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authorMichael Kaufmann <mail@michael-kaufmann.ch>2016-12-18 12:51:48 +0100
committerMichael Kaufmann <mail@michael-kaufmann.ch>2016-12-18 12:56:23 +0100
commitafff64dbcde9cf45956f5557a8270b21c0e93dd5 (patch)
treefb610f970b9bf214d46877d8fb7555653eaca216 /docs
parent82245eaa56c368f6b6b9abf4de63e7d6fb786f71 (diff)
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
Diffstat (limited to 'docs')
-rw-r--r--docs/examples/sendrecv.c91
-rw-r--r--docs/libcurl/curl_easy_recv.329
-rw-r--r--docs/libcurl/curl_easy_send.323
-rw-r--r--docs/libcurl/opts/CURLOPT_CONNECT_ONLY.31
4 files changed, 91 insertions, 53 deletions
diff --git a/docs/examples/sendrecv.c b/docs/examples/sendrecv.c
index 41e283cdc..662323487 100644
--- a/docs/examples/sendrecv.c
+++ b/docs/examples/sendrecv.c
@@ -62,10 +62,9 @@ int main(void)
CURLcode res;
/* Minimalistic http request */
const char *request = "GET / HTTP/1.0\r\nHost: example.com\r\n\r\n";
- curl_socket_t sockfd; /* socket */
- long sockextr;
- size_t iolen;
- curl_off_t nread;
+ size_t request_len = strlen(request);
+ curl_socket_t sockfd;
+ size_t nsent_total = 0;
/* A general note of caution here: if you're using curl_easy_recv() or
curl_easy_send() to implement HTTP or _any_ other protocol libcurl
@@ -82,54 +81,76 @@ int main(void)
curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
res = curl_easy_perform(curl);
- if(CURLE_OK != res) {
- printf("Error: %s\n", strerror(res));
+ if(res != CURLE_OK) {
+ printf("Error: %s\n", curl_easy_strerror(res));
return 1;
}
- /* Extract the socket from the curl handle - we'll need it for waiting.
- * Note that this API takes a pointer to a 'long' while we use
- * curl_socket_t for sockets otherwise.
- */
- res = curl_easy_getinfo(curl, CURLINFO_LASTSOCKET, &sockextr);
+ /* Extract the socket from the curl handle - we'll need it for waiting. */
+ res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
- if(CURLE_OK != res) {
+ if(res != CURLE_OK) {
printf("Error: %s\n", curl_easy_strerror(res));
return 1;
}
- sockfd = (curl_socket_t)sockextr;
+ printf("Sending request.\n");
- /* wait for the socket to become ready for sending */
- if(!wait_on_socket(sockfd, 0, 60000L)) {
- printf("Error: timeout.\n");
- return 1;
- }
+ do {
+ /* Warning: This example program may loop indefinitely.
+ * A production-quality program must define a timeout and exit this loop
+ * as soon as the timeout has expired. */
+ size_t nsent;
+ do {
+ nsent = 0;
+ res = curl_easy_send(curl, request + nsent_total,
+ request_len - nsent_total, &nsent);
+ nsent_total += nsent;
- puts("Sending request.");
- /* Send the request. Real applications should check the iolen
- * to see if all the request has been sent */
- res = curl_easy_send(curl, request, strlen(request), &iolen);
+ if(res == CURLE_AGAIN && !wait_on_socket(sockfd, 0, 60000L)) {
+ printf("Error: timeout.\n");
+ return 1;
+ }
+ } while(res == CURLE_AGAIN);
- if(CURLE_OK != res) {
- printf("Error: %s\n", curl_easy_strerror(res));
- return 1;
- }
- puts("Reading response.");
+ if(res != CURLE_OK) {
+ printf("Error: %s\n", curl_easy_strerror(res));
+ return 1;
+ }
- /* read the response */
- for(;;) {
- char buf[1024];
+ printf("Sent %" CURL_FORMAT_CURL_OFF_T " bytes.\n",
+ (curl_off_t)nsent);
+
+ } while(nsent_total < request_len);
- wait_on_socket(sockfd, 1, 60000L);
- res = curl_easy_recv(curl, buf, 1024, &iolen);
+ printf("Reading response.\n");
- if(CURLE_OK != res)
+ for(;;) {
+ /* Warning: This example program may loop indefinitely (see above). */
+ char buf[1024];
+ size_t nread;
+ do {
+ nread = 0;
+ res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
+
+ if(res == CURLE_AGAIN && !wait_on_socket(sockfd, 1, 60000L)) {
+ printf("Error: timeout.\n");
+ return 1;
+ }
+ } while(res == CURLE_AGAIN);
+
+ if(res != CURLE_OK) {
+ printf("Error: %s\n", curl_easy_strerror(res));
break;
+ }
- nread = (curl_off_t)iolen;
+ if(nread == 0) {
+ /* end of the response */
+ break;
+ }
- printf("Received %" CURL_FORMAT_CURL_OFF_T " bytes.\n", nread);
+ printf("Received %" CURL_FORMAT_CURL_OFF_T " bytes.\n",
+ (curl_off_t)nread);
}
/* always cleanup */
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"
diff --git a/docs/libcurl/curl_easy_send.3 b/docs/libcurl/curl_easy_send.3
index 2a7443985..47976f391 100644
--- a/docs/libcurl/curl_easy_send.3
+++ b/docs/libcurl/curl_easy_send.3
@@ -40,16 +40,20 @@ connection set-up.
The variable \fBn\fP points to will receive the number of sent bytes.
To establish the connection, set \fICURLOPT_CONNECT_ONLY(3)\fP option before
-calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform()\fP. Note that
+calling \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP. Note that
\fIcurl_easy_send(3)\fP will not work on connections that were created without
this option.
-You must ensure that the socket is writable before calling
-\fIcurl_easy_send(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 can be written to.
+The call will return \fBCURLE_AGAIN\fP if it's not possible to send data right
+now - 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 until the socket is writable. The socket may be
+obtained using \fIcurl_easy_getinfo(3)\fP with \fICURLINFO_ACTIVESOCKET(3)\fP.
+
+Furthermore if you wait on the socket and it tells you it's writable,
+\fIcurl_easy_send(3)\fP may return \fBCURLE_AGAIN\fP if the only data that was
+sent was for internal SSL processing, and no other data could be sent.
+
.SH AVAILABILITY
Added in 7.18.2.
.SH RETURN VALUE
@@ -59,8 +63,11 @@ wanted to send.
On failure, returns the appropriate error code.
+This function may return \fBCURLE_AGAIN\fP. In this case, use your operating
+system facilities to wait until the socket is writable, and retry.
+
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"
diff --git a/docs/libcurl/opts/CURLOPT_CONNECT_ONLY.3 b/docs/libcurl/opts/CURLOPT_CONNECT_ONLY.3
index 61289e8d2..973c2aedc 100644
--- a/docs/libcurl/opts/CURLOPT_CONNECT_ONLY.3
+++ b/docs/libcurl/opts/CURLOPT_CONNECT_ONLY.3
@@ -49,3 +49,4 @@ Added in 7.15.2
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_VERBOSE "(3), " CURLOPT_HTTPPROXYTUNNEL "(3), "
+.BR curl_easy_recv "(3), " curl_easy_send "(3) "