common: compile libcommon as C++

[lttng-tools.git] / src / common / readwrite.cpp

diff --git a/src/common/readwrite.cpp b/src/common/readwrite.cpp
new file mode 100644 (file)
index 0000000..857781c
--- /dev/null
+++ b/src/common/readwrite.cpp
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2013 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ */
+
+#define _LGPL_SOURCE
+#include <limits.h>
+#include <unistd.h>
+
+#include <common/compat/errno.h>
+
+#include "readwrite.h"
+
+/*
+ * lttng_read and lttng_write take care of EINTR and partial read/write.
+ * Upon success, they return the "count" received as parameter.
+ * They can return a negative value if an error occurs.
+ * If a value lower than the requested "count" is returned, it means an
+ * error occurred.
+ * The error can be checked by querying errno.
+ */
+ssize_t lttng_read(int fd, void *buf, size_t count)
+{
+       size_t i = 0;
+       ssize_t ret;
+
+       LTTNG_ASSERT(buf);
+
+       /*
+        * Deny a read count that can be bigger then the returned value max size.
+        * This makes the function to never return an overflow value.
+        */
+       if (count > SSIZE_MAX) {
+               return -EINVAL;
+       }
+
+       do {
+               ret = read(fd, (char *) buf + i, count - i);
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               continue;       /* retry operation */
+                       } else {
+                               goto error;
+                       }
+               }
+               i += ret;
+               LTTNG_ASSERT(i <= count);
+       } while (count - i > 0 && ret > 0);
+       return i;
+
+error:
+       if (i == 0) {
+               return -1;
+       } else {
+               return i;
+       }
+}
+
+ssize_t lttng_write(int fd, const void *buf, size_t count)
+{
+       size_t i = 0;
+       ssize_t ret;
+
+       LTTNG_ASSERT(buf);
+
+       /*
+        * Deny a write count that can be bigger then the returned value max size.
+        * This makes the function to never return an overflow value.
+        */
+       if (count > SSIZE_MAX) {
+               return -EINVAL;
+       }
+
+       do {
+               ret = write(fd, (char *) buf + i, count - i);
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               continue;       /* retry operation */
+                       } else {
+                               goto error;
+                       }
+               }
+               i += ret;
+               LTTNG_ASSERT(i <= count);
+       } while (count - i > 0 && ret > 0);
+       return i;
+
+error:
+       if (i == 0) {
+               return -1;
+       } else {
+               return i;
+       }
+}