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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftNIO open source project
//
// Copyright (c) 2017-2021 Apple Inc. and the SwiftNIO project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
// This file contains code that ensures errno is captured correctly when doing syscalls and no ARC traffic can happen inbetween that *could* change the errno
// value before we were able to read it.
// It's important that all static methods are declared with `@inline(never)` so it's not possible any ARC traffic happens while we need to read errno.
//
// Created by Norman Maurer on 11/10/17.
//
// This file arguably shouldn't be here in NIOCore, but due to early design decisions we accidentally exposed a few types that
// know about system calls into the core API (looking at you, FileHandle). As a result we need support for a small number of system calls.
#if canImport(Darwin)
import Darwin.C
#elseif canImport(Glibc)
import Glibc
#elseif canImport(Musl)
import Musl
#elseif os(Windows)
import CNIOWindows
#else
#error("The system call helpers module was unable to identify your C library.")
#endif
#if os(Windows)
private let sysDup: @convention(c) (CInt) -> CInt = _dup
private let sysClose: @convention(c) (CInt) -> CInt = _close
private let sysLseek: @convention(c) (CInt, off_t, CInt) -> off_t = _lseek
private let sysRead: @convention(c) (CInt, UnsafeMutableRawPointer?, CUnsignedInt) -> CInt = _read
#else
private let sysDup: @convention(c) (CInt) -> CInt = dup
private let sysClose: @convention(c) (CInt) -> CInt = close
private let sysOpenWithMode: @convention(c) (UnsafePointer<CChar>, CInt, NIOPOSIXFileMode) -> CInt = open
private let sysLseek: @convention(c) (CInt, off_t, CInt) -> off_t = lseek
private let sysRead: @convention(c) (CInt, UnsafeMutableRawPointer?, size_t) -> size_t = read
#endif
#if os(Android)
private let sysIfNameToIndex: @convention(c) (UnsafePointer<CChar>) -> CUnsignedInt = if_nametoindex
private let sysGetifaddrs: @convention(c) (UnsafeMutablePointer<UnsafeMutablePointer<ifaddrs>?>) -> CInt = getifaddrs
#else
private let sysIfNameToIndex: @convention(c) (UnsafePointer<CChar>?) -> CUnsignedInt = if_nametoindex
#if !os(Windows)
private let sysGetifaddrs: @convention(c) (UnsafeMutablePointer<UnsafeMutablePointer<ifaddrs>?>?) -> CInt = getifaddrs
#endif
#endif
private func isUnacceptableErrno(_ code: Int32) -> Bool {
switch code {
case EFAULT, EBADF:
return true
default:
return false
}
}
private func preconditionIsNotUnacceptableErrno(err: CInt, where function: String) -> Void {
// strerror is documented to return "Unknown error: ..." for illegal value so it won't ever fail
precondition(!isUnacceptableErrno(err), "unacceptable errno \(err) \(String(cString: strerror(err)!)) in \(function))")
}
/*
* Sorry, we really try hard to not use underscored attributes. In this case
* however we seem to break the inlining threshold which makes a system call
* take twice the time, ie. we need this exception.
*/
@inline(__always)
@discardableResult
internal func syscall<T: FixedWidthInteger>(blocking: Bool,
where function: String = #function,
_ body: () throws -> T)
throws -> CoreIOResult<T> {
while true {
let res = try body()
if res == -1 {
#if os(Windows)
var err: CInt = 0
ucrt._get_errno(&err)
#else
let err = errno
#endif
switch (err, blocking) {
case (EINTR, _):
continue
case (EWOULDBLOCK, true):
return .wouldBlock(0)
default:
preconditionIsNotUnacceptableErrno(err: err, where: function)
throw IOError(errnoCode: err, reason: function)
}
}
return .processed(res)
}
}
enum SystemCalls {
@discardableResult
@inline(never)
internal static func dup(descriptor: CInt) throws -> CInt {
return try syscall(blocking: false) {
sysDup(descriptor)
}.result
}
@inline(never)
internal static func close(descriptor: CInt) throws {
let res = sysClose(descriptor)
if res == -1 {
#if os(Windows)
var err: CInt = 0
ucrt._get_errno(&err)
#else
let err = errno
#endif
// There is really nothing "sane" we can do when EINTR was reported on close.
// So just ignore it and "assume" everything is fine == we closed the file descriptor.
//
// For more details see:
// - https://bugs.chromium.org/p/chromium/issues/detail?id=269623
// - https://lwn.net/Articles/576478/
if err != EINTR {
preconditionIsNotUnacceptableErrno(err: err, where: #function)
throw IOError(errnoCode: err, reason: "close")
}
}
}
@inline(never)
internal static func open(file: UnsafePointer<CChar>, oFlag: CInt,
mode: NIOPOSIXFileMode) throws -> CInt {
#if os(Windows)
return try syscall(blocking: false) {
var fh: CInt = -1
let _ = ucrt._sopen_s(&fh, file, oFlag, _SH_DENYNO, mode)
return fh
}.result
#else
return try syscall(blocking: false) {
sysOpenWithMode(file, oFlag, mode)
}.result
#endif
}
@discardableResult
@inline(never)
internal static func lseek(descriptor: CInt, offset: off_t, whence: CInt) throws -> off_t {
return try syscall(blocking: false) {
sysLseek(descriptor, offset, whence)
}.result
}
#if os(Windows)
@inline(never)
internal static func read(descriptor: CInt, pointer: UnsafeMutableRawPointer, size: CUnsignedInt) throws -> CoreIOResult<CInt> {
return try syscall(blocking: true) {
sysRead(descriptor, pointer, size)
}
}
#else
@inline(never)
internal static func read(descriptor: CInt, pointer: UnsafeMutableRawPointer, size: size_t) throws -> CoreIOResult<ssize_t> {
return try syscall(blocking: true) {
sysRead(descriptor, pointer, size)
}
}
#endif
@inline(never)
internal static func if_nametoindex(_ name: UnsafePointer<CChar>?) throws -> CUnsignedInt {
return try syscall(blocking: false) {
sysIfNameToIndex(name!)
}.result
}
#if !os(Windows)
@inline(never)
internal static func getifaddrs(_ addrs: UnsafeMutablePointer<UnsafeMutablePointer<ifaddrs>?>) throws {
_ = try syscall(blocking: false) {
sysGetifaddrs(addrs)
}
}
#endif
}
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