Python struct.unpack() Examples

def valid_ranges(*types):
    # given a sequence of numeric types, collect their _type_
    # attribute, which is a single format character compatible with
    # the struct module, use the struct module to calculate the
    # minimum and maximum value allowed for this format.
    # Returns a list of (min, max) values.
    result = []
    for t in types:
        fmt = t._type_
        size = struct.calcsize(fmt)
        a = struct.unpack(fmt, ("\x00"*32)[:size])[0]
        b = struct.unpack(fmt, ("\xFF"*32)[:size])[0]
        c = struct.unpack(fmt, ("\x7F"+"\x00"*32)[:size])[0]
        d = struct.unpack(fmt, ("\x80"+"\xFF"*32)[:size])[0]
        result.append((min(a, b, c, d), max(a, b, c, d)))
    return result 

def _readheader(self):
        len = self._read(1)
        fname = self._read(ord(len))
        rest = self._read(1+4+4+2+4+4)
        self._checkcrc()

        type = rest[1:5]
        creator = rest[5:9]
        flags = struct.unpack('>h', rest[9:11])[0]
        self.dlen = struct.unpack('>l', rest[11:15])[0]
        self.rlen = struct.unpack('>l', rest[15:19])[0]

        self.FName = fname
        self.FInfo = FInfo()
        self.FInfo.Creator = creator
        self.FInfo.Type = type
        self.FInfo.Flags = flags

        self.state = _DID_HEADER 

def test_ioctl_signed_unsigned_code_param(self):
        if not pty:
            raise unittest.SkipTest('pty module required')
        mfd, sfd = pty.openpty()
        try:
            if termios.TIOCSWINSZ < 0:
                set_winsz_opcode_maybe_neg = termios.TIOCSWINSZ
                set_winsz_opcode_pos = termios.TIOCSWINSZ & 0xffffffffL
            else:
                set_winsz_opcode_pos = termios.TIOCSWINSZ
                set_winsz_opcode_maybe_neg, = struct.unpack("i",
                        struct.pack("I", termios.TIOCSWINSZ))

            our_winsz = struct.pack("HHHH",80,25,0,0)
            # test both with a positive and potentially negative ioctl code
            new_winsz = fcntl.ioctl(mfd, set_winsz_opcode_pos, our_winsz)
            new_winsz = fcntl.ioctl(mfd, set_winsz_opcode_maybe_neg, our_winsz)
        finally:
            os.close(mfd)
            os.close(sfd) 

def test_consistence(self):
        self.assertRaises(struct.error, struct.calcsize, 'Z')

        sz = struct.calcsize('i')
        self.assertEqual(sz * 3, struct.calcsize('iii'))

        fmt = 'cbxxxxxxhhhhiillffd?'
        fmt3 = '3c3b18x12h6i6l6f3d3?'
        sz = struct.calcsize(fmt)
        sz3 = struct.calcsize(fmt3)
        self.assertEqual(sz * 3, sz3)

        self.assertRaises(struct.error, struct.pack, 'iii', 3)
        self.assertRaises(struct.error, struct.pack, 'i', 3, 3, 3)
        self.assertRaises((TypeError, struct.error), struct.pack, 'i', 'foo')
        self.assertRaises((TypeError, struct.error), struct.pack, 'P', 'foo')
        self.assertRaises(struct.error, struct.unpack, 'd', 'flap')
        s = struct.pack('ii', 1, 2)
        self.assertRaises(struct.error, struct.unpack, 'iii', s)
        self.assertRaises(struct.error, struct.unpack, 'i', s) 

def test_transitiveness(self):
        c = 'a'
        b = 1
        h = 255
        i = 65535
        l = 65536
        f = 3.1415
        d = 3.1415
        t = True

        for prefix in ('', '@', '<', '>', '=', '!'):
            for format in ('xcbhilfd?', 'xcBHILfd?'):
                format = prefix + format
                s = struct.pack(format, c, b, h, i, l, f, d, t)
                cp, bp, hp, ip, lp, fp, dp, tp = struct.unpack(format, s)
                self.assertEqual(cp, c)
                self.assertEqual(bp, b)
                self.assertEqual(hp, h)
                self.assertEqual(ip, i)
                self.assertEqual(lp, l)
                self.assertEqual(int(100 * fp), int(100 * f))
                self.assertEqual(int(100 * dp), int(100 * d))
                self.assertEqual(tp, t) 

