Extract u-boot multi-file image in Python
25 Oct 2011 
Matteo Mattei 
embedded linux python 
2 Comments 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 very 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.
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| #!/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() |