client_write() writes a buffer to the client and buffers it if
required. client_puts() does the same for a C string. The next patch
will add more tools which will replace fdprintf() later.
Since client->fd==-1 has become our "expired" flag, it may already be
-1 when client_close() is called. Don't assert that it is still
non-negative, and call client_set_expired() instead.
Instead of passing the pointer to the "expired" flag to
processListOfCommands(), this function should use the client API to
check this flag. We can now remove the "global_expired" hack
introduced recently.
Start exporting the client struct as an opaque struct. For now, pass
it only to processCommand() and processListOfCommands(), and provide a
function to extract the socket handle. Later, we will propagate the
pointer to all command implementations, and of course to
client_print() etc.
The old code tried to write a response to the client, without even
checking if it was already closed. Now that we have added more
assertions, these may fail... perform the "expired" check earlier.
Patch bdeb8e14 ("client: moved "expired" accesses into inline
function") was created under the wrong assumption that
processListOfCommands() could modify the expired flag, which is not
the case. Although "expired" is a non-const pointer,
processListOfCommands() just reads it, using it as the break condition
in a "while" loop. I will address this issue with a better overall
solution, but for now provide a pointer to a global "expired" flag.
client_defer_output() was modified so that it can create the
deferred_send list. With this patch, the assertion on
"deferred_send!=NULL" has become invalid. Remove it.
Previously, when select() failed, we assumed that there was an invalid
file descriptor in one of the client structs. Thus we tried select()
one by one. This is bogus, because we should never have invalid file
descriptors. Remove it, and make select() errors fatal.
All of the client's resources are freed in client_close(). It is
enough to set the "expired" flag, no need to duplicate lots of
destruction code again and again.
Due to the large buffers in the client struct, the static client array
eats several megabytes of RAM with a maximum of only 10 clients. Stop
this waste and allocate each client struct from the heap.
Second patch: rename the internal struct name. We will eventually
export this type as an opaque forward-declared struct later, so we
can pass a struct pointer instead of a file descriptor, which would
save us an expensive linear lookup.
I don't believe "interface" is a good name for something like
"connection by a client to MPD", let's call it "client". This is the
first patch in the series which changes the name, beginning with the
file name.
