[libxml2] Fix return value of xmlCharEncOutput

[Nick Wellnhofer <nwellnhof src gnome org>]

commit a697ed1e24234a9e6a4a4639555dcca230f752c1
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Mon Jun 15 14:49:22 2020 +0200

    Fix return value of xmlCharEncOutput
    
    Commit 407b393d introduced a regression caused by xmlCharEncOutput
    returning 0 in case of success instead of the number of bytes written.
    Always use its return value for nbchars in xmlOutputBufferWrite.
    
    Fixes #166.

 encoding.c |  6 +++---
 xmlIO.c    | 20 ++++----------------
 2 files changed, 7 insertions(+), 19 deletions(-)
---
diff --git a/encoding.c b/encoding.c
index 65c58894..8b6f349c 100644
--- a/encoding.c
+++ b/encoding.c
@@ -2394,7 +2394,7 @@ xmlCharEncOutput(xmlOutputBufferPtr output, int init)
 {
     int ret;
     size_t written;
-    size_t writtentot = 0;
+    int writtentot = 0;
     size_t toconv;
     int c_in;
     int c_out;
@@ -2427,7 +2427,7 @@ retry:
        xmlGenericError(xmlGenericErrorContext,
                "initialized encoder\n");
 #endif
-        return(0);
+        return(c_out);
     }
 
     /*
@@ -2540,7 +2540,7 @@ retry:
             goto retry;
        }
     }
-    return(ret);
+    return(writtentot ? writtentot : ret);
 }
 #endif
 
diff --git a/xmlIO.c b/xmlIO.c
index 7827dcf3..57312b97 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -3401,18 +3401,12 @@ xmlOutputBufferWrite(xmlOutputBufferPtr out, int len, const char *buf) {
                out->error = XML_IO_ENCODER;
                return(-1);
            }
-            if (out->writecallback)
-               nbchars = xmlBufUse(out->conv);
-            else
-                nbchars = ret;
+            nbchars = ret >= 0 ? ret : 0;
        } else {
            ret = xmlBufAdd(out->buffer, (const xmlChar *) buf, chunk);
            if (ret != 0)
                return(-1);
-            if (out->writecallback)
-               nbchars = xmlBufUse(out->buffer);
-            else
-                nbchars = chunk;
+            nbchars = chunk;
        }
        buf += chunk;
        len -= chunk;
@@ -3599,19 +3593,13 @@ xmlOutputBufferWriteEscape(xmlOutputBufferPtr out, const xmlChar *str,
                out->error = XML_IO_ENCODER;
                return(-1);
            }
-            if (out->writecallback)
-               nbchars = xmlBufUse(out->conv);
-            else
-                nbchars = ret;
+            nbchars = ret >= 0 ? ret : 0;
        } else {
            ret = escaping(xmlBufEnd(out->buffer), &chunk, str, &cons);
            if ((ret < 0) || (chunk == 0)) /* chunk==0 => nothing done */
                return(-1);
             xmlBufAddLen(out->buffer, chunk);
-            if (out->writecallback)
-               nbchars = xmlBufUse(out->buffer);
-            else
-                nbchars = chunk;
+            nbchars = chunk;
        }
        str += cons;
        len -= cons;