{
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'FID var
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'Size var
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'Action var
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'Buffer var
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:-eof? (-f) @FID file:tell @Size lt? ;
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:preserve (q-) &FID [ &Size &call v:preserve ] v:preserve ;
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---reveal---
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:file:read-line (f-s)
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!FID
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[ here dup !Buffer buffer:set
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[ @FID file:read dup buffer:add
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[ ASCII:CR eq? ] [ ASCII:LF eq? ] [ ASCII:NUL eq? ] tri or or ] until
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buffer:get drop ] buffer:preserve
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@Buffer ;
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:file:for-each-line (sq-)
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[ !Action
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file:open-for-reading !FID !Size
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[ @FID file:read-line @Action call -eof? ] while
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@FID file:close
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] preserve ;
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}}
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~~~
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`file:slurp` reads a file into a buffer.
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~~~
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{{
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'FID var
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---reveal---
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:file:slurp (as-)
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[ swap buffer:set file:open-for-reading !FID
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[ @FID file:read buffer:add ] times
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@FID file:close
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] buffer:preserve ;
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}}
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~~~
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`file:spew` writes a string to a file.
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~~~
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:file:spew (ss-)
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file:open-for-writing swap [ over file:write ] s:for-each file:close ;
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~~~
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