ec_crazy_rebuild.py

#!/usr/bin/env python
import sys
from hashlib import md5
from pyeclib.ec_iface import ECDriver

try:
    ec_type = sys.argv[1]
except IndexError:
    sys.exit('usage: %s <ec_type>' % sys.argv[0])

driver = ECDriver(k=4, m=2, ec_type=ec_type)


SEGSIZE = 1048576


def make_fragment_payloads(driver, test_body):
    # split up the body into buffers
    chunks = [test_body[x:x + SEGSIZE]
              for x in range(0, len(test_body), SEGSIZE)]
    # encode the buffers into fragment payloads
    fragment_payloads = []
    for chunk in chunks:
        fragments = driver.encode(chunk)
        if not fragments:
            break
        fragment_payloads.append(fragments)
    return fragment_payloads


test_body = ('crazy' * SEGSIZE)[:-565]

fragment_payloads = make_fragment_payloads(driver, test_body)

index_to_rebuild = 5
index_set1 = [0, 1, 2, 4]
rebuild_hash1 = md5()
decode_hash1 = md5()

for frags in fragment_payloads:
    payload = [frags[i] for i in index_set1]
    fragment = driver.reconstruct(payload, [index_to_rebuild])[0]
    rebuild_hash1.update(fragment)
    segment = driver.decode(payload)
    decode_hash1.update(segment)
    fragments = driver.encode(segment)
    # assert fragment == fragments[index_to_rebuild]

index_set2 = [0, 1, 2, 3]
rebuild_hash2 = md5()
decode_hash2 = md5()

for frags in fragment_payloads:
    payload = [frags[i] for i in index_set2]
    fragment = driver.reconstruct(payload, [index_to_rebuild])[0]
    rebuild_hash2.update(fragment)
    segment = driver.decode(payload)
    decode_hash2.update(segment)
    fragments = driver.encode(segment)
    assert fragment == fragments[index_to_rebuild]

print "decode doesn't care about index"
print md5(test_body).hexdigest()
print decode_hash1.hexdigest()
print decode_hash2.hexdigest()

print "reconstruct seems to care about index"
print rebuild_hash1.hexdigest()
print rebuild_hash2.hexdigest()