CURLOPT_CO...K_FUNCTION(3)

💅 CURLOPT_CONV_FROM_NETWORK_FUNCTION(3) 💅

okay so, bestie, this page comes from the Library Functions Manual, and it’s giving deprecated callback realness — but don’t worry, we’re gonna get through it together, no cap. This is the one about converting data from network encoding to host encoding. 🦋

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🌸 NAME 🌸

CURLOPT_CONV_FROM_NETWORK_FUNCTION — convert data from network to host encoding. periodt.

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✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode conv_callback(char *ptr, size_t length);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CONV_FROM_NETWORK_FUNCTION,
                          conv_callback);

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🦋 DESCRIPTION 🦋

Drop in a pointer to your callback function, and it has to match the prototype shown above exactly, bestie. No improvising. 💅

This one applies to non-ASCII platforms. curl_version_info(3) returns the CURL_VERSION_CONV feature bit set if this option is provided.

The data to be converted lives in a buffer pointed to by the ptr parameter. The amount of data to convert is indicated by the length parameter. The converted data overlays the input data in the buffer pointed to by the ptr parameter. You must return CURLE_OK upon successful conversion. If you hit an error, return a CURLcode return value defined by curl.h, such as CURLE_CONV_FAILED.

CURLOPT_CONV_FROM_NETWORK_FUNCTION(3) converts to host encoding from the network encoding. It is used when commands or ASCII data are received over the network. 🛰️

If you set a callback pointer to NULL, or do not set it at all, the built-in libcurl iconv functions are used. If HAVE_ICONV was not defined when libcurl was built, and no callback has been established, the conversion returns the CURLE_CONV_REQD error code. 😭

If HAVE_ICONV is defined, CURL_ICONV_CODESET_OF_HOST must also be defined. For example:

#define CURL_ICONV_CODESET_OF_HOST "IBM-1047"

The iconv code in libcurl defaults the network and UTF8 codeset names as follows:

#define CURL_ICONV_CODESET_OF_NETWORK "ISO8859-1"

#define CURL_ICONV_CODESET_FOR_UTF8  "UTF-8"

You need to override these definitions if they are different on your system. fr fr. 🫶

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🎀 DEFAULT 🎀

The default is literally NULL.

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🌐 PROTOCOLS 🌐

This functionality affects all supported protocols. all of them, bestie. 🌈

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🧚 EXAMPLE 🧚

Here’s the whole vibe, with my_conv_from_ascii_to_ebcdic doing the callback thing:

static CURLcode my_conv_from_ascii_to_ebcdic(char *buffer, size_t length)
{
  int rc = 0;

  /* in-place convert 'buffer' from ASCII to EBCDIC */

  if(rc == 0) {
    /* success */
    return CURLE_OK;
  }
  else {
    return CURLE_CONV_FAILED;
  }
}

int main(void)
{
  CURL *curl = curl_easy_init();

  /* use platform-specific functions for codeset conversions */
  curl_easy_setopt(curl, CURLOPT_CONV_FROM_NETWORK_FUNCTION,
                   my_conv_from_ascii_to_ebcdic);
}

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💀 DEPRECATED 💀

Warning bestie: Not available and deprecated since 7.82.0.

Available only if CURL_DOES_CONVERSIONS was defined when libcurl was built. like, vintage behavior only. 🕰️

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⭐ AVAILABILITY ⭐

Added in curl 7.15.4. iconic little historical moment. 👑

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🔥 RETURN VALUE 🔥

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

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👑 SEE ALSO 👑

• CURLOPT_CONV_FROM_UTF8_FUNCTION(3)
• CURLOPT_CONV_TO_NETWORK_FUNCTION(3)

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that’s the whole page, bestie. source/version line is libcurl, date is 2026-10-12, and the footer page is CURLOPT_CO...K_FUNCTION(3). mwah 💖🎀🦋