From 27b49a60d0fdb3b37ae6380896488b7e5381c6b9 Mon Sep 17 00:00:00 2001
From: sin-ack <sin-ack@users.noreply.github.com>
Date: Fri, 14 Jan 2022 13:22:54 +0000
Subject: [PATCH] LibCore: Implement LocalSocket::read_without_waiting

This uses recv with MSG_DONTWAIT to disable blocking operation for a
single call. LibIPC uses this to read in a non-blocking manner from an
otherwise blocking socket.
---
 Userland/Libraries/LibCore/Stream.cpp | 11 ++++++++---
 Userland/Libraries/LibCore/Stream.h   |  3 ++-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibCore/Stream.cpp b/Userland/Libraries/LibCore/Stream.cpp
index 58d99e6349c..b24b56514f1 100644
--- a/Userland/Libraries/LibCore/Stream.cpp
+++ b/Userland/Libraries/LibCore/Stream.cpp
@@ -341,15 +341,15 @@ ErrorOr<void> Socket::connect_inet(int fd, SocketAddress const& address)
     return {};
 }
 
-ErrorOr<size_t> PosixSocketHelper::read(Bytes buffer)
+ErrorOr<size_t> PosixSocketHelper::read(Bytes buffer, int flags)
 {
     if (!is_open()) {
         return Error::from_errno(ENOTCONN);
     }
 
-    ssize_t rc = ::recv(m_fd, buffer.data(), buffer.size(), 0);
+    ssize_t rc = ::recv(m_fd, buffer.data(), buffer.size(), flags);
     if (rc < 0) {
-        return Error::from_errno(errno);
+        return Error::from_syscall("recv", -errno);
     }
 
     m_last_read_was_eof = rc == 0;
@@ -556,4 +556,9 @@ ErrorOr<void> LocalSocket::send_fd(int fd)
 #endif
 }
 
+ErrorOr<size_t> LocalSocket::read_without_waiting(Bytes buffer)
+{
+    return m_helper.read(buffer, MSG_DONTWAIT);
+}
+
 }
diff --git a/Userland/Libraries/LibCore/Stream.h b/Userland/Libraries/LibCore/Stream.h
index 7999eef53c4..d3820ab3797 100644
--- a/Userland/Libraries/LibCore/Stream.h
+++ b/Userland/Libraries/LibCore/Stream.h
@@ -229,7 +229,7 @@ public:
     int fd() const { return m_fd; }
     void set_fd(int fd) { m_fd = fd; }
 
-    ErrorOr<size_t> read(Bytes);
+    ErrorOr<size_t> read(Bytes, int flags = 0);
     ErrorOr<size_t> write(ReadonlyBytes);
 
     bool is_eof() const { return !is_open() || m_last_read_was_eof; }
@@ -412,6 +412,7 @@ public:
 
     ErrorOr<int> receive_fd(int flags);
     ErrorOr<void> send_fd(int fd);
+    ErrorOr<size_t> read_without_waiting(Bytes buffer);
 
     virtual ~LocalSocket() { close(); }