Re: [RFC/WIP PATCH 06/11] remote.h: add get_remote_capabilities, request_capabilities

[Eric Sunshine <sunshine@sunshineco.com>]

On Tue, May 26, 2015 at 6:01 PM, Stefan Beller <sbeller@google.com> wrote:
> Instead of calling get_remote_heads as a first command during the
> protocol exchange, we need to have fine grained control over the
> capability negotiation in version 2 of the protocol.
>
> Introduce get_remote_capabilities, which will just listen to
> capabilities of the remote and request_capabilities which will
> tell the selection of capabilities to the remote.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
> diff --git a/connect.c b/connect.c
> index c0144d8..bb17618 100644
> --- a/connect.c
> +++ b/connect.c
> @@ -105,8 +105,54 @@ static void annotate_refs_with_symref_info(struct ref *ref)
>         string_list_clear(&symref, 0);
>  }
>
> +void get_remote_capabilities(int in, char *src_buf, size_t src_len)
> +{
> +       struct strbuf capabilities_string = STRBUF_INIT;
> +       for (;;) {
> +               int len;
> +               char *line = packet_buffer;
> +               const char *arg;
> +
> +               len = packet_read(in, &src_buf, &src_len,
> +                                 packet_buffer, sizeof(packet_buffer),
> +                                 PACKET_READ_GENTLE_ON_EOF |
> +                                 PACKET_READ_CHOMP_NEWLINE);
> +               if (len < 0)
> +                       die_initial_contact(0);
> +
> +               if (!len)
> +                       break;
> +
> +               if (len > 4 && skip_prefix(line, "ERR ", &arg))

The 'len > 4' check is needed because there's no guarantee that 'line'
is NUL-terminated. Correct?

> +                       die("remote error: %s", arg);
> +
> +               if (starts_with(line, "capability:")) {
> +                       strbuf_addstr(&capabilities_string, line + strlen("capability:"));

skip_prefix() maybe?

> +                       strbuf_addch(&capabilities_string, ' ');
> +               }
> +       }
> +       free(server_capabilities);
> +       server_capabilities = xmalloc(capabilities_string.len + 1);
> +       server_capabilities = strbuf_detach(&capabilities_string, NULL);

So, you're allocating a buffer for server_capabilities and then
immediately throwing away (leaking) that buffer. Seems fishy.

> +       strbuf_release(&capabilities_string);

Not outright incorrect, but you've just detached capabilities_string's
buffer, so releasing it doesn't buy anything.

> +}
> +
> +int request_capabilities(int out)
> +{
> +       fprintf(stderr, "request_capabilities\n");
> +       // todo: send our capabilities
> +       packet_write(out, "capability:foo");
> +       packet_flush(out);
> +}
> +
>  /*
> - * Read all the refs from the other end
> + * Read all the refs from the other end,
> + * in is a file descriptor input stream
> + * src_buf and src_len may be an alternative way to specify the input.

The bit about src_buf and src_len conveys little or nothing. After
reading it, I'm as clueless to their purpose as I would be if they
were undocumented.

> + * list is the output of refs
> + * extra_have is a list to store information learned about sha1 the other side has.
> + * shallow_points

'shallow_points' what?

>   */
>  struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
>                               struct ref **list, unsigned int flags,
> diff --git a/remote.h b/remote.h
> index 04e2310..7381ddf 100644
> --- a/remote.h
> +++ b/remote.h
> @@ -146,6 +146,9 @@ int check_ref_type(const struct ref *ref, int flags);
>  void free_refs(struct ref *ref);
>
>  struct sha1_array;
> +
> +extern void get_remote_capabilities(int in, char *src_buf, size_t src_len);
> +extern int request_capabilities(int out);
>  extern struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
>                                      struct ref **list, unsigned int flags,
>                                      struct sha1_array *extra_have,
> --
> 2.4.1.345.gab207b6.dirty