On date Saturday 2011-04-09 02:03:19 +0200, Stefano Sabatini wrote:
> On date Friday 2011-04-08 23:33:33 +0200, Luca Barbato wrote:
> > On 4/8/11 8:10 PM, Anton Khirnov wrote:
> > >From: Stefano Sabatini<stefano.sabatini-l...@poste.it>
> >
> > Seems fine in principle even if I won't use "check" and I'd merge it
> > using ffurl namespace.
>
> Please wait because I have an updated patchset.
Attached updated proof of concept patchset, completely untested (it's
late and i need to sleep).
I was trying to address Michael's comments:
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/102825/focus=118515
|requiring one call to url_check() for testing each flag is bad
|a better api would be
|
|flags are a bit mask of which properties we want
|and the return value provides these through similar flags
I forgot why I didn't consider the patchset ready for posting after I
tried to address that comment, but I vaguely remember there was some
problematic corner case so it needs more testing.
--
Driver does not carry cash.
>From b563c12cb285f1e6eb8dc19d1a18323cd9280ea1 Mon Sep 17 00:00:00 2001
From: Stefano Sabatini <stefano.sabatini-l...@poste.it>
Date: Fri, 8 Apr 2011 18:32:25 +0200
Subject: [PATCH] avio: add avio_check()
The new function is more flexible than url_exist(), as it allows to
specify which access flags to check, and does not require an explicit
open of the checked resource.
---
libavformat/avio.c | 19 +++++++++++++++++++
libavformat/avio.h | 15 +++++++++++++++
2 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/libavformat/avio.c b/libavformat/avio.c
index 7b066e3..cc57529 100644
--- a/libavformat/avio.c
+++ b/libavformat/avio.c
@@ -362,6 +362,25 @@ int url_exist(const char *filename)
return 1;
}
+int avio_check(const char *url, int flags)
+{
+ URLContext *h;
+ int ret = ffurl_alloc(&h, url, flags);
+ if (ret)
+ return ret;
+
+ if (h->prot->url_check) {
+ ret = h->prot->url_check(h, flags);
+ } else {
+ ret = ffurl_connect(h);
+ if (ret >= 0)
+ ret = flags;
+ }
+
+ ffurl_close(h);
+ return ret;
+}
+
int64_t ffurl_size(URLContext *h)
{
int64_t pos, size;
diff --git a/libavformat/avio.h b/libavformat/avio.h
index 03b6f6f..051c06e 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -127,6 +127,20 @@ attribute_deprecated void url_set_interrupt_cb(URLInterruptCB *interrupt_cb);
int url_exist(const char *url);
/**
+ * Return AVIO_* access flags corresponding to the access permissions
+ * of the resource in url, or a negative value corresponding to an
+ * AVERROR code in case of failure. The returned access flags are
+ * masked by the value in flags.
+ *
+ * @note This function is intrinsecally unsafe, in the sense that the
+ * checked resource may change its existence or permission status from
+ * one call to another. Thus you should not trust the returned value,
+ * unless you are sure that no other processes are accessing the
+ * checked resource.
+ */
+int avio_check(const char *url, int flags);
+
+/**
* The callback is called in blocking functions to test regulary if
* asynchronous interruption is needed. AVERROR_EXIT is returned
* in this case by the interrupted function. 'NULL' means no interrupt
@@ -157,6 +171,7 @@ typedef struct URLProtocol {
int priv_data_size;
const AVClass *priv_data_class;
int flags;
+ int (*url_check)(URLContext *h, int mask);
} URLProtocol;
#if FF_API_REGISTER_PROTOCOL
--
1.7.2.3
>From 1dc3e93dc0ed88272dd427af81cf40410e1dad13 Mon Sep 17 00:00:00 2001
From: Stefano Sabatini <stefano.sabatini-l...@poste.it>
Date: Thu, 30 Sep 2010 13:21:42 +0200
Subject: [PATCH] file: implement url_check() callback in the file and pipe protocols
---
libavformat/file.c | 16 ++++++++++++++++