def py_suffix_importer(filename, finfo, fqname):
    file = filename[:-3] + _suffix
    t_py = long(finfo[8])
    t_pyc = _timestamp(file)

    code = None
    if t_pyc is not None and t_pyc >= t_py:
        f = open(file, 'rb')
        if f.read(4) == imp.get_magic():
            t = struct.unpack('<I', f.read(4))[0]
            if t == t_py:
                code = marshal.load(f)
        f.close()
    if code is None:
        file = filename
        code = _compile(file, t_py)

    return 0, code, { '__file__' : file } 

def gen_subkey(self, K):
        AES_128 = AES.new(K)

        L = AES_128.encrypt('\x00'*16)

        LHigh = unpack('>Q',L[:8])[0]
        LLow  = unpack('>Q',L[8:])[0]

        K1High = ((LHigh << 1) | ( LLow >> 63 )) & 0xFFFFFFFFFFFFFFFF
        K1Low  = (LLow << 1) & 0xFFFFFFFFFFFFFFFF

        if (LHigh >> 63):
            K1Low ^= 0x87

        K2High = ((K1High << 1) | (K1Low >> 63)) & 0xFFFFFFFFFFFFFFFF
        K2Low  = ((K1Low << 1)) & 0xFFFFFFFFFFFFFFFF

        if (K1High >> 63):
            K2Low ^= 0x87

        K1 = pack('>QQ', K1High, K1Low)
        K2 = pack('>QQ', K2High, K2Low)

        return K1, K2 

def _parse_image_info_bytes(data: bytes) -> Optional[_ImageInfo]:
    try:
        parsed = list(struct.unpack(_IMAGE_INFO_FORMAT, data))
    except struct.error:
        pass
    else:
        magic_begin = parsed[:_IMAGE_INFO_MAGIC_SIZE]
        magic_end = parsed[-_IMAGE_INFO_MAGIC_SIZE:]
        if magic_begin == magic_end == _IMAGE_INFO_MAGIC:
            image_name_bytes = b"".join(parsed[
                _IMAGE_INFO_MAGIC_SIZE  # noqa: E203
                :
                _IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE
            ])
            return _ImageInfo(
                name=image_name_bytes.decode("utf-8", errors="ignore").strip("\x00").strip(),
                size=parsed[_IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE + 1],
                complete=parsed[_IMAGE_INFO_MAGIC_SIZE + _IMAGE_INFO_NAME_SIZE],
            )
    return None 

def read_compress_mat(fd):
    """ 
        Reference to function Read in CompressMatrix
        Return a numpy ndarray object
    """
    cps_type = read_token(fd)
    print_info('\tFollowing matrix type: {}'.format(cps_type))
    head = struct.unpack('ffii', fd.read(16))
    print_info('\tCompress matrix header: {}'.format(head))
    # 8: sizeof PerColHeader
    # head: {min_value, range, num_rows, num_cols}
    num_rows, num_cols = head[2], head[3]
    if cps_type == 'CM':
        remain_size = num_cols * (8 + num_rows)
    elif cps_type == 'CM2':
        remain_size = 2 * num_rows * num_cols
    elif cps_type == 'CM3':
        remain_size = num_rows * num_cols
    else:
        throw_on_error(False,
                       'Unknown matrix compressing type: {}'.format(cps_type))
    # now uncompress it
    compress_data = fd.read(remain_size)
    mat = uncompress(compress_data, cps_type, head)
    return mat 

def getFloat(self, index=None):
        if index is None:
            index = self.position
        tmp = bytearray(4)
        self.get(tmp)
        # Swap bytes.
        tmp2 = tmp[0]
        tmp[0] = tmp[3]
        tmp[3] = tmp2
        tmp2 = tmp[1]
        tmp[1] = tmp[2]
        tmp[2] = tmp2
        return struct.unpack("f", tmp) 

def getDouble(self, index=None):
        if index is None:
            index = self.position
        tmp = bytearray(8)
        self.get(tmp)
        # Swap bytes.
        tmp2 = tmp[0]
        tmp[0] = tmp[7]
        tmp[7] = tmp2
        tmp2 = tmp[1]
        tmp[1] = tmp[6]
        tmp[6] = tmp2
        tmp2 = tmp[2]
        tmp[2] = tmp[5]
        tmp[5] = tmp2
        tmp2 = tmp[3]
        tmp[3] = tmp[4]
        tmp[4] = tmp2
        return struct.unpack("d", tmp) 

