CURLOPT_XFERINFOFUNCTION: introducing a new progress callback

CURLOPT_XFERINFOFUNCTION is now the preferred progress callback function
and CURLOPT_PROGRESSFUNCTION is considered deprecated.

This new callback uses pure 'curl_off_t' arguments to pass on full
resolution sizes. It otherwise retains the same characteristics: the
same call rate, the same meanings for the arguments and the return code
is used the same way.

The progressfunc.c example is updated to show how to use the new
callback for newer libcurls while supporting the older one if built with
an older libcurl or even built with a newer libcurl while running with
an older.

4 files changed, 92 insertions, 21 deletions

diff --git a/docs/TODO b/docs/TODO
index 79bd43006..8b133dc16 100644
--- a/docs/TODO
+++ b/docs/TODO
@@ -16,9 +16,8 @@
  1.3 struct lifreq
  1.4 signal-based resolver timeouts
  1.5 get rid of PATH_MAX
- 1.6 progress callback without doubles
- 1.7 Happy Eyeball dual stack connect
- 1,8 Modified buffer size approach
+ 1.6 Happy Eyeball dual stack connect
+ 1.7 Modified buffer size approach
 
  2. libcurl - multi interface
  2.1 More non-blocking
@@ -158,16 +157,7 @@
  we need libssh2 to properly tell us when we pass in a too small buffer and
  its current API (as of libssh2 1.2.7) doesn't.
 
-1.6 progress callback without doubles
-
- The progress callback was introduced way back in the days and the choice to
- use doubles in the arguments was possibly good at the time. Today the doubles
- only confuse users and make the amounts less precise. We should introduce
- another progress callback option that take precedence over the old one and
- have both co-exist for a forseeable time until we can remove the double-using
- one.
-
-1.7 Happy Eyeball dual stack connect
+1.6 Happy Eyeball dual stack connect
 
  In order to make alternative technologies not suffer when transitioning, like
  when introducing IPv6 as an alternative to IPv4 and there are more than one
@@ -179,7 +169,7 @@
 
     http://tools.ietf.org/html/rfc6555
 
-1.8 Modified buffer size approach
+1.7 Modified buffer size approach
 
  Current libcurl allocates a fixed 16K size buffer for download and an
  additional 16K for upload. They are always unconditionally part of the easy
diff --git a/docs/examples/progressfunc.c b/docs/examples/progressfunc.c
index 51a9c9b5e..b2635bc8a 100644
--- a/docs/examples/progressfunc.c
+++ b/docs/examples/progressfunc.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2013, 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
@@ -30,9 +30,10 @@ struct myprogress {
   CURL *curl;
 };
 
-static int progress(void *p,
-                    double dltotal, double dlnow,
-                    double ultotal, double ulnow)
+/* this is how the CURLOPT_XFERINFOFUNCTION callback works */
+static int xferinfo(void *p,
+                    curl_off_t dltotal, curl_off_t dlnow,
+                    curl_off_t ultotal, curl_off_t ulnow)
 {
   struct myprogress *myp = (struct myprogress *)p;
   CURL *curl = myp->curl;
@@ -48,7 +49,9 @@ static int progress(void *p,
     fprintf(stderr, "TOTAL TIME: %f \r\n", curtime);
   }
 
-  fprintf(stderr, "UP: %g of %g  DOWN: %g of %g\r\n",
+  fprintf(stderr, "UP: %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T
+          "  DOWN: %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T
+          "\r\n",
           ulnow, ultotal, dlnow, dltotal);
 
   if(dlnow > STOP_DOWNLOAD_AFTER_THIS_MANY_BYTES)
@@ -56,6 +59,19 @@ static int progress(void *p,
   return 0;
 }
 
+/* for libcurl older than 7.32.0 (CURLOPT_PROGRESSFUNCTION) */
+static int older_progress(void *p,
+                          double dltotal, double dlnow,
+                          double ultotal, double ulnow)
+{
+  return xferinfo(p,
+                  (curl_off_t)dltotal,
+                  (curl_off_t)dlnow,
+                  (curl_off_t)ultotal,
+                  (curl_off_t)ulnow);
+}
+
+
 int main(void)
 {
   CURL *curl;
@@ -68,9 +84,28 @@ int main(void)
     prog.curl = curl;
 
     curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/");
-    curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress);
+
+    curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, older_progress);
     /* pass the struct pointer into the progress function */
     curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &prog);
+
+#if LIBCURL_VERSION_NUM >= 0x072000
+    /* xferinfo was introduced in 7.32.0, no earlier libcurl versions will
+       compile as they won't have the symbols around.
+
+       If built with a newer libcurl, but running with an older libcurl:
+       curl_easy_setopt() will fail in run-time trying to set the new
+       callback, making the older callback get used.
+
+       New libcurls will prefer the new callback and instead use that one even
+       if both callbacks are set. */
+
+    curl_easy_setopt(curl, CURLOPT_XFERINFOFUNCTION, xferinfo);
+    /* pass the struct pointer into the xferinfo function, note that this is
+       an alias to CURLOPT_PROGRESSDATA */
+    curl_easy_setopt(curl, CURLOPT_XFERINFODATA, &prog);
+#endif
+
     curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0L);
     res = curl_easy_perform(curl);
 
diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3
index e5ca09f4b..bebf8c08d 100644
--- a/docs/libcurl/curl_easy_setopt.3
+++ b/docs/libcurl/curl_easy_setopt.3
@@ -377,10 +377,54 @@ function that performs transfers.
 
 \fICURLOPT_NOPROGRESS\fP must be set to 0 to make this function actually
 get called.
+.IP CURLOPT_XFERINFOFUNCTION
+Pass a pointer to a function that matches the following prototype:
+
+.nf
+\fBint function(void *clientp, curl_off_t dltotal, curl_off_t dlnow,
+                curl_off_t ultotal, curl_off_t ulnow);\fP
+.fi
+
+This function gets called by libcurl instead of its internal equivalent with a
+frequent interval. While data is being transferred it will be called very
+frequently, and during slow periods like when nothing is being transferred it
+can slow down to about one call per second.
+
+\fIclientp\fP is the pointer set with \fICURLOPT_XFERINFODATA\fP, it is only
+passed along from the application to the callback.
+
+The callback gets told how much data libcurl will transfer and has
+transferred, in number of bytes. \fIdltotal\fP is the total number of bytes
+libcurl expects to download in this transfer. \fIdlnow\fP is the number of
+bytes downloaded so far. \fIultotal\fP is the total number of bytes libcurl
+expects to upload in this transfer. \fIulnow\fP is the number of bytes
+uploaded so far.
+
+Unknown/unused argument values passed to the callback will be set to zero
+(like if you only download data, the upload size will remain 0). Many times
+the callback will be called one or more times first, before it knows the data
+sizes so a program must be made to handle that.
+
+Returning a non-zero value from this callback will cause libcurl to abort the
+transfer and return \fICURLE_ABORTED_BY_CALLBACK\fP.
+
+If you transfer data with the multi interface, this function will not be
+called during periods of idleness unless you call the appropriate libcurl
+function that performs transfers.
+
+\fICURLOPT_NOPROGRESS\fP must be set to 0 to make this function actually
+get called.
+
+(Added in 7.32.0)
 .IP CURLOPT_PROGRESSDATA
 Pass a pointer that will be untouched by libcurl and passed as the first
 argument in the progress callback set with \fICURLOPT_PROGRESSFUNCTION\fP.
 The default value of this parameter is unspecified.
+.IP CURLOPT_XFERINFODATA
+Pass a pointer that will be untouched by libcurl and passed as the first
+argument in the progress callback set with \fICURLOPT_XFERINFOFUNCTION\fP.
+The default value of this parameter is unspecified. This option is an alias
+for CURLOPT_PROGRESSDATA. (Added in 7.32.0)
 .IP CURLOPT_HEADERFUNCTION
 Pass a pointer to a function that matches the following prototype:
 \fBsize_t function( void *ptr, size_t size, size_t nmemb, void
diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 54b6dbc3d..e61cbbee9 100644
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -428,7 +428,7 @@ CURLOPT_POSTREDIR               7.19.1
 CURLOPT_PREQUOTE                7.9.5
 CURLOPT_PRIVATE                 7.10.3
 CURLOPT_PROGRESSDATA            7.1
-CURLOPT_PROGRESSFUNCTION        7.1
+CURLOPT_PROGRESSFUNCTION        7.1           7.32.0
 CURLOPT_PROTOCOLS               7.19.4
 CURLOPT_PROXY                   7.1
 CURLOPT_PROXYAUTH               7.10.7
@@ -525,6 +525,8 @@ CURLOPT_WRITEDATA               7.9.7
 CURLOPT_WRITEFUNCTION           7.1
 CURLOPT_WRITEHEADER             7.1
 CURLOPT_WRITEINFO               7.1
+CURLOPT_XFERINFODATA            7.32.0
+CURLOPT_XFERINFOFUNCTION        7.32.0
 CURLPAUSE_ALL                   7.18.0
 CURLPAUSE_CONT                  7.18.0
 CURLPAUSE_RECV                  7.18.0