# 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.
