tests/test-pathencode.py

# This is a randomized test that generates different pathnames every
# time it is invoked, and tests the encoding of those pathnames.
#
# It uses a simple probabilistic model to generate valid pathnames
# that have proven likely to expose bugs and divergent behavior in
# different encoding implementations.


import binascii
import collections
import itertools
import math
import os
import random
import sys
import time
from mercurial import (
    pycompat,
    store,
)

validchars = set(map(pycompat.bytechr, range(0, 256)))
alphanum = range(ord('A'), ord('Z'))

for c in (b'\0', b'/'):
    validchars.remove(c)

winreserved = (
    b'aux con prn nul'.split()
    + [b'com%d' % i for i in range(1, 10)]
    + [b'lpt%d' % i for i in range(1, 10)]
)


def casecombinations(names):
    '''Build all case-diddled combinations of names.'''

    combos = set()

    for r in names:
        for i in range(len(r) + 1):
            for c in itertools.combinations(range(len(r)), i):
                d = r
                for j in c:
                    d = b''.join((d[:j], d[j : j + 1].upper(), d[j + 1 :]))
                combos.add(d)
    return sorted(combos)


def buildprobtable(fp, cmd='hg manifest tip'):
    """Construct and print a table of probabilities for path name
    components.  The numbers are percentages."""

    counts = collections.defaultdict(lambda: 0)
    for line in os.popen(cmd).read().splitlines():
        if line[-2:] in ('.i', '.d'):
            line = line[:-2]
        if line.startswith('data/'):
            line = line[5:]
        for c in line:
            counts[c] += 1
    for c in '\r/\n':
        counts.pop(c, None)
    t = sum(counts.values()) / 100.0
    fp.write('probtable = (')
    for i, (k, v) in enumerate(
        sorted(counts.items(), key=lambda x: x[1], reverse=True)
    ):
        if (i % 5) == 0:
            fp.write('\n    ')
        vt = v / t
        if vt < 0.0005:
            break
        fp.write('(%r, %.03f), ' % (k, vt))
    fp.write('\n    )\n')


# A table of character frequencies (as percentages), gleaned by
# looking at filelog names from a real-world, very large repo.

probtable = (
    (b't', 9.828),
    (b'e', 9.042),
    (b's', 8.011),
    (b'a', 6.801),
    (b'i', 6.618),
    (b'g', 5.053),
    (b'r', 5.030),
    (b'o', 4.887),
    (b'p', 4.363),
    (b'n', 4.258),
    (b'l', 3.830),
    (b'h', 3.693),
    (b'_', 3.659),
    (b'.', 3.377),
    (b'm', 3.194),
    (b'u', 2.364),
    (b'd', 2.296),
    (b'c', 2.163),
    (b'b', 1.739),
    (b'f', 1.625),
    (b'6', 0.666),
    (b'j', 0.610),
    (b'y', 0.554),
    (b'x', 0.487),
    (b'w', 0.477),
    (b'k', 0.476),
    (b'v', 0.473),
    (b'3', 0.336),
    (b'1', 0.335),
    (b'2', 0.326),
    (b'4', 0.310),
    (b'5', 0.305),
    (b'9', 0.302),
    (b'8', 0.300),
    (b'7', 0.299),
    (b'q', 0.298),
    (b'0', 0.250),
    (b'z', 0.223),
    (b'-', 0.118),
    (b'C', 0.095),
    (b'T', 0.087),
    (b'F', 0.085),
    (b'B', 0.077),
    (b'S', 0.076),
    (b'P', 0.076),
    (b'L', 0.059),
    (b'A', 0.058),
    (b'N', 0.051),
    (b'D', 0.049),
    (b'M', 0.046),
    (b'E', 0.039),
    (b'I', 0.035),
    (b'R', 0.035),
    (b'G', 0.028),
    (b'U', 0.026),
    (b'W', 0.025),
    (b'O', 0.017),
    (b'V', 0.015),
    (b'H', 0.013),
    (b'Q', 0.011),
    (b'J', 0.007),
    (b'K', 0.005),
    (b'+', 0.004),
    (b'X', 0.003),
    (b'Y', 0.001),
)

for c, _ in probtable:
    validchars.remove(c)
validchars = list(validchars)


def pickfrom(rng, table):
    c = 0
    r = rng.random() * sum(i[1] for i in table)
    for i, p in table:
        c += p
        if c >= r:
            return i


reservedcombos = casecombinations(winreserved)

# The first component of a name following a slash.

firsttable = (
    (lambda rng: pickfrom(rng, probtable), 90),
    (lambda rng: rng.choice(validchars), 5),
    (lambda rng: rng.choice(reservedcombos), 5),
)

# Components of a name following the first.

resttable = firsttable[:-1]

# Special suffixes.

internalsuffixcombos = casecombinations(b'.hg .i .d'.split())

# The last component of a path, before a slash or at the end of a name.

lasttable = resttable + (
    (lambda rng: b'', 95),
    (lambda rng: rng.choice(internalsuffixcombos), 5),
)


def makepart(rng, k):
    '''Construct a part of a pathname, without slashes.'''

    p = pickfrom(rng, firsttable)(rng)
    l = len(p)
    ps = [p]
    maxl = rng.randint(1, k)
    while l < maxl:
        p = pickfrom(rng, resttable)(rng)
        l += len(p)
        ps.append(p)
    ps.append(pickfrom(rng, lasttable)(rng))
    return b''.join(ps)


def makepath(rng, j, k):
    '''Construct a complete pathname.'''

    return (
        b'data/'
        + b'/'.join(makepart(rng, k) for _ in range(j))
        + rng.choice([b'.d', b'.i'])
    )


def genpath(rng, count):
    '''Generate random pathnames with gradually increasing lengths.'''

    mink, maxk = 1, 4096

    def steps():
        for i in range(count):
            yield mink + int(round(math.sqrt((maxk - mink) * float(i) / count)))

    for k in steps():
        x = rng.randint(1, k)
        y = rng.randint(1, k)
        yield makepath(rng, x, y)


def runtests(rng, seed, count):
    nerrs = 0
    for p in genpath(rng, count):
        h = store._pathencode(p)  # uses C implementation, if available
        r = store._hybridencode(p, True)  # reference implementation in Python
        if h != r:
            if nerrs == 0:
                print('seed:', hex(seed)[:-1], file=sys.stderr)
            print("\np: '%s'" % p.encode("string_escape"), file=sys.stderr)
            print("h: '%s'" % h.encode("string_escape"), file=sys.stderr)
            print("r: '%s'" % r.encode("string_escape"), file=sys.stderr)
            nerrs += 1
    return nerrs


def main():
    import getopt

    # Empirically observed to take about a second to run
    count = 100
    seed = None
    opts, args = getopt.getopt(
        sys.argv[1:], 'c:s:', ['build', 'count=', 'seed=']
    )
    for o, a in opts:
        if o in ('-c', '--count'):
            count = int(a)
        elif o in ('-s', '--seed'):
            seed = int(a, base=0)  # accepts base 10 or 16 strings
        elif o == '--build':
            buildprobtable(
                sys.stdout,
                'find .hg/store/data -type f && '
                'cat .hg/store/fncache 2>/dev/null',
            )
            sys.exit(0)

    if seed is None:
        try:
            seed = int(binascii.hexlify(os.urandom(16)), 16)
        except AttributeError:
            seed = int(time.time() * 1000)

    rng = random.Random(seed)
    if runtests(rng, seed, count):
        sys.exit(1)


if __name__ == '__main__':
    main()