The commit title is wrong: It's AVSEEK_SIZE.
Nicolas George:
> Signed-off-by: Nicolas George <geo...@nsup.org>
> ---
> libavformat/concat.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/libavformat/concat.c b/libavformat/concat.c
> index 19c83c309a..ea3bc1dfde 100644
> --- a/libavformat/concat.c
> +++ b/libavformat/concat.c
> @@ -38,6 +38,7 @@ struct concat_data {
> struct concat_nodes *nodes; ///< list of nodes to concat
> size_t length; ///< number of cat'ed nodes
> size_t current; ///< index of currently read node
> + uint64_t total_size;
> };
>
> static av_cold int concat_close(URLContext *h)
> @@ -59,7 +60,7 @@ static av_cold int concat_open(URLContext *h, const char
> *uri, int flags)
> {
> char *node_uri = NULL;
> int err = 0;
> - int64_t size;
> + int64_t size, total_size = 0;
> size_t len, i;
> URLContext *uc;
> struct concat_data *data = h->priv_data;
> @@ -112,6 +113,7 @@ static av_cold int concat_open(URLContext *h, const char
> *uri, int flags)
> /* assembling */
> nodes[i].uc = uc;
> nodes[i].size = size;
> + total_size += size;
There is a potential for overflow here which is undefined behaviour as
total_size is signed. Simply making it unsigned (like you store it)
will solve the undefined behaviour here, but if a wraparound happened,
then seeking may return a nonsense value (not only when using
AVSEEK_SIZE, but certainly when using AVSEEK_SIZE) and may not work at
all. I see two solutions for this:
a) Erroring out when the total size doesn't fit into a int64_t.
b) Disallow seeking if the total size doesn't fit into a int64_t (in
this case, one might even allow input files that don't report a usable
size).
I don't know if a) would break any use cases (maybe some (buggy)
protocol reports INT64_MAX if the size is unknown?).
> }
> av_free(node_uri);
> data->length = i;
> @@ -123,6 +125,7 @@ static av_cold int concat_open(URLContext *h, const char
> *uri, int flags)
> err = AVERROR(ENOMEM);
> } else
> data->nodes = nodes;
> + data->total_size = total_size;
> return err;
> }
>
> @@ -158,6 +161,8 @@ static int64_t concat_seek(URLContext *h, int64_t pos,
> int whence)
> struct concat_nodes *nodes = data->nodes;
> size_t i;
>
> + if ((whence & AVSEEK_SIZE))
Unnecessary parentheses.
> + return data->total_size;
> switch (whence) {
> case SEEK_END:
> for (i = data->length - 1; i && pos < -nodes[i].size; i--)
>
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