[vlc-commits] http: define an error value for stream read (refs #17159)

[Rémi Denis-Courmont]

vlc | branch: master | Rémi Denis-Courmont <remi at remlab.net> | Mon Aug 22 05:24:07 2016 +0300| [df24c69f34e8202a8fd1cbe375419b6566ef1934] | committer: Rémi Denis-Courmont

http: define an error value for stream read (refs #17159)

This distinguishes unexpected error from regular end-of-stream.

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=df24c69f34e8202a8fd1cbe375419b6566ef1934
---

 modules/access/http/file.c    |  9 ++++++---
 modules/access/http/live.c    |  2 +-
 modules/access/http/message.c |  6 ++++++
 modules/access/http/message.h | 20 +++++++++++++++++++-
 4 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/modules/access/http/file.c b/modules/access/http/file.c
index a6b6bb0..ce101f6 100644
--- a/modules/access/http/file.c
+++ b/modules/access/http/file.c
@@ -234,18 +234,21 @@ block_t *vlc_http_file_read(struct vlc_http_resource *res)
     struct vlc_http_file *file = (struct vlc_http_file *)res;
     block_t *block = vlc_http_res_read(res);
 
-    if (block == NULL)
-    {   /* Automatically reconnect if server supports seek */
+    if (block == vlc_http_error)
+    {   /* Automatically reconnect on error if server supports seek */
         if (res->response != NULL
          && vlc_http_msg_can_seek(res->response)
          && file->offset < vlc_http_msg_get_file_size(res->response)
          && vlc_http_file_seek(res, file->offset) == 0)
             block = vlc_http_res_read(res);
 
-        if (block == NULL)
+        if (block == vlc_http_error)
             return NULL;
     }
 
+    if (block == NULL)
+        return NULL; /* End of stream */
+
     file->offset += block->i_buffer;
     return block;
 }
diff --git a/modules/access/http/live.c b/modules/access/http/live.c
index 3ef1870..6daf967 100644
--- a/modules/access/http/live.c
+++ b/modules/access/http/live.c
@@ -75,7 +75,7 @@ struct vlc_http_resource *vlc_http_live_create(struct vlc_http_mgr *mgr,
 block_t *vlc_http_live_read(struct vlc_http_resource *res)
 {
     struct block_t *block = vlc_http_res_read(res);
-    if (block != NULL)
+    if (block != NULL && block != vlc_http_error)
         return block;
 
     /* Automatically try to reconnect */
diff --git a/modules/access/http/message.c b/modules/access/http/message.c
index b3dd48a..b3874be 100644
--- a/modules/access/http/message.c
+++ b/modules/access/http/message.c
@@ -24,6 +24,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <stdalign.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -48,6 +49,11 @@ struct vlc_http_msg
     struct vlc_http_stream *payload;
 };
 
+/* Maximum alignment for safe conversion to/from any specific pointer type */
+static const char alignas (max_align_t) vlc_http_error_loc;
+
+void *const vlc_http_error = (char *)&vlc_http_error_loc;
+
 static bool vlc_http_is_token(const char *);
 
 static ssize_t vlc_http_msg_find_header(const struct vlc_http_msg *m,
diff --git a/modules/access/http/message.h b/modules/access/http/message.h
index 302184e..0c34e85 100644
--- a/modules/access/http/message.h
+++ b/modules/access/http/message.h
@@ -280,7 +280,9 @@ struct vlc_http_msg *vlc_http_msg_get_final(struct vlc_http_msg *) VLC_USED;
  * been received, waits until data is received, the stream ends or the
  * underlying connection fails.
  *
- * @return data block, or NULL on end-of-stream or error
+ * @return data block
+ * @retval NULL on end-of-stream
+ * @retval vlc_http_error on fatal error
  */
 struct block_t *vlc_http_msg_read(struct vlc_http_msg *) VLC_USED;
 
@@ -306,6 +308,18 @@ struct block_t *vlc_http_msg_read(struct vlc_http_msg *) VLC_USED;
 
 struct vlc_http_stream;
 
+/**
+ * Error pointer value
+ *
+ * This is an error value for some HTTP functions that can return NULL in
+ * non-error circumstances. Another return value is necessary to express
+ * error/failure, which this is.
+ * This compares different to NULL and to any valid pointer.
+ *
+ * @warning Dereferencing this pointer is undefined.
+ */
+extern void *const vlc_http_error;
+
 void vlc_http_msg_attach(struct vlc_http_msg *m, struct vlc_http_stream *s);
 struct vlc_http_msg *vlc_http_msg_get_initial(struct vlc_http_stream *s)
 VLC_USED;
@@ -348,6 +362,10 @@ struct vlc_http_msg *vlc_http_stream_read_headers(struct vlc_http_stream *s)
  * Reads message payload data.
  *
  * Reads the next block of data from the message payload of an HTTP stream.
+ *
+ * @return a block of data (use block_Release() to free it)
+ * @retval NULL The end of the stream was reached.
+ * @retval vlc_http_error The stream encountered a fatal error.
  */
 static inline struct block_t *vlc_http_stream_read(struct vlc_http_stream *s)
 {