otConverters.py :  » GUI » TTX-FontTools » fonttools-2.3 » Lib » fontTools » ttLib » tables » Python Open Source

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Python Open Source » GUI » TTX FontTools 
TTX FontTools » fonttools 2.3 » Lib » fontTools » ttLib » tables » otConverters.py
from types import TupleType
from fontTools.misc.textTools import safeEval


def buildConverters(tableSpec, tableNamespace):
  """Given a table spec from otData.py, build a converter object for each
  field of the table. This is called for each table in otData.py, and
  the results are assigned to the corresponding class in otTables.py."""
  converters = []
  convertersByName = {}
  for tp, name, repeat, repeatOffset, descr in tableSpec:
    if name.startswith("ValueFormat"):
      assert tp == "uint16"
      converterClass = ValueFormat
    elif name == "DeltaValue":
      assert tp == "uint16"
      converterClass = DeltaValue
    elif name.endswith("Count"):
      assert tp == "uint16"
      converterClass = Count
    elif name == "SubTable":
      converterClass = SubTable
    elif name == "ExtSubTable":
      converterClass = ExtSubTable
    else:
      converterClass = converterMapping[tp]
    tableClass = tableNamespace.get(name)
    conv = converterClass(name, repeat, repeatOffset, tableClass)
    if name in ["SubTable", "ExtSubTable"]:
      conv.lookupTypes = tableNamespace['lookupTypes']
      # also create reverse mapping
      for t in conv.lookupTypes.values():
        for cls in t.values():
          convertersByName[cls.__name__] = Table(name, repeat, repeatOffset, cls)
    converters.append(conv)
    assert not convertersByName.has_key(name)
    convertersByName[name] = conv
  return converters, convertersByName


class BaseConverter:
  
  """Base class for converter objects. Apart from the constructor, this
  is an abstract class."""
  
  def __init__(self, name, repeat, repeatOffset, tableClass):
    self.name = name
    self.repeat = repeat
    self.repeatOffset = repeatOffset
    self.tableClass = tableClass
    self.isCount = name.endswith("Count")
  
  def read(self, reader, font, tableStack):
    """Read a value from the reader."""
    raise NotImplementedError, self
  
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    """Write a value to the writer."""
    raise NotImplementedError, self
  
  def xmlRead(self, attrs, content, font):
    """Read a value from XML."""
    raise NotImplementedError, self
  
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    """Write a value to XML."""
    raise NotImplementedError, self


class SimpleValue(BaseConverter):
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    xmlWriter.simpletag(name, attrs + [("value", value)])
    xmlWriter.newline()
  def xmlRead(self, attrs, content, font):
    return attrs["value"]

class IntValue(SimpleValue):
  def xmlRead(self, attrs, content, font):
    return int(attrs["value"])

class Long(IntValue):
  def read(self, reader, font, tableStack):
    return reader.readLong()
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeLong(value)

class Fixed(IntValue):
  def read(self, reader, font, tableStack):
    return float(reader.readLong()) / 0x10000
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeLong(int(round(value * 0x10000)))
  def xmlRead(self, attrs, content, font):
    return float(attrs["value"])

class Short(IntValue):
  def read(self, reader, font, tableStack):
    return reader.readShort()
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeShort(value)

class UShort(IntValue):
  def read(self, reader, font, tableStack):
    return reader.readUShort()
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeUShort(value)

class Count(Short):
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    xmlWriter.comment("%s=%s" % (name, value))
    xmlWriter.newline()

class Tag(SimpleValue):
  def read(self, reader, font, tableStack):
    return reader.readTag()
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeTag(value)

class GlyphID(SimpleValue):
  def read(self, reader, font, tableStack):
    value = reader.readUShort()
    value =  font.getGlyphName(value)
    return value

  def write(self, writer, font, tableStack, value, repeatIndex=None):
    value =  font.getGlyphID(value)
    writer.writeUShort(value)


class Struct(BaseConverter):
  
  def read(self, reader, font, tableStack):
    table = self.tableClass()
    table.decompile(reader, font, tableStack)
    return table
  
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    value.compile(writer, font, tableStack)
  
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    if value is None:
      pass  # NULL table, ignore
    else:
      value.toXML(xmlWriter, font, attrs)
  
  def xmlRead(self, attrs, content, font):
    table = self.tableClass()
    Format = attrs.get("Format")
    if Format is not None:
      table.Format = int(Format)
    for element in content:
      if type(element) == TupleType:
        name, attrs, content = element
        table.fromXML((name, attrs, content), font)
      else:
        pass
    return table


class Table(Struct):
  
  def read(self, reader, font, tableStack):
    offset = reader.readUShort()
    if offset == 0:
      return None
    if offset <= 3:
      # XXX hack to work around buggy pala.ttf
      print "*** Warning: offset is not 0, yet suspiciously low (%s). table: %s" \
          % (offset, self.tableClass.__name__)
      return None
    subReader = reader.getSubReader(offset)
    table = self.tableClass()
    table.decompile(subReader, font, tableStack)
    return table
  
