include timegm fallback

2 files changed, 77 insertions, 0 deletions

diff --git a/crypto/Makefile.am b/crypto/Makefile.am
index e1e785d..40d82cd 100644
--- a/crypto/Makefile.am
+++ b/crypto/Makefile.am
@@ -73,6 +73,12 @@ if !HAVE_INET_PTON
 libcompat_la_SOURCES += compat/inet_pton.c
 endif
 
+if !HAVE_TIMEGM
+if !HAVE__MKGMTIME
+libcompat_la_SOURCES += compat/timegm.c
+endif
+endif
+
 if !HAVE_REALLOCARRAY
 libcompat_la_SOURCES += compat/reallocarray.c
 endif
diff --git a/crypto/compat/timegm.c b/crypto/compat/timegm.c
new file mode 100644
index 0000000..2007140
--- /dev/null
+++ b/crypto/compat/timegm.c
@@ -0,0 +1,71 @@
+/*
+ * timegm shims based on example code from in the glibc timegm manpage.
+ *
+ * These should be replaced with lockless versions that do not require
+ * modifying global state.
+ */
+
+#include <time.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#ifdef _WIN32
+#include <windows.h>
+time_t
+timegm(struct tm *tm)
+{
+        time_t ret;
+        char *tz, *buf;
+        static volatile HANDLE mtx = NULL;
+
+        if (!mtx) {
+                HANDLE p = CreateMutex(NULL, FALSE, NULL);
+                if (InterlockedCompareExchangePointer(
+                    (void **)&mtx, (void *)p, NULL))
+                        CloseHandle(p);
+        }
+        WaitForSingleObject(mtx, INFINITE);
+        tz = getenv("TZ");
+        if (tz) {
+                if (asprintf(&buf, "TZ=%s", tz) == -1)
+                        buf = NULL;
+        }
+        putenv("TZ=UTC");
+        tzset();
+        ret = mktime(tm);
+        if (buf) {
+                putenv(buf);
+                free(buf);
+        } else
+                putenv("TZ=");
+        tzset();
+        ReleaseMutex(mtx);
+        return ret;
+}
+#else
+#include <pthread.h>
+time_t
+timegm(struct tm *tm)
+{
+        time_t ret;
+        char *tz;
+        static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
+
+        pthread_mutex_lock(&mtx);
+        tz = getenv("TZ");
+        if (tz)
+                tz = strdup(tz);
+        setenv("TZ", "", 1);
+        tzset();
+        ret = mktime(tm);
+        if (tz) {
+                setenv("TZ", tz, 1);
+                free(tz);
+        } else
+                unsetenv("TZ");
+        tzset();
+        pthread_mutex_unlock(&mtx);
+        return ret;
+}
+#endif