[FFmpeg-devel] [PATCH 9/9] doc/example: Add http multi-client example code

[Stephan Holljes]

On Thu, Jul 9, 2015 at 3:47 PM, Nicolas George <george at nsup.org> wrote:
> Le decadi 20 messidor, an CCXXIII, Stephan Holljes a écrit :
>> Signed-off-by: Stephan Holljes <klaxa1337 at googlemail.com>
>> ---
>>  doc/examples/Makefile           |   1 +
>>  doc/examples/http_multiclient.c | 120 ++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 121 insertions(+)
>>  create mode 100644 doc/examples/http_multiclient.c
>>     Changes since first version:
>>       - Move client handling code in separate function
>>       - Close filedescriptors earlier
>>
>> diff --git a/doc/examples/Makefile b/doc/examples/Makefile
>> index 9699f11..8c9501b 100644
>> --- a/doc/examples/Makefile
>> +++ b/doc/examples/Makefile
>> @@ -18,6 +18,7 @@ EXAMPLES=       avio_list_dir                      \
>>                  extract_mvs                        \
>>                  filtering_video                    \
>>                  filtering_audio                    \
>> +                http_multiclient                   \
>>                  metadata                           \
>>                  muxing                             \
>>                  remuxing                           \
>> diff --git a/doc/examples/http_multiclient.c b/doc/examples/http_multiclient.c
>> new file mode 100644
>> index 0000000..a780321
>> --- /dev/null
>> +++ b/doc/examples/http_multiclient.c
>> @@ -0,0 +1,120 @@
>> +/*
>> + * copyright (c) 2015 Stephan Holljes
>> + *
>> + * This file is part of FFmpeg.
>> + *
>> + * FFmpeg 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; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * FFmpeg 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 FFmpeg; if not, write to the Free Software
>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>> + */
>> +
>> +/**
>> + * @file
>> + * libavformat multi-client network API usage example.
>> + *
>> + * @example http_multiclient.c
>> + * This example will serve a file without decoding or demuxing it over http.
>> + * Multiple clients can connect and will receive the same file.
>> + */
>> +
>> +#include <libavformat/avformat.h>
>> +#include <unistd.h>
>> +
>> +void process_client(AVIOContext *client, const char* in_uri)
>> +{
>
>> +    AVIOContext *input =NULL;
>
> Nit: space.
>
>> +    uint8_t buf[1024];
>> +    int ret, n;
>
>> +    avio_handshake(client);
>
> Check for error.
>
>> +    fprintf(stderr, "Handshake performed.\n");
>> +    fprintf(stderr, "Opening input file.\n");
>
>> +    if ((ret = avio_open2(&input, in_uri, AVIO_FLAG_READ, NULL, NULL)) < 0) {
>> +        av_log(input, AV_LOG_ERROR, "Failed to open input: %s\n", in_uri);
>> +        return;
>> +    }
>
> I just realized this: how would you go about returning 404 to the client
> here?

Good question, I haven't thought about that myself. Adding a 404 error
to handle_http_errors() and calling it with AVERROR_HTTP_NOT_FOUND
could be a solution. I feel like the name "handle_http_errors" is not
well chosen then, though.

>
>> +    for(;;) {
>> +        n = avio_read(input, buf, sizeof(buf));
>> +        if (n < 0) {
>> +            if (n == AVERROR_EOF)
>> +                break;
>> +            av_log(input, AV_LOG_ERROR, "Error reading from input: %s.\n",
>> +                   av_err2str(n));
>> +            ret = n;
>> +            break;
>> +        }
>> +        avio_write(client, buf, n);
>> +        avio_flush(client);
>> +    }
>> +    fprintf(stderr, "Flushing client\n");
>> +    avio_flush(client);
>> +    fprintf(stderr, "Closing client\n");
>> +    avio_close(client);
>> +    fprintf(stderr, "Closing input\n");
>> +    avio_close(input);
>> +}
>> +
>> +int main(int argc, char **argv)
>> +{
>> +    AVDictionary *options = NULL;
>> +    AVIOContext *client = NULL, *server = NULL;
>> +    const char *in_uri, *out_uri;
>> +    int ret, pid;
>> +    if (argc < 3) {
>> +        printf("usage: %s input http://hostname[:port]\n"
>> +               "API example program to serve http to multiple clients.\n"
>> +               "\n", argv[0]);
>> +        return 1;
>> +    }
>> +
>> +    in_uri = argv[1];
>> +    out_uri = argv[2];
>> +
>> +    av_register_all();
>> +    avformat_network_init();
>> +
>> +    if ((ret = av_dict_set(&options, "listen", "2", 0)) < 0)
>> +        goto end;
>> +    if ((ret = avio_open2(&server, out_uri, AVIO_FLAG_READ_WRITE, NULL, &options)) < 0)
>> +        goto end;
>> +    fprintf(stderr, "Entering main loop.\n");
>> +    for(;;) {
>> +        if ((ret = avio_accept(server, &client)) < 0)
>> +            goto end;
>> +        fprintf(stderr, "Accepted client, forking process.\n");
>> +        // XXX: Since we don't reap our children and don't ignore signals
>> +        //      this produces zombie processes.
>> +        pid = fork();
>> +        if (pid < 0) {
>
>> +            fprintf(stderr, "Fork failed.\n");
>
> perror()
>
>> +            ret = AVERROR(errno);
>> +            goto end;
>> +        }
>> +        if (pid == 0) {
>> +            fprintf(stderr, "In child.\n");
>> +            process_client(client, in_uri);
>> +            avio_close(server);
>> +            exit(0);
>> +        }
>> +        if (pid > 0)
>> +            avio_close(client);
>> +    }
>> +
>> +end:
>> +    avio_close(server);
>
>> +    if (ret < 0 && ret != AVERROR_EOF) {
>
> At this point, I believe yo do not have to worry about EOF.
>
>> +        fprintf(stderr, "Some errors occured: ");
>> +        fprintf(stderr, "%s\n", av_err2str(ret));
>
> Could be a single line.
>
>> +        return 1;
>> +    }
>> +    return 0;
>> +}
>
> These are all my remarks for the series for now, I'd say it is almost ready
> for inclusion.

Great!

>
> Regards,
>
> --
>   Nicolas George
>
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>

Regards,
Stephan