quickjs-tart

quickjs-based runtime for wallet-core logic
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curl_easy_recv.md (3231B)

      1 ---
      2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
      3 SPDX-License-Identifier: curl
      4 Title: curl_easy_recv
      5 Section: 3
      6 Source: libcurl
      7 See-also:
      8   - curl_easy_getinfo (3)
      9   - curl_easy_perform (3)
     10   - curl_easy_send (3)
     11   - curl_easy_setopt (3)
     12 Protocol:
     13   - All
     14 Added-in: 7.18.2
     15 ---
     16 
     17 # NAME
     18 
     19 curl_easy_recv - receives raw data on an "easy" connection
     20 
     21 # SYNOPSIS
     22 
     23 ~~~c
     24 #include <curl/curl.h>
     25 
     26 CURLcode curl_easy_recv(CURL *curl, void *buffer, size_t buflen, size_t *n);
     27 ~~~
     28 
     29 # DESCRIPTION
     30 
     31 This function receives raw data from the established connection. You may use
     32 it together with curl_easy_send(3) to implement custom protocols using
     33 libcurl. This functionality can be particularly useful if you use proxies
     34 and/or SSL encryption: libcurl takes care of proxy negotiation and connection
     35 setup.
     36 
     37 **buffer** is a pointer to your buffer memory that gets populated by the
     38 received data. **buflen** is the maximum amount of data you can get in that
     39 buffer. The variable **n** points to receives the number of received bytes.
     40 
     41 To establish the connection, set CURLOPT_CONNECT_ONLY(3) option before
     42 calling curl_easy_perform(3) or curl_multi_perform(3). Note that
     43 curl_easy_recv(3) does not work on connections that were created without
     44 this option.
     45 
     46 The call returns **CURLE_AGAIN** if there is no data to read - the socket is
     47 used in non-blocking mode internally. When **CURLE_AGAIN** is returned, use
     48 your operating system facilities like *select(2)* to wait for data. The
     49 socket may be obtained using curl_easy_getinfo(3) with
     50 CURLINFO_ACTIVESOCKET(3).
     51 
     52 Wait on the socket only if curl_easy_recv(3) returns **CURLE_AGAIN**.
     53 The reason for this is libcurl or the SSL library may internally cache some
     54 data, therefore you should call curl_easy_recv(3) until all data is
     55 read which would include any cached data.
     56 
     57 Furthermore if you wait on the socket and it tells you there is data to read,
     58 curl_easy_recv(3) may return **CURLE_AGAIN** if the only data that was
     59 read was for internal SSL processing, and no other data is available.
     60 
     61 # %PROTOCOLS%
     62 
     63 # EXAMPLE
     64 
     65 ~~~c
     66 int main(void)
     67 {
     68   CURL *curl = curl_easy_init();
     69   if(curl) {
     70     CURLcode res;
     71     curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
     72     /* Do not do the transfer - only connect to host */
     73     curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
     74     res = curl_easy_perform(curl);
     75 
     76     if(res == CURLE_OK) {
     77       char buf[256];
     78       size_t nread;
     79       curl_socket_t sockfd;
     80 
     81       /* Extract the socket from the curl handle - we need it for waiting. */
     82       res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
     83 
     84       /* read data */
     85       res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
     86     }
     87   }
     88 }
     89 ~~~
     90 
     91 # %AVAILABILITY%
     92 
     93 # RETURN VALUE
     94 
     95 On success, returns **CURLE_OK**, stores the received data into
     96 **buffer**, and the number of bytes it actually read into ***n**.
     97 
     98 On failure, returns the appropriate error code.
     99 
    100 The function may return **CURLE_AGAIN**. In this case, use your operating
    101 system facilities to wait until data can be read, and retry.
    102 
    103 Reading exactly 0 bytes indicates a closed connection.
    104 
    105 If there is no socket available to use from the previous transfer, this
    106 function returns **CURLE_UNSUPPORTED_PROTOCOL**.