3 files changed, 46 insertions, 0 deletions
diff --git a/src/core/file.c b/src/core/file.c
index 4715be2a..b76fdcda 100644
--- a/src/core/file.c
+++ b/src/core/file.c
@@ -128,4 +128,32 @@ const char *
 nni_file_basename(const char *path)
 {
 	return (nni_plat_file_basename(path));
+}
+
+struct nni_file_lockh {
+	nni_plat_flock lk;
+};
+
+int
+nni_file_lock(const char *path, nni_file_lockh **hp)
+{
+	nni_file_lockh *h;
+	int             rv;
+	if ((h = NNI_ALLOC_STRUCT(h)) == NULL) {
+		return (NNG_ENOMEM);
+	}
+	rv = nni_plat_file_lock(path, &h->lk);
+	if (rv != 0) {
+		NNI_FREE_STRUCT(h);
+		return (rv);
+	}
+	*hp = h;
+	return (0);
+}
+
+void
+nni_file_unlock(nni_file_lockh *h)
+{
+	nni_plat_file_unlock(&h->lk);
+	NNI_FREE_STRUCT(h);
 }
 \ No newline at end of file
diff --git a/src/core/file.h b/src/core/file.h
index 7969ae5f..3baa1ccd 100644
--- a/src/core/file.h
+++ b/src/core/file.h
@@ -84,4 +84,10 @@ extern bool nni_file_is_file(const char *);
 // false if an error occurs, or the path references something else.
 extern bool nni_file_is_dir(const char *);
 
+typedef struct nni_file_lockh nni_file_lockh;
+
+extern int nni_file_lock(const char *, nni_file_lockh **);
+
+extern void nni_file_unlock(nni_file_lockh *);
+
 #endif // CORE_FILE_H
diff --git a/src/core/platform.h b/src/core/platform.h
index 3f336f11..d5fc40f7 100644
--- a/src/core/platform.h
+++ b/src/core/platform.h
@@ -434,6 +434,18 @@ typedef int (*nni_plat_file_walker)(const char *, void *);
 // with the path name, and the supplied void * argument.
 extern int nni_plat_file_walk(const char *, nni_plat_file_walker, void *, int);
 
+typedef struct nni_plat_flock nni_plat_flock;
+
+// nni_plat_file_lock locks the file.  This usually means open it (creating
+// if it does not exist) and doing a lock operation.  The nni_plat_flock
+// is our handle for the lock, to unlock.  Usually its just a file descriptor,
+// and we can unlock by doing close().  Note that this is a "try-lock"
+// operation -- if the file is already locked then NNG_EBUSY is returned.
+extern int nni_plat_file_lock(const char *path, nni_plat_flock *);
+
+// nni_plat_file_unlock unlocks the previously locked file.
+extern void nni_plat_file_unlock(nni_plat_flock *);
+
 // nni_plat_dir_open attempts to "open a directory" for listing.  The
 // handle for further operations is returned in the first argument, and
 // the directory name is supplied in the second.