mythzoneminder: Add support for mmap

Newer versions of ZoneMinder can use both shm and mmap for it's inter process
shared memory this updates mythzmserver to be able to read the live camera
images and status using both methods. Closes #10174.

Note: Only tested to make sure shm still works.
Signed-off-by: Paul Harrison <pharrison@mythtv.org>

mythplugins/mythzoneminder/mythzmserver/zmserver.cpp

@@ -25,6 +25,10 @@
 #include <sys/stat.h>
 #include <sys/shm.h>
 
+#if _POSIX_MAPPED_FILES > 0L
+#include <sys/mman.h>
+#endif
+
 #ifdef linux
 #  include <sys/vfs.h>
 #  include <sys/statvfs.h>
@@ -218,6 +222,13 @@ ZMServer::ZMServer(int sock, bool debug)
         cout << "Shared memory key is: " << buf << endl;
     }
 
+    // get the MMAP path
+    m_mmapPath = getZMSetting("ZM_PATH_MAP");
+    if (m_debug)
+    {
+        cout << "Memory path directory is: " << m_mmapPath << endl;
+    }
+
     // get the event filename format
     setting = getZMSetting("ZM_EVENT_IMAGE_DIGITS");
     int eventDigits = atoi(setting.c_str());
@@ -1301,7 +1312,7 @@ void ZMServer::getMonitorList(void)
 
 void ZMServer::initMonitor(MONITOR *monitor)
 {
-    void *shm_ptr;
+    void *shm_ptr = NULL;
 
     monitor->shared_data = NULL;
     monitor->shared_images = NULL;
@@ -1324,35 +1335,69 @@ void ZMServer::initMonitor(MONITOR *monitor)
             ((monitor->image_buffer_count) * (sizeof(struct timeval))) +
             ((monitor->image_buffer_count) * monitor->frame_size);
 
-    int shmid;
 
-    if ((shmid = shmget((m_shmKey & 0xffffff00) | monitor->mon_id,
-         shared_data_size, SHM_R)) == -1)
+#if _POSIX_MAPPED_FILES > 0L
+    /*
+     * Try to open the mmap file first if the architecture supports it.
+     * Otherwise, legacy shared memory will be used below.
+     */
+    stringstream mmap_filename;
+    mmap_filename << m_mmapPath << "/zm.mmap." << monitor->mon_id;
+
+    int mapFile = open(mmap_filename.str().c_str(), O_RDONLY, 0x0);
+    if (mapFile >= 0)
     {
-        cout << "Failed to shmget for monitor: " << monitor->mon_id << endl;
-        monitor->status = "Error";
-        switch(errno)
+        if (m_debug)
+            cout << "Opened mmap file: " << mmap_filename << endl;
+
+        shm_ptr = mmap(NULL, shared_data_size, PROT_READ,
+                                            MAP_SHARED, mapFile, 0x0);
+        if (shm_ptr == NULL)
         {
-            case EACCES: cout << "EACCES - no rights to access segment\n"; break;
-            case EEXIST: cout << "EEXIST - segment already exists\n"; break;
-            case EINVAL: cout << "EINVAL - size < SHMMIN or size > SHMMAX\n"; break;
-            case ENFILE: cout << "ENFILE - limit on open files has been reached\n"; break;
-            case ENOENT: cout << "ENOENT - no segment exists for the given key\n"; break;
-            case ENOMEM: cout << "ENOMEM - couldn't reserve memory for segment\n"; break;
-            case ENOSPC: cout << "ENOSPC - shmmni or shmall limit reached\n"; break;
+            cout << "Failed to map shared memory from file [" << 
+                mmap_filename << "] " <<
+                "for monitor: " << 
+                monitor->mon_id << 
+                endl;
+            monitor->status = "Error";
+            return;
         }
-
-        return;
     }
-
-    shm_ptr = shmat(shmid, 0, SHM_RDONLY);
-
+#endif
 
     if (shm_ptr == NULL)
     {
-        cout << "Failed to shmat for monitor: " << monitor->mon_id << endl;
-        monitor->status = "Error";
-        return;
+        // fail back to shmget() functionality if mapping memory above failed.
+        int shmid;
+
+        if ((shmid = shmget((m_shmKey & 0xffffff00) | monitor->mon_id,
+             shared_data_size, SHM_R)) == -1)
+        {
+            cout << "Failed to shmget for monitor: " << monitor->mon_id << endl;
+            monitor->status = "Error";
+            switch(errno)
+            {
+                case EACCES: cout << "EACCES - no rights to access segment\n"; break;
+                case EEXIST: cout << "EEXIST - segment already exists\n"; break;
+                case EINVAL: cout << "EINVAL - size < SHMMIN or size > SHMMAX\n"; break;
+                case ENFILE: cout << "ENFILE - limit on open files has been reached\n"; break;
+                case ENOENT: cout << "ENOENT - no segment exists for the given key\n"; break;
+                case ENOMEM: cout << "ENOMEM - couldn't reserve memory for segment\n"; break;
+                case ENOSPC: cout << "ENOSPC - shmmni or shmall limit reached\n"; break;
+            }
+
+            return;
+        }
+
+        shm_ptr = shmat(shmid, 0, SHM_RDONLY);
+
+
+        if (shm_ptr == NULL)
+        {
+            cout << "Failed to shmat for monitor: " << monitor->mon_id << endl;
+            monitor->status = "Error";
+            return;
+        }
     }
 
     monitor->shared_data = (SharedData*)shm_ptr;

mythplugins/mythzoneminder/mythzmserver/zmserver.h

@@ -192,6 +192,7 @@ class ZMServer
     string               m_eventFileFormat;
     string               m_analyseFileFormat;
     key_t                m_shmKey;
+    string               m_mmapPath;
 };