build: portability groundwork toward a Windows/MSVC viewer

- CMakeLists.txt: fetch libzmq at the top level (zeromq/libzmq v4.3.5) before
  slsDetectorPackage, so this project controls the ZeroMQ version instead of sls's
  bundled archive. sls reuses it via its if(NOT libzmq_POPULATED) guard, so a single
  libzmq-static target is built (no duplicate-target/double-symbol clash). Verified the
  full Linux build still links (JFJochZMQ -> JFJochReceiver -> jfjoch_process).
- common/NetworkAddressConvert.cpp: guard the network includes for _WIN32
  (winsock2/ws2tcpip vs arpa/inet).
- common/ImageBuffer.cpp: use std::malloc/std::free for the non-NUMA path instead of an
  anonymous mmap (the mapping had no huge-page/mbind flags, so it was equivalent) -
  portable and removes the POSIX-only dependency. The NUMA-interleave path is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CMakeLists.txt

@@ -144,6 +144,26 @@ FetchContent_Declare(
         EXCLUDE_FROM_ALL
 )
 
+# ZeroMQ (libzmq): fetch it here, at the top level, so that THIS project - not
+# slsDetectorPackage - controls the version. slsDetectorPackage bundles its own libzmq
+# archive, but only populates it behind `if(NOT libzmq_POPULATED)`; by making libzmq
+# available before sls below, sls reuses this copy and a single libzmq-static target is
+# built (no duplicate target / double-symbol clash). A future viewer-only / Windows build
+# (which does not build sls) fetches the same libzmq standalone.
+SET(BUILD_SHARED   OFF CACHE BOOL "" FORCE)   # libzmq: static only (matches sls)
+SET(BUILD_TESTS    OFF CACHE BOOL "" FORCE)   # libzmq: no test build
+SET(WITH_PERF_TOOL OFF CACHE BOOL "" FORCE)   # libzmq: no perf tools
+SET(WITH_DOCS      OFF CACHE BOOL "" FORCE)   # libzmq: no docs
+SET(ENABLE_CPACK   OFF CACHE BOOL "" FORCE)   # libzmq: no CPack injection
+FetchContent_Declare(
+        libzmq
+        GIT_REPOSITORY https://github.com/zeromq/libzmq.git
+        GIT_TAG v4.3.5
+        EXCLUDE_FROM_ALL
+)
+
+# libzmq must be made available BEFORE sls_detector_package for the override above to take effect.
+FetchContent_MakeAvailable(libzmq)
 FetchContent_MakeAvailable(zstd sls_detector_package catch2 hdf5 spdlog httplib)
 
 ADD_SUBDIRECTORY(jungfrau)

common/ImageBuffer.cpp

@@ -6,28 +6,27 @@
 #include "JFJochException.h"
 #include "ZeroCopyReturnValue.h"
 
+#include <cstdlib>
+
 #ifdef JFJOCH_USE_NUMA
 #include <numa.h>
 #endif
-#include <sys/mman.h>
 
 
 ImageBuffer::ImageBuffer(size_t buffer_size_bytes)
         : buffer_size(buffer_size_bytes) {
 
 #ifdef JFJOCH_USE_NUMA
+    // Interleave the buffer across NUMA nodes - throughput-critical path (receiver), Linux-only.
     buffer = static_cast<uint8_t *>(numa_alloc_interleaved(buffer_size));
+#else
+    // The non-NUMA mapping carried no huge-page / mbind flags, so a plain heap allocation is
+    // equivalent (and portable). The buffer is zeroed below.
+    buffer = static_cast<uint8_t *>(std::malloc(buffer_size));
+#endif
     if (buffer == nullptr)
-        throw JFJochException(JFJochExceptionCategory::MemAllocFailed,
-            "Failed to allocate image buffer");
-
-    #else
-    buffer = (uint8_t *) mmap (nullptr, buffer_size, PROT_READ | PROT_WRITE,
-                               MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) ;
-    if (buffer == MAP_FAILED)
         throw JFJochException(JFJochExceptionCategory::MemAllocFailed,
                               "Failed to allocate image buffer");
-#endif
     memset(buffer, 0, buffer_size);
 }
 
@@ -39,7 +38,7 @@ ImageBuffer::~ImageBuffer() {
 #ifdef JFJOCH_USE_NUMA
     numa_free(buffer, buffer_size);
 #else
-    munmap(buffer, buffer_size);
+    std::free(buffer);
 #endif
 }
 

common/NetworkAddressConvert.cpp

@@ -1,7 +1,12 @@
 // SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
 // SPDX-License-Identifier: GPL-3.0-only
 
+#ifdef _WIN32
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#else
 #include <arpa/inet.h>
+#endif
 #include <sstream>
 #include <iomanip>