Extract u-boot multi-file image in Python
Posted by Matteo Mattei / 25th October 2011
This simple piece of code shows how to extract/decompress a u-boot multi-file image created with mkimage using Python. The image format is pretty simple:
64 bytes of image header.
4 bytes for the size of first image.
4 bytes for the size of second image.
...
4 bytes of zeros for termination.
image1.
image2.
...
You need to remember also that each image is padded to 4 bytes.
#!/usr/bin/env python
import sys
def toNumber(buf):
""" Convert string in number """
size = 0
for b in buf: size=size*256+ord(b)
return size
if len(sys.argv)!=2:
sys.stdout.write('Usage %s uboot_image_file\n' % sys.argv[0])
sys.exit(1)
f = open(sys.argv[1],'rb')
f.seek(64) # skip image header
parts = []
# get file size of all images
while True:
buf = f.read(4)
size = toNumber(buf)
if size==0: break
parts.append(size)
i = 0
for size in parts:
pattern = 'file%d.img' % i
p = open(pattern, 'wb')
buf = f.read(size)
p.write(buf)
p.close()
if size%4 != 0:
# 4 byte padding
f.read(4-(size%4))
i+=1
f.close()
