util: add os_file_create_unique()

Signed-off-by: Eric Engestrom <[email protected]>
Reviewed-by: Kristian H. Kristensen <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>

2 files changed, 34 insertions, 0 deletions

diff --git a/src/util/os_file.c b/src/util/os_file.c
index 756164c3dfe..ae41506332d 100644
--- a/src/util/os_file.c
+++ b/src/util/os_file.c
@@ -6,7 +6,30 @@
 #include "os_file.h"
 
 #include <errno.h>
+#include <fcntl.h>
 #include <stdlib.h>
+#include <sys/stat.h>
+
+
+#if defined(WIN32)
+#include <io.h>
+#define open _open
+#define fdopen _fdopen
+#define O_CREAT _O_CREAT
+#define O_EXCL _O_EXCL
+#define O_WRONLY _O_WRONLY
+#endif
+
+
+FILE *
+os_file_create_unique(const char *filename, int filemode)
+{
+   int fd = open(filename, O_CREAT | O_EXCL | O_WRONLY, filemode);
+   if (fd == -1)
+      return NULL;
+   return fdopen(fd, "w");
+}
+
 
 #if defined(__linux__)
 
diff --git a/src/util/os_file.h b/src/util/os_file.h
index 2f97c19ed55..d691302d12d 100644
--- a/src/util/os_file.h
+++ b/src/util/os_file.h
@@ -8,11 +8,22 @@
 #ifndef _OS_FILE_H_
 #define _OS_FILE_H_
 
+#include <stdio.h>
+
 #ifdef  __cplusplus
 extern "C" {
 #endif
 
 /*
+ * Create a new file and opens it for writing-only.
+ * If the given filename already exists, nothing is done and NULL is returned.
+ * `errno` gets set to the failure reason; if that is not EEXIST, the caller
+ * might want to do something other than trying again.
+ */
+FILE *
+os_file_create_unique(const char *filename, int filemode);
+
+/*
  * Read a file.
  * Returns a char* that the caller must free(), or NULL and sets errno.
  */