Be fully compliant with wbits values

Author: rhpvorderman

src/isal/isal_zlib.pyx

@@ -256,7 +256,8 @@ def decompress(data,
 
     wbits_to_flag_and_hist_bits_inflate(wbits,
                                         &stream.hist_bits,
-                                        &stream.crc_flag)
+                                        &stream.crc_flag,
+                                        data[:2] == b"\037\213")
 
     # initialise input
     cdef Py_buffer buffer_data
@@ -310,7 +311,6 @@ def decompress(data,
 
 def decompressobj(int wbits=ISAL_DEF_MAX_HIST_BITS,
                   zdict = None):
-
     return Decompress.__new__(Decompress, wbits, zdict)
 
 
@@ -464,13 +464,18 @@ cdef class Decompress:
     cdef inflate_state stream
     cdef unsigned char * obuf
     cdef unsigned int obuflen
+    cdef bint method_set
 
     def __cinit__(self, wbits=ISAL_DEF_MAX_HIST_BITS, zdict = None):
         isal_inflate_init(&self.stream)
 
         wbits_to_flag_and_hist_bits_inflate(wbits,
                                             &self.stream.hist_bits,
                                             &self.stream.crc_flag)
+        if 40 <= wbits <= 47:
+            self.method_set = 0
+        else:
+            self.method_set = 1
 
         cdef Py_ssize_t zdict_length
         if zdict:
@@ -516,6 +521,11 @@ cdef class Decompress:
         elif max_length < 0:
             raise ValueError("max_length can not be smaller than 0")
 
+        if not self.method_set:
+            # Try to detect method from the first two bytes of the data.
+            self.stream.crc_flag = ISAL_GZIP if data[:2] == b"\037\213" else ISAL_ZLIB
+            self.method_set = 1
+
         # initialise input
         cdef Py_buffer buffer_data
         cdef Py_buffer* buffer = &buffer_data
@@ -634,7 +644,8 @@ cdef wbits_to_flag_and_hist_bits_deflate(int wbits,
 
 cdef wbits_to_flag_and_hist_bits_inflate(int wbits,
                                          unsigned int * hist_bits,
-                                         unsigned int * crc_flag):
+                                         unsigned int * crc_flag,
+                                         bint gzip = 0):
     if wbits == 0:
         hist_bits[0] = 0
         crc_flag[0] = ISAL_ZLIB
@@ -647,6 +658,9 @@ cdef wbits_to_flag_and_hist_bits_inflate(int wbits,
     elif -15 <= wbits <= -8:  # raw compressed stream
         hist_bits[0] = -wbits
         crc_flag[0] = ISAL_DEFLATE
+    elif 40 <= wbits <= 47:  # Accept gzip or zlib
+        hist_bits[0] = wbits - 32
+        crc_flag[0] = ISAL_GZIP if gzip else ISAL_ZLIB
     elif 72 <=wbits <= 79:
         hist_bits[0] = wbits - 64
         crc_flag[0] = ISAL_GZIP_NO_HDR_VER

tests/test_zlib_compliance.py

@@ -828,14 +828,12 @@ def test_wbits(self):
         isal_zlib15 = co.compress(HAMLET_SCENE) + co.flush()
         self.assertEqual(isal_zlib.decompress(isal_zlib15, 15), HAMLET_SCENE)
         self.assertEqual(isal_zlib.decompress(isal_zlib15, 0), HAMLET_SCENE)
-        # This behaviour is not defined in either the zlib documentation or the
-        # python documentation.
-        # self.assertEqual(isal_zlib.decompress(isal_zlib15, 32 + 15),
-        # HAMLET_SCENE)
+        self.assertEqual(isal_zlib.decompress(isal_zlib15, 32 + 15),
+                         HAMLET_SCENE)
         with self.assertRaisesRegex(isal_zlib.error, 'nvalid'):
             isal_zlib.decompress(isal_zlib15, 9)
-        # dco = isal_zlib.decompressobj(wbits=32 + 15)
-        # self.assertEqual(dco.decompress(isal_zlib15), HAMLET_SCENE)
+        dco = isal_zlib.decompressobj(wbits=32 + 15)
+        self.assertEqual(dco.decompress(isal_zlib15), HAMLET_SCENE)
         dco = isal_zlib.decompressobj(wbits=9)
         with self.assertRaisesRegex(isal_zlib.error, 'nvalid'):
             dco.decompress(isal_zlib15)
@@ -845,10 +843,10 @@ def test_wbits(self):
         self.assertEqual(isal_zlib.decompress(isal_zlib9, 9), HAMLET_SCENE)
         self.assertEqual(isal_zlib.decompress(isal_zlib9, 15), HAMLET_SCENE)
         self.assertEqual(isal_zlib.decompress(isal_zlib9, 0), HAMLET_SCENE)
-        # self.assertEqual(isal_zlib.decompress(isal_zlib9, 32 + 9),
-        # HAMLET_SCENE)
-        # dco = isal_zlib.decompressobj(wbits=32 + 9)
-        # self.assertEqual(dco.decompress(isal_zlib9), HAMLET_SCENE)
+        self.assertEqual(isal_zlib.decompress(isal_zlib9, 32 + 9),
+                         HAMLET_SCENE)
+        dco = isal_zlib.decompressobj(wbits=32 + 9)
+        self.assertEqual(dco.decompress(isal_zlib9), HAMLET_SCENE)
 
         co = isal_zlib.compressobj(level=1, wbits=-15)
         deflate15 = co.compress(HAMLET_SCENE) + co.flush()
@@ -866,9 +864,9 @@ def test_wbits(self):
         co = isal_zlib.compressobj(level=1, wbits=16 + 15)
         gzip = co.compress(HAMLET_SCENE) + co.flush()
         self.assertEqual(isal_zlib.decompress(gzip, 16 + 15), HAMLET_SCENE)
-        # self.assertEqual(isal_zlib.decompress(gzip, 32 + 15), HAMLET_SCENE)
-        # dco = isal_zlib.decompressobj(32 + 15)
-        # self.assertEqual(dco.decompress(gzip), HAMLET_SCENE)
+        self.assertEqual(isal_zlib.decompress(gzip, 32 + 15), HAMLET_SCENE)
+        dco = isal_zlib.decompressobj(32 + 15)
+        self.assertEqual(dco.decompress(gzip), HAMLET_SCENE)
 
 
 def choose_lines(source, number, seed=None, generator=random):