By interrogate conventions, char * means a string, while unsigned char * means a data buffer.

dtool/src/prc/streamReader.cxx

@@ -140,12 +140,12 @@ extract_bytes(size_t size) {
 //               that were successfully written.
 ////////////////////////////////////////////////////////////////////
 size_t StreamReader::
-extract_bytes(char *into, size_t size) {
+extract_bytes(unsigned char *into, size_t size) {
   if (_in->eof() || _in->fail()) {
     return 0;
   }
 
-  _in->read(into, size);
+  _in->read((char *)into, size);
   return _in->gcount();
 }
 

dtool/src/prc/streamReader.h

@@ -67,7 +67,7 @@ PUBLISHED:
 
   BLOCKING void skip_bytes(size_t size);
   BLOCKING string extract_bytes(size_t size);
-  BLOCKING size_t extract_bytes(char *into, size_t size);
+  BLOCKING size_t extract_bytes(unsigned char *into, size_t size);
 
   BLOCKING string readline();
 

panda/src/express/datagramIterator.cxx

@@ -159,7 +159,7 @@ extract_bytes(size_t size) {
 //               that were successfully written.
 ////////////////////////////////////////////////////////////////////
 size_t DatagramIterator::
-extract_bytes(char *into, size_t size) {
+extract_bytes(unsigned char *into, size_t size) {
   nassertr((int)size >= 0, 0);
   nassertr(_datagram != (const Datagram *)NULL, 0);
   nassertr(_current_index + size <= _datagram->get_length(), 0);

panda/src/express/datagramIterator.h

@@ -68,7 +68,7 @@ PUBLISHED:
 
   INLINE void skip_bytes(size_t size);
   string extract_bytes(size_t size);
-  size_t extract_bytes(char *into, size_t size);
+  size_t extract_bytes(unsigned char *into, size_t size);
 
   INLINE string get_remaining_bytes() const;
   INLINE int get_remaining_size() const;