1 files changed, 87 insertions, 0 deletions
diff --git a/portable/mkstemp.c b/portable/mkstemp.c
new file mode 100644
index 0000000..dd2a485
--- /dev/null
+++ b/portable/mkstemp.c
@@ -0,0 +1,87 @@
+/*
+ * Replacement for a missing mkstemp.
+ *
+ * Provides the same functionality as the library function mkstemp for those
+ * systems that don't have it.
+ *
+ * Written by Russ Allbery <rra@stanford.edu>
+ * This work is hereby placed in the public domain by its author.
+ */
+
+#include <config.h>
+#include <portable/system.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/time.h>
+
+/*
+ * If we're running the test suite, rename mkstemp to avoid conflicts with the
+ * system version.  #undef it first because some systems may define it to
+ * another name.
+ */
+#if TESTING
+# undef mkstemp
+# define mkstemp test_mkstemp
+int test_mkstemp(char *);
+#endif
+
+/* Pick the longest available integer type. */
+#if HAVE_LONG_LONG
+typedef unsigned long long long_int_type;
+#else
+typedef unsigned long long_int_type;
+#endif
+
+int
+mkstemp(char *template)
+{
+    static const char letters[] =
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+    size_t length;
+    char *XXXXXX;
+    struct timeval tv;
+    long_int_type randnum, working;
+    int i, tries, fd;
+
+    /*
+     * Make sure we have a valid template and initialize p to point at the
+     * beginning of the template portion of the string.
+     */
+    length = strlen(template);
+    if (length < 6) {
+        errno = EINVAL;
+        return -1;
+    }
+    XXXXXX = template + length - 6;
+    if (strcmp(XXXXXX, "XXXXXX") != 0) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    /* Get some more-or-less random information. */
+    gettimeofday(&tv, NULL);
+    randnum = ((long_int_type) tv.tv_usec << 16) ^ tv.tv_sec ^ getpid();
+
+    /*
+     * Now, try to find a working file name.  We try no more than TMP_MAX file
+     * names.
+     */
+    for (tries = 0; tries < TMP_MAX; tries++) {
+        for (working = randnum, i = 0; i < 6; i++) {
+            XXXXXX[i] = letters[working % 62];
+            working /= 62;
+        }
+        fd = open(template, O_RDWR | O_CREAT | O_EXCL, 0600);
+        if (fd >= 0 || (errno != EEXIST && errno != EISDIR))
+            return fd;
+
+        /*
+         * This is a relatively random increment.  Cut off the tail end of
+         * tv_usec since it's often predictable.
+         */
+        randnum += (tv.tv_usec >> 10) & 0xfff;
+    }
+    errno = EEXIST;
+    return -1;
+}