1 files changed, 16 insertions(+), 0 deletions(-)
diff --git a/libavformat/file.c b/libavformat/file.c
index b8c7c4c..f939a8e 100644
--- a/libavformat/file.c
+++ b/libavformat/file.c
@@ -94,6 +94,20 @@ static int file_close(URLContext *h)
return close(fd);
}
+static int file_check(URLContext *h, int mask)
+{
+ struct stat st;
+ int ret = stat(h->filename, &st);
+ if (ret < 0)
+ return AVERROR(errno);
+
+ ret |= st.st_mode&S_IRUSR ? mask&AVIO_RDONLY : 0;
+ ret |= st.st_mode&S_IWUSR ? mask&AVIO_WRONLY : 0;
+ ret |= st.st_mode&S_IWUSR && st.st_mode&S_IRUSR ? mask&AVIO_RDWR : 0;
+
+ return ret;
+}
+
URLProtocol ff_file_protocol = {
"file",
file_open,
@@ -102,6 +116,7 @@ URLProtocol ff_file_protocol = {
file_seek,
file_close,
.url_get_file_handle = file_get_handle,
+ .url_check = file_check,
};
#endif /* CONFIG_FILE_PROTOCOL */
@@ -136,6 +151,7 @@ URLProtocol ff_pipe_protocol = {
file_read,
file_write,
.url_get_file_handle = file_get_handle,
+ .url_check = file_check,
};
#endif /* CONFIG_PIPE_PROTOCOL */
--
1.7.2.3
>From 3337ee5fd1ca5772c293f76e7c15267077c8001f Mon Sep 17 00:00:00 2001
From: Stefano Sabatini <stefano.sabatini-l...@poste.it>
Date: Sat, 9 Apr 2011 01:32:37 +0200
Subject: [PATCH] prefer avio_check() over url_exist()
The problem with url_exist() is that it tries to open a resource in
RDONLY mode. If the file is a FIFO and there is already a reading
client, the open() call will hang.
By using avio_check() with access mode of 0, the second reading
process will check if the file exists without attempting to open it,
thus avoiding the lock.
Fix issue #1663.
---
ffmpeg.c | 2 +-
ffserver.c | 4 ++--
libavformat/img2.c | 6 +++---
3 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/ffmpeg.c b/ffmpeg.c
index 40e5e67..9153a5b 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -3870,7 +3870,7 @@ static void opt_output_file(const char *filename)
(strchr(filename, ':') == NULL ||
filename[1] == ':' ||
av_strstart(filename, "file:", NULL))) {
- if (url_exist(filename)) {
+ if (avio_check(filename, 0) != AVERROR(ENOENT)) {
if (!using_stdin) {
fprintf(stderr,"File '%s' already exists. Overwrite ? [y/N] ", filename);
fflush(stderr);
diff --git a/ffserver.c b/ffserver.c
index 6e42979..5f165dd 100644
--- a/ffserver.c
+++ b/ffserver.c
@@ -3684,7 +3684,7 @@ static void build_feed_streams(void)
for(feed = first_feed; feed != NULL; feed = feed->next_feed) {
int fd;
- if (url_exist(feed->feed_filename)) {
+ if (url_check(feed->feed_filename, URL_RDONLY)) {
/* See if it matches */
AVFormatContext *s;
int matches = 0;
@@ -3757,7 +3757,7 @@ static void build_feed_streams(void)
unlink(feed->feed_filename);
}
}
- if (!url_exist(feed->feed_filename)) {
+ if (!avio_check(feed->feed_filename, AVIO_RDONLY)) {
AVFormatContext s1 = {0}, *s = &s1;
if (feed->readonly) {
diff --git a/libavformat/img2.c b/libavformat/img2.c
index 4e55c22..0c7de97 100644
--- a/libavformat/img2.c
+++ b/libavformat/img2.c
@@ -132,11 +132,11 @@ static int find_image_range(int *pfirst_index, int *plast_index,
if (av_get_frame_filename(buf, sizeof(buf), path, first_index) < 0){
*pfirst_index =
*plast_index = 1;
- if(url_exist(buf))
+ if (avio_check(buf, AVIO_RDONLY) != AVERROR(ENOENT))
return 0;
return -1;
}
- if (url_exist(buf))
+ if (avio_check(buf, AVIO_RDONLY) != AVERROR(ENOENT))
break;
}
if (first_index == 5)
@@ -154,7 +154,7 @@ static int find_image_range(int *pfirst_index, int *plast_index,
if (av_get_frame_filename(buf, sizeof(buf), path,
last_index + range1) < 0)
goto fail;
- if (!url_exist(buf))
+ if (avio_check(buf, AVIO_RDONLY) != AVERROR(ENOENT))
break;
range = range1;
/* just in case... */
--
1.7.2.3
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