Added comments to cbm.h.

load/save returns oserror code.
Added open/close and read (which is not tested yet).


git-svn-id: svn://svn.cc65.org/cc65/trunk@637 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/cbm/cbm_read.c

@@ -0,0 +1,24 @@
+
+#include <cbm.h>
+
+extern unsigned char _oserror;
+
+int cbm_read(unsigned char lfn, void* buffer, unsigned int size)
+{
+    static unsigned int bytesread;
+    static unsigned char tmp;
+        
+    if (_oserror = cbm_k_chkin(lfn)) return -1;
+    
+    bytesread = 0;
+    
+    while (bytesread<size) {
+        tmp = cbm_k_basin();
+        if (cbm_k_readst()) break;
+        ((unsigned char*)buffer)[bytesread++] = tmp;
+    }
+    
+    cbm_k_clrch();
+    
+    return bytesread;
+}