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std.Io: delete the poll API

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Andrew Kelley 2026-01-05 22:19:08 -08:00
parent 90890fcb5c
commit bd4b6d8b14
1 changed files with 8 additions and 458 deletions
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466
lib/std/Io.zig
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@ -15,463 +15,13 @@
const Io = @This();
const builtin = @import("builtin");
const is_windows = builtin.os.tag == .windows;
const std = @import("std.zig");
const windows = std.os.windows;
const posix = std.posix;
const math = std.math;
const assert = std.debug.assert;
const Allocator = std.mem.Allocator;
const Alignment = std.mem.Alignment;
pub fn poll(
gpa: Allocator,
comptime StreamEnum: type,
files: PollFiles(StreamEnum),
) Poller(StreamEnum) {
const enum_fields = @typeInfo(StreamEnum).@"enum".fields;
var result: Poller(StreamEnum) = .{
.gpa = gpa,
.readers = @splat(.failing),
.poll_fds = undefined,
.windows = if (is_windows) .{
.first_read_done = false,
.overlapped = [1]windows.OVERLAPPED{
std.mem.zeroes(windows.OVERLAPPED),
} ** enum_fields.len,
.small_bufs = undefined,
.active = .{
.count = 0,
.handles_buf = undefined,
.stream_map = undefined,
},
} else {},
};
inline for (enum_fields, 0..) |field, i| {
if (is_windows) {
result.windows.active.handles_buf[i] = @field(files, field.name).handle;
} else {
result.poll_fds[i] = .{
.fd = @field(files, field.name).handle,
.events = posix.POLL.IN,
.revents = undefined,
};
}
}
return result;
}
pub fn Poller(comptime StreamEnum: type) type {
return struct {
const enum_fields = @typeInfo(StreamEnum).@"enum".fields;
const PollFd = if (is_windows) void else posix.pollfd;
gpa: Allocator,
readers: [enum_fields.len]Reader,
poll_fds: [enum_fields.len]PollFd,
windows: if (is_windows) struct {
first_read_done: bool,
overlapped: [enum_fields.len]windows.OVERLAPPED,
small_bufs: [enum_fields.len][128]u8,
active: struct {
count: math.IntFittingRange(0, enum_fields.len),
handles_buf: [enum_fields.len]windows.HANDLE,
stream_map: [enum_fields.len]StreamEnum,
pub fn removeAt(self: *@This(), index: u32) void {
assert(index < self.count);
for (index + 1..self.count) |i| {
self.handles_buf[i - 1] = self.handles_buf[i];
self.stream_map[i - 1] = self.stream_map[i];
}
self.count -= 1;
}
},
} else void,
const Self = @This();
pub fn deinit(self: *Self) void {
const gpa = self.gpa;
if (is_windows) {
// cancel any pending IO to prevent clobbering OVERLAPPED value
for (self.windows.active.handles_buf[0..self.windows.active.count]) |h| {
_ = windows.kernel32.CancelIo(h);
}
}
inline for (&self.readers) |*r| gpa.free(r.buffer);
self.* = undefined;
}
pub fn poll(self: *Self) !bool {
if (is_windows) {
return pollWindows(self, null);
} else {
return pollPosix(self, null);
}
}
pub fn pollTimeout(self: *Self, nanoseconds: u64) !bool {
if (is_windows) {
return pollWindows(self, nanoseconds);
} else {
return pollPosix(self, nanoseconds);
}
}
pub fn reader(self: *Self, which: StreamEnum) *Reader {
return &self.readers[@intFromEnum(which)];
}
pub fn toOwnedSlice(self: *Self, which: StreamEnum) error{OutOfMemory}![]u8 {
const gpa = self.gpa;
const r = reader(self, which);
if (r.seek == 0) {
const new = try gpa.realloc(r.buffer, r.end);
r.buffer = &.{};
r.end = 0;
return new;
}
const new = try gpa.dupe(u8, r.buffered());
gpa.free(r.buffer);
r.buffer = &.{};
r.seek = 0;
r.end = 0;
return new;
}
fn pollWindows(self: *Self, nanoseconds: ?u64) !bool {
const bump_amt = 512;
const gpa = self.gpa;
if (!self.windows.first_read_done) {
var already_read_data = false;
for (0..enum_fields.len) |i| {
const handle = self.windows.active.handles_buf[i];
switch (try windowsAsyncReadToFifoAndQueueSmallRead(
gpa,
handle,
&self.windows.overlapped[i],
&self.readers[i],
&self.windows.small_bufs[i],
bump_amt,
)) {
