I'm using hyperterminal and trying to send strings a to 6 digit scoreboard. I was sent a sample string from the manufacturer to test with and it worked, but to be able change the displayed message I was told to calculate a new Checksum value.
The sample string is: &AHELLO N-12345\71
Charactors A and N are addresses for the scoreboards(allowing two displays be used through one RS232 connection). HELLO and -12345 are the characters to be shown on the display. The "71" is where I am getting stuck.
How can you obtain 71 from "AHELLO N-12345"?
In the literature supplied with the scoreboard, the "71" from the sample string is described as a character by character logical XOR operation on characters "AHELLO N-12345". The manufacturer however called it a checksum. I'm not trained in this type of language and I did try to research but I can't put it together on my own.
The text below is copied from the supplied literature and describes the "71" (ckck) in question...
- ckck = 2 ASCII control characters: corresponds to the two hexadecimal digits obtained by
performing the character by character logical XOR operation on characters
"AxxxxxxByyyyyy". If there is an error in these characters, the string is ignored
Example: if the byte by byte logical XOR operation carried out on the ASCII codes of the
characters of the "AxxxxxxByyyyyy" string returns the hexadecimal value 0x2A,
the control characters ckck are "2" and "A".
You don't specify a language but here's the algorithm in C#. Basically xor the values of the string all together and you'll end up with a value of 113, 71 in hex. Hence 71 is on the end of the input string.
string input = "AHELLO N-12345";
UInt16 chk = 0;
foreach(char ch in input) {
chk ^= ch;
}
MessageBox.Show("value is " + chk);
Outputs "value is 113"
I am using ruby to parse a datastream, some parts of which are IEEE-754 floats, but am not sure how to print these as floats. For example:
f = 0xbe80fd31 # -0.2519317
puts "%f" % f
3196124465.000000
how do I get -0.2519317 ?
Any time your converting a binary byte stream to something else, you usually end up using String#unpack (and Array#pack if you're going the other way).
If you have these bytes:
bytes = [0xbe, 0x80, 0xfd, 0x31]
then you could say:
bytes.map(&:chr).join.unpack('g')
# [-0.25193169713020325]
and then unwrap the array. This:
bytes.map(&:chr).join
packs the bytes into the string:
"\xbe\x80\xfd\x31"
which is suitable for #unpack. You could also (thanks Stefan) say:
# Variations on getting the bytes into a string for `#unpack`
bytes.pack('C4').unpack('g').first
[0xbe80fd31].pack('L>').unpack('g').first
# Variations using `#unpack1`
bytes.map(&:chr).join.unpack1('g')
bytes.pack('C4').unpack1('g')
[0xbe80fd31].pack('L>').unpack1('g')
If you already have the string then you go can straight to #unpack or #unpack1.
You'll want to use 'e' instead of 'g' your bytes are in a different order and 'E' or 'G' if you actually have an eight byte double rather than a four byte float.
I've seen follownig construction in a tutorial of Ruby:
irb(main):001:0> "abc".each_byte { |c| printf "<%c>", c }
<a><b><c>=> "abc"
However, if I put string Здравствуйте! instead of abc, I get
irb(main):003:0> "Здравствуйте!".each_byte { |c| printf "<%c>", c }
<Ð><><Ð><´><Ñ><><Ð><°><Ð><²><Ñ><><Ñ><><Ð><²><Ñ><><Ð><¹><Ñ><><Ð><µ><!>=> "Здравствуйте!"
How to deal with Unicode strings?
irb(main):005:0> RUBY_VERSION
=> "1.9.3"
▶ "Здравствуйте!".each_char { |c| printf "<%c>", c }
# ⇒ <З><д><р><а><в><с><т><в><у><й><т><е><!>=> "Здравствуйте!"
Byte is byte, while char is char, consisting of bytes.
