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std.fs: Split Iterator.next on Linux and WASI to allow for handling platform-specific errors

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Follow up to #12226, implements the compromise detailed in https://github.com/ziglang/zig/issues/12211#issuecomment-1196011590
This commit is contained in:
Ryan Liptak 2022-07-30 23:41:24 -07:00 committed by Veikka Tuominen
parent ff125db53d
commit e7b6a18331
2 changed files with 34 additions and 2 deletions
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31
lib/std/fs.zig
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@ -595,6 +595,19 @@ pub const IterableDir = struct {
/// Memory such as file names referenced in this returned entry becomes invalid
/// with subsequent calls to `next`, as well as when this `Dir` is deinitialized.
pub fn next(self: *Self) Error!?Entry {
return self.nextLinux() catch |err| switch (err) {
// To be consistent across platforms, iteration ends if the directory being iterated is deleted during iteration.
// This matches the behavior of non-Linux UNIX platforms.
error.DirNotFound => null,
else => |e| return e,
};
}
pub const ErrorLinux = error{DirNotFound} || IteratorError;
/// Implementation of `next` that can return `error.DirNotFound` if the directory being
/// iterated was deleted during iteration (this error is Linux specific).
pub fn nextLinux(self: *Self) ErrorLinux!?Entry {
start_over: while (true) {
if (self.index >= self.end_index) {
if (self.first_iter) {
@ -607,7 +620,7 @@ pub const IterableDir = struct {
.BADF => unreachable, // Dir is invalid or was opened without iteration ability
.FAULT => unreachable,
.NOTDIR => unreachable,
.NOENT => return null, // The directory being iterated was deleted during iteration.
.NOENT => return error.DirNotFound, // The directory being iterated was deleted during iteration.
.INVAL => return error.Unexpected, // Linux may in some cases return EINVAL when reading /proc/$PID/net.
else => |err| return os.unexpectedErrno(err),
}
@ -729,6 +742,20 @@ pub const IterableDir = struct {
/// Memory such as file names referenced in this returned entry becomes invalid
/// with subsequent calls to `next`, as well as when this `Dir` is deinitialized.
pub fn next(self: *Self) Error!?Entry {
return self.nextWasi() catch |err| switch (err) {
// To be consistent across platforms, iteration ends if the directory being iterated is deleted during iteration.
// This matches the behavior of non-Linux UNIX platforms.
error.DirNotFound => null,
else => |e| return e,
};
}
pub const ErrorWasi = error{DirNotFound} || IteratorError;
/// Implementation of `next` that can return platform-dependent errors depending on the host platform.
/// When the host platform is Linux, `error.DirNotFound` can be returned if the directory being
/// iterated was deleted during iteration.
pub fn nextWasi(self: *Self) ErrorWasi!?Entry {
// We intentinally use fd_readdir even when linked with libc,
// since its implementation is exactly the same as below,
// and we avoid the code complexity here.
@ -742,7 +769,7 @@ pub const IterableDir = struct {
.FAULT => unreachable,
.NOTDIR => unreachable,
.INVAL => unreachable,
.NOENT => return null, // The directory being iterated was deleted during iteration.
.NOENT => return error.DirNotFound, // The directory being iterated was deleted during iteration.
.NOTCAPABLE => return error.AccessDenied,
else => |err| return os.unexpectedErrno(err),
}

5
lib/std/fs/test.zig
View File

@ -241,6 +241,11 @@ test "Dir.Iterator but dir is deleted during iteration" {
// Now, when we try to iterate, the next call should return null immediately.
const entry = try iterator.next();
try std.testing.expect(entry == null);
// On Linux, we can opt-in to receiving a more specific error by calling `nextLinux`
if (builtin.os.tag == .linux) {
try std.testing.expectError(error.DirNotFound, iterator.nextLinux());
}
}
fn entryEql(lhs: IterableDir.Entry, rhs: IterableDir.Entry) bool {