rpm5 & ts.hdrFromFdno from .hdr file

[Elan Ruusamäe]

On 05/18/2013 08:58 PM, Jeffrey Johnson wrote:
>> >header is extracted from this repodata info:
>> >
>> >    <rpm:header-range start="368" end="7947"/>
>> >
>> >perhaps those offsets are incorrect?
>> >
> Heh: offsets being different.
so, i found rpm5 has the offsets stored in headers already, and those 
give the same offsets out, which seem to be correct (compared to what 
rpm/yum on fedora does)

# ./hw5.py blockdev-2.22.2-4.i686.rpm
st: 368, end: 7947
START: 368, END: 7947, SIZE: 7579
Wrote: blockdev-2.22.2-4.i686.rpm.rpm5.hdr

# md5sum *.hdr
ce84368ce713e81ad50214c9021f46d3  blockdev-2.22.2-4.i686.rpm.hdr
ce84368ce713e81ad50214c9021f46d3 blockdev-2.22.2-4.i686.rpm.rpm5.hdr

altho all the files used in the tests are in this [1] archive, showing 
the .py here as well:

[1] http://carme.pld-linux.org/~glen/rpm5-hdr.tar

# cat hw5.py
#!/usr/bin/python

import os, sys, rpm

def get_hdr(rpm_file):
     ts = rpm.ts()
     fdno = os.open(rpm_file, os.O_RDONLY)
     hdr = ts.hdrFromFdno(fdno)
     os.close(fdno)
     return hdr

def _get_header_byte_range(localpath):
     hdr = get_hdr(localpath)
     print "st: %s, end: %s" % (hdr[1211], hdr[1212])
     q = hdr.sprintf('%{HEADERSTARTOFF} %{HEADERENDOFF}')
     (start, end) = q.split(' ')
     return (int(start), int(end))

fn = sys.argv[1]
(start,end) = _get_header_byte_range(fn)
size = end-start
print "START: %d, END: %d, SIZE: %d" % (start,end,size)

f = open(fn, 'r')
f.seek(start)
h = f.read(size)
f.close()

hfn = '%s.rpm5.hdr' % fn
f = open(hfn, 'w')
f.write(h)
f.close()

print "Wrote: %s" % hfn


-- 
glen