From 3d0f3cca048ba18e02186db0b68e6dfe8dfb6f56 Mon Sep 17 00:00:00 2001
From: Jon Scheiding <jon@examspark.com>
Date: Fri, 8 May 2026 16:35:50 -0400
Subject: [PATCH] Add StreamLog::isOpen() to detect closed stdin pipe

Exposes a non-blocking check for whether the stdin pipe is still
connected, so callers can distinguish a stream that's transiently
empty from one whose peer has closed the pipe.

POSIX uses poll(POLLIN) and treats POLLHUP/POLLERR/POLLNVAL as
closed; Windows uses PeekNamedPipe (matching getNextLine).

isFinished() is intentionally left unchanged.
---
 seeklog.cpp | 31 +++++++++++++++++++++++++++++++
 seeklog.h   |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/seeklog.cpp b/seeklog.cpp
index 4dad928..6bae889 100644
--- a/seeklog.cpp
+++ b/seeklog.cpp
@@ -32,6 +32,10 @@
 #include <unistd.h>
 #endif
 
+#ifndef _WIN32
+#include <poll.h>
+#endif
+
 long long gSeekLogMaxBufferSize = 104857600;
 
 //StreamLog
@@ -95,6 +99,33 @@ bool StreamLog::isFinished() {
     return false;
 }
 
+bool StreamLog::isOpen() {
+    if(fcntl_fail) return false;
+
+#ifdef _WIN32
+    DWORD available_bytes;
+    if(!PeekNamedPipe(stdin_handle, 0, 0, 0, &available_bytes, 0)) {
+        return false;
+    }
+    return true;
+#else
+    struct pollfd pfd;
+    pfd.fd     = STDIN_FILENO;
+    pfd.events = POLLIN;
+
+    int ret = poll(&pfd, 1, 0);
+
+    if(ret < 0)  return false;
+    if(ret == 0) return true;
+
+    if(pfd.revents & (POLLHUP | POLLERR | POLLNVAL)) {
+        return false;
+    }
+
+    return true;
+#endif
+}
+
 // SeekLog
 
 SeekLog::SeekLog(std::string logfile) {
diff --git a/seeklog.h b/seeklog.h
index 19abe6e..5df09b1 100644
--- a/seeklog.h
+++ b/seeklog.h
@@ -44,6 +44,7 @@ class BaseLog {
     virtual ~BaseLog() {};
     virtual bool getNextLine(std::string& line) { return false; };
     virtual bool isFinished() { return false; };
+    virtual bool isOpen()     { return !isFinished(); };
 };
 
 class StreamLog : public BaseLog {
@@ -58,6 +59,7 @@ class StreamLog : public BaseLog {
 
     bool getNextLine(std::string& line);
     bool isFinished();
+    bool isOpen();
 };
 
 class SeekLogException : public std::exception {