Amiga DOS library includes some simple file i/o functions to open, read,write and close files. The following functions are commonly used:
BPTR Open( CONST_STRPTR name, LONG accessMode ); /* Open a file for read
or write */
LONG Close( BPTR file ); /* Close a file */
LONG Read( BPTR file, APTR buffer, LONG length ); /* Read n bytes into a buffer
(unbuffered) */
LONG Write( BPTR file, CONST APTR buffer, LONG length ); /* Write n bytes into
a buffer (unbuffered) */
LONG Seek( BPTR file, LONG position, LONG offset ); /* Seek to a n bytes from
current, beginning or end of file */
LONG FGetC( BPTR fh ); /* Get a character from file */
LONG FPutC( BPTR fh, LONG ch ); /* Write a character to file */
LONG UnGetC( BPTR fh, LONG character ); /* Return a character to buffer */
LONG FRead( BPTR fh, APTR block, ULONG blocklen, ULONG number ); /* Read a number
of blocks from file (buffered) */
LONG FWrite( BPTR fh, CONST APTR block, ULONG blocklen, ULONG number ); /* Write
a number of blocks to a file (buffered) */
STRPTR FGets( BPTR fh, STRPTR buf, ULONG buflen ); /* Gets a string from a file
*/
LONG FPuts( BPTR fh, CONST_STRPTR str ); /* Writes a string to a file */
VOID VFWritef( BPTR fh, CONST_STRPTR format, CONST LONG *argarray ); /* Write
a BCPL formatted string to a file */
LONG VFPrintf( BPTR fh, CONST_STRPTR format, CONST APTR argarray ); /* Format
and print a string to a file */
LONG Flush( BPTR fh ); /* Flush buffers to file */
LONG SetVBuf( BPTR fh, STRPTR buff, LONG type, LONG size ); /*Set buffering
modes and size */
Amiga DOS supports buffered and unbuffered file I/O. Buffered file I/O is more efficient than unbuffered i/o for small files. FPuts and FGets would be ideal for getting lines of text from a text file with line feed or null terminated strings. FGetC and FPutC would be ideal for reading binary files. To detect End of File, most functions will return -1 (EOF), 0 or NULL values depending on the return value of the function, there is no EOF type function as in ANSI C. When opening a file, you need to specify the accessMode which can be MODE_OLDFILE (read an existing file), MODE_NEWFILE (create a new file for writing) or MODE_READWRITE (for read/writing to an existing file), the Open command returns a file handle of BPTR type which is used in most I/O functions.
The following example, will write out 20 numbers to a file, and read them back in and print them to the console.
/* File Example
using DOS.library
by PHutchison
3/1/05
*/
#include <proto/dos.h>
#include <stdio.h>
#include <stdlib.h>
/* Write some numbers to a file */
void WriteNumbers(void) {
BPTR fh;
int n;
UBYTE numstr[5];
printf("Writing numbers to numbers.dat\n\n");
/* Open file for writing */
fh = Open("numbers.dat", MODE_NEWFILE);
if (fh) {
for (n=1; n<=20; n++) {
/* Convert number to a string with new line
& write string
to file */
sprintf(numstr, "%d\n", n);
FPuts(fh, numstr);
}
Close(fh);
}
}
/* Read numbers from a file */
void ReadNumbers(void) {
BPTR fh;
int i;
UBYTE numstr[5];
UBYTE *buffer;
printf("Reading file numbers.dat.\n");
/* Open existing file for reading */
fh = Open("numbers.dat", MODE_OLDFILE);
if (fh) {
/* Read a string and check for End of File */
while (buffer = FGets(fh, numstr, 5L)) {
/* Convert string to number
and print it */
i = atoi(numstr);
printf("Number %d\n",
i);
}
Close(fh);
}
printf("EOF found\n");
}
int main(void)
{
WriteNumbers();
ReadNumbers();
return 0;
}