[os2]: Implement pipe_has_data procedure

core/os/os2/pipe.odin

@@ -1,6 +1,43 @@
 package os2
 
+/*
+Create an anonymous pipe.
+
+This procedure creates an anonymous pipe, returning two ends of the pipe, `r`
+and `w`. The file `r` is the readable end of the pipe. The file `w` is a
+writeable end of the pipe.
+
+Pipes are used as an inter-process communication mechanism, to communicate
+between a parent and a child process. The child uses one end of the pipe to
+write data, and the parent uses the other end to read from the pipe
+(or vice-versa). When a parent passes one of the ends of the pipe to the child
+process, that end of the pipe needs to be closed by the parent, before any data
+is attempted to be read.
+
+Although pipes look like files and is compatible with most file APIs in package
+os2, the way it's meant to be read is different. Due to asynchronous nature of
+the communication channel, the data may not be present at the time of a read
+request. The other scenario is when a pipe has no data because the other end
+of the pipe was closed by the child process.
+*/
 @(require_results)
 pipe :: proc() -> (r, w: ^File, err: Error) {
 	return _pipe()
 }
+
+/*
+Check if the pipe has any data.
+
+This procedure checks whether a read-end of the pipe has data that can be
+read, and returns `true`, if the pipe has readable data, and `false` if the
+pipe is empty. This procedure does not block the execution of the current
+thread.
+
+**Note**: If the other end of the pipe was closed by the child process, the
+`.Broken_Pipe`
+can be returned by this procedure. Handle these errors accordingly.
+*/
+@(require_results)
+pipe_has_data :: proc(r: ^File) -> (ok: bool, err: Error) {
+	return _pipe_has_data(r)
+}