Implement lttng_read()/lttng_write()

Handle EINTR and partial read/write in wrapper functions.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/src/common/Makefile.am b/src/common/Makefile.am
index 0c02d533c021105cd73c6d1e105f77b251955fba..7817b40ae8cc2f1a364cf5501702299ff7f3e045 100644 (file)
--- a/src/common/Makefile.am
+++ b/src/common/Makefile.am
@@ -14,7 +14,7 @@ noinst_LTLIBRARIES = libcommon.la
 
 libcommon_la_SOURCES = error.h error.c utils.c utils.h runas.c runas.h \
                        common.h futex.c futex.h uri.c uri.h defaults.c \
-                       pipe.c pipe.h
+                       pipe.c pipe.h readwrite.c readwrite.h
 libcommon_la_LIBADD = -luuid
 
 # Consumer library

diff --git a/src/common/common.h b/src/common/common.h
index 2b2081c48cc15161ee89b1e76868362646c7dfb8..41eb03613c26c80b8bc77b07d4bb8dc348ad7c66 100644 (file)
--- a/src/common/common.h
+++ b/src/common/common.h
@@ -22,5 +22,6 @@
 #include "error.h"
 #include "macros.h"
 #include "runas.h"
+#include "readwrite.h"
 
 #endif /* _COMMON_H */

diff --git a/src/common/readwrite.c b/src/common/readwrite.c
new file mode 100644 (file)
index 0000000..43d4e39
--- /dev/null
+++ b/src/common/readwrite.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License, version 2.1 only,
+ * as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <unistd.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 occured.
+ * 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;
+
+       do {
+               ret = read(fd, &buf[i], count - i);
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               continue;       /* retry operation */
+                       } else {
+                               goto error;
+                       }
+               }
+               i += ret;
+               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;
+
+       do {
+               ret = write(fd, &buf[i], count - i);
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               continue;       /* retry operation */
+                       } else {
+                               goto error;
+                       }
+               }
+               i += ret;
+               assert(i <= count);
+       } while (count - i > 0 && ret > 0);
+       return i;
+
+error:
+       if (i == 0) {
+               return -1;
+       } else {
+               return i;
+       }
+}

diff --git a/src/common/readwrite.h b/src/common/readwrite.h
new file mode 100644 (file)
index 0000000..39f5a11
--- /dev/null
+++ b/src/common/readwrite.h
@@ -0,0 +1,34 @@
+#ifndef LTTNG_COMMON_READWRITE_H
+#define LTTNG_COMMON_READWRITE_H
+
+/*
+ * Copyright (C) 2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License, version 2.1 only,
+ * as published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <unistd.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 occured.
+ * The error can be checked by querying errno.
+ */
+ssize_t lttng_read(int fd, void *buf, size_t count);
+ssize_t lttng_write(int fd, const void *buf, size_t count);
+
+#endif /* LTTNG_COMMON_READWRITE_H */