test_largefile.py revision 063606a0d5302d8a5530297a70494a9cad334e83 
1#!python
2
3#----------------------------------------------------------------------
4# test largefile support on system where this makes sense
5#
6#----------------------------------------------------------------------
7
8from test import test_support
9import os, struct, stat, sys
10
11try:
12    import signal
13    # The default handler for SIGXFSZ is to abort the process.
14    # By ignoring it, system calls exceeding the file size resource
15    # limit will raise IOError instead of crashing the interpreter.
16    oldhandler = signal.signal(signal.SIGXFSZ, signal.SIG_IGN)
17except (ImportError, AttributeError):
18    pass
19
20
21# create >2GB file (2GB = 2147483648 bytes)
22size = 2500000000L
23name = test_support.TESTFN
24
25
26# On Windows and Mac OSX this test comsumes large resources; It takes
27# a long time to build the >2GB file and takes >2GB of disk space
28# therefore the resource must be enabled to run this test.  If not,
29# nothing after this line stanza will be executed.
30if sys.platform[:3] == 'win' or sys.platform == 'darwin':
31    test_support.requires(
32        'largefile',
33        'test requires %s bytes and a long time to run' % str(size))
34else:
35    # Only run if the current filesystem supports large files.
36    # (Skip this test on Windows, since we now always support large files.)
37    f = open(test_support.TESTFN, 'wb')
38    try:
39        # 2**31 == 2147483648
40        f.seek(2147483649L)
41        # Seeking is not enough of a test: you must write and flush, too!
42        f.write("x")
43        f.flush()
44    except (IOError, OverflowError):
45        f.close()
46        os.unlink(test_support.TESTFN)
47        raise test_support.TestSkipped, \
48              "filesystem does not have largefile support"
49    else:
50        f.close()
51
52
53def expect(got_this, expect_this):
54    if test_support.verbose:
55        print '%r =?= %r ...' % (got_this, expect_this),
56    if got_this != expect_this:
57        if test_support.verbose:
58            print 'no'
59        raise test_support.TestFailed, 'got %r, but expected %r' %\
60              (got_this, expect_this)
61    else:
62        if test_support.verbose:
63            print 'yes'
64
65
66# test that each file function works as expected for a large (i.e. >2GB, do
67# we have to check >4GB) files
68
69if test_support.verbose:
70    print 'create large file via seek (may be sparse file) ...'
71f = open(name, 'wb')
72try:
73    f.write('z')
74    f.seek(0)
75    f.seek(size)
76    f.write('a')
77    f.flush()
78    if test_support.verbose:
79        print 'check file size with os.fstat'
80    expect(os.fstat(f.fileno())[stat.ST_SIZE], size+1)
81finally:
82    f.close()
83if test_support.verbose:
84    print 'check file size with os.stat'
85expect(os.stat(name)[stat.ST_SIZE], size+1)
86
87if test_support.verbose:
88    print 'play around with seek() and read() with the built largefile'
89f = open(name, 'rb')
90try:
91    expect(f.tell(), 0)
92    expect(f.read(1), 'z')
93    expect(f.tell(), 1)
94    f.seek(0)
95    expect(f.tell(), 0)
96    f.seek(0, 0)
97    expect(f.tell(), 0)
98    f.seek(42)
99    expect(f.tell(), 42)
100    f.seek(42, 0)
101    expect(f.tell(), 42)
102    f.seek(42, 1)
103    expect(f.tell(), 84)
104    f.seek(0, 1)
105    expect(f.tell(), 84)
106    f.seek(0, 2) # seek from the end
107    expect(f.tell(), size + 1 + 0)
108    f.seek(-10, 2)
109    expect(f.tell(), size + 1 - 10)
110    f.seek(-size-1, 2)
111    expect(f.tell(), 0)
112    f.seek(size)
113    expect(f.tell(), size)
114    expect(f.read(1), 'a') # the 'a' that was written at the end of file above
115    f.seek(-size-1, 1)
116    expect(f.read(1), 'z')
117    expect(f.tell(), 1)
118finally:
119    f.close()
120
121if test_support.verbose:
122    print 'play around with os.lseek() with the built largefile'
123f = open(name, 'rb')
124try:
125    expect(os.lseek(f.fileno(), 0, 0), 0)
126    expect(os.lseek(f.fileno(), 42, 0), 42)
127    expect(os.lseek(f.fileno(), 42, 1), 84)
128    expect(os.lseek(f.fileno(), 0, 1), 84)
129    expect(os.lseek(f.fileno(), 0, 2), size+1+0)
130    expect(os.lseek(f.fileno(), -10, 2), size+1-10)
131    expect(os.lseek(f.fileno(), -size-1, 2), 0)
132    expect(os.lseek(f.fileno(), size, 0), size)
133    expect(f.read(1), 'a') # the 'a' that was written at the end of file above
134finally:
135    f.close()
136
137if hasattr(f, 'truncate'):
138    if test_support.verbose:
139        print 'try truncate'
140    f = open(name, 'r+b')
141    try:
142        f.seek(0, 2)
143        expect(f.tell(), size+1)    # else we've lost track of the true size
144        # Cut it back via seek + truncate with no argument.
145        newsize = size - 10
146        f.seek(newsize)
147        f.truncate()
148        expect(f.tell(), newsize)   # else pointer moved
149        f.seek(0, 2)
150        expect(f.tell(), newsize)   # else wasn't truncated
151        # Ensure that truncate(smaller than true size) shrinks the file.
152        newsize -= 1
153        f.seek(42)
154        f.truncate(newsize)
155        expect(f.tell(), 42)        # else pointer moved
156        f.seek(0, 2)
157        expect(f.tell(), newsize)   # else wasn't truncated
158
159        # XXX truncate(larger than true size) is ill-defined across platforms
160
161        # cut it waaaaay back
162        f.seek(0)
163        f.truncate(1)
164        expect(f.tell(), 0)         # else pointer moved
165        expect(len(f.read()), 1)    # else wasn't truncated
166
167    finally:
168        f.close()
169
170os.unlink(name)
171