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# Copyright 2007 Jeff Epler <jepler@unpythonic.net>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
#
# Info about Xilinx bitfiles:
#
# The format consists of several variable length chunks, preceded by what
# seems to be a constant header (a magic number).
#
# After the header, each "chunk" consists of a one byte "tag", a two or
# four byte length, and "length" bytes of data (the body).
#
# In some chunks, the body is a zero terminated printable string. In
# others it is a blob of binary data. The file format doesn't care.
#
# Standard Xilinx files use 5 chunks: 'a' through 'd' are zero-terminated
# strings with information about the file. 'e' is a large binary blob
# with the actual bitstream in it. Xilinx uses 2 byte lengths for chunks
# 'a' thru 'd', and 4 bytes for chunk 'e'. This library allows other
# chunks, and assume that all have 4 byte lengths, except 'a' thru 'd'.
#
import struct
class BitFile:
MAXCHUNKS = 50
SMALLCHUNKS = "abcd"
MAGIC = "\x00\x09" \
"\x0f\xf0\x0f\xf0" \
"\x0f\xf0\x0f\xf0" \
"\x00\x00\x01"
ORDER = "abcde"
def __init__(self, chunks={}):
self.chunks = dict(chunks)
def __getitem__(self, item):
return self.chunks[item]
def __setitem__(self, item, value):
self.chunks[item] = value
def __delitem__(self, item):
del self.chunks[item]
def chunkorder(self, xxx_todo_changeme):
(tag, value) = xxx_todo_changeme
if tag in self.ORDER:
return self.ORDER.index(tag)
return 256 + ord(tag)
@classmethod
def fromstring(cls, data):
if not data.startswith(cls.MAGIC):
raise ValueError("data does not start with the magic number")
i = len(cls.MAGIC)
chunks = {}
while i < len(data):
tag = data[i]
if tag in cls.SMALLCHUNKS:
chunksize = struct.unpack(">H", data[i+1:i+3])[0]
i = i + 3
else:
chunksize = struct.unpack(">I", data[i+1:i+5])[0]
i = i + 5
chunkdata = data[i:i+chunksize]
if tag in chunks:
raise ValueError("bitfile has chunk %r more than once" % tag)
chunks[tag] = chunkdata
i = i + chunksize
return cls(chunks)
@classmethod
def fromfile(cls, file):
return cls.fromstring(file.read())
@classmethod
def fromfilename(cls, filename):
return cls.fromstring(open(filename, "rb").read())
def tostring(self):
result = self.MAGIC
for tag, chunkdata in sorted(list(self.chunks.items()), key=self.chunkorder):
if len(tag) != 1:
raise ValueError("Tag %r must be a length-1 string" % tag)
result = result + tag
if tag in self.SMALLCHUNKS:
result += struct.pack(">H", len(chunkdata))
else:
result += struct.pack(">I", len(chunkdata))
result += chunkdata
return result
def tofile(self, file):
return file.write(self.tostring())
def tofilename(self, filename):
return open(filename, "wb").write(self.tostring())
if __name__ == '__main__':
import sys
if len(sys.argv) < 2:
c = BitFile()
c['a'] = "hello world"
c['e'] = "goodbye"
c['A'] = "shazam"
s = c.tostring()
print((repr(s)))
d = BitFile.fromstring(s)
print((d.chunks))
assert d.tostring() == s
for bitfile in sys.argv[1:]:
bits = open(bitfile, "rb").read()
c = BitFile.fromstring(bits)
for k, v in sorted(c.chunks.items()):
if k in 'abcd':
print((k, v))
else:
print((k, len(v)))
newbits = c.tostring()
assert bits == newbits # Assuming the original is in canonical order!
print()
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