Current File : //usr/lib/calibre/calibre/utils/fonts/sfnt/loca.py
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
__docformat__ = 'restructuredtext en'
import array, sys
from operator import itemgetter
from itertools import repeat
from calibre.utils.fonts.sfnt import UnknownTable
from polyglot.builtins import iteritems
def four_byte_type_code():
for c in 'IL':
a = array.array(c)
if a.itemsize == 4:
return c
def read_array(data, fmt='H'):
ans = array.array(fmt, data)
if sys.byteorder != 'big':
ans.byteswap()
return ans
class LocaTable(UnknownTable):
def load_offsets(self, head_table, maxp_table):
fmt = 'H' if head_table.index_to_loc_format == 0 else four_byte_type_code()
locs = read_array(self.raw, fmt)
self.offset_map = locs.tolist()
if fmt == 'H':
self.offset_map = [2*i for i in self.offset_map]
self.fmt = fmt
def glyph_location(self, glyph_id):
offset = self.offset_map[glyph_id]
next_offset = self.offset_map[glyph_id+1]
return offset, next_offset - offset
def update(self, resolved_glyph_map):
'''
Update this table to contain pointers only to the glyphs in
resolved_glyph_map which must be a map of glyph_ids to (offset, sz)
Note that the loca table is generated for all glyphs from 0 to the
largest glyph that is either in resolved_glyph_map or was present
originally. The pointers to glyphs that have no data will be set to
zero. This preserves glyph ids.
'''
current_max_glyph_id = len(self.offset_map) - 2
max_glyph_id = max(resolved_glyph_map or (0,))
max_glyph_id = max(max_glyph_id, current_max_glyph_id)
self.offset_map = list(repeat(0, max_glyph_id + 2))
glyphs = [(glyph_id, x[0], x[1]) for glyph_id, x in
iteritems(resolved_glyph_map)]
glyphs.sort(key=itemgetter(1))
for glyph_id, offset, sz in glyphs:
self.offset_map[glyph_id] = offset
self.offset_map[glyph_id+1] = offset + sz
# Fix all zero entries to be the same as the previous entry, which
# means that if the ith entry is zero, the i-1 glyph is not present.
for i in range(1, len(self.offset_map)):
if self.offset_map[i] == 0:
self.offset_map[i] = self.offset_map[i-1]
vals = self.offset_map
max_offset = max(vals) if vals else 0
if max_offset < 0x20000 and all(l % 2 == 0 for l in vals):
self.fmt = 'H'
vals = array.array(self.fmt, (i // 2 for i in vals))
else:
self.fmt = four_byte_type_code()
vals = array.array(self.fmt, vals)
if sys.byteorder != "big":
vals.byteswap()
self.raw = vals.tobytes()
subset = update
def dump_glyphs(self, sfnt):
if not hasattr(self, 'offset_map'):
self.load_offsets(sfnt[b'head'], sfnt[b'maxp'])
for i in range(len(self.offset_map)-1):
off, noff = self.offset_map[i], self.offset_map[i+1]
if noff != off:
print('Glyph id:', i, 'size:', noff-off)
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