sx/library/modules/fs.sx

#import "std.sx";

// =====================================================================
// fs.sx — file system stdlib (POSIX backend, macOS values).
//
// Allocation contract: every returned `string` or slice is allocated
// from `context.allocator`. Callers are responsible for releasing it
// (typically via an arena reset).
//
// Handle ownership: `File` is a small value-typed handle wrapping the
// POSIX file descriptor. Methods are provided for read/write/close;
// the value is invalid (fd == -1) after `close()`.
//
// Scope (Phase 1A): file I/O + directory creation/deletion + path
// helpers needed for `.app` bundling. Recursive walkers, `stat`, and
// the full path module land in subsequent phases.
// =====================================================================

libc :: #library "c";

// ── Low-level libc bindings ─────────────────────────────────────────
// These declare the actual libc symbols and must use the libc names
// verbatim (no prefix), so they live at module top-level. The public
// API below wraps them. Users should not call these directly.
//
// macOS `open` is variadic in C (`int open(const char*, int, ...)`);
// declared with `..args: []s32` so the mode is passed via the C
// variadic tail. Without that, the mode arg goes to the wrong
// register on arm64 and the file ends up with mode 0.

open   :: (path: [:0]u8, flags: s32, ..args: []s32) -> s32 #foreign libc;
close  :: (fd: s32) -> s32 #foreign libc;
read   :: (fd: s32, buf: [*]u8, count: usize) -> isize #foreign libc;
write  :: (fd: s32, buf: [*]u8, count: usize) -> isize #foreign libc;
lseek  :: (fd: s32, offset: s64, whence: s32) -> s64 #foreign libc;
unlink :: (path: [:0]u8) -> s32 #foreign libc;
rmdir  :: (path: [:0]u8) -> s32 #foreign libc;
mkdir  :: (path: [:0]u8, mode: u32) -> s32 #foreign libc;
access :: (path: [:0]u8, mode: s32) -> s32 #foreign libc;
chmod  :: (path: [:0]u8, mode: u32) -> s32 #foreign libc;
rename :: (oldp: [:0]u8, newp: [:0]u8) -> s32 #foreign libc;

// macOS POSIX constants. Linux values differ; split into platform-
// conditional includes when we gain a Linux host.
O_RDONLY :s32: 0x0000;
O_WRONLY :s32: 0x0001;
O_RDWR   :s32: 0x0002;
O_APPEND :s32: 0x0008;
O_CREAT  :s32: 0x0200;
O_TRUNC  :s32: 0x0400;

SEEK_SET :s32: 0;
SEEK_CUR :s32: 1;
SEEK_END :s32: 2;

F_OK :s32: 0;

// ── Public types ─────────────────────────────────────────────────────

OpenMode :: enum {
    read;        // O_RDONLY
    write;       // O_WRONLY | O_CREAT | O_TRUNC
    append;      // O_WRONLY | O_CREAT | O_APPEND
    read_write;  // O_RDWR
}

SeekFrom :: enum { set; current; end; }

File :: struct {
    fd: s32 = -1;

    is_valid :: (self: *File) -> bool { self.fd >= 0 }

    close :: (self: *File) -> bool {
        if self.fd < 0 { return false; }
        rc := close(self.fd);
        self.fd = -1;
        rc == 0
    }

    read :: (self: *File, buf: string) -> s64 {
        if self.fd < 0 { return -1; }
        n := read(self.fd, buf.ptr, xx buf.len);
        cast(s64) n
    }

    write :: (self: *File, data: string) -> s64 {
        if self.fd < 0 { return -1; }
        n := write(self.fd, data.ptr, xx data.len);
        cast(s64) n
    }

    seek :: (self: *File, offset: s64, whence: SeekFrom) -> s64 {
        if self.fd < 0 { return -1; }
        w := SEEK_SET;
        if whence == .current { w = SEEK_CUR; }
        if whence == .end     { w = SEEK_END; }
        lseek(self.fd, offset, w)
    }
}

// ── High-level file API ─────────────────────────────────────────────
// Named `open_file` (not `open`) so they don't shadow libc's `open`
// symbol; the latter is needed for `#foreign libc` to resolve. Same
// idea for `delete_file`/`delete_dir` vs libc's `unlink`/`rmdir`,
// `set_mode` vs libc's `chmod`, etc.

mode_to_flags :: (m: OpenMode) -> s32 {
    if m == .read       { return O_RDONLY; }
    if m == .write      { return O_WRONLY | O_CREAT | O_TRUNC; }
    if m == .append     { return O_WRONLY | O_CREAT | O_APPEND; }
    if m == .read_write { return O_RDWR; }
    O_RDONLY
}

open_file :: (path: [:0]u8, mode: OpenMode) -> ?File {
    fd := open(path, mode_to_flags(mode), 420); // 0o644 = 420
    if fd < 0 { return null; }
    File.{ fd = fd }
}

