1 files changed, 152 insertions, 0 deletions
diff --git a/rsa/transform.py b/rsa/transform.py
new file mode 100644
index 0000000..5e53d06
--- /dev/null
+++ b/rsa/transform.py
@@ -0,0 +1,152 @@
+'''Data transformation functions.
+
+From bytes to a number, number to bytes, base64-like-encoding, etc.
+'''
+
+import math
+import types
+
+def bit_size(number):
+    """Returns the number of bits required to hold a specific long number"""
+
+    return int(math.ceil(math.log(number,2)))
+
+def bytes2int(bytes):
+    """Converts a list of bytes or a string to an integer
+
+    >>> (((128 * 256) + 64) * 256) + 15
+    8405007
+    >>> l = [128, 64, 15]
+    >>> bytes2int(l)              #same as bytes2int('\x80@\x0f')
+    8405007
+    """
+
+    if not (type(bytes) is types.ListType or type(bytes) is types.StringType):
+        raise TypeError("You must pass a string or a list")
+
+    # Convert byte stream to integer
+    integer = 0
+    for byte in bytes:
+        integer *= 256
+        if type(byte) is types.StringType: byte = ord(byte)
+        integer += byte
+
+    return integer
+
+def int2bytes(number):
+    """Converts a number to a string of bytes
+    
+    >>>int2bytes(123456789)
+    '\x07[\xcd\x15'
+    >>> bytes2int(int2bytes(123456789))
+    123456789
+    """
+
+    if not (type(number) is types.LongType or type(number) is types.IntType):
+        raise TypeError("You must pass a long or an int")
+
+    string = ""
+
+    while number > 0:
+        string = "%s%s" % (chr(number & 0xFF), string)
+        number /= 256
+    
+    return string
+
+
+def to64(number):
+    """Converts a number in the range of 0 to 63 into base 64 digit
+    character in the range of '0'-'9', 'A'-'Z', 'a'-'z','-','_'.
+    
+    >>> to64(10)
+    'A'
+    """
+
+    if not (type(number) is types.LongType or type(number) is types.IntType):
+        raise TypeError("You must pass a long or an int")
+
+    if 0 <= number <= 9:            #00-09 translates to '0' - '9'
+        return chr(number + 48)
+
+    if 10 <= number <= 35:
+        return chr(number + 55)     #10-35 translates to 'A' - 'Z'
+
+    if 36 <= number <= 61:
+        return chr(number + 61)     #36-61 translates to 'a' - 'z'
+
+    if number == 62:                # 62   translates to '-' (minus)
+        return chr(45)
+
+    if number == 63:                # 63   translates to '_' (underscore)
+        return chr(95)
+
+    raise ValueError(u'Invalid Base64 value: %i' % number)
+
+
+def from64(number):
+    """Converts an ordinal character value in the range of
+    0-9,A-Z,a-z,-,_ to a number in the range of 0-63.
+    
+    >>> from64(49)
+    1
+    """
+
+    if not (type(number) is types.LongType or type(number) is types.IntType):
+        raise TypeError("You must pass a long or an int")
+
+    if 48 <= number <= 57:         #ord('0') - ord('9') translates to 0-9
+        return(number - 48)
+
+    if 65 <= number <= 90:         #ord('A') - ord('Z') translates to 10-35
+        return(number - 55)
+
+    if 97 <= number <= 122:        #ord('a') - ord('z') translates to 36-61
+        return(number - 61)
+
+    if number == 45:               #ord('-') translates to 62
+        return(62)
+
+    if number == 95:               #ord('_') translates to 63
+        return(63)
+
+    raise ValueError(u'Invalid Base64 value: %i' % number)
+
+
+def int2str64(number):
+    """Converts a number to a string of base64 encoded characters in
+    the range of '0'-'9','A'-'Z,'a'-'z','-','_'.
+    
+    >>> int2str64(123456789)
+    '7MyqL'
+    """
+
+    if not (type(number) is types.LongType or type(number) is types.IntType):
+        raise TypeError("You must pass a long or an int")
+
+    string = ""
+
+    while number > 0:
+        string = "%s%s" % (to64(number & 0x3F), string)
+        number /= 64
+
+    return string
+
+
+def str642int(string):
+    """Converts a base64 encoded string into an integer.
+    The chars of this string in in the range '0'-'9','A'-'Z','a'-'z','-','_'
+    
+    >>> str642int('7MyqL')
+    123456789
+    """
+
+    if not (type(string) is types.ListType or type(string) is types.StringType):
+        raise TypeError("You must pass a string or a list")
+
+    integer = 0
+    for byte in string:
+        integer *= 64
+        if type(byte) is types.StringType: byte = ord(byte)
+        integer += from64(byte)
+
+    return integer