.populated, .empty => |state| {
if (state == .populated) already_read_data = true;
self.windows.active.handles_buf[self.windows.active.count] = handle;
self.windows.active.stream_map[self.windows.active.count] = @as(StreamEnum, @enumFromInt(i));
self.windows.active.count += 1;
},
.closed => {}, // don't add to the wait_objects list
.closed_populated => {
// don't add to the wait_objects list, but we did already get data
already_read_data = true;
},
}
}
self.windows.first_read_done = true;
if (already_read_data) return true;
}
while (true) {
if (self.windows.active.count == 0) return false;
const status = windows.kernel32.WaitForMultipleObjects(
self.windows.active.count,
&self.windows.active.handles_buf,
0,
if (nanoseconds) |ns|
@min(std.math.cast(u32, ns / std.time.ns_per_ms) orelse (windows.INFINITE - 1), windows.INFINITE - 1)
else
windows.INFINITE,
);
if (status == windows.WAIT_FAILED)
return windows.unexpectedError(windows.GetLastError());
if (status == windows.WAIT_TIMEOUT)
return true;
if (status < windows.WAIT_OBJECT_0 or status > windows.WAIT_OBJECT_0 + enum_fields.len - 1)
unreachable;
const active_idx = status - windows.WAIT_OBJECT_0;
const stream_idx = @intFromEnum(self.windows.active.stream_map[active_idx]);
const handle = self.windows.active.handles_buf[active_idx];
const overlapped = &self.windows.overlapped[stream_idx];
const stream_reader = &self.readers[stream_idx];
const small_buf = &self.windows.small_bufs[stream_idx];
const num_bytes_read = switch (try windowsGetReadResult(handle, overlapped, false)) {
.success => |n| n,
.closed => {
self.windows.active.removeAt(active_idx);
continue;
},
.aborted => unreachable,
};
const buf = small_buf[0..num_bytes_read];
const dest = try writableSliceGreedyAlloc(stream_reader, gpa, buf.len);
@memcpy(dest[0..buf.len], buf);
advanceBufferEnd(stream_reader, buf.len);
switch (try windowsAsyncReadToFifoAndQueueSmallRead(
gpa,
handle,
overlapped,
stream_reader,
small_buf,
bump_amt,
)) {
.empty => {}, // irrelevant, we already got data from the small buffer
.populated => {},
.closed,
.closed_populated, // identical, since we already got data from the small buffer
=> self.windows.active.removeAt(active_idx),
}
return true;
}
}
fn pollPosix(self: *Self, nanoseconds: ?u64) !bool {
const gpa = self.gpa;
// We ask for ensureUnusedCapacity with this much extra space. This
// has more of an effect on small reads because once the reads
// start to get larger the amount of space an ArrayList will
// allocate grows exponentially.
const bump_amt = 512;
const err_mask = posix.POLL.ERR | posix.POLL.NVAL | posix.POLL.HUP;
const events_len = try posix.poll(&self.poll_fds, if (nanoseconds) |ns|
std.math.cast(i32, ns / std.time.ns_per_ms) orelse std.math.maxInt(i32)
else
-1);
if (events_len == 0) {
for (self.poll_fds) |poll_fd| {
if (poll_fd.fd != -1) return true;
} else return false;
}
var keep_polling = false;
for (&self.poll_fds, &self.readers) |*poll_fd, *r| {
// Try reading whatever is available before checking the error
// conditions.
// It's still possible to read after a POLL.HUP is received,
// always check if there's some data waiting to be read first.
if (poll_fd.revents & posix.POLL.IN != 0) {
const buf = try writableSliceGreedyAlloc(r, gpa, bump_amt);
const amt = posix.read(poll_fd.fd, buf) catch |err| switch (err) {
error.BrokenPipe => 0, // Handle the same as EOF.
else => |e| return e,
};
advanceBufferEnd(r, amt);
if (amt == 0) {
// Remove the fd when the EOF condition is met.
poll_fd.fd = -1;
} else {
keep_polling = true;
}
} else if (poll_fd.revents & err_mask != 0) {
// Exclude the fds that signaled an error.
poll_fd.fd = -1;
} else if (poll_fd.fd != -1) {
keep_polling = true;
}
}
return keep_polling;
}
/// Returns a slice into the unused capacity of `buffer` with at least
/// `min_len` bytes, extending `buffer` by resizing it with `gpa` as necessary.
