[libxml2] Fix random dropping of characters on dumping ASCII encoded XML

[Nick Wellnhofer <nwellnhof src gnome org>]

commit eb4c1bf85545db74b4f8fa42ffb09c92b847b271
Author: Mohammad Razavi <mrazavi64 gmail com>
Date:   Wed Nov 3 09:48:13 2021 +0330

    Fix random dropping of characters on dumping ASCII encoded XML
    
    Fix a bug in xmlCharEncOutput return value which will cause
    xmlNodeDumpOutput to drop characters randomly.
    
    xmlCharEncOutput returns zero if the length of the input buffer is
    zero but ignores the fact that it may already encoded the input buffer
    and the input's length is zero due to the fact that xmlEncOutputChunk
    returned -2 errors and underlying code tries to fix the error by
    encoding the input.
    
    xmlCharEncOutput is collecting the number of bytes written to the
    output buffer but is returning zero instead of the total number of
    bytes in this situation. This commit will fix this issue by returning
    the total number of bytes instead. So the xmlNodeDumpOutput will also
    continue writing and will not stop due to the fact that it mistakenly
    thinks the output buffer is not changed in that iteration.
    
    Fixes #314

 encoding.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/encoding.c b/encoding.c
index 5d28e4f1..5e7b03af 100644
--- a/encoding.c
+++ b/encoding.c
@@ -2496,7 +2496,7 @@ retry:
      */
     toconv = xmlBufUse(in);
     if (toconv == 0)
-        return (0);
+        return (writtentot);
     if (toconv > 64 * 1024)
         toconv = 64 * 1024;
     if (toconv * 4 >= written) {