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libssh2_session_callback_set.3: explain the recv/send callbacks

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Describe how to actually use these callbacks.

Closes #518
This commit is contained in:
Daniel Stenberg
2020-09-28 15:53:29 +02:00
parent 00d5b0c385
commit 4afcb8cd9b
1 changed files with 36 additions and 4 deletions
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40
docs/libssh2_session_callback_set.3
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@@ -32,11 +32,43 @@ function returns 0, the packet will be accepted nonetheless.
.IP LIBSSH2_CALLBACK_X11 .IP LIBSSH2_CALLBACK_X11
Called when an X11 connection has been accepted Called when an X11 connection has been accepted
.IP LIBSSH2_CALLBACK_SEND .IP LIBSSH2_CALLBACK_SEND
Called when libssh2 wants to send some data on the connection. Called when libssh2 wants to send data on the connection. Can be set to a
Can be set to a custom function to handle I/O your own way. custom function to handle I/O your own way.
The prototype of the callback:
.nf
ssize_t sendcb(libssh2_socket_t sockfd, const void *buffer,
size_t length, int flags, void **abstract);
.fi
\fBsockfd\fP is the socket to write to, \fBbuffer\fP points to the data to
send, \fBlength\fP is the size of the data, \fBflags\fP is the flags that
would've been used to a \fIsend()\fP call and \fBabstract\fP is a pointer to
the abstract pointer set in the \fIlibssh2_session_init_ex(3)\fP call.
The callback returns the number of bytes sent, or -1 for error. The special
return code \fB-EAGAIN\fP can be returned to signal that the send was aborted
to prevent getting blocked and it needs to be called again.
.IP LIBSSH2_CALLBACK_RECV .IP LIBSSH2_CALLBACK_RECV
Called when libssh2 wants to receive some data from the connection. Called when libssh2 wants to read data from the connection. Can be set to a
Can be set to a custom function to handle I/O your own way. custom function to handle I/O your own way.
The prototype of the callback:
.nf
ssize_t recvcb(libssh2_socket_t sockfd, void *buffer,
size_t length, int flags, void **abstract);
.fi
\fBsockfd\fP is the socket to read from, \fBbuffer\fP where to store received
data into, \fBlength\fP is the size of the buffer, \fBflags\fP is the flags
that would've been used to a \fIrecv()\fP call and \fBabstract\fP is a pointer
to the abstract pointer set in the \fIlibssh2_session_init_ex(3)\fP call.
The callback returns the number of bytes read, or -1 for error. The special
return code \fB-EAGAIN\fP can be returned to signal that the read was aborted
to prevent getting blocked and it needs to be called again.
.SH RETURN VALUE .SH RETURN VALUE
Pointer to previous callback handler. Returns NULL if no prior callback Pointer to previous callback handler. Returns NULL if no prior callback
handler was set or the callback type was unknown. handler was set or the callback type was unknown.