///
/// After calling this function, typically the caller will follow up with a
/// call to `advanceBufferEnd` to report the actual number of bytes buffered.
fn writableSliceGreedyAlloc(r: *Reader, allocator: Allocator, min_len: usize) Allocator.Error![]u8 {
{
const unused = r.buffer[r.end..];
if (unused.len >= min_len) return unused;
}
if (r.seek > 0) {
const data = r.buffer[r.seek..r.end];
@memmove(r.buffer[0..data.len], data);
r.seek = 0;
r.end = data.len;
}
{
var list: std.ArrayList(u8) = .{
.items = r.buffer[0..r.end],
.capacity = r.buffer.len,
};
defer r.buffer = list.allocatedSlice();
try list.ensureUnusedCapacity(allocator, min_len);
}
const unused = r.buffer[r.end..];
assert(unused.len >= min_len);
return unused;
}
/// After writing directly into the unused capacity of `buffer`, this function
/// updates `end` so that users of `Reader` can receive the data.
fn advanceBufferEnd(r: *Reader, n: usize) void {
assert(n <= r.buffer.len - r.end);
r.end += n;
}
/// The `ReadFile` docuementation states that `lpNumberOfBytesRead` does not have a meaningful
/// result when using overlapped I/O, but also that it cannot be `null` on Windows 7. For
/// compatibility, we point it to this dummy variables, which we never otherwise access.
/// See: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-readfile
var win_dummy_bytes_read: u32 = undefined;
/// Read as much data as possible from `handle` with `overlapped`, and write it to the FIFO. Before
/// returning, queue a read into `small_buf` so that `WaitForMultipleObjects` returns when more data
/// is available. `handle` must have no pending asynchronous operation.
fn windowsAsyncReadToFifoAndQueueSmallRead(
gpa: Allocator,
handle: windows.HANDLE,
overlapped: *windows.OVERLAPPED,
r: *Reader,
small_buf: *[128]u8,
bump_amt: usize,
) !enum { empty, populated, closed_populated, closed } {
var read_any_data = false;
while (true) {
const fifo_read_pending = while (true) {
const buf = try writableSliceGreedyAlloc(r, gpa, bump_amt);
const buf_len = math.cast(u32, buf.len) orelse math.maxInt(u32);
if (0 == windows.kernel32.ReadFile(
handle,
buf.ptr,
buf_len,
&win_dummy_bytes_read,
overlapped,
)) switch (windows.GetLastError()) {
.IO_PENDING => break true,
.BROKEN_PIPE => return if (read_any_data) .closed_populated else .closed,
else => |err| return windows.unexpectedError(err),
};
const num_bytes_read = switch (try windowsGetReadResult(handle, overlapped, false)) {
.success => |n| n,
.closed => return if (read_any_data) .closed_populated else .closed,
.aborted => unreachable,
};
read_any_data = true;
advanceBufferEnd(r, num_bytes_read);
if (num_bytes_read == buf_len) {
// We filled the buffer, so there's probably more data available.
continue;
} else {
// We didn't fill the buffer, so assume we're out of data.
// There is no pending read.
break false;
}
};
if (fifo_read_pending) cancel_read: {
// Cancel the pending read into the FIFO.
_ = windows.kernel32.CancelIo(handle);
// We have to wait for the handle to be signalled, i.e. for the cancelation to complete.
switch (windows.kernel32.WaitForSingleObject(handle, windows.INFINITE)) {
windows.WAIT_OBJECT_0 => {},
windows.WAIT_FAILED => return windows.unexpectedError(windows.GetLastError()),
else => unreachable,
}
// If it completed before we canceled, make sure to tell the FIFO!
const num_bytes_read = switch (try windowsGetReadResult(handle, overlapped, true)) {
.success => |n| n,
.closed => return if (read_any_data) .closed_populated else .closed,
.aborted => break :cancel_read,
};
read_any_data = true;
advanceBufferEnd(r, num_bytes_read);
}
// Try to queue the 1-byte read.
if (0 == windows.kernel32.ReadFile(
handle,
small_buf,
small_buf.len,
&win_dummy_bytes_read,
overlapped,
)) switch (windows.GetLastError()) {
.IO_PENDING => {
// 1-byte read pending as intended
return if (read_any_data) .populated else .empty;
},
.BROKEN_PIPE => return if (read_any_data) .closed_populated else .closed,
else => |err| return windows.unexpectedError(err),
};
// We got data back this time. Write it to the FIFO and run the main loop again.
const num_bytes_read = switch (try windowsGetReadResult(handle, overlapped, false)) {
.success => |n| n,
.closed => return if (read_any_data) .closed_populated else .closed,
.aborted => unreachable,
};
const buf = small_buf[0..num_bytes_read];
const dest = try writableSliceGreedyAlloc(r, gpa, buf.len);
@memcpy(dest[0..buf.len], buf);
advanceBufferEnd(r, buf.len);
read_any_data = true;
}
}
/// Simple wrapper around `GetOverlappedResult` to determine the result of a `ReadFile` operation.
