[ #403753 ] zlib decompress; uncontrollable memory usage
Mostly by Toby Dickenson and Titus Brown.
Add an optional argument to a decompression object's decompress()
method. The argument specifies the maximum length of the return
value. If the uncompressed data exceeds this length, the excess data
is stored as the unconsumed_tail attribute. (Not to be confused with
unused_data, which is a separate issue.)
Difference from SF patch: Default value for unconsumed_tail is ""
rather than None. It's simpler if the attribute is always a string.
diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index 439db22..915f582 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -76,6 +76,36 @@
else:
print "decompressobj with init options succeeded"
+print "should be '':", `deco.unconsumed_tail`
+
+# Check a decompression object with max_length specified
+deco = zlib.decompressobj(-12)
+cb = combuf
+bufs = []
+while cb:
+ max_length = 1 + len(cb)/10
+ chunk = deco.decompress(cb, max_length)
+ if len(chunk) > max_length:
+ print 'chunk too big (%d>%d)' % (len(chunk),max_length)
+ bufs.append(chunk)
+ cb = deco.unconsumed_tail
+bufs.append(deco.flush())
+decomp2 = ''.join(buf)
+if decomp2 != buf:
+ print "max_length decompressobj failed"
+else:
+ print "max_length decompressobj succeeded"
+
+# Misc tests of max_length
+deco = zlib.decompressobj(-12)
+try:
+ deco.decompress("", -1)
+except ValueError:
+ pass
+else:
+ print "failed to raise value error on bad max_length"
+print "unconsumed_tail should be '':", `deco.unconsumed_tail`
+
# Test flush() with the various options, using all the different levels
# in order to provide more variations.
sync_opt = ['Z_NO_FLUSH', 'Z_SYNC_FLUSH', 'Z_FULL_FLUSH']