A byte is 8 bits. But unicode characters can take up multiple bytes when stored on your computer. So for example, lets say the integer code for some unicode character is 8,000, which is what is actually stored on your computer. When ruby reads in 8,000, ruby knows that represents some unicode character. However, 8,000 cannot be stored in one byte on your computer(the largest number that can be stored in one byte is 1111 1111, which is 255). If you tell ruby that each byte of the several bytes stored on your computer for 8,000 represents one character, i.e. by calling each_byte(), then ruby will never see the 8,000. Instead, ruby will read in a piece of 8,000 and think that represents one character, then read in another piece of 8,000 and think that represents another character.
each_byte() tells ruby to ignore the clusters of bytes, and just read in one byte at a time and then determine what character is represented by the integer stored in that byte.
I am having a very difficult time with this:
# contained within:
"MA\u008EEIKIAI"
# should be
"MAŽEIKIAI"
# nature of string
$ p string3
"MA\u008EEIKIAI"
$ puts string3
MAEIKIAI
$ string3.inspect
"\"MA\\u008EEIKIAI\""
$ string3.bytes
#<Enumerator: "MA\u008EEIKIAI":bytes>
Any ideas on where to start?
Note: this is not a duplicate of my previous question.
\u008E means that the unicode character with the codepoint 8e (in hex) appears at that point in the string. This character is the control character “SINGLE SHIFT TWO” (see the code chart (pdf)). The character Ž is at the codepoint u017d. However it is at position 8e in the Windows CP-1252 encoding. Somehow you’ve got your encodings mixed up.
The easiest way to “fix” this is probably just to open the file containing the string (or the database record or whatever) and edit it to be correct. The real solution will depend on where the string in question came from and how many bad strings you have.
Assuming the string is in UTF-8 encoding, \u008E will consist of the two bytes c2 and 8e. Note that the second byte, 8e, is the same as the encoding of Ž in CP-1252. On way to convert the string would be something like this:
string3.force_encoding('BINARY') # treat the string just as bytes for now
string3.gsub!(/\xC2/n, '') # remove the C2 byte
string3.force_encoding('CP1252') # give the string the correct encoding
string3.encode('UTF-8') # convert to the desired encoding
Note that this isn’t a general solution to fix all issues like this. Not all CP-1252 characters, when mangled and expressed in UTF-8 this way will amenable to conversion like this. Some will be two bytes c2 xx where xx the correct byte (like in this case), others will be c3 yy where yy is a different byte.
What about using Regexp & String#pack to convert the Unicode escape?
str = "MA\\u008EEIKIAI"
puts str #=> MA\u008EEIKIAI
str.gsub!(/\\u(.{4})/) do |match|
[$1.to_i(16)].pack('U')
end
puts str #=> MA EIKIAI
Imagine I have String in C#: "I Don’t see ya.."
I want to remove (replace to nothing or etc.) these "’" symbols.
How do I do this?
That 'junk' looks a lot like someone interpreted UTF-8 data as ISO 8859-1 or Windows-1252, probably repeatedly.
’ is the sequence C3 A2, E2 82 AC, E2 84 A2.
UTF-8 C3 A2 = U+00E2 = â
UTF-8 E2 82 AC = U+20AC = €
UTF-8 E2 84 A2 = U+2122 = ™
We then do it again: in Windows 1252 this sequence is E2 80 99, so the character should have been U+2019, RIGHT SINGLE QUOTATION MARK (’)
You could make multiple passes with byte arrays, Encoding.UTF8 and Encoding.GetEncoding(1252) to correctly turn the junk back into what was originally entered. You will need to check your processing to find the two places that UTF-8 data was incorrectly interpreted as Windows-1252.
"I Don’t see ya..".Replace( "’", string.Empty);
How did that junk get in there the first place? That's the real question.
By removing any non-latin character you'll be intentionally breaking some internationalization support.
Don't forget the poor guy who's name has a "â" in it.
This looks disturbingly familiar to a character encoding issue dealing with the Windows character set being stored in a database using the standard character encoding. I see someone voted Will down, but he has a point. You may be solving the immediate issue, but the combinations of characters are limitless if this is the issue.
If you really have to do this, regular expressions are probably the best solution.
I would strongly recommend that you think about why you have to do this, though - at least some of the characters your listing as undesirable are perfectly valid and useful in other languages, and just filtering them out will most likely annoy at least some of your international users. As a swede, I can't emphasize enough how much I hate systems that can't handle our å, ä and ö characters correctly.