/// If `!allow_aborted`, then `aborted` is never returned (`OPERATION_ABORTED` is considered unexpected).
///
/// The `ReadFile` documentation states that the number of bytes read by an overlapped `ReadFile` must be determined using `GetOverlappedResult`, even if the
/// operation immediately returns data:
/// "Use NULL for [lpNumberOfBytesRead] if this is an asynchronous operation to avoid potentially
/// erroneous results."
/// "If `hFile` was opened with `FILE_FLAG_OVERLAPPED`, the following conditions are in effect: [...]
/// The lpNumberOfBytesRead parameter should be set to NULL. Use the GetOverlappedResult function to
/// get the actual number of bytes read."
/// See: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-readfile
fn windowsGetReadResult(
handle: windows.HANDLE,
overlapped: *windows.OVERLAPPED,
allow_aborted: bool,
) !union(enum) {
success: u32,
closed,
aborted,
} {
var num_bytes_read: u32 = undefined;
if (0 == windows.kernel32.GetOverlappedResult(
handle,
overlapped,
&num_bytes_read,
0,
)) switch (windows.GetLastError()) {
.BROKEN_PIPE => return .closed,
.OPERATION_ABORTED => |err| if (allow_aborted) {
return .aborted;
} else {
return windows.unexpectedError(err);
},
else => |err| return windows.unexpectedError(err),
};
return .{ .success = num_bytes_read };
}
};
}
/// Given an enum, returns a struct with fields of that enum, each field
/// representing an I/O stream for polling.
pub fn PollFiles(comptime StreamEnum: type) type {
return @Struct(.auto, null, std.meta.fieldNames(StreamEnum), &@splat(Io.File), &@splat(.{}));
}
userdata: ?*anyopaque,
vtable: *const VTable,
@ -704,18 +254,18 @@ pub const VTable = struct {
pub const Limit = enum(usize) {
nothing = 0,
unlimited = std.math.maxInt(usize),
unlimited = math.maxInt(usize),
_,
/// `std.math.maxInt(usize)` is interpreted to mean `.unlimited`.
/// `math.maxInt(usize)` is interpreted to mean `.unlimited`.
pub fn limited(n: usize) Limit {
return @enumFromInt(n);
}
/// Any value grater than `std.math.maxInt(usize)` is interpreted to mean
/// Any value grater than `math.maxInt(usize)` is interpreted to mean
/// `.unlimited`.
pub fn limited64(n: u64) Limit {
return @enumFromInt(@min(n, std.math.maxInt(usize)));
return @enumFromInt(@min(n, math.maxInt(usize)));
}
pub fn countVec(data: []const []const u8) Limit {
@ -929,9 +479,9 @@ pub const Clock = enum {
};
}
pub fn compare(lhs: Clock.Timestamp, op: std.math.CompareOperator, rhs: Clock.Timestamp) bool {
pub fn compare(lhs: Clock.Timestamp, op: math.CompareOperator, rhs: Clock.Timestamp) bool {
assert(lhs.clock == rhs.clock);
return std.math.compare(lhs.raw.nanoseconds, op, rhs.raw.nanoseconds);
return math.compare(lhs.raw.nanoseconds, op, rhs.raw.nanoseconds);
}
};
@ -996,7 +546,7 @@ pub const Duration = struct {
nanoseconds: i96,
pub const zero: Duration = .{ .nanoseconds = 0 };
pub const max: Duration = .{ .nanoseconds = std.math.maxInt(i96) };
pub const max: Duration = .{ .nanoseconds = math.maxInt(i96) };
pub fn fromNanoseconds(x: i96) Duration {
return .{ .nanoseconds = x };
@ -1652,7 +1202,7 @@ pub const Event = enum(u32) {
pub fn set(e: *Event, io: Io) void {
switch (@atomicRmw(Event, e, .Xchg, .is_set, .release)) {
.unset, .is_set => {},
.waiting => io.futexWake(Event, e, std.math.maxInt(u32)),
.waiting => io.futexWake(Event, e, math.maxInt(u32)),
}
}