lib: pass in 'struct Curl_easy *' to most functions

... in most cases instead of 'struct connectdata *' but in some cases in
addition to.

- We mostly operate on transfers and not connections.

- We need the transfer handle to log, store data and more. Everything in
  libcurl is driven by a transfer (the CURL * in the public API).

- This work clarifies and separates the transfers from the connections
  better.

- We should avoid "conn->data". Since individual connections can be used
  by many transfers when multiplexing, making sure that conn->data
  points to the current and correct transfer at all times is difficult
  and has been notoriously error-prone over the years. The goal is to
  ultimately remove the conn->data pointer for this reason.

Closes #6425

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/pop3.h b/lib/pop3.h
index 6ca3fd511..6869c8d59 100644
--- a/lib/pop3.h
+++ b/lib/pop3.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 2009 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 2009 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -90,6 +90,6 @@ extern const struct Curl_handler Curl_handler_pop3s;
 
 /* This function scans the body after the end-of-body and writes everything
  * until the end is found */
-CURLcode Curl_pop3_write(struct connectdata *conn, char *str, size_t nread);
+CURLcode Curl_pop3_write(struct Curl_easy *data, char *str, size_t nread);
 
 #endif /* HEADER_CURL_POP3_H */