fs — file I/O

Source: std/fs.mw. Imports string.mw and io.mw.

A thin, buffered-I/O wrapper around the C <stdio.h> file API (fopen/fclose/fseek/ftell/fread/fwrite). File handles are plain rawptr values (the underlying FILE*) — there’s no dedicated File struct.

Foreign bindings

Function	Binds to (C)
c_fopen(path: *u8, mode: *u8) -> rawptr	fopen
c_fclose(stream: rawptr) -> i32	fclose
c_fseek(stream: rawptr, offset: i64, whence: i32) -> i32	fseek
c_ftell(stream: rawptr) -> i64	ftell
c_fread(ptr: rawptr, size: i64, nmemb: i64, stream: rawptr) -> i64	fread
c_fwrite(ptr: rawptr, size: i64, nmemb: i64, stream: rawptr) -> i64	fwrite

Functions

file_open_read(path: *u8) -> rawptr

Opens path for binary reading (fopen(path, "rb")). Returns a null pointer on failure (file doesn’t exist, permissions, etc.).

file_open_write(path: *u8) -> rawptr

Opens (creating or truncating) path for binary writing (fopen(path, "wb")).

file_close(handle: rawptr)

Closes a handle previously returned by file_open_read/file_open_write. Safe to call with a null handle (it’s a no-op).

file_get_size(handle: rawptr) -> i64

Returns the total size in bytes of an open file, by seeking to the end (SEEK_END), reading the position (ftell), then seeking back to the start (SEEK_SET). Returns 0 for a null handle.

read_to_string(path: *u8) -> *String

Opens path, reads its entire contents into a freshly-allocated String (see the string module), closes the file, and returns it. On any failure (file doesn’t open, allocation fails) it prints a diagnostic to stderr (prefixed [ERREUR FS], French for “FS ERROR”) and returns a null pointer — always check the result before using it. The resulting String is null-terminated, so its .data field can also be passed anywhere a *u8 C-string is expected.

write_string_to_file(path: *u8, content: *String) -> i32

Opens (or creates/truncates) path for writing and writes the full contents of a String to it. Returns 1 on success, 0 if content is null or the file couldn’t be opened (in which case it also prints a diagnostic to stderr). An empty string (len == 0) is treated as success without performing an actual write.

Example

@import("fs.mw")

fn copy_file(src: *u8, dst: *u8) -> i32 {
    var content: *String = read_to_string(src);
    if (content == 0) {
        ret 0;
    }

    var ok: i32 = write_string_to_file(dst, content);
    string_free(content);
    ret ok;
}