def _header_parse(self, data):
        header = {}
        header["prefix"],   = struct.unpack('B', data[0])
        if header["prefix"] == 0x4c:
            return header
        if header["prefix"] == 0x4e:
            header["len"] = 2
            return header
        header["checksum"], = struct.unpack('B', data[1])
        header["crc"],      = struct.unpack('!H', data[2:4])
        header["msg_len"],  = struct.unpack('!H', data[4:6])
        header["type"],     = struct.unpack('!H', data[6:8])
        header["len"] = HEADERLENS[header["type"]]
        if header["type"] == TYPE_HELLO:
            header["token"],  = struct.unpack('!L', data[8:12])
            header["srv_ver"] = struct.unpack('2B', data[20:22])
            header["suffix"], = struct.unpack('!H', data[22:24])
        elif header["type"] == TYPE_RESP:
            timeval, = struct.unpack('!L', data[8:12])
            header["time"] = time.gmtime(timeval)
            header["txt_len"], = struct.unpack('!H', data[22:24])
        elif header["type"] == TYPE_REQLIC2:
            timeval, = struct.unpack('!L', data[8:12])
            header["time"] = time.gmtime(timeval)
        self._header_validate(data, header)
        return header 

def _query(self, request=None):
        if request:
            if self.debug:
                sys.stderr.write("Request: %s\n" % binascii.hexlify(request))
            self.s.sendall(request)
        response = self.s.recv(1)
        prefix = ord(response[0])
        if prefix not in PREFIXES:
            raise Exception("Unexpected response prefix %s" % hex(prefix))
        ### Older versions, data chunked in 147-byte segments
        if prefix == 0x4c:
            response += self.s.recv(147-1)
            length_remaining = self._length_remaining(response)
            while length_remaining > (147-13):
                newbytes = self.s.recv(147)
                while len(newbytes) < 147:
                    newbytes += self.s.recv(147-len(newbytes))
                response += newbytes
                length_remaining = self._length_remaining(newbytes)
        elif prefix == 0x4e:
            response += self.s.recv(147-1)
        ### Newer versions, length is given in header
        else:
            while len(response) < 20:
                response += self.s.recv(20-len(response))
            len_total, = struct.unpack('!H', response[4:6])
            torecv = len_total - len(response)
            # Now get remaining data
            while torecv>0:
                response += self.s.recv(min(4096, torecv))
                torecv = len_total - len(response)
        if self.debug:
            sys.stderr.write("Response: %s\n" % binascii.hexlify(response))
        return response 

def file_unpack(fmt, infile):
    size = struct.calcsize(fmt)
    b = infile.read(size)
    if len(b) != size:
        raise RuntimeError(f'Not enough bytes {b} for format {fmt}')
    return struct.unpack(fmt, b) 

def conv_uint64(s: bytes) -> int:
    i, = struct.unpack('<Q', s)
    return i 

def conv_time(s: bytes) -> float:
    return struct.unpack('<QI', s) 

def api_md5(api):
    return unpack('BBB', md5(api).digest()[:3])

# Extract API sequences and convert them to pixels 

def _get_terminal_size_windows(self):
        try:
            from ctypes import windll, create_string_buffer

            # stdin handle is -10
            # stdout handle is -11
            # stderr handle is -12
            h = windll.kernel32.GetStdHandle(-12)
            csbi = create_string_buffer(22)
            res = windll.kernel32.GetConsoleScreenBufferInfo(h, csbi)
            if res:
                (
                    bufx,
                    bufy,
                    curx,
                    cury,
                    wattr,
                    left,
                    top,
                    right,
                    bottom,
                    maxx,
                    maxy,
                ) = struct.unpack("hhhhHhhhhhh", csbi.raw)
                sizex = right - left + 1
                sizey = bottom - top + 1
                return sizex, sizey
        except:
            pass 

def _get_terminal_size_linux(self):
        def ioctl_GWINSZ(fd):
            try:
                import fcntl
                import termios

                cr = struct.unpack("hh", fcntl.ioctl(fd, termios.TIOCGWINSZ, "1234"))
                return cr
            except:
                pass

