1 files changed, 116 insertions, 0 deletions
diff --git a/src/port/thread.c b/src/port/thread.c
new file mode 100644
index 0000000..1f3bcbd
--- /dev/null
+++ b/src/port/thread.c
@@ -0,0 +1,116 @@
+/*-------------------------------------------------------------------------
+ *
+ * thread.c
+ *
+ *		  Prototypes and macros around system calls, used to help make
+ *		  threaded libraries reentrant and safe to use from threaded applications.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ *
+ * src/port/thread.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <pwd.h>
+
+
+/*
+ *	Threading sometimes requires specially-named versions of functions
+ *	that return data in static buffers, like strerror_r() instead of
+ *	strerror().  Other operating systems use pthread_setspecific()
+ *	and pthread_getspecific() internally to allow standard library
+ *	functions to return static data to threaded applications. And some
+ *	operating systems have neither.
+ *
+ *	Additional confusion exists because many operating systems that
+ *	use pthread_setspecific/pthread_getspecific() also have *_r versions
+ *	of standard library functions for compatibility with operating systems
+ *	that require them.  However, internally, these *_r functions merely
+ *	call the thread-safe standard library functions.
+ *
+ *	For example, BSD/OS 4.3 uses Bind 8.2.3 for getpwuid().  Internally,
+ *	getpwuid() calls pthread_setspecific/pthread_getspecific() to return
+ *	static data to the caller in a thread-safe manner.  However, BSD/OS
+ *	also has getpwuid_r(), which merely calls getpwuid() and shifts
+ *	around the arguments to match the getpwuid_r() function declaration.
+ *	Therefore, while BSD/OS has getpwuid_r(), it isn't required.  It also
+ *	doesn't have strerror_r(), so we can't fall back to only using *_r
+ *	functions for threaded programs.
+ *
+ *	The current setup is to try threading in this order:
+ *
+ *		use *_r function names if they exit
+ *			(*_THREADSAFE=yes)
+ *		use non-*_r functions if they are thread-safe
+ *
+ *	One thread-safe solution for gethostbyname() might be to use getaddrinfo().
+ */
+
+
+/*
+ * Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
+ * behaviour, if that function is not available or required.
+ *
+ * Per POSIX, the possible cases are:
+ * success: returns zero, *result is non-NULL
+ * uid not found: returns zero, *result is NULL
+ * error during lookup: returns an errno code, *result is NULL
+ * (caller should *not* assume that the errno variable is set)
+ */
+#ifndef WIN32
+int
+pqGetpwuid(uid_t uid, struct passwd *resultbuf, char *buffer,
+		   size_t buflen, struct passwd **result)
+{
+#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETPWUID_R)
+	return getpwuid_r(uid, resultbuf, buffer, buflen, result);
+#else
+	/* no getpwuid_r() available, just use getpwuid() */
+	errno = 0;
+	*result = getpwuid(uid);
+	/* paranoia: ensure we return zero on success */
+	return (*result == NULL) ? errno : 0;
+#endif
+}
+#endif
+
+/*
+ * Wrapper around gethostbyname() or gethostbyname_r() to mimic
+ * POSIX gethostbyname_r() behaviour, if it is not available or required.
+ * This function is called _only_ by our getaddrinfo() portability function.
+ */
+#ifndef HAVE_GETADDRINFO
+int
+pqGethostbyname(const char *name,
+				struct hostent *resultbuf,
+				char *buffer, size_t buflen,
+				struct hostent **result,
+				int *herrno)
+{
+#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETHOSTBYNAME_R)
+
+	/*
+	 * broken (well early POSIX draft) gethostbyname_r() which returns 'struct
+	 * hostent *'
+	 */
+	*result = gethostbyname_r(name, resultbuf, buffer, buflen, herrno);
+	return (*result == NULL) ? -1 : 0;
+#else
+
+	/* no gethostbyname_r(), just use gethostbyname() */
+	*result = gethostbyname(name);
+
+	if (*result != NULL)
+		*herrno = h_errno;
+
+	if (*result != NULL)
+		return 0;
+	else
+		return -1;
+#endif
+}
+
+#endif