From afff64dbcde9cf45956f5557a8270b21c0e93dd5 Mon Sep 17 00:00:00 2001 From: Michael Kaufmann Date: Sun, 18 Dec 2016 12:51:48 +0100 Subject: curl_easy_recv: Improve documentation and example program Follow-up to 82245ea: Fix the example program sendrecv.c (handle CURLE_AGAIN, handle incomplete send). Improve the documentation for curl_easy_recv() and curl_easy_send(). Reviewed-by: Frank Meier Assisted-by: Jay Satiro See https://github.com/curl/curl/pull/1134 --- docs/libcurl/curl_easy_recv.3 | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) (limited to 'docs/libcurl/curl_easy_recv.3') diff --git a/docs/libcurl/curl_easy_recv.3 b/docs/libcurl/curl_easy_recv.3 index 3560cc511..7a812dd00 100644 --- a/docs/libcurl/curl_easy_recv.3 +++ b/docs/libcurl/curl_easy_recv.3 @@ -46,12 +46,21 @@ calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that \fIcurl_easy_recv(3)\fP does not work on connections that were created without this option. -You must ensure that the socket has data to read before calling -\fIcurl_easy_recv(3)\fP, otherwise the call will return \fBCURLE_AGAIN\fP - -the socket is used in non-blocking mode internally. Use -\fIcurl_easy_getinfo(3)\fP with \fICURLINFO_ACTIVESOCKET(3)\fP to obtain the -socket; use your operating system facilities like \fIselect(2)\fP to check if -it has any data you can read. +The call will return \fBCURLE_AGAIN\fP if there is no data to read - the +socket is used in non-blocking mode internally. When \fBCURLE_AGAIN\fP is +returned, use your operating system facilities like \fIselect(2)\fP to wait +for data. The socket may be obtained using \fIcurl_easy_getinfo(3)\fP with +\fICURLINFO_ACTIVESOCKET(3)\fP. + +Wait on the socket only if \fIcurl_easy_recv(3)\fP returns \fBCURLE_AGAIN\fP. +The reason for this is libcurl or the SSL library may internally cache some +data, therefore you should call \fIcurl_easy_recv(3)\fP until all data is +read which would include any cached data. + +Furthermore if you wait on the socket and it tells you there is data to read, +\fIcurl_easy_recv(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was +read was for internal SSL processing, and no other data is available. + .SH AVAILABILITY Added in 7.18.2. .SH RETURN VALUE @@ -60,13 +69,13 @@ On success, returns \fBCURLE_OK\fP, stores the received data into On failure, returns the appropriate error code. -If there is no data to read, the function returns \fBCURLE_AGAIN\fP. Use your -operating system facilities to wait until the data is ready, and retry. +The function may return \fBCURLE_AGAIN\fP. In this case, use your operating +system facilities to wait until data can be read, and retry. -Reading exactly 0 bytes would indicate a closed connection. +Reading exactly 0 bytes indicates a closed connection. If there's no socket available to use from the previous transfer, this function -returns CURLE_UNSUPPORTED_PROTOCOL. +returns \fBCURLE_UNSUPPORTED_PROTOCOL\fP. .SH EXAMPLE See \fBsendrecv.c\fP in \fBdocs/examples\fP directory for usage example. .SH "SEE ALSO" -- cgit v1.2.3