From ee6c6084e58ab114bddd06453790d22b08e45d93 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Sun, 13 Nov 2022 16:30:46 +0100
Subject: [PATCH] io: Remove xmlInputReadCallbackNop

In some cases, for example when using encoders, the read callback was
set to NULL, in other cases it was set to xmlInputReadCallbackNop.
xmlGROW only tested for xmlInputReadCallbackNop, resulting in errors
when parsing large encoded content from memory.

Always use a NULL callback for memory buffers to avoid ambiguities.

Fixes #262.

Reference:https://github.com/GNOME/libxml2/commit/46cd7d224ed5c4cdbd4f72ec899db24e18d21fe7
Conflict:include/private/io.h
---
 parser.c          |  2 +-
 parserInternals.c |  3 ++-
 xmlIO.c           | 30 ++++--------------------------
 3 files changed, 7 insertions(+), 28 deletions(-)

diff --git a/parser.c b/parser.c
index adc449c..f13287a 100644
--- a/parser.c
+++ b/parser.c
@@ -2134,7 +2134,7 @@ static void xmlGROW (xmlParserCtxtPtr ctxt) {
     if (((curEnd > XML_MAX_LOOKUP_LIMIT) ||
          (curBase > XML_MAX_LOOKUP_LIMIT)) &&
          ((ctxt->input->buf) &&
-          (ctxt->input->buf->readcallback != xmlInputReadCallbackNop)) &&
+          (ctxt->input->buf->readcallback != NULL)) &&
         ((ctxt->options & XML_PARSE_HUGE) == 0)) {
         xmlFatalErr(ctxt, XML_ERR_INTERNAL_ERROR, "Huge input lookup");
         xmlHaltParser(ctxt);
diff --git a/parserInternals.c b/parserInternals.c
index 0ef44fe..ef18ccf 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -311,7 +311,8 @@ xmlParserInputGrow(xmlParserInputPtr in, int len) {
     if (in->buf->buffer == NULL) return(-1);
 
     /* Don't grow memory buffers. */
-    if (in->buf->readcallback == NULL) return(0);
+    if ((in->buf->encoder == NULL) && (in->buf->readcallback == NULL))
+        return(0);
 
     CHECK_BUFFER(in);
 
diff --git a/xmlIO.c b/xmlIO.c
index 0762034..71c9fbf 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -729,20 +729,6 @@ xmlCheckFilename (const char *path)
     return 1;
 }
 
-/**
- * xmlInputReadCallbackNop:
- *
- * No Operation xmlInputReadCallback function, does nothing.
- *
- * Returns zero
- */
-int
-xmlInputReadCallbackNop(void *context ATTRIBUTE_UNUSED,
-                        char *buffer ATTRIBUTE_UNUSED,
-                        int len ATTRIBUTE_UNUSED) {
-    return(0);
-}
-
 /**
  * xmlFdRead:
  * @context:  the I/O context
@@ -2963,7 +2949,7 @@ xmlParserInputBufferCreateMem(const char *mem, int size, xmlCharEncoding enc) {
     ret = xmlAllocParserInputBuffer(enc);
     if (ret != NULL) {
         ret->context = (void *) mem;
-	ret->readcallback = xmlInputReadCallbackNop;
+	ret->readcallback = NULL;
 	ret->closecallback = NULL;
 	errcode = xmlBufAdd(ret->buffer, (const xmlChar *) mem, size);
 	if (errcode != 0) {
@@ -3261,10 +3247,8 @@ xmlParserInputBufferGrow(xmlParserInputBufferPtr in, int len) {
 	res = in->readcallback(in->context, &buffer[0], len);
 	if (res <= 0)
 	    in->readcallback = endOfInput;
-    } else {
-	xmlIOErr(XML_IO_NO_INPUT, NULL);
-	in->error = XML_IO_NO_INPUT;
-	return(-1);
+    } else if (in->encoder == NULL) {
+	return(0);
     }
     if (res < 0) {
 	return(-1);
@@ -3331,13 +3315,7 @@ xmlParserInputBufferGrow(xmlParserInputBufferPtr in, int len) {
  */
 int
 xmlParserInputBufferRead(xmlParserInputBufferPtr in, int len) {
-    if ((in == NULL) || (in->error)) return(-1);
-    if (in->readcallback != NULL)
-	return(xmlParserInputBufferGrow(in, len));
-    else if (xmlBufGetAllocationScheme(in->buffer) == XML_BUFFER_ALLOC_IMMUTABLE)
-	return(0);
-    else
-        return(-1);
+    return(xmlParserInputBufferGrow(in, len));
 }
 
 #ifdef LIBXML_OUTPUT_ENABLED
-- 
2.27.0