Reading a binary file into a struct

Question

I have a binary file with a known format/structure.

How do I read all the binary data in to an array of the structure?

Something like (in pseudo code)

<

Answer 1

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import struct 

First just read the binary into an array

mbr = file('mbrcontent', 'rb').read() 

So you can just fetch some piece of the the array

partition_table = mbr[446:510] 

and then unpack it as an integer

signature = struct.unpack('

a more complex example

little_endian = (signature == 0xaa55) # should be True 
print "Little endian:", little_endian 
PART_FMT = (little_endian and '<' or '>') + ( 
"B" # status (0x80 = bootable (active), 0x00 = non-bootable) 
# CHS of first block 
"B" # Head 
"B" # Sector is in bits 5; bits 9 of cylinder are in bits 7-6 
"B" # bits 7-0 of cylinder 
"B" # partition type 
# CHS of last block 
"B" # Head 
"B" # Sector is in bits 5; bits 9 of cylinder are in bits 7-6 
"B" # bits 7-0 of cylinder 
"L" # LBA of first sector in the partition 
"L" # number of blocks in partition, in little-endian format 
) 

PART_SIZE = 16 
fmt_size = struct.calcsize(PART_FMT) 
# sanity check expectations 
assert fmt_size == PART_SIZE, "Partition format string is %i bytes, not %i" % (fmt_size, PART_SIZE) 

def cyl_sector(sector_cyl, cylinder7_0): 
    sector = sector_cyl & 0x1F # bits 5-0 

    # bits 7-6 of sector_cyl contain bits 9-8 of the cylinder 
    cyl_high = (sector_cyl >> 5) & 0x03 
    cyl = (cyl_high << 8) | cylinder7_0 
    return sector, cyl 

#I have corrected the indentation, but the change is refused because less than 6 characters, so I am adding this useful comment.
for partition in range(4): 
    print "Partition #%i" % partition, 
    offset = PART_SIZE * partition 
    (status, start_head, start_sector_cyl, start_cyl7_0, part_type, end_head, end_sector_cyl, end_cyl7_0, 
    lba, blocks ) = struct.unpack( PART_FMT,partition_table[offset:offset + PART_SIZE]) 
    if status == 0x80: 
        print "Bootable", 
    elif status: 
        print "Unknown status [%s]" % hex(status), 
        print "Type=0x%x" % part_type 
        start = (start_head,) + cyl_sector(start_sector_cyl, start_cyl7_0) 
        end = (end_head,) + cyl_sector(end_sector_cyl, end_cyl7_0) 
        print " (Start: Heads:%i\tCyl:%i\tSect:%i)" % start 
        print " (End: Heads:%i\tCyl:%i\tSect:%i)" % end 
        print " LBA:", lba 
        print " Blocks:", blocks