Merge branch 'docs-default-ipcshm'

docs/transports.md

@@ -56,6 +56,11 @@ be used to *summon* the transport:
     <td><code>  can://&lt;interface&gt;?msgid=&lt;id&gt;                </code></td>
     <td><code>  zcm_create("can://can0?msgid=65536")                    </code></td>
   </tr>
+  <tr>
+    <td>        Inter-process via Shared Memory (IPCSHM)                </td>
+    <td><code>  ipcshm://&lt;shm-region-name&gt;?mtu=&lt;mtu&gt;&amp;depth=&lt;depth&gt; </code></td>
+    <td><code>  zcm_create("ipcshm"), zcm_create("ipcshm://myregion?mtu=100000&depth=128")   </code></td>
+  </tr>
 </table>
 
 When no url is provided (i.e. `zcm_create(NULL)`), the `ZCM_DEFAULT_URL` environment variable is

zcm/transport/lockfree/lf_shm.c

@@ -6,43 +6,64 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <libgen.h>
 
+// like mkdir -p but skips the trailing component
+static void mkdir_with_parents(const char *path, mode_t mode)
+{
+    int len = strlen(path);
+    for (int i = 0; i < len; i++) {
+        if (path[i]=='/') {
+            char *dirpath = (char *) malloc(i+1);
+            strncpy(dirpath, path, i);
+            dirpath[i]=0;
+
+            mkdir(dirpath, mode);
+            free(dirpath);
+
+            i++; // skip the '/'
+        }
+    }
+}
 
-bool lf_shm_create(const char *name, size_t size)
+bool lf_shm_create(const char *path, size_t size)
 {
-  int shm_fd = shm_open(name, O_CREAT|O_RDWR|O_EXCL, 0644);
-  if (shm_fd < 0) return false;
-  if (ftruncate(shm_fd, size) < 0) {
+    mkdir_with_parents(path, 0775);
+
+    int shm_fd = open(path, O_CREAT|O_EXCL|O_RDWR|O_CLOEXEC, 0644);
+    if (shm_fd < 0) return false;
+
+    if (ftruncate(shm_fd, size) < 0) {
+        close(shm_fd);
+        return false;
+    }
     close(shm_fd);
-    return false;
-  }
-  close(shm_fd);
-  return true;
+    return true;
 }
 
-void lf_shm_remove(const char *name)
+void lf_shm_remove(const char *path)
 {
-  shm_unlink(name);
+    unlink(path);
 }
 
-void * lf_shm_open(const char *name, size_t * _opt_size)
+void * lf_shm_open(const char *path, size_t * _opt_size)
 {
-  int shm_fd = shm_open(name, O_CREAT|O_RDWR, 0755);
-  if (shm_fd < 0) return NULL;
+    int shm_fd = open(path, O_RDWR|O_CLOEXEC);
+    if (shm_fd < 0) return NULL;
 
-  struct stat st[1];
-  if (0 != fstat(shm_fd, st)) return NULL;
-  size_t size = st->st_size;
+    struct stat st[1];
+    if (0 != fstat(shm_fd, st)) return NULL;
+    size_t size = st->st_size;
 
-  void *mem = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, shm_fd, 0);
-  if (mem == MAP_FAILED) return NULL;
+    void *mem = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, shm_fd, 0);
+    if (mem == MAP_FAILED) return NULL;
 
-  close(shm_fd);
-  if (_opt_size) *_opt_size = size;
-  return mem;
+    close(shm_fd);
+    if (_opt_size) *_opt_size = size;
+    return mem;
 }
 
 void lf_shm_close(void *shm, size_t size)
 {
-  munmap(shm, size);
+    munmap(shm, size);
 }

zcm/transport/lockfree/lf_shm.h

@@ -6,9 +6,9 @@
 extern "C" {
 #endif
 
-bool   lf_shm_create(const char *name, size_t size);
-void   lf_shm_remove(const char *name);
-void * lf_shm_open(const char *name, size_t * _opt_size);
+bool   lf_shm_create(const char *path, size_t size);
+void   lf_shm_remove(const char *path);
+void * lf_shm_open(const char *path, size_t * _opt_size);
 void   lf_shm_close(void *shm, size_t size);
 
 #ifdef __cplusplus

zcm/transport/transport_ipcshm.cpp

@@ -85,6 +85,8 @@ struct ZCM_TRANS_CLASSNAME : public zcm_trans_t
         ZCM_DEBUG("Init ipcshm:");
 
         const char *region_name = zcm_url_address(url);
+        if (!region_name[0]) region_name = "default";
+
         ZCM_DEBUG("  address='%s'", region_name);
 
         // Process any url options
@@ -120,10 +122,14 @@ struct ZCM_TRANS_CLASSNAME : public zcm_trans_t
         assert(LF_IS_POW2(page_size)); // Sanity or paranoia..
         region_size = LF_ALIGN_UP(region_size, page_size);
 
-        bool created = lf_shm_create(region_name, region_size);
-        ZCM_DEBUG("Shm region created: %d", (int)created);
+        char region_path[PATH_MAX+1];
+        snprintf(region_path, sizeof(region_path), "/dev/shm/zcm/ipcshm/%s", region_name);
+        region_path[PATH_MAX] = 0;
+
+        bool created = lf_shm_create(region_path, region_size);
+        ZCM_DEBUG("Shm region created: %s", created ? "true" : "false");
 
-        mem = lf_shm_open(region_name, &shm_size);
+        mem = lf_shm_open(region_path, &shm_size);
         if (shm_size != region_size) {
             char *err = sprintf_alloc("IPCSHM Region size mismatch for '%s': "
                                       "expected %zu, got %zu\n"
@@ -132,8 +138,8 @@ struct ZCM_TRANS_CLASSNAME : public zcm_trans_t
                                       "If you have recently changed the URL parameters "
                                       "and you're certain the\n      old segment "
                                       "is unused, then you can simply remove it "
-                                      "with 'rm /dev/shm/%s'",
-                                      region_name, region_size, shm_size, region_name);
+                                      "with 'rm %s'",
+                                      region_name, region_size, shm_size, region_path);
             ZCM_DEBUG("%s", err);
             lf_shm_close(mem, shm_size);
             *errmsg = err;