s3-tests/s3tests/realistic.py
Tommi Virtanen 02a4c82dfa Make generate_objects.py and rand_readwrite.py inside the package.
Handle dependencies properly. Now e.g. "./bootstrap &&
./virtualenv/bin/s3tests-test-readwrite" should just work.
2011-07-13 13:52:54 -07:00

126 lines
4 KiB
Python

import hashlib
import random
import string
import struct
class RandomContentFile(object):
def __init__(self, size, seed):
self.seed = seed
self.random = random.Random(self.seed)
self.offset = 0
self.buffer = ''
self.size = size
self.hash = hashlib.md5()
self.digest_size = self.hash.digest_size
self.digest = None
def seek(self, offset):
assert offset == 0
self.random.seed(self.seed)
self.offset = offset
self.buffer = ''
def tell(self):
return self.offset
def _generate(self):
# generate and return a chunk of pseudorandom data
# 256 bits = 32 bytes at a time
size = 1*1024*1024
l = [self.random.getrandbits(64) for _ in xrange(size/8)]
s = struct.pack((size/8)*'Q', *l)
return s
def read(self, size=-1):
if size < 0:
size = self.size - self.offset
r = []
random_count = min(size, self.size - self.offset - self.digest_size)
if random_count > 0:
while len(self.buffer) < random_count:
self.buffer += self._generate()
self.offset += random_count
size -= random_count
data, self.buffer = self.buffer[:random_count], self.buffer[random_count:]
if self.hash is not None:
self.hash.update(data)
r.append(data)
digest_count = min(size, self.size - self.offset)
if digest_count > 0:
if self.digest is None:
self.digest = self.hash.digest()
self.hash = None
self.offset += digest_count
size -= digest_count
data = self.digest[:digest_count]
r.append(data)
return ''.join(r)
class FileVerifier(object):
def __init__(self):
self.size = 0
self.hash = hashlib.md5()
self.buf = ''
def write(self, data):
self.size += len(data)
self.buf += data
digsz = -1*self.hash.digest_size
new_data, self.buf = self.buf[0:digsz], self.buf[digsz:]
self.hash.update(new_data)
def valid(self):
"""
Returns True if this file looks valid. The file is valid if the end
of the file has the md5 digest for the first part of the file.
"""
return self.buf == self.hash.digest()
def files(mean, stddev, seed=None):
"""
Yields file-like objects with effectively random contents, where
the size of each file follows the normal distribution with `mean`
and `stddev`.
Beware, the file-likeness is very shallow. You can use boto's
`key.set_contents_from_file` to send these to S3, but they are not
full file objects.
The last 128 bits are the MD5 digest of the previous bytes, for
verifying round-trip data integrity. For example, if you
re-download the object and place the contents into a file called
``foo``, the following should print two identical lines:
python -c 'import sys, hashlib; data=sys.stdin.read(); print hashlib.md5(data[:-16]).hexdigest(); print "".join("%02x" % ord(c) for c in data[-16:])' <foo
Except for objects shorter than 16 bytes, where the second line
will be proportionally shorter.
"""
rand = random.Random(seed)
while True:
while True:
size = int(rand.normalvariate(mean, stddev))
if size >= 0:
break
yield RandomContentFile(size=size, seed=rand.getrandbits(32))
def names(mean, stddev, charset=None, seed=None):
"""
Yields strings that are somewhat plausible as file names, where
the lenght of each filename follows the normal distribution with
`mean` and `stddev`.
"""
if charset is None:
charset = string.ascii_lowercase
rand = random.Random(seed)
while True:
while True:
length = int(rand.normalvariate(mean, stddev))
if length >= 0:
break
name = ''.join(rand.choice(charset) for _ in xrange(length))
yield name