1 files changed, 152 insertions, 0 deletions
diff --git a/docs/libcurl/opts/CURLOPT_CHUNK_BGN_FUNCTION.md b/docs/libcurl/opts/CURLOPT_CHUNK_BGN_FUNCTION.md
new file mode 100644
index 000000000..a208c9bbe
--- /dev/null
+++ b/docs/libcurl/opts/CURLOPT_CHUNK_BGN_FUNCTION.md
@@ -0,0 +1,152 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_CHUNK_BGN_FUNCTION
+Section: 3
+Source: libcurl
+See-also:
+  - CURLOPT_CHUNK_END_FUNCTION (3)
+  - CURLOPT_WILDCARDMATCH (3)
+---
+
+# NAME
+
+CURLOPT_CHUNK_BGN_FUNCTION - callback before a transfer with FTP wildcard match
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+struct curl_fileinfo {
+  char *filename;
+  curlfiletype filetype;
+  time_t time;   /* always zero! */
+  unsigned int perm;
+  int uid;
+  int gid;
+  curl_off_t size;
+  long int hardlinks;
+
+  struct {
+    /* If some of these fields is not NULL, it is a pointer to b_data. */
+    char *time;
+    char *perm;
+    char *user;
+    char *group;
+    char *target; /* pointer to the target filename of a symlink */
+  } strings;
+
+  unsigned int flags;
+
+  /* used internally */
+  char *b_data;
+  size_t b_size;
+  size_t b_used;
+};
+
+long chunk_bgn_callback(const void *transfer_info, void *ptr,
+                        int remains);
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CHUNK_BGN_FUNCTION,
+                          chunk_bgn_callback);
+~~~
+
+# DESCRIPTION
+
+Pass a pointer to your callback function, which should match the prototype
+shown above.
+
+This callback function gets called by libcurl before a part of the stream is
+going to be transferred (if the transfer supports chunks).
+
+The *transfer_info* pointer points to a **curl_fileinfo** struct with
+details about the file that is about to get transferred.
+
+This callback makes sense only when using the CURLOPT_WILDCARDMATCH(3)
+option for now.
+
+The target of transfer_info parameter is a "feature depended" structure. For
+the FTP wildcard download, the target is **curl_fileinfo** structure (see
+*curl/curl.h*). The parameter *ptr* is a pointer given by
+CURLOPT_CHUNK_DATA(3). The parameter remains contains number of chunks
+remaining per the transfer. If the feature is not available, the parameter has
+zero value.
+
+Return *CURL_CHUNK_BGN_FUNC_OK* if everything is fine,
+*CURL_CHUNK_BGN_FUNC_SKIP* if you want to skip the concrete chunk or
+*CURL_CHUNK_BGN_FUNC_FAIL* to tell libcurl to stop if some error occurred.
+
+# DEFAULT
+
+NULL
+
+# PROTOCOLS
+
+FTP
+
+# EXAMPLE
+
+~~~c
+#include <stdio.h>
+
+struct callback_data {
+   FILE *output;
+};
+
+static long file_is_coming(struct curl_fileinfo *finfo,
+                           void *ptr,
+                           int remains)
+{
+  struct callback_data *data = ptr;
+  printf("%3d %40s %10luB ", remains, finfo->filename,
+         (unsigned long)finfo->size);
+
+  switch(finfo->filetype) {
+  case CURLFILETYPE_DIRECTORY:
+    printf(" DIR\n");
+    break;
+  case CURLFILETYPE_FILE:
+    printf("FILE ");
+    break;
+  default:
+    printf("OTHER\n");
+    break;
+  }
+
+  if(finfo->filetype == CURLFILETYPE_FILE) {
+    /* do not transfer files >= 50B */
+    if(finfo->size > 50) {
+      printf("SKIPPED\n");
+      return CURL_CHUNK_BGN_FUNC_SKIP;
+    }
+
+    data->output = fopen(finfo->filename, "wb");
+    if(!data->output) {
+      return CURL_CHUNK_BGN_FUNC_FAIL;
+    }
+  }
+
+  return CURL_CHUNK_BGN_FUNC_OK;
+}
+
+int main()
+{
+  /* data for callback */
+  struct callback_data callback_info;
+
+  CURL *curl = curl_easy_init();
+
+  /* callback is called before download of concrete file started */
+  curl_easy_setopt(curl, CURLOPT_CHUNK_BGN_FUNCTION, file_is_coming);
+  curl_easy_setopt(curl, CURLOPT_CHUNK_DATA, &callback_info);
+}
+~~~
+
+# AVAILABILITY
+
+This was added in 7.21.0
+
+# RETURN VALUE
+
+Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.