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C02/doc/file.txt
2018-01-28 14:00:23 -05:00

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File System Input/Output Functions for C02 Programs
This library contains functions for file handling. These functions
are included here instead of in stdio.h because not all 6502 systems
support file based input/output. Functions that are not part of the
standard C libraries begin with the letters "fs".
At the beginning of the program use the directives
#include <stdio.h02>
#include <file.h02>
The following functions are defined:
fsinit(); Initialize file system.
This function should be called before calling
before any other file functions.
Note: Closes any open files and initializes
the library's internal file table.
f = fsptr(); Find an available file pointer.
Returns 0 if no more file pointers are available.
Note: This is called by the fopen() function, which
does the actual file allocation and is of limited
use in application programming.
r = fschk(f); Check to see if f is a valid file pointer.
Returns 0 if valid, otherwise 255.
Note: Called by the fclose(), feof(), fgetc(),
fgets(), fputc(), fputs(), fread(), and fwrite()
functions.
r = fstat(f); Get status of file table entry or last file error.
If f is 0, returns a system dependent value
corresponding to the last filesystem I/O error.
If f is a potentially valid file pointer. returns a
value representing the state of the corresponding
entry in the file table. If the file table entry is
unused, then a 0 is returned. Otherwise, a system
dependent system dependent value is returned.
If f does not point to a valid file table entry,
then 255 is returned.
Note: On CBM machines, fstat(0) returns the result
of READST directly after the last error. Valid file
pointer values are between 1 and FOMAX, inclusive
and return a value with bits 0 through 3 containing
the Kernal device number, and bit 7 set if an End of
File or other error was encountered.
f = fopen(d, &n); Open file specified from null-terminated string n
on device d, returning a pointer to the file.
Return 0 if the file could not be opened.
Note: On CBM machines, d is the device number and
f is a logical file nunber as used in a Basic Open
statement. Up to 7 files may be opened at a time.
r = fclose(f); Close file pointed to by f, returning 0 if
successful or 255 if there was an error.
Note: Returns 255 if f is not a valid file pointer.
c = fgetc(f); Read character from file opened to by filepointer f.
Returns character read from file.
Note: Returns 255 if f is not a valid file pointer.
Returns a system dependent garbage character if end
of file has been reached or any other I/O error. Use
feof(f) and fstat(0) to check for these conditions.
fputc(f, c); Write character c to file opened to filepointer f.
Use feof(f) and fstat(0) to check for errors after
write.
-----------------------------------------------------------------
r = getstr(&s); Reads a maximum of 128 characters from keyboard
until the Return/Enter key is pressed, storing the
entered characters as null-terminated string s.
Allows corrections using Backspace/Delete.
Pressing the Escape/Abort key terminates entry,
leaving the string in an undefined state.
Returns number of characters entered, or 255
if entry was aborted.
Note: Calls getchr() in a loop and uses constants
DELKEY, RTNKEY, and ESCKEY from the system library.
r = putstr(&s): Writes up to 128 characters of null-terminated
string s to the screen and advances the cursor to
the beginning of the next line.
Returns number of characters printed.
Note: Calls outstr(&s) followed by newlin().
Note: This library expects the following functions to be defined:
setdst(&s); Set destination string pointer
setsrc(&s); Set source string pointer and initialize index
along with the zero page variable pairs
dstlo,dsthi: Destination string pointer
srclo,srchi: Source string pointer
the static array
ftbl[FOMAX]
and the assembler constant
FOMAX The maximum number of files that can be opened
at one time.
as well as the data structure
FTBL A system dependent table of bytes containing data
related to files opened by the fopen() function.
See function fstat() for more information.