        cr = ioctl_GWINSZ(0) or ioctl_GWINSZ(1) or ioctl_GWINSZ(2)
        if not cr:
            try:
                fd = os.open(os.ctermid(), os.O_RDONLY)
                cr = ioctl_GWINSZ(fd)
                os.close(fd)
            except:
                pass

        if not cr:
            try:
                cr = (os.environ["LINES"], os.environ["COLUMNS"])
            except:
                return None

        return int(cr[1]), int(cr[0]) 

def get_calibrated(self, addr: int):
        return struct.unpack(
            ">f",
            struct.pack(
                "BBBB",
                self.read_reg(addr + 0),
                self.read_reg(addr + 1),
                self.read_reg(addr + 2),
                self.read_reg(addr + 3)))[0] 

def _sc_decode(soundcheck):
    """Convert a Sound Check bytestring value to a (gain, peak) tuple as
    used by ReplayGain.
    """
    # We decode binary data. If one of the formats gives us a text
    # string, interpret it as UTF-8.
    if isinstance(soundcheck, six.text_type):
        soundcheck = soundcheck.encode('utf-8')

    # SoundCheck tags consist of 10 numbers, each represented by 8
    # characters of ASCII hex preceded by a space.
    try:
        soundcheck = codecs.decode(soundcheck.replace(b' ', b''), 'hex')
        soundcheck = struct.unpack('!iiiiiiiiii', soundcheck)
    except (struct.error, TypeError, binascii.Error):
        # SoundCheck isn't in the format we expect, so return default
        # values.
        return 0.0, 0.0

    # SoundCheck stores absolute calculated/measured RMS value in an
    # unknown unit. We need to find the ratio of this measurement
    # compared to a reference value of 1000 to get our gain in dB. We
    # play it safe by using the larger of the two values (i.e., the most
    # attenuation).
    maxgain = max(soundcheck[:2])
    if maxgain > 0:
        gain = math.log10(maxgain / 1000.0) * -10
    else:
        # Invalid gain value found.
        gain = 0.0

    # SoundCheck stores peak values as the actual value of the sample,
    # and again separately for the left and right channels. We need to
    # convert this to a percentage of full scale, which is 32768 for a
    # 16 bit sample. Once again, we play it safe by using the larger of
    # the two values.
    peak = max(soundcheck[6:8]) / 32768.0

    return round(gain, 2), round(peak, 6) 

def scan_opcodes(self, co,
                     unpack = struct.unpack):
        # Scan the code, and yield 'interesting' opcode combinations
        # Version for Python 2.4 and older
        code = co.co_code
        names = co.co_names
        consts = co.co_consts
        while code:
            c = code[0]
            if c in STORE_OPS:
                oparg, = unpack('<H', code[1:3])
                yield "store", (names[oparg],)
                code = code[3:]
                continue
            if c == LOAD_CONST and code[3] == IMPORT_NAME:
                oparg_1, oparg_2 = unpack('<xHxH', code[:6])
                yield "import", (consts[oparg_1], names[oparg_2])
                code = code[6:]
                continue
            if c >= HAVE_ARGUMENT:
                code = code[3:]
            else:
                code = code[1:] 

def scan_opcodes_25(self, co,
                     unpack = struct.unpack):
        # Scan the code, and yield 'interesting' opcode combinations
        # Python 2.5 version (has absolute and relative imports)
        code = co.co_code
        names = co.co_names
        consts = co.co_consts
        LOAD_LOAD_AND_IMPORT = LOAD_CONST + LOAD_CONST + IMPORT_NAME
        while code:
            c = code[0]
            if c in STORE_OPS:
                oparg, = unpack('<H', code[1:3])
                yield "store", (names[oparg],)
                code = code[3:]
                continue
            if code[:9:3] == LOAD_LOAD_AND_IMPORT:
                oparg_1, oparg_2, oparg_3 = unpack('<xHxHxH', code[:9])
                level = consts[oparg_1]
                if level == -1: # normal import
                    yield "import", (consts[oparg_2], names[oparg_3])
                elif level == 0: # absolute import
                    yield "absolute_import", (consts[oparg_2], names[oparg_3])
                else: # relative import
                    yield "relative_import", (level, consts[oparg_2], names[oparg_3])
                code = code[9:]
                continue
            if c >= HAVE_ARGUMENT:
                code = code[3:]
            else:
                code = code[1:] 

