Using File I/O Functions

What are File I/O Functions?

File I/O functions are any of the standard fopen, fgets, fread, and related file functions. These functions are meant to perform OS-level file access for reading and writing. However, the CE doesn’t expose any standard UNIX or similar file capabilities.

To mitigate this, the CE Toolchain includes these functions as wrappers around the fileioc library. This allows AppVars to act as file storage for read and write operations.

For stdin, stdout, and stderr file streams, the default implementation uses the getchar and putchar functions respectively.

Using Custom File I/O

If you do not wish to have the file I/O functions backed by the fileioc library, you can instead redefine the functions that you need in any source file. The new functions will override the default implementation.

Additionally, the makefile needs to be updated accordingly. Add the below lines to the makefile to enable the custom file operations:

CUSTOM_FILE_FILE := stdio_file.h

The option CUSTOM_FILE_FILE should be set to the name of the file which redefines the FILE structure used by the standard file I/O functions. Additionally, it should redefine stdin, stdout, and stderr, however if your program doesn’t require these this isn’t necessary.

An example stdio_file.h might look like this:

#ifndef STDIO_FILE_H
#define STDIO_FILE_H

typedef struct
    unsigned char slot;
    unsigned char eof;
    unsigned char err;
#define FOPEN_MAX  5
#define stdin      ((FILE*)1)
#define stdout     ((FILE*)2)
#define stderr     ((FILE*)3)


Be sure to clean the project via make clean if the implementation changes from the default and project files need to be rebuilt to use the updates.