// One-shot read: opens, slurps the whole file into a fresh buffer,
// closes. Returns null on any failure. Uses libc directly (not File
// methods) so it remains callable from the post-link IR interpreter,
// which doesn't yet handle `*Self` method dispatch on locally-
// unwrapped optionals.
read_file :: (path: [:0]u8) -> ?string {
    fd := open(path, O_RDONLY, 0);
    if fd < 0 { return null; }
    size := lseek(fd, 0, SEEK_END);
    if size < 0 { close(fd); return null; }
    lseek(fd, 0, SEEK_SET);
    buf := cstring(size);
    n := read(fd, buf.ptr, xx size);
    close(fd);
    if cast(s64) n != size { return null; }
    buf
}

// One-shot write: creates / truncates and writes the whole buffer.
write_file :: (path: [:0]u8, data: string) -> bool {
    fd := open(path, O_WRONLY | O_CREAT | O_TRUNC, 420); // 0o644
    if fd < 0 { return false; }
    n := write(fd, data.ptr, xx data.len);
    close(fd);
    cast(s64) n == cast(s64) data.len
}

append_file :: (path: [:0]u8, data: string) -> bool {
    fd := open(path, O_WRONLY | O_CREAT | O_APPEND, 420);
    if fd < 0 { return false; }
    n := write(fd, data.ptr, xx data.len);
    close(fd);
    cast(s64) n == cast(s64) data.len
}

// ── Single-syscall ops ───────────────────────────────────────────────

exists :: (path: [:0]u8) -> bool {
    access(path, F_OK) == 0
}

delete_file :: (path: [:0]u8) -> bool {
    unlink(path) == 0
}

delete_dir :: (path: [:0]u8) -> bool {
    rmdir(path) == 0
}

create_dir :: (path: [:0]u8) -> bool {
    mkdir(path, 493) == 0 // 0o755 = 493
}

set_mode :: (path: [:0]u8, mode: u32) -> bool {
    chmod(path, mode) == 0
}

move :: (oldp: [:0]u8, newp: [:0]u8) -> bool {
    rename(oldp, newp) == 0
}

// Recursive mkdir -p. Walks the path and creates each missing
// segment. Treats existing directories as success.
create_dir_all :: (path: [:0]u8) -> bool {
    if path.len == 0 { return true; }
    if exists(path) { return true; }
    last := path.len - 1;
    while last > 0 {
        if path[last] == 47 { break; }
        last -= 1;
    }
    if last > 0 {
        parent := cstring(last);
        memcpy(parent.ptr, path.ptr, last);
        if !create_dir_all(parent) { return false; }
    }
    create_dir(path)
}

// Copy a file by streaming through a 64KB buffer. Uses libc directly
// (not File methods) — same interpreter-compat reason as read_file.
// No metadata is preserved beyond what `open` creates (mode 0644).
// Caller is responsible for setting executable bits with `set_mode`.
copy_file :: (src: [:0]u8, dst: [:0]u8) -> bool {
    src_fd := open(src, O_RDONLY, 0);
    if src_fd < 0 { return false; }
    dst_fd := open(dst, O_WRONLY | O_CREAT | O_TRUNC, 420);
    if dst_fd < 0 {
        close(src_fd);
        return false;
    }
    ok := true;
    buf := cstring(65536);
    loop := true;
    while loop {
        n := read(src_fd, buf.ptr, 65536);
        if n < 0 { ok = false; loop = false; }
        if n == 0 { loop = false; }
        if n > 0 {
            w := write(dst_fd, buf.ptr, xx n);
            if w != cast(isize) n { ok = false; loop = false; }
        }
    }
    close(src_fd);
    close(dst_fd);
    ok
}

// ── Path helpers ─────────────────────────────────────────────────────
// `path_join` is in std.sx (used widely beyond fs). These are the
// fs-adjacent helpers — basename/dirname operate purely on text.

basename :: (p: string) -> string {
    if p.len == 0 { return ""; }
    last := p.len - 1;
    while last > 0 {
        if p[last] != 47 { break; }
        last -= 1;
    }
    end := last + 1;
    while last > 0 {
        if p[last - 1] == 47 { return substr(p, last, end - last); }
        last -= 1;
    }
    substr(p, 0, end)
}

dirname :: (p: string) -> string {
    if p.len == 0 { return ""; }
    last := p.len - 1;
    while last > 0 {
        if p[last] != 47 { break; }
        last -= 1;
    }
    while last > 0 {
        if p[last] == 47 {
            while last > 0 {
                if p[last - 1] != 47 { break; }
                last -= 1;
            }
            return substr(p, 0, last);
        }
        last -= 1;
    }
    if p[0] == 47 { return "/"; }
    "."
}