def _read_fmt_chunk(self, chunk):
        wFormatTag, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack('<HHLLH', chunk.read(14))
        if wFormatTag == WAVE_FORMAT_PCM:
            sampwidth = struct.unpack('<H', chunk.read(2))[0]
            self._sampwidth = (sampwidth + 7) // 8
        else:
            raise Error, 'unknown format: %r' % (wFormatTag,)
        self._framesize = self._nchannels * self._sampwidth
        self._comptype = 'NONE'
        self._compname = 'not compressed' 

def itn(n, digits=8, format=DEFAULT_FORMAT):
    """Convert a python number to a number field.
    """
    # POSIX 1003.1-1988 requires numbers to be encoded as a string of
    # octal digits followed by a null-byte, this allows values up to
    # (8**(digits-1))-1. GNU tar allows storing numbers greater than
    # that if necessary. A leading 0200 byte indicates this particular
    # encoding, the following digits-1 bytes are a big-endian
    # representation. This allows values up to (256**(digits-1))-1.
    if 0 <= n < 8 ** (digits - 1):
        s = "%0*o" % (digits - 1, n) + NUL
    else:
        if format != GNU_FORMAT or n >= 256 ** (digits - 1):
            raise ValueError("overflow in number field")

        if n < 0:
            # XXX We mimic GNU tar's behaviour with negative numbers,
            # this could raise OverflowError.
            n = struct.unpack("L", struct.pack("l", n))[0]

        s = ""
        for i in xrange(digits - 1):
            s = chr(n & 0377) + s
            n >>= 8
        s = chr(0200) + s
    return s 

def calc_chksums(buf):
    """Calculate the checksum for a member's header by summing up all
       characters except for the chksum field which is treated as if
       it was filled with spaces. According to the GNU tar sources,
       some tars (Sun and NeXT) calculate chksum with signed char,
       which will be different if there are chars in the buffer with
       the high bit set. So we calculate two checksums, unsigned and
       signed.
    """
    unsigned_chksum = 256 + sum(struct.unpack("148B", buf[:148]) + struct.unpack("356B", buf[156:512]))
    signed_chksum = 256 + sum(struct.unpack("148b", buf[:148]) + struct.unpack("356b", buf[156:512]))
    return unsigned_chksum, signed_chksum 

def b32encode(s):
    """Encode a string using Base32.

    s is the string to encode.  The encoded string is returned.
    """
    parts = []
    quanta, leftover = divmod(len(s), 5)
    # Pad the last quantum with zero bits if necessary
    if leftover:
        s += ('\0' * (5 - leftover))
        quanta += 1
    for i in range(quanta):
        # c1 and c2 are 16 bits wide, c3 is 8 bits wide.  The intent of this
        # code is to process the 40 bits in units of 5 bits.  So we take the 1
        # leftover bit of c1 and tack it onto c2.  Then we take the 2 leftover
        # bits of c2 and tack them onto c3.  The shifts and masks are intended
        # to give us values of exactly 5 bits in width.
        c1, c2, c3 = struct.unpack('!HHB', s[i*5:(i+1)*5])
        c2 += (c1 & 1) << 16 # 17 bits wide
        c3 += (c2 & 3) << 8  # 10 bits wide
        parts.extend([_b32tab[c1 >> 11],         # bits 1 - 5
                      _b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10
                      _b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15
                      _b32tab[c2 >> 12],         # bits 16 - 20 (1 - 5)
                      _b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10)
                      _b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15)
                      _b32tab[c3 >> 5],          # bits 31 - 35 (1 - 5)
                      _b32tab[c3 & 0x1f],        # bits 36 - 40 (1 - 5)
                      ])
    encoded = EMPTYSTRING.join(parts)
    # Adjust for any leftover partial quanta
    if leftover == 1:
        return encoded[:-6] + '======'
    elif leftover == 2:
        return encoded[:-4] + '===='
    elif leftover == 3:
        return encoded[:-3] + '==='
    elif leftover == 4:
        return encoded[:-1] + '='
    return encoded 