Consider Regex.Replace(your_string, regex, "") - that's what I use.
Test each character in turn to see if it is a valid alphabetic or numeric character and if not then remove it from the string. The character test is very simple, just use...
char.IsLetterOrDigit;
Please there are various others such as...
char.IsSymbol;
char.IsControl;
Regex.Replace("The string", "[^a-zA-Z ]","");
That's how you'd do it in C#, although that regular expression ([^a-zA-Z ]) should work in most languages.
[Edited: forgot the space in the regex]
The ASCII / Integer code for these characters would be out of the normal alphabetic Ranges. Seek and replace with empty characters. String has a Replace method I believe.
Either use a blacklist of stuff you do not want, or preferably a white list (set). With a white list you iterate over the string and only copy the letters that are in your white list to the result string. You said remove, and the way you do that is having two pointers one you read from (R) and one you write to (W):
I Donââ‚
W R
if comma is in your whitelist then you would in this case read the comma and write it where à is then advance both pointers. UTF-8 is a multi-byte encoding, so you advancing the pointer may not just be adding to the address.
With C an easy to way to get a white list by using one of the predefined functions (or macros): isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit. In this case you send up with a white list function instead of a set of course.
Usually when I see data like you have I look for memory corruption, or evidence to suggest that the encoding I expect is different than the one the data was entered with.
/Allan
I had the same problem with extraneous junk thrown in by adobe in an EXIF dump. I spent an hour looking for a straight answer and trying numerous half-baked suggestions which did not work here.
This thread more than most I have read was replete with deep, probing questions like 'how did it get there?', 'what if somebody has this character in their name?', 'are you sure you want to break internationalization?'.
There were some impressive displays of erudition positing how this junk could have gotten here and explaining the evolution of the various character encoding schemes. The person wanted to know how to remove it, not how it came to be or what the standards orgs are up to, interesting as this trivia may be.
I wrote a tiny program which gave me the right answer. Instead of paraphrasing the main concept, here is the entire, self-contained, working (at least on my system) program and the output I used to nuke the junk:
#!/usr/local/bin/perl -w
# This runs in a dos window and shows the char, integer and hex values
# for the weird chars. Install the HEX values in the REGEXP below until
# the final test line looks normal.
$str = 's: “Brian'; # Nuke the 3 werid chars in front of Brian.
#str = split(//, $str);
printf("len str '$str' = %d, scalar \#str = %d\n",
length $str, scalar #str);
$ii = -1;
foreach $c (#str) {
$ii++;
printf("$ii) char '$c', ord=%03d, hex='%s'\n",
ord($c), unpack("H*", $c));
}
# Take the hex characters shown above, plug them into the below regexp
# until the junk disappears!
($s2 = $str) =~ s/[\xE2\x80\x9C]//g; # << Insert HEX values HERE
print("S2=>$s2<\n"); # Final test
Result:
M:\new\6s-2014.1031-nef.halloween>nuke_junk.pl
len str 's: GÇ£Brian' = 11, scalar #str = 11
0) char 's', ord=115, hex='73'
1) char ':', ord=058, hex='3a'
2) char ' ', ord=032, hex='20'
3) char 'G', ord=226, hex='e2'
4) char 'Ç', ord=128, hex='80'
5) char '£', ord=156, hex='9c'
6) char 'B', ord=066, hex='42'
7) char 'r', ord=114, hex='72'
8) char 'i', ord=105, hex='69'
9) char 'a', ord=097, hex='61'
10) char 'n', ord=110, hex='6e'
S2=>s: Brian<
It's NORMAL!!!
One other actionable, working suggestion I ran across:
iconv -c -t ASCII < 6s-2014.1031-238246.halloween.exf.dif > exf.ascii.dif
If String having the any Junk date , This is good to way remove those junk date
string InputString = "This is grate kingdom¢Ã‚¬â";
string replace = "’";
string OutputString= Regex.Replace(InputString, replace, "");
//OutputString having the following result
It's working good to me , thanks for looking this review.