# Parsers/generators for QuickTime media descriptions

import struct

Error = 'MediaDescr.Error'

class _MediaDescriptionCodec:

    def __init__(self, trunc, size, names, fmt):

        self.trunc = trunc

        self.size = size

        self.names = names

        self.fmt = fmt

    def decode(self, data):

        if self.trunc:

            data = data[:self.size]

        values = struct.unpack(self.fmt, data)

        if len(values) != len(self.names):

            raise Error, ('Format length does not match number of names', descr)

        rv = {}

        for i in range(len(values)):

            name = self.names[i]

            value = values[i]

            if type(name) == type(()):

                name, cod, dec = name

                value = dec(value)

            rv[name] = value

        return rv

    def encode(dict):

        list = [self.fmt]

        for name in self.names:

            if type(name) == type(()):

                name, cod, dec = name

            else:

                cod = dec = None

            value = dict[name]

            if cod:

                value = cod(value)

            list.append(value)

        rv = struct.pack(*list)

        return rv

# Helper functions

def _tofixed(float):

    hi = int(float)

    lo = int(float*0x10000) & 0xffff

    return (hi<<16)|lo

def _fromfixed(fixed):

    hi = (fixed >> 16) & 0xffff

    lo = (fixed & 0xffff)

    return hi + (lo / float(0x10000))

def _tostr31(str):

    return chr(len(str)) + str + '\0'*(31-len(str))

def _fromstr31(str31):

    return str31[1:1+ord(str31[0])]

SampleDescription = _MediaDescriptionCodec(

        1,      # May be longer, truncate

        16,     # size

        ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex'), # Attributes

        "l4slhh"        # Format

)

SoundDescription = _MediaDescriptionCodec(

        1,

        36,

        ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',

        'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',

        'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed)),

        "l4slhhhh4shhhhl"       # Format

)

SoundDescriptionV1 = _MediaDescriptionCodec(

        1,

        52,

        ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',

        'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',

        'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed), 'samplesPerPacket',

        'bytesPerPacket', 'bytesPerFrame', 'bytesPerSample'),

        "l4slhhhh4shhhhlllll"   # Format

)

ImageDescription = _MediaDescriptionCodec(

        1,      # May be longer, truncate

        86,     # size

        ('idSize', 'cType', 'resvd1', 'resvd2', 'dataRefIndex', 'version',

         'revisionLevel', 'vendor', 'temporalQuality', 'spatialQuality',

         'width', 'height', ('hRes', _tofixed, _fromfixed), ('vRes', _tofixed, _fromfixed),

        'dataSize', 'frameCount', ('name', _tostr31, _fromstr31),

         'depth', 'clutID'),

        'l4slhhhh4sllhhlllh32shh',

)

# XXXX Others, like TextDescription and such, remain to be done.