def _checkcrc(self):
        filecrc = struct.unpack('>h', self.ifp.read(2))[0] & 0xffff
        #self.crc = binascii.crc_hqx('\0\0', self.crc)
        # XXXX Is this needed??
        self.crc = self.crc & 0xffff
        if filecrc != self.crc:
            raise Error, 'CRC error, computed %x, read %x' \
                  %(self.crc, filecrc)
        self.crc = 0 

def load_binfloat(self, unpack=struct.unpack):
        self.append(unpack('>d', self.read(8))[0]) 

def _read_long(file):
    try:
        return struct.unpack('>l', file.read(4))[0]
    except struct.error:
        raise EOFError 

def _read_ulong(file):
    try:
        return struct.unpack('>L', file.read(4))[0]
    except struct.error:
        raise EOFError 

def _read_short(file):
    try:
        return struct.unpack('>h', file.read(2))[0]
    except struct.error:
        raise EOFError 

def _read_ushort(file):
    try:
        return struct.unpack('>H', file.read(2))[0]
    except struct.error:
        raise EOFError 

def _EndRecData64(fpin, offset, endrec):
    """
    Read the ZIP64 end-of-archive records and use that to update endrec
    """
    try:
        fpin.seek(offset - sizeEndCentDir64Locator, 2)
    except IOError:
        # If the seek fails, the file is not large enough to contain a ZIP64
        # end-of-archive record, so just return the end record we were given.
        return endrec

    data = fpin.read(sizeEndCentDir64Locator)
    if len(data) != sizeEndCentDir64Locator:
        return endrec
    sig, diskno, reloff, disks = struct.unpack(structEndArchive64Locator, data)
    if sig != stringEndArchive64Locator:
        return endrec

    if diskno != 0 or disks != 1:
        raise BadZipfile("zipfiles that span multiple disks are not supported")

    # Assume no 'zip64 extensible data'
    fpin.seek(offset - sizeEndCentDir64Locator - sizeEndCentDir64, 2)
    data = fpin.read(sizeEndCentDir64)
    if len(data) != sizeEndCentDir64:
        return endrec
    sig, sz, create_version, read_version, disk_num, disk_dir, \
            dircount, dircount2, dirsize, diroffset = \
            struct.unpack(structEndArchive64, data)
    if sig != stringEndArchive64:
        return endrec

    # Update the original endrec using data from the ZIP64 record
    endrec[_ECD_SIGNATURE] = sig
    endrec[_ECD_DISK_NUMBER] = disk_num
    endrec[_ECD_DISK_START] = disk_dir
    endrec[_ECD_ENTRIES_THIS_DISK] = dircount
    endrec[_ECD_ENTRIES_TOTAL] = dircount2
    endrec[_ECD_SIZE] = dirsize
    endrec[_ECD_OFFSET] = diroffset
    return endrec 

def _decodeExtra(self):
        # Try to decode the extra field.
        extra = self.extra
        unpack = struct.unpack
        while len(extra) >= 4:
            tp, ln = unpack('<HH', extra[:4])
            if tp == 1:
                if ln >= 24:
                    counts = unpack('<QQQ', extra[4:28])
                elif ln == 16:
                    counts = unpack('<QQ', extra[4:20])
                elif ln == 8:
                    counts = unpack('<Q', extra[4:12])
                elif ln == 0:
                    counts = ()
                else:
                    raise RuntimeError, "Corrupt extra field %s"%(ln,)

                idx = 0

                # ZIP64 extension (large files and/or large archives)
                if self.file_size in (0xffffffffffffffffL, 0xffffffffL):
                    self.file_size = counts[idx]
                    idx += 1

                if self.compress_size == 0xFFFFFFFFL:
                    self.compress_size = counts[idx]
                    idx += 1

                if self.header_offset == 0xffffffffL:
                    old = self.header_offset
                    self.header_offset = counts[idx]
                    idx+=1

            extra = extra[ln+4:] 

def unpack_uint(self):
        i = self.__pos
        self.__pos = j = i+4
        data = self.__buf[i:j]
        if len(data) < 4:
            raise EOFError
        x = struct.unpack('>L', data)[0]
        try:
            return int(x)
        except OverflowError:
            return x 

def unpack_int(self):
        i = self.__pos
        self.__pos = j = i+4
        data = self.__buf[i:j]
        if len(data) < 4:
            raise EOFError
        return struct.unpack('>l', data)[0] 

