Module enthought.kiva.fonttools.fontTools.ttLib.sfnt

API Reference for Enthought Tool Suite 3.0.1

ttLib/sfnt.py -- low-level module to deal with the sfnt file format.

Defines two public classes:: SFNTReader SFNTWriter

(Normally you don't have to use these classes explicitly; they are used automatically by ttLib.TTFont.)

The reading and writing of sfnt files is separated in two distinct classes, since whenever to number of tables changes or whenever a table's length chages you need to rewrite the whole file anyway.

Variables
Classes
Functions
Imported Names

Variables

CHECKSUM_MAGIC

magic value corresponding to 0xb1b0afba; used in lieu of the hex constant to avoid signedness issues with python 2.4
```
CHECKSUM_MAGIC = -Const(1313820742)
```

sfntDirectoryEntryFormat

sfntDirectoryEntryFormat = """
		> # big endian
		tag:            4s
		checkSum:       l
		offset:         l
		length:         l
"""

sfntDirectoryEntrySize

sfntDirectoryEntrySize = sstruct.calcsize(sfntDirectoryEntryFormat)

sfntDirectoryFormat

sfntDirectoryFormat = """
		> # big endian
		sfntVersion:    4s
		numTables:      H    # number of tables
		searchRange:    H    # (max2 <= numTables)*16
		entrySelector:  H    # log2(max2 <= numTables)
		rangeShift:     H    # numTables*16-searchRange
"""

sfntDirectorySize

sfntDirectorySize = sstruct.calcsize(sfntDirectoryFormat)

Classes

Function summary

calcChecksum(data, start = 0)
getSearchRange(n)
maxPowerOfTwo(x)

Functions

calcChecksum(data, start = 0)

Calculate the checksum for an arbitrary block of data. Optionally takes a 'start' argument, which allows you to calculate a checksum in chunks by feeding it a previous result.

If the data length is not a multiple of four, it assumes it is to be padded with null byte.
getSearchRange(n)

Calculate searchRange, entrySelector, rangeShift for the sfnt directory. 'n' is the number of tables.
maxPowerOfTwo(x)

Return the highest exponent of two, so that (2 ** exponent) <= x

Imported Names