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    if value is None:
      writer.writeUShort(0)
    else:
      subWriter = writer.getSubWriter()
      subWriter.name = self.name
      if repeatIndex is not None:
        subWriter.repeatIndex = repeatIndex
      value.preCompile()
      writer.writeSubTable(subWriter)
      value.compile(subWriter, font, tableStack)

class SubTable(Table):
  def getConverter(self, tableType, lookupType):
    lookupTypes = self.lookupTypes[tableType]
    tableClass = lookupTypes[lookupType]
    return SubTable(self.name, self.repeat, self.repeatOffset, tableClass)


class ExtSubTable(Table):
  def getConverter(self, tableType, lookupType):
    lookupTypes = self.lookupTypes[tableType]
    tableClass = lookupTypes[lookupType]
    return ExtSubTable(self.name, self.repeat, self.repeatOffset, tableClass)
  
  def read(self, reader, font, tableStack):
    offset = reader.readULong()
    if offset == 0:
      return None
    subReader = reader.getSubReader(offset)
    table = self.tableClass()
    table.reader = subReader
    table.font = font
    table.compileStatus = 1
    table.start = table.reader.offset
    return table
  
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.Extension = 1 # actually, mere presence of the field flags it as an Ext Subtable writer.
    if value is None:
      writer.writeULong(0)
    else:
      # If the subtable has not yet been decompiled, we need to do so.
      if  value.compileStatus == 1:
        value.decompile(value.reader, value.font, tableStack)
       subWriter = writer.getSubWriter()
      subWriter.name = self.name
      writer.writeSubTable(subWriter)
      # If the subtable has been sorted and we can just write the original
      # data, then do so.
      if value.compileStatus == 3:
        data = value.reader.data[value.start:value.end]
        subWriter.writeData(data)
      else:
        value.compile(subWriter, font, tableStack)


class ValueFormat(IntValue):
  def __init__(self, name, repeat, repeatOffset, tableClass):
    BaseConverter.__init__(self, name, repeat, repeatOffset, tableClass)
    self.which = name[-1] == "2"
  def read(self, reader, font, tableStack):
    format = reader.readUShort()
    reader.setValueFormat(format, self.which)
    return format
  def write(self, writer, font, tableStack, format, repeatIndex=None):
    writer.writeUShort(format)
    writer.setValueFormat(format, self.which)


class ValueRecord(ValueFormat):
  def read(self, reader, font, tableStack):
    return reader.readValueRecord(font, self.which)
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    writer.writeValueRecord(value, font, self.which)
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    if value is None:
      pass  # NULL table, ignore
    else:
      value.toXML(xmlWriter, font, self.name, attrs)
  def xmlRead(self, attrs, content, font):
    from otBase import ValueRecord
    value = ValueRecord()
    value.fromXML((None, attrs, content), font)
    return value


class DeltaValue(BaseConverter):
  
  def read(self, reader, font, tableStack):
    table = tableStack.getTop()
    StartSize = table["StartSize"]
    EndSize = table["EndSize"]
    DeltaFormat = table["DeltaFormat"]
    assert DeltaFormat in (1, 2, 3), "illegal DeltaFormat"
    nItems = EndSize - StartSize + 1
    nBits = 1 << DeltaFormat
    minusOffset = 1 << nBits
    mask = (1 << nBits) - 1
    signMask = 1 << (nBits - 1)
    
    DeltaValue = []
    tmp, shift = 0, 0
    for i in range(nItems):
      if shift == 0:
        tmp, shift = reader.readUShort(), 16
      shift = shift - nBits
      value = (tmp >> shift) & mask
      if value & signMask:
        value = value - minusOffset
      DeltaValue.append(value)
    return DeltaValue
  
  def write(self, writer, font, tableStack, value, repeatIndex=None):
    table = tableStack.getTop()
    StartSize = table["StartSize"]
    EndSize = table["EndSize"]
    DeltaFormat = table["DeltaFormat"]
    DeltaValue = table["DeltaValue"]
    assert DeltaFormat in (1, 2, 3), "illegal DeltaFormat"
    nItems = EndSize - StartSize + 1
    nBits = 1 << DeltaFormat
    assert len(DeltaValue) == nItems
    mask = (1 << nBits) - 1
    
    tmp, shift = 0, 16
    for value in DeltaValue:
      shift = shift - nBits
      tmp = tmp | ((value & mask) << shift)
      if shift == 0:
        writer.writeUShort(tmp)
        tmp, shift = 0, 16
    if shift <> 16:
      writer.writeUShort(tmp)
  
  def xmlWrite(self, xmlWriter, font, value, name, attrs):
    # XXX this could do with a nicer format
    xmlWriter.simpletag(name, attrs + [("value", value)])
    xmlWriter.newline()
  
  def xmlRead(self, attrs, content, font):
    return safeEval(attrs["value"])


converterMapping = {
  # type         class
  "int16":       Short,
  "uint16":      UShort,
  "ULONG":       Long,
  "Fixed":       Fixed,
  "Tag":         Tag,
  "GlyphID":     GlyphID,
  "struct":      Struct,
  "Offset":      Table,
  "LOffset":     ExtSubTable,
  "ValueRecord": ValueRecord,
}

# equivalents:
converterMapping["USHORT"] = converterMapping["uint16"]
converterMapping["fixed32"] = converterMapping["Fixed"]

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