def unpack_double(self):
        i = self.__pos
        self.__pos = j = i+8
        data = self.__buf[i:j]
        if len(data) < 8:
            raise EOFError
        return struct.unpack('>d', data)[0] 

def test_ioctl(self):
        # If this process has been put into the background, TIOCGPGRP returns
        # the session ID instead of the process group id.
        ids = (os.getpgrp(), os.getsid(0))
        tty = open("/dev/tty", "r")
        r = fcntl.ioctl(tty, termios.TIOCGPGRP, "    ")
        rpgrp = struct.unpack("i", r)[0]
        self.assertIn(rpgrp, ids) 

def test_double_specials_dont_unpack(self):
        for fmt, data in [('>d', BE_DOUBLE_INF),
                          ('>d', BE_DOUBLE_NAN),
                          ('<d', LE_DOUBLE_INF),
                          ('<d', LE_DOUBLE_NAN)]:
            self.assertRaises(ValueError, struct.unpack, fmt, data) 

def test_float_specials_dont_unpack(self):
        for fmt, data in [('>f', BE_FLOAT_INF),
                          ('>f', BE_FLOAT_NAN),
                          ('<f', LE_FLOAT_INF),
                          ('<f', LE_FLOAT_NAN)]:
            self.assertRaises(ValueError, struct.unpack, fmt, data)


# on an IEEE platform, all we guarantee is that bit patterns
# representing infinities or NaNs do not raise an exception; all else
# is accident (today).
# let's also try to guarantee that -0.0 and 0.0 don't get confused. 

def test_float_specials_do_unpack(self):
        for fmt, data in [('>f', BE_FLOAT_INF),
                          ('>f', BE_FLOAT_NAN),
                          ('<f', LE_FLOAT_INF),
                          ('<f', LE_FLOAT_NAN)]:
            struct.unpack(fmt, data) 

def to_ulps(x):
    """Convert a non-NaN float x to an integer, in such a way that
    adjacent floats are converted to adjacent integers.  Then
    abs(ulps(x) - ulps(y)) gives the difference in ulps between two
    floats.

    The results from this function will only make sense on platforms
    where C doubles are represented in IEEE 754 binary64 format.

    """
    n = struct.unpack('<q', struct.pack('<d', x))[0]
    if n < 0:
        n = ~(n+2**63)
    return n 

def test_pyc_mtime(self):
        # Test for issue #13863: .pyc timestamp sometimes incorrect on Windows.
        sys.path.insert(0, os.curdir)
        try:
            # Jan 1, 2012; Jul 1, 2012.
            mtimes = 1325376000, 1341100800

            # Different names to avoid running into import caching.
            tails = "spam", "eggs"
            for mtime, tail in zip(mtimes, tails):
                module = TESTFN + tail
                source = module + ".py"
                compiled = source + ('c' if __debug__ else 'o')

                # Create a new Python file with the given mtime.
                with open(source, 'w') as f:
                    f.write("# Just testing\nx=1, 2, 3\n")
                os.utime(source, (mtime, mtime))

                # Generate the .pyc/o file; if it couldn't be created
                # for some reason, skip the test.
                m = __import__(module)
                if not os.path.exists(compiled):
                    unlink(source)
                    self.skipTest("Couldn't create .pyc/.pyo file.")

                # Actual modification time of .py file.
                mtime1 = int(os.stat(source).st_mtime) & 0xffffffff

                # mtime that was encoded in the .pyc file.
                with open(compiled, 'rb') as f:
                    mtime2 = struct.unpack('<L', f.read(8)[4:])[0]

                unlink(compiled)
                unlink(source)

                self.assertEqual(mtime1, mtime2)
        finally:
            sys.path.pop(0) 

def test_p_code(self):
        # Test p ("Pascal string") code.
        for code, input, expected, expectedback in [
                ('p','abc', '\x00', ''),
                ('1p', 'abc', '\x00', ''),
                ('2p', 'abc', '\x01a', 'a'),
                ('3p', 'abc', '\x02ab', 'ab'),
                ('4p', 'abc', '\x03abc', 'abc'),
                ('5p', 'abc', '\x03abc\x00', 'abc'),
                ('6p', 'abc', '\x03abc\x00\x00', 'abc'),
                ('1000p', 'x'*1000, '\xff' + 'x'*999, 'x'*255)]:
            got = struct.pack(code, input)
            self.assertEqual(got, expected)
            (got,) = struct.unpack(code, got)
            self.assertEqual(got, expectedback) 

