I just followed the steps from Forging WiFi Beacon, but my output is strange, it added 'c2' byte between '0f' and 'ac' byte, Why this happened? How do I solve this problem?
Please look at the image
It seems that you're on Python 3 (as IPython > 5 requires Python > 3)
In that case, you should remember to append a b in front of bytes strings: b"\x01\x02..." as it is required on Python 3+
Related
I am not able to understand bit packing in erlang.
Suppose:
R=4, G=6 and B=8
then why is the output like this:
<< R:5,G:5,B:6 >>
output: <<33,136>>.
I don't get it. Can anyone please explain?
<< R:5,G:5,B:6 >>
This record we allocate 5,5 and 6 bits, and the result is a 2-byte binary sequence. To better understand why this happens, start the reverse conversion. Transform numbers 33 and 136 in binary form:
integer_to_list(33,2).
integer_to_list(136,2).
"100001"
"10001000"
We get the following lines. Since each segment of the binary sequence is a multiple of 8, supplement the presentation of 33 zeros to the left.
L2=lists:append("00",lists:append(integer_to_list(33,2),integer_to_list(136,2))).
"0010000110001000"
Proceed to the decoding of. The third argument indicates the number of bits
V1 = list_to_integer(lists:sublist(L2,5),2).
V2 = list_to_integer(lists:sublist(L2,6,5),2).
V3 = list_to_integer(lists:sublist(L2,11,6),2).
4
6
8
Sorry for my English,hope I explained clearly.
Can someone please help me understand call x"91" function 11 and function 12 with simple example. I have tried to search and couldn't understand it. Right now I an using this code in COBOL under UNIX environment,Does this call works in windows environment as well?
http://opencobol.add1tocobol.com/#what-are-the-xf4-xf5-and-x91-routines
The CALL's X"F4", X"F5", X"91" are from MF.
You can find them in the online MF doc under
Library Routines.
F4/F5 are for packing/unpacking bits from/to bytes.
91 is a multi-use call. Implemented are the subfunctions
get/set cobol switches (11, 12) and get number of call params (16).
Use
CALL X"F4" USING
BYTE-VAR
ARRAY-VAR
RETURNING STATUS-VAR
to pack the last bit of each byte in the 8 byte ARRAY-VAR into corresponding bits of the 1 byte BYTE-VAR.
The X”F5” routine takes the eight bits of byte and moves them to the corresponding occurrence within array.
X”91” is a multi-function routine.
CALL X"91" USING
RESULT-VAR
FUNCTION-NUM
PARAMETER-VAR
RETURNING STATUS-VAR
As mentioned by Roger, OpenCOBOL supports FUNCTION-NUM of 11, 12 and 16.
11 and 12 get and set the on off status of the 8 (eight) run-time OpenCOBOL switches definable in the SPECIAL-NAMES paragraph. 16 returns the number of call parameters given to the current module.
x'91' is a general library routine, for a complete list of those see the MF documentation.
This documentation also specifies what its function 11 and function 12 do: they set/read the COBOL runtime switches 0-7 and the internal debugging mode switch.
Other than these library routines you can also read them one by one from COBOL and set "some" switches via the SET statement.
I have several ~50 GB text files that I need to parse for specific contents. My files contents are organized in 4 line blocks. To perform this analysis I read in subsections of the file using file.read(chunk_size) and split into blocks of 4 then analyze them.
Because I run this script often, I've been optimizing and have tried varying the chunk size. I run 64 bit 2.7.1 python on OSX Lion on a computer with 16 GB RAM and I noticed that when I load chunks >= 2^31, instead of the expected text, I get large amounts of /x00 repeated. This continues as far as my testing has shown all the way to, and including 2^32, after which I once again get text. However, it seems that it's only returning as many characters as bytes have been added to the buffer above 4 GB.
My test code:
for i in range((2**31)-3, (2**31)+3)+range((2**32)-3, (2**32)+10):
with open('mybigtextfile.txt', 'rU') as inf:
print '%s\t%r'%(i, inf.read(i)[0:10])
My output:
2147483645 '#HWI-ST550'
2147483646 '#HWI-ST550'
2147483647 '#HWI-ST550'
2147483648 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
2147483649 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
2147483650 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967293 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967294 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967295 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967296 '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967297 '#\x00\x00\x00\x00\x00\x00\x00\x00\x00'
4294967298 '#H\x00\x00\x00\x00\x00\x00\x00\x00'
4294967299 '#HW\x00\x00\x00\x00\x00\x00\x00'
4294967300 '#HWI\x00\x00\x00\x00\x00\x00'
4294967301 '#HWI-\x00\x00\x00\x00\x00'
4294967302 '#HWI-S\x00\x00\x00\x00'
4294967303 '#HWI-ST\x00\x00\x00'
4294967304 '#HWI-ST5\x00\x00'
4294967305 '#HWI-ST55\x00'
What exactly is going on?
Yes, this is the known issue according to the comment in cpython's source code. You can check it in Modules/_io/fileio.c. And the code add a workaround on Microsoft windows 64bit only.
