libxml2 fails to parse from buffer but parses successfully from file - c

Question

I have a function that writes an XML document to a buffer using the libxml2 writer, but when I try to parse the document from memory using xmlParseMemory, it only returns parser errors. I have also tried writing the document to a file and parsing it using xmlParseFile and it parses successfully.
This is how I initialize the writer and buffer for the xml document.
int rc, i = 0;
xmlTextWriterPtr writer;
xmlBufferPtr buf;
// Create a new XML buffer, to which the XML document will be written
buf = xmlBufferCreate();
if (buf == NULL)
{
printf("testXmlwriterMemory: Error creating the xml buffer\n");
return;
}
// Create a new XmlWriter for memory, with no compression.
// Remark: there is no compression for this kind of xmlTextWriter
writer = xmlNewTextWriterMemory(buf, 0);
if (writer == NULL)
{
printf("testXmlwriterMemory: Error creating the xml writer\n");
return;
}
// Start the document with the xml default for the version,
// encoding UTF-8 and the default for the standalone
// declaration.
rc = xmlTextWriterStartDocument(writer, NULL, ENCODING, NULL);
if (rc < 0)
{
printf
("testXmlwriterMemory: Error at xmlTextWriterStartDocument\n");
return;
}
I pass the xml document to another function to be validated using
int ret = validateXML(buf->content);
Here is the first part of validateXML
int validateXML(char *buffer)
{
xmlDocPtr doc;
xmlSchemaPtr schema = NULL;
xmlSchemaParserCtxtPtr ctxt;
char *XSDFileName = XSDFILE;
char *XMLFile = buffer;
int ret = 1;
doc = xmlReadMemory(XMLFile, sizeof(XMLFile), "noname.xml", NULL, 0);
doc is always NULL after calling this function, which means that it failed to parse the document.
Here are the errors that running the program returns
Entity: line 1: parser error : ParsePI: PI xm space expected
<?xm
^
Entity: line 1: parser error : ParsePI: PI xm never end ...
<?xm
^
Entity: line 1: parser error : Start tag expected, '<' not found
<?xm
^
I have been unable to figure this out for quite a while now and I am out of ideas. If anyone has any, I would be grateful if you would share it.

Answer 1

You are using sizeof to determine the size of the xml data. For a char pointer that is always going to return 4. What you probably need is strlen.
doc = xmlReadMemory(XMLFile, strlen(XMLFile), "noname.xml", NULL, 0);