def test_705836(self):
        # SF bug 705836.  "<f" and ">f" had a severe rounding bug, where a carry
        # from the low-order discarded bits could propagate into the exponent
        # field, causing the result to be wrong by a factor of 2.
        import math

        for base in range(1, 33):
            # smaller <- largest representable float less than base.
            delta = 0.5
            while base - delta / 2.0 != base:
                delta /= 2.0
            smaller = base - delta
            # Packing this rounds away a solid string of trailing 1 bits.
            packed = struct.pack("<f", smaller)
            unpacked = struct.unpack("<f", packed)[0]
            # This failed at base = 2, 4, and 32, with unpacked = 1, 2, and
            # 16, respectively.
            self.assertEqual(base, unpacked)
            bigpacked = struct.pack(">f", smaller)
            self.assertEqual(bigpacked, string_reverse(packed))
            unpacked = struct.unpack(">f", bigpacked)[0]
            self.assertEqual(base, unpacked)

        # Largest finite IEEE single.
        big = (1 << 24) - 1
        big = math.ldexp(big, 127 - 23)
        packed = struct.pack(">f", big)
        unpacked = struct.unpack(">f", packed)[0]
        self.assertEqual(big, unpacked)

        # The same, but tack on a 1 bit so it rounds up to infinity.
        big = (1 << 25) - 1
        big = math.ldexp(big, 127 - 24)
        self.assertRaises(OverflowError, struct.pack, ">f", big) 

def test_unpack_with_buffer(self):
        with check_py3k_warnings(("buffer.. not supported in 3.x",
                                  DeprecationWarning)):
            # SF bug 1563759: struct.unpack doesn't support buffer protocol objects
            data1 = array.array('B', '\x12\x34\x56\x78')
            data2 = buffer('......\x12\x34\x56\x78......', 6, 4)
            for data in [data1, data2]:
                value, = struct.unpack('>I', data)
                self.assertEqual(value, 0x12345678)

            self.test_unpack_from(cls=buffer) 

def test_unpack_with_memoryview(self):
        # Bug 10212: struct.unpack doesn't support new buffer protocol objects
        data1 = memoryview('\x12\x34\x56\x78')
        for data in [data1,]:
            value, = struct.unpack('>I', data)
            self.assertEqual(value, 0x12345678)
        self.test_unpack_from(cls=memoryview) 

def test_bool(self):
        class ExplodingBool(object):
            def __nonzero__(self):
                raise IOError
        for prefix in tuple("<>!=")+('',):
            false = (), [], [], '', 0
            true = [1], 'test', 5, -1, 0xffffffffL+1, 0xffffffff//2

            falseFormat = prefix + '?' * len(false)
            packedFalse = struct.pack(falseFormat, *false)
            unpackedFalse = struct.unpack(falseFormat, packedFalse)

            trueFormat = prefix + '?' * len(true)
            packedTrue = struct.pack(trueFormat, *true)
            unpackedTrue = struct.unpack(trueFormat, packedTrue)

            self.assertEqual(len(true), len(unpackedTrue))
            self.assertEqual(len(false), len(unpackedFalse))

            for t in unpackedFalse:
                self.assertFalse(t)
            for t in unpackedTrue:
                self.assertTrue(t)

            packed = struct.pack(prefix+'?', 1)

            self.assertEqual(len(packed), struct.calcsize(prefix+'?'))

            if len(packed) != 1:
                self.assertFalse(prefix, msg='encoded bool is not one byte: %r'
                                             %packed)

            self.assertRaises(IOError, struct.pack, prefix + '?',
                              ExplodingBool())

        for c in [b'\x01', b'\x7f', b'\xff', b'\x0f', b'\xf0']:
            self.assertTrue(struct.unpack('>?', c)[0]) 

def read_uint2(f):
    r"""
    >>> import StringIO
    >>> read_uint2(StringIO.StringIO('\xff\x00'))
    255
    >>> read_uint2(StringIO.StringIO('\xff\xff'))
    65535
    """

    data = f.read(2)
    if len(data) == 2:
        return _unpack("<H", data)[0]
    raise ValueError("not enough data in stream to read uint2")