From ea4c864d4b74b7297268debfaf043dd1e4243619 Mon Sep 17 00:00:00 2001
From: Jooris Hadeler <115401775+jooris-hadeler@users.noreply.github.com>
Date: Fri, 7 Feb 2025 21:00:54 +0100
Subject: [PATCH] Add `Socket.peek` to allow peeking at the receiving queue.
 (#1933)

* Add `Socket.peek` to allow peeking at the receiving queue.

This uses the `MSG_PEEK` flag to peek at the beginning of the
receiving queue without removing data from said queue.
---
 lib/std/net/os/darwin.c3 |  1 +
 lib/std/net/os/linux.c3  |  2 ++
 lib/std/net/os/win32.c3  |  2 ++
 lib/std/net/socket.c3    | 10 ++++++++++
 4 files changed, 15 insertions(+)

diff --git a/lib/std/net/os/darwin.c3 b/lib/std/net/os/darwin.c3
index ac6550115..9b74fb24b 100644
--- a/lib/std/net/os/darwin.c3
+++ b/lib/std/net/os/darwin.c3
@@ -94,3 +94,4 @@ const CShort POLLATTRIB          = 0x0400; // file attributes may have changed
 const CShort POLLNLINK           = 0x0800; // (un)link/rename may have happened
 const CShort POLLWRITE           = 0x1000; // file's contents may have changed
 
+const CInt MSG_PEEK = 0x0002;
\ No newline at end of file
diff --git a/lib/std/net/os/linux.c3 b/lib/std/net/os/linux.c3
index e82ca9eef..fb800ffbb 100644
--- a/lib/std/net/os/linux.c3
+++ b/lib/std/net/os/linux.c3
@@ -88,3 +88,5 @@ const CUShort POLLREMOVE              = 0x1000;
 const CUShort POLLRDHUP               = 0x2000;
 const CUShort POLLFREE                = 0x4000;
 const CUShort POLL_BUSY_LOOP          = 0x8000;
+
+const CInt MSG_PEEK = 0x0002;
\ No newline at end of file
diff --git a/lib/std/net/os/win32.c3 b/lib/std/net/os/win32.c3
index 826c9a8db..062be2825 100644
--- a/lib/std/net/os/win32.c3
+++ b/lib/std/net/os/win32.c3
@@ -101,3 +101,5 @@ const CUShort POLLRDNORM  = win32::POLLRDNORM;
 const CUShort POLLRDBAND  = win32::POLLRDBAND;
 const CUShort POLLWRNORM  = win32::POLLWRNORM;
 const CUShort POLLWRBAND  = win32::POLLWRBAND;
+
+const int MSG_PEEK = 0x0002;
\ No newline at end of file
diff --git a/lib/std/net/socket.c3 b/lib/std/net/socket.c3
index d1fce6a4b..1eef49722 100644
--- a/lib/std/net/socket.c3
+++ b/lib/std/net/socket.c3
@@ -156,6 +156,16 @@ fn void! Socket.close(&self) @inline @dynamic
 	self.sock.close()!;
 }
 
+fn usz! Socket.peek(&self, char[] bytes) @dynamic
+{
+  $if env::WIN32:
+	  isz n = libc::recv(self.sock, bytes.ptr, (int)bytes.len, os::MSG_PEEK);
+  $else
+	  isz n = libc::recv(self.sock, bytes.ptr, bytes.len, os::MSG_PEEK);
+  $endif
+	if (n < 0) return os::socket_error()?;
+	return (usz)n;
+}
 
 enum SocketShutdownHow : (inline CInt native_value)
 {