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//! Native-shell ownership of `New`'s one filesystem operation.
//!
//! The core asks for a temporary file by effect and receives only its path.
//! `mkstemp` creates and opens the name atomically with mode 0600, so there is
//! no name-then-open race and repeated requests cannot collide. A file the
//! core declines is unlinked here immediately; an adopted file becomes an
//! ordinary Pardes document and is deliberately left on disk when its pane is
//! closed, just like every other document (and so a dump remains restorable).
const std = @import("std");
const libc = std.c;
extern "c" fn mkstemp(template: [*:0]u8) c_int;
extern "c" fn lseek(fd: c_int, offset: libc.off_t, whence: c_int) libc.off_t;
pub const Created = struct {
fd: c_int,
path: [:0]u8,
/// The core copied the path and now owns the document. Close our creation
/// handle; Save and watching reopen/use the pathname through their normal
/// seams.
pub fn adopt(f: Created) void {
_ = libc.close(f.fd);
}
/// Creation succeeded but the request became stale or the core could not
/// allocate a pane. Nothing user-visible owns this name, so remove it.
pub fn discard(f: Created) void {
_ = libc.close(f.fd);
_ = libc.unlink(f.path);
}
};
/// Create in the platform's conventional temporary directory. TMPDIR is a
/// shell concern (environment + filesystem), intentionally outside the core.
pub fn create(buf: *[4096:0]u8) ?Created {
const env = libc.getenv("TMPDIR");
const dir = if (env) |p| std.mem.span(p) else "/tmp";
return createIn(buf, if (dir.len > 0) dir else "/tmp");
}
/// Split out for a hermetic failure test and to keep template construction
/// independently checkable. The six Xs are consumed by mkstemp itself.
pub fn createIn(buf: *[4096:0]u8, dir_arg: []const u8) ?Created {
const dir = std.mem.trimEnd(u8, dir_arg, "/");
const path = std.fmt.bufPrintSentinel(
buf,
"{s}{s}pardes-XXXXXX",
.{ if (dir.len == 0) "/" else dir, if (dir.len == 0) "" else "/" },
0,
) catch return null;
const fd = mkstemp(path.ptr);
if (fd < 0) return null;
return .{ .fd = fd, .path = path };
}
test "mkstemp creates distinct empty files and rejected files are removable" {
var abuf: [4096:0]u8 = undefined;
var bbuf: [4096:0]u8 = undefined;
const a = createIn(&abuf, "/tmp") orelse return error.TempCreateFailed;
const b = createIn(&bbuf, "/tmp") orelse return error.TempCreateFailed;
defer b.discard();
try std.testing.expect(!std.mem.eql(u8, a.path, b.path));
try std.testing.expectEqual(@as(libc.off_t, 0), lseek(a.fd, 0, 2)); // SEEK_END
try std.testing.expectEqual(@as(libc.off_t, 0), lseek(b.fd, 0, 2));
a.discard();
try std.testing.expect(libc.unlink(a.path) < 0); // already removed
}
test "an adopted tempfile remains named for the document" {
var buf: [4096:0]u8 = undefined;
const made = createIn(&buf, "/tmp") orelse return error.TempCreateFailed;
made.adopt();
// Adoption closes only the creation handle. The ordinary file document
// keeps this path for Save, watch, Del and dump/restore.
try std.testing.expectEqual(@as(c_int, 0), libc.unlink(made.path));
}
test "mkstemp failure creates no candidate file" {
var buf: [4096:0]u8 = undefined;
try std.testing.expect(createIn(&buf, "/definitely/not/a/pardes/temp/directory") == null);
}
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