From: Aman Karmani <a...@tmm1.net>
The HTTP spec allows '*' for document size in Content-Range response headers,
to specify that the file size is unknown:
Content-Range: <unit> <range-start>-<range-end>/<size>
Content-Range: <unit> <range-start>-<range-end>/*
Content-Range: <unit> */<size>
In the case where the filesize is unknown, this patch keeps track of a new
fileend variable
which is the approximate size based on the range and data returned by the
server.
Practically speaking, this patch can be used effectively "tail" a stream that is
still being appended to. For example, a PVR system may record an mpegts stream
to disk,
and serve up the same file to players while the stream is actively being
recorded.
By adding a `Content-Range: bytes X-Y/*` header to the response, the server can
inform the ffmpeg-based player that the stream is "active" and that the file
size
will continue to grow. For every incoming request, the server would:
- open file handle to recording in progress
- seek file handle to offset requested by the incoming `Range` header
- query the current file size of the file
- return a `Content-Range` header with the format `bytes <start
offset>-<current file size>/*`
- copy bytes from the file to the http socket
- on eof, wait and try reading from the file again to "tail" it as long as the
recording is "active"
On the ffmpeg size, we simply use MAX(s->off, s->fileend) to decide how large
the file is
whenever requested via AVSEEK_SIZE. This effectively allows ffmpeg based
players to
watch and seek around a growing mpegts stream even while it is being appended
to.
Signed-off-by: Aman Karmani <a...@tmm1.net>
---
libavformat/http.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/libavformat/http.c b/libavformat/http.c
index 476b9a8456..9dc0ff935d 100644
--- a/libavformat/http.c
+++ b/libavformat/http.c
@@ -68,7 +68,7 @@ typedef struct HTTPContext {
/* Used if "Transfer-Encoding: chunked" otherwise -1. */
uint64_t chunksize;
int chunkend;
- uint64_t off, end_off, filesize;
+ uint64_t off, end_off, filesize, fileend;
char *location;
HTTPAuthState auth_state;
HTTPAuthState proxy_auth_state;
@@ -621,6 +621,7 @@ static int http_open(URLContext *h, const char *uri, int
flags,
h->is_streamed = 1;
s->filesize = UINT64_MAX;
+ s->fileend = UINT64_MAX;
s->location = av_strdup(uri);
if (!s->location)
return AVERROR(ENOMEM);
@@ -750,13 +751,22 @@ static int parse_location(HTTPContext *s, const char *p)
static void parse_content_range(URLContext *h, const char *p)
{
HTTPContext *s = h->priv_data;
- const char *slash;
+ const char *slash, *dash;
+ uint64_t range_end = UINT64_MAX;
if (!strncmp(p, "bytes ", 6)) {
p += 6;
s->off = strtoull(p, NULL, 10);
- if ((slash = strchr(p, '/')) && strlen(slash) > 0)
- s->filesize = strtoull(slash + 1, NULL, 10);
+ if ((dash = strchr(p, '-')))
+ range_end = strtoll(dash + 1, NULL, 10);
+ if ((slash = strchr(p, '/')) && strlen(slash) > 0) {
+ if (slash[0] == '*') {
+ s->fileend = range_end;
+ } else {
+ s->filesize = strtoull(slash + 1, NULL, 10);
+ s->fileend = UINT64_MAX;
+ }
+ }
}
if (s->seekable == -1 && (!s->is_akamai || s->filesize != 2147483647))
h->is_streamed = 0; /* we _can_ in fact seek */
@@ -1404,6 +1414,7 @@ static int http_connect(URLContext *h, const char *path,
const char *local_path,
s->off = 0;
s->icy_data_read = 0;
s->filesize = UINT64_MAX;
+ s->fileend = UINT64_MAX;
s->willclose = 0;
s->end_chunked_post = 0;
s->end_header = 0;
@@ -1779,19 +1790,21 @@ static int64_t http_seek_internal(URLContext *h,
int64_t off, int whence, int fo
int old_buf_size, ret;
AVDictionary *options = NULL;
- if (whence == AVSEEK_SIZE)
+ if (whence == AVSEEK_SIZE && s->fileend != UINT64_MAX)
+ return s->off > s->fileend ? s->off : s->fileend;
+ else if (whence == AVSEEK_SIZE)
return s->filesize;
else if (!force_reconnect &&
((whence == SEEK_CUR && off == 0) ||
(whence == SEEK_SET && off == s->off)))
return s->off;
- else if ((s->filesize == UINT64_MAX && whence == SEEK_END))
+ else if ((s->filesize == UINT64_MAX && s->fileend == UINT64_MAX && whence
== SEEK_END))
return AVERROR(ENOSYS);
if (whence == SEEK_CUR)
off += s->off;
else if (whence == SEEK_END)
- off += s->filesize;
+ off += s->fileend > 0 ? s->fileend : s->filesize;
else if (whence != SEEK_SET)
return AVERROR(EINVAL);
if (off < 0)
--
2.33.0
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