# Source code for fontTools.misc.sstruct

    """sstruct.py -- SuperStruct

    Higher level layer on top of the struct module, enabling to
    bind names to struct elements. The interface is similar to
    struct, except the objects passed and returned are not tuples
    (or argument lists), but dictionaries or instances.

    Just like struct, we use fmt strings to describe a data
    structure, except we use one line per element. Lines are
    separated by newlines or semi-colons. Each line contains
    either one of the special struct characters ('@', '=', '<',
    '>' or '!') or a 'name:formatchar' combo (eg. 'myFloat:f').
    Repetitions, like the struct module offers them are not useful
    in this context, except for fixed length strings  (eg. 'myInt:5h'
    is not allowed but 'myString:5s' is). The 'x' fmt character
    (pad byte) is treated as 'special', since it is by definition
    anonymous. Extra whitespace is allowed everywhere.

    The sstruct module offers one feature that the "normal" struct
    module doesn't: support for fixed point numbers. These are spelled
    as "n.mF", where n is the number of bits before the point, and m
    the number of bits after the point. Fixed point numbers get
    converted to floats.

    pack(fmt, object):
    	'object' is either a dictionary or an instance (or actually
    	anything that has a __dict__ attribute). If it is a dictionary,
    	its keys are used for names. If it is an instance, it's
    	attributes are used to grab struct elements from. Returns
    	a string containing the data.

    unpack(fmt, data, object=None)
    	If 'object' is omitted (or None), a new dictionary will be
    	returned. If 'object' is a dictionary, it will be used to add
    	struct elements to. If it is an instance (or in fact anything
    	that has a __dict__ attribute), an attribute will be added for
    	each struct element. In the latter two cases, 'object' itself
    	is returned.

    unpack2(fmt, data, object=None)
    	Convenience function. Same as unpack, except data may be longer
    	than needed. The returned value is a tuple: (object, leftoverdata).

    calcsize(fmt)
    	like struct.calcsize(), but uses our own fmt strings:
    	it returns the size of the data in bytes.
    """

    from fontTools.misc.fixedTools import fixedToFloat as fi2fl, floatToFixed as fl2fi
    from fontTools.misc.textTools import tobytes, tostr
    import struct
    import re

    __version__ = "1.2"
    __copyright__ = "Copyright 1998, Just van Rossum <just@letterror.com>"

    class Error(Exception):
    	pass

    def pack(fmt, obj):
    	formatstring, names, fixes = getformat(fmt, keep_pad_byte=True)
    	elements = []
    	if not isinstance(obj, dict):
    		obj = obj.__dict__
    	for name in names:
    		value = obj[name]
    		if name in fixes:
    			# fixed point conversion
    			value = fl2fi(value, fixes[name])
    		elif isinstance(value, str):
    			value = tobytes(value)
    		elements.append(value)
    	data = struct.pack(*(formatstring,) + tuple(elements))
    	return data

    def unpack(fmt, data, obj=None):
    	if obj is None:
    		obj = {}
    	data = tobytes(data)
    	formatstring, names, fixes = getformat(fmt)
    	if isinstance(obj, dict):
    		d = obj
    	else:
    		d = obj.__dict__
    	elements = struct.unpack(formatstring, data)
    	for i in range(len(names)):
    		name = names[i]
    		value = elements[i]
    		if name in fixes:
    			# fixed point conversion
    			value = fi2fl(value, fixes[name])
    		elif isinstance(value, bytes):
    			try:
    				value = tostr(value)
    			except UnicodeDecodeError:
    				pass
    		d[name] = value
    	return obj

    def unpack2(fmt, data, obj=None):
    	length = calcsize(fmt)
    	return unpack(fmt, data[:length], obj), data[length:]

    def calcsize(fmt):
    	formatstring, names, fixes = getformat(fmt)
    	return struct.calcsize(formatstring)

    # matches "name:formatchar" (whitespace is allowed)
    _elementRE = re.compile(
    		r"\s*"							# whitespace
    		r"([A-Za-z_][A-Za-z_0-9]*)"		# name (python identifier)
    		r"\s*:\s*"						# whitespace : whitespace
    		r"([xcbB?hHiIlLqQfd]|"			# formatchar...
    			r"[0-9]+[ps]|"				# ...formatchar...
    			r"([0-9]+)\.([0-9]+)(F))"	# ...formatchar
    		r"\s*"							# whitespace
    		r"(#.*)?$"						# [comment] + end of string
    	)

    # matches the special struct fmt chars and 'x' (pad byte)
    _extraRE = re.compile(r"\s*([x@=<>!])\s*(#.*)?$")

    # matches an "empty" string, possibly containing whitespace and/or a comment
    _emptyRE = re.compile(r"\s*(#.*)?$")

    _fixedpointmappings = {
    		8: "b",
    		16: "h",
    		32: "l"}

    _formatcache = {}

    def getformat(fmt, keep_pad_byte=False):
    	fmt = tostr(fmt, encoding="ascii")
    	try:
    		formatstring, names, fixes = _formatcache[fmt]
    	except KeyError:
    		lines = re.split("[\n;]", fmt)
    		formatstring = ""
    		names = []
    		fixes = {}
    		for line in lines:
    			if _emptyRE.match(line):
    				continue
    			m = _extraRE.match(line)
    			if m:
    				formatchar = m.group(1)
    				if formatchar != 'x' and formatstring:
    					raise Error("a special fmt char must be first")
    			else:
    				m = _elementRE.match(line)
    				if not m:
    					raise Error("syntax error in fmt: '%s'" % line)
    				name = m.group(1)
    				formatchar = m.group(2)
    				if keep_pad_byte or formatchar != "x":
    					names.append(name)
    				if m.group(3):
    					# fixed point
    					before = int(m.group(3))
    					after = int(m.group(4))
    					bits = before + after
    					if bits not in [8, 16, 32]:
    						raise Error("fixed point must be 8, 16 or 32 bits long")
    					formatchar = _fixedpointmappings[bits]
    					assert m.group(5) == "F"
    					fixes[name] = after
    			formatstring = formatstring + formatchar
    		_formatcache[fmt] = formatstring, names, fixes
    	return formatstring, names, fixes

    def _test():
    	fmt = """
    		# comments are allowed
    		>  # big endian (see documentation for struct)
    		# empty lines are allowed:

    		ashort: h
    		along: l
    		abyte: b	# a byte
    		achar: c
    		astr: 5s
    		afloat: f; adouble: d	# multiple "statements" are allowed
    		afixed: 16.16F
    		abool: ?
    		apad: x
    	"""

    	print('size:', calcsize(fmt))

    	class foo(object):
    		pass

    	i = foo()

    	i.ashort = 0x7fff
    	i.along = 0x7fffffff
    	i.abyte = 0x7f
    	i.achar = "a"
    	i.astr = "12345"
    	i.afloat = 0.5
    	i.adouble = 0.5
    	i.afixed = 1.5
    	i.abool = True

    	data = pack(fmt, i)
    	print('data:', repr(data))
    	print(unpack(fmt, data))
    	i2 = foo()
    	unpack(fmt, data, i2)
    	print(vars(i2))

    if __name__ == "__main__":
    	_test()