Fix: handle writes of length 0

[lttng-ust.git] / libringbuffer / backend.h

diff --git a/libringbuffer/backend.h b/libringbuffer/backend.h
index 83e07e426b3de3458a995bcfa953e0e33ee9d1fb..feefc7a3229f1314cf6813b1f05178a0cc6176e8 100644 (file)
--- a/libringbuffer/backend.h
+++ b/libringbuffer/backend.h
@@ -1,14 +1,26 @@
-#ifndef _LINUX_RING_BUFFER_BACKEND_H
-#define _LINUX_RING_BUFFER_BACKEND_H
+#ifndef _LTTNG_RING_BUFFER_BACKEND_H
+#define _LTTNG_RING_BUFFER_BACKEND_H
 
 /*
- * linux/ringbuffer/backend.h
- *
- * Copyright (C) 2008-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * libringbuffer/backend.h
  *
  * Ring buffer backend (API).
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * Copyright (C) 2011-2012 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 as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * 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
  *
  * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
  * the reader in flight recorder mode.
@@ -16,8 +28,6 @@
 
 #include <unistd.h>
 
-#include "ust/core.h"
-
 /* Internal helpers */
 #include "backend_internal.h"
 #include "frontend_internal.h"
@@ -26,13 +36,13 @@
 
 /* Ring buffer backend access (read/write) */
 
-extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb,
+extern size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb,
                                   size_t offset, void *dest, size_t len,
-                                  struct shm_handle *handle);
+                                  struct lttng_ust_shm_handle *handle);
 
-extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
+extern int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb,
                                     size_t offset, void *dest, size_t len,
-                                    struct shm_handle *handle);
+                                    struct lttng_ust_shm_handle *handle);
 
 /*
  * Return the address where a given offset is located.
@@ -41,13 +51,13 @@ extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
  * as long as the write is never bigger than a page size.
  */
 extern void *
-lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
+lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
                               size_t offset,
-                              struct shm_handle *handle);
+                              struct lttng_ust_shm_handle *handle);
 extern void *
-lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
+lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
                                    size_t offset,
-                                   struct shm_handle *handle);
+                                   struct lttng_ust_shm_handle *handle);
 
 /**
  * lib_ring_buffer_write - write data to a buffer backend
@@ -62,18 +72,20 @@ lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
  * if copy is crossing a page boundary.
  */
 static inline
-void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
-                          struct lib_ring_buffer_ctx *ctx,
+void lib_ring_buffer_write(const struct lttng_ust_lib_ring_buffer_config *config,
+                          struct lttng_ust_lib_ring_buffer_ctx *ctx,
                           const void *src, size_t len)
 {
-       struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+       struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend;
        struct channel_backend *chanb = &ctx->chan->backend;
-       struct shm_handle *handle = ctx->handle;
+       struct lttng_ust_shm_handle *handle = ctx->handle;
        size_t sbidx;
        size_t offset = ctx->buf_offset;
-       struct lib_ring_buffer_backend_pages_shmp *rpages;
+       struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
        unsigned long sb_bindex, id;
 
+       if (caa_unlikely(!len))
+               return;
        offset &= chanb->buf_size - 1;
        sbidx = offset >> chanb->subbuf_size_order;
        id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
@@ -100,12 +112,12 @@ void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
  */
 static inline
 unsigned long lib_ring_buffer_get_records_unread(
-                               const struct lib_ring_buffer_config *config,
-                               struct lib_ring_buffer *buf,
-                               struct shm_handle *handle)
+                               const struct lttng_ust_lib_ring_buffer_config *config,
+                               struct lttng_ust_lib_ring_buffer *buf,
+                               struct lttng_ust_shm_handle *handle)
 {
-       struct lib_ring_buffer_backend *bufb = &buf->backend;
-       struct lib_ring_buffer_backend_pages_shmp *pages;
+       struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
+       struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages;
        unsigned long records_unread = 0, sb_bindex, id;
        unsigned int i;
 
@@ -124,4 +136,4 @@ unsigned long lib_ring_buffer_get_records_unread(
        return records_unread;
 }
 
-#endif /* _LINUX_RING_BUFFER_BACKEND_H */
+#endif /* _LTTNG_RING_BUFFER_BACKEND_H */