I have a Client/Server architecture (C# .Net 4.0) that send's command packets of data as byte arrays. There is a variable number of parameters in any command, and each paramater is of variable length. Because of this I use delimiters for the end of a parameter and the command as a whole. The operand is always 2 bytes and both types of delimiter are 1 byte. The last parameter_delmiter is redundant as command_delmiter provides the same functionality.
The command structure is as follow:
FIELD SIZE(BYTES)
operand 2
parameter1 x
parameter_delmiter 1
parameter2 x
parameter_delmiter 1
parameterN x
.............
.............
command_delmiter 1
Parameters are sourced from many different types, ie, ints, strings etc all encoded into byte arrays.
The problem I have is that sometimes parameters when encoded into byte arrays contain bytes that are the same value as a delimiter. For example command_delmiter=255.. and a paramater may have that byte inside of it.
There is 3 ways I can think of fixing this:
1) Encode the parameters differently so that they can never be the same value as a delimiter (255 and 254) Modulus?. This will mean that paramaters will become larger, ie Int16 will be more than 2 bytes etc.
2) Do not use delimiters at all, use count and length values at the start of the command structure.
3) Use something else.
To my knowledge, the way TCP/IP buffers work is that SOME SORT of delimiter has to be used to seperate 'commands' or 'bundles of data' as a buffer may contain multiple commands, or a command may span multiple buffers.. So this
BinaryReader / Writer seems like an obvious candidate, the only issue is that the byte array may contain multiple commands ( with parameters inside). So the byte array would still have to be chopped up in order to feel into the BinaryReader.
Suggestions?
Thanks.
The standard way to do this is to have the length of the message in the (fixed) first few bytes of a message. So you could have the first 4 bytes to denote the length of a message, read those many bytes for the content of the message. The next 4 bytes would be the length of the next message. A length of 0 could indicate end of messages. Or you could use a header with a message count.
Also, remember TCP is a byte stream, so don't expect a complete message to be available every time you read data from a socket. You could receive an arbitrary number of bytes at ever read.
I want to display the progress of a calculation done with a DO-loop, on the console screen. I can print out the progress variable to the terminal like this:
PROGRAM TextOverWrite_WithLoop
IMPLICIT NONE
INTEGER :: Number, Maximum = 10
DO Number = 1, MAXIMUM
WRITE(*, 100, ADVANCE='NO') REAL(Number)/REAL(Maximum)*100
100 FORMAT(TL10, F10.2)
! Calcultations on Number
END DO
END PROGRAM TextOverWrite_WithLoop
The output of the above code on the console screen is:
10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00
90.00 100.00
All on the same line, wrapped only by the console window.
The ADVANCE='No' argument and the TL10 (tab left so many spaces) edit descriptor works well to overwrite text on the same line, e.g. the output of the following code:
WRITE(*, 100, ADVANCE='NO') 100, 500
100 FORMAT(I3, 1X, TL4, I3)
Is:
500
Instead of:
100 500
Because of the TL4 edit descriptor.
From these two instances one can conclude that the WRITE statement cannot overwrite what has been written by another WRITE statement or by a previous execution of the same WRITE satement (as in a DO-loop).
Can this be overcome somehow?
I am using the FTN95 compiler on Windows 7 RC1. (The setup program of the G95 compiler bluescreens Windows 7 RC1, even thought it works fine on Vista.)
I know about the question Supressing line breaks in Fortran 95 write statements, but it does not work for me, because the answer to that question means new ouput is added to the previous output on the same line; instead of new output overwriting the previous output.
Thanks in advance.
The following should be portable across systems by use of ACHAR(13) to encode the carriage return.
character*1 creturn
! CODE::
creturn = achar(13) ! generate carriage return
! other code ...
WRITE( * , 101 , ADVANCE='NO' ) creturn , i , npoint
101 FORMAT( a , 'Point number : ',i7,' out of a total of ',i7)
There is no solution to this question within the scope of the Fortran standards. However, if your compiler understand backslash in Fortran strings (GNU Fortran does if you use the option -fbackslash), you can write
write (*,"(A)",advance="no") "foo"
call sleep(1)
write (*,"(A)",advance="no") "\b\b\bbar"
call sleep(1)
write (*,"(A)",advance="no") "\b\b\bgee"
call sleep(1)
write (*,*)
end
This uses the backslash character (\b) to erase previously written characters on that line.
NB: if your compiler does not understand advance="no", you can use related non-standard tricks, such as using the $ specifier in the format string.
The following worked perfectly using g95 fortran:
NF = NF + 1
IF(MOD(NF,5).EQ.0) WRITE(6,42,ADVANCE='NO') NF, ' PDFs'//CHAR(13)
42 FORMAT(I6,A)
gave:
5 PDFs
leaving the cursor at the #1 position on the same line. On the next update,
the 5 turned into a 10. ASCII 13 (decimal) is a carriage return.
OPEN(6,CARRIAGECONTROL ='FORTRAN')
DO I=1,5
WRITE(6,'(1H+" ",I)') I
ENDDO