dtoc: Updates BytesToValue() for Python 3

The difference between the bytes and str types in Python 3 requires a
number of minor changes to this function. Update it to handle the input
data using the 'bytes' type. Create two useful helper functions which can
be used by other modules too.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/dtoc/fdt.py

@@ -30,50 +30,59 @@ def CheckErr(errnum, msg):
             (errnum, libfdt.fdt_strerror(errnum), msg))
 
 
-def BytesToValue(bytes):
+def BytesToValue(data):
     """Converts a string of bytes into a type and value
 
     Args:
-        A string containing bytes
+        A bytes value (which on Python 2 is an alias for str)
 
     Return:
         A tuple:
             Type of data
             Data, either a single element or a list of elements. Each element
             is one of:
-                TYPE_STRING: string value from the property
-                TYPE_INT: a byte-swapped integer stored as a 4-byte string
-                TYPE_BYTE: a byte stored as a single-byte string
+                TYPE_STRING: str/bytes value from the property
+                TYPE_INT: a byte-swapped integer stored as a 4-byte str/bytes
+                TYPE_BYTE: a byte stored as a single-byte str/bytes
     """
-    bytes = str(bytes)
-    size = len(bytes)
-    strings = bytes.split('\0')
+    data = bytes(data)
+    size = len(data)
+    strings = data.split(b'\0')
     is_string = True
     count = len(strings) - 1
-    if count > 0 and not strings[-1]:
+    if count > 0 and not len(strings[-1]):
         for string in strings[:-1]:
             if not string:
                 is_string = False
                 break
             for ch in string:
-                if ch < ' ' or ch > '~':
+                # Handle Python 2 treating bytes as str
+                if type(ch) == str:
+                    ch = ord(ch)
+                if ch < 32 or ch > 127:
                     is_string = False
                     break
     else:
         is_string = False
     if is_string:
-        if count == 1:
-            return TYPE_STRING, strings[0]
+        if count == 1: 
+            if sys.version_info[0] >= 3:  # pragma: no cover
+                return TYPE_STRING, strings[0].decode()
+            else:
+                return TYPE_STRING, strings[0]
         else:
-            return TYPE_STRING, strings[:-1]
+            if sys.version_info[0] >= 3:  # pragma: no cover
+                return TYPE_STRING, [s.decode() for s in strings[:-1]]
+            else:
+                return TYPE_STRING, strings[:-1]
     if size % 4:
         if size == 1:
-            return TYPE_BYTE, bytes[0]
+            return TYPE_BYTE, tools.ToChar(data[0])
         else:
-            return TYPE_BYTE, list(bytes)
+            return TYPE_BYTE, [tools.ToChar(ch) for ch in list(data)]
     val = []
     for i in range(0, size, 4):
-        val.append(bytes[i:i + 4])
+        val.append(data[i:i + 4])
     if size == 4:
         return TYPE_INT, val[0]
     else:

tools/patman/tools.py

@@ -290,3 +290,30 @@ def FromUnicode(val):
     if sys.version_info[0] >= 3:
         return val
     return val if isinstance(val, str) else val.encode('utf-8')
+
+def ToByte(ch):
+    """Convert a character to an ASCII value
+
+    This is useful because in Python 2 bytes is an alias for str, but in
+    Python 3 they are separate types. This function converts the argument to
+    an ASCII value in either case.
+
+    Args:
+        ch: A string (Python 2) or byte (Python 3) value
+
+    Returns:
+        integer ASCII value for ch
+    """
+    return ord(ch) if type(ch) == str else ch
+
+def ToChar(byte):
+    """Convert a byte to a character
+
+    This is useful because in Python 2 bytes is an alias for str, but in
+    Python 3 they are separate types. This function converts an ASCII value to
+    a value with the appropriate type in either case.
+
+    Args:
+        byte: A byte or str value
+    """
+    return chr(byte) if type(byte) != str else byte