From 4365a5e1153dd5ed7d269d00f8f14daee0fac5c8 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Mon, 26 Feb 2024 15:14:28 +0100
Subject: [PATCH] xmlreader: Fix xmlTextReaderConstEncoding

Regression from commit f1c1f5c6.

Fixes #697.
---
 SAX2.c                   | 12 +-----------
 include/private/parser.h |  2 ++
 parserInternals.c        | 24 ++++++++++++++++++++++++
 xmlreader.c              | 24 +++++++++++-------------
 4 files changed, 38 insertions(+), 24 deletions(-)

diff --git a/SAX2.c b/SAX2.c
index ed21a559..bb72e160 100644
--- a/SAX2.c
+++ b/SAX2.c
@@ -955,17 +955,7 @@ xmlSAX2EndDocument(void *ctx)
 
     doc = ctxt->myDoc;
     if ((doc != NULL) && (doc->encoding == NULL)) {
-        const xmlChar *encoding = NULL;
-
-        if ((ctxt->input->flags & XML_INPUT_USES_ENC_DECL) ||
-            (ctxt->input->flags & XML_INPUT_AUTO_ENCODING)) {
-            /* Preserve encoding exactly */
-            encoding = ctxt->encoding;
-        } else if ((ctxt->input->buf) && (ctxt->input->buf->encoder)) {
-            encoding = BAD_CAST ctxt->input->buf->encoder->name;
-        } else if (ctxt->input->flags & XML_INPUT_HAS_ENCODING) {
-            encoding = BAD_CAST "UTF-8";
-        }
+        const xmlChar *encoding = xmlGetActualEncoding(ctxt);
 
         if (encoding != NULL) {
             doc->encoding = xmlStrdup(encoding);
diff --git a/include/private/parser.h b/include/private/parser.h
index 40d179fe..7f8f6912 100644
--- a/include/private/parser.h
+++ b/include/private/parser.h
@@ -48,6 +48,8 @@ XML_HIDDEN void
 xmlDetectEncoding(xmlParserCtxtPtr ctxt);
 XML_HIDDEN void
 xmlSetDeclaredEncoding(xmlParserCtxtPtr ctxt, xmlChar *encoding);
+XML_HIDDEN const xmlChar *
+xmlGetActualEncoding(xmlParserCtxtPtr ctxt);
 
 XML_HIDDEN xmlParserNsData *
 xmlParserNsCreate(void);
diff --git a/parserInternals.c b/parserInternals.c
index e6b4cb14..166397bd 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -1479,6 +1479,30 @@ xmlSetDeclaredEncoding(xmlParserCtxtPtr ctxt, xmlChar *encoding) {
     }
 }
 
+/**
+ * xmlGetActualEncoding:
+ * @ctxt:  the parser context
+ *
+ * Returns the actual used to parse the document. This can differ from
+ * the declared encoding.
+ */
+const xmlChar *
+xmlGetActualEncoding(xmlParserCtxtPtr ctxt) {
+    const xmlChar *encoding = NULL;
+
+    if ((ctxt->input->flags & XML_INPUT_USES_ENC_DECL) ||
+        (ctxt->input->flags & XML_INPUT_AUTO_ENCODING)) {
+        /* Preserve encoding exactly */
+        encoding = ctxt->encoding;
+    } else if ((ctxt->input->buf) && (ctxt->input->buf->encoder)) {
+        encoding = BAD_CAST ctxt->input->buf->encoder->name;
+    } else if (ctxt->input->flags & XML_INPUT_HAS_ENCODING) {
+        encoding = BAD_CAST "UTF-8";
+    }
+
+    return(encoding);
+}
+
 /************************************************************************
  *									*
  *	Commodity functions to handle entities processing		*
diff --git a/xmlreader.c b/xmlreader.c
index 1f903306..5fdeb2b8 100644
--- a/xmlreader.c
+++ b/xmlreader.c
@@ -40,6 +40,7 @@
 #endif
 
 #include "private/buf.h"
+#include "private/parser.h"
 #include "private/tree.h"
 #ifdef LIBXML_XINCLUDE_ENABLED
 #include "private/xinclude.h"
@@ -2795,20 +2796,17 @@ xmlTextReaderReadAttributeValue(xmlTextReaderPtr reader) {
  */
 const xmlChar *
 xmlTextReaderConstEncoding(xmlTextReaderPtr reader) {
-    xmlDocPtr doc = NULL;
-    if (reader == NULL)
-	return(NULL);
-    if (reader->doc != NULL)
-        doc = reader->doc;
-    else if (reader->ctxt != NULL)
-	doc = reader->ctxt->myDoc;
-    if (doc == NULL)
-	return(NULL);
+    const xmlChar *encoding = NULL;
 
-    if (doc->encoding == NULL)
-	return(NULL);
-    else
-      return(CONSTSTR(doc->encoding));
+    if (reader == NULL)
+        return(NULL);
+
+    if (reader->ctxt != NULL)
+        encoding = xmlGetActualEncoding(reader->ctxt);
+    else if (reader->doc != NULL)
+        encoding = reader->doc->encoding;
+
+    return(CONSTSTR(encoding));
 }