I'm retrieving a string from an NSData object dataOut (coming from a CBCharacteristic), and defining a testString as well which is defined as the same value as shown below:
The problem is when I try to compare the two, I get that the two strings are not equal, even though the debugger shows otherwise:
Here is the comparison:
The log keeps logging "Strings are not equal!"
What am I doing wrong? Is the encoding incorrect, even though the strings are the same?
You will see them are different when you convert them to NSData and print out the data.
What you see is not always what you get especially with Unicode characters. There maybe invisible characters or some characters that looks similar.
Related
i am trying to check if a string is empty by doing the following
if trim(somestring) = '' then
begin
//that an empty string
end
i am doing this empty check in my client application , but i notice that some clients inserts empty strings even with this check applied .
on my Linux server side those empty chars showing as squares and when i copy those chars i can be able to bypass the empty string check like the follwing example
if you copy this empty chars the check will not be effected how can i avoid that ?
Your code is working correctly and the strings are not empty. An empty string is one whose length is zero, it has no characters. You refer to empty characters, but there is no such thing. When. your system displays a small empty square that indicates that the chosen font has no glyph for that character.
Let us assume that these strings are invalid. In that case the real problem you have is that you don't yet fully understand what properties are required for a string to be valid. Your code is written assuming that a string is valid if it contains at least one character with ordinal value greater than 32. Clearly that test is not correct. You need to step back and work out the precise rules for validity. Only when these are clear in your mind can you correct you program and check for validity correctly.
On the other hand perhaps these strings are valid and the mistake is simply that you are erroneously determining otherwise when you inspect the data. Only you can know this, we don't have the information.
A useful technique in all of this is to inspect the ordinal values of the strings. Loop through the characters printing the ordinal value of each one. That allows you to see what is really there and not be at the mercy of non-printing characters, characters with no glyph, invalid encodings, etc.
Since Trim is pretty simple function, it omits only characters with less than or equal dec 32 in ASCII table
( Sample from System.SysUtils.pas )
while S.Chars[L] <= ' ' do Dec(L);
Therefore it's possible that You just can't see some exotic chars ( > ASCII 128) due to bad encoding used with Your input string.
try to use :
StrToInt(Ord(SomeChar))
On every char that is not "trimmed" and remove them by hand or check Your encoding.
Kind Regards
I have a string that, by using string.format("%02X", char), I've received the following:
74657874000000EDD37001000300
In the end, I'd like that string to look like the following:
t e x t NUL NUL NUL í Ó p SOH NUL ETX NUL (spaces are there just for clarification of characters desired in example).
I've tried to use \x..(hex#), string.char(0x..(hex#)) (where (hex#) is alphanumeric representation of my desired character) and I am still having issues with getting the result I'm looking for. After reading another thread about this topic: what is the way to represent a unichar in lua and the links provided in the answers, I am not fully understanding what I need to do in my final code that is acceptable for this to work.
I'm looking for some help in better understanding an approach that would help me to achieve my desired result provided below.
ETA:
Well I thought that I had fixed it with the following code:
function hexToAscii(input)
local convString = ""
for char in input:gmatch("(..)") do
convString = convString..(string.char("0x"..char))
end
return convString
end
It appeared to work, but didnt think about characters above 127. Rookie mistake. Now I'm unsure how I can get the additional characters up to 256 display their ASCII values.
I did the following to check since I couldn't truly "see" them in the file.
function asciiSub(input)
input = input:gsub(string.char(0x00), "<NUL>") -- suggested by a coworker
print(input)
end
I did a few gsub strings to substitute in other characters and my file comes back with the replacement strings. But when I ran into characters in the extended ASCII table, it got all forgotten.
Can anyone assist me in understanding a fix or new approach to this problem? As I've stated before, I read other topics on this and am still confused as to the best approach towards this issue.
The simple way to transform a base16-encoded string is just to
function unhex( input )
return (input:gsub( "..", function(c)
return string.char( tonumber( c, 16 ) )
end))
end
This is basically what you have, just a bit cleaner. (There's no need to say "(..)", ".." is enough – if you specify no captures, you'll automatically get the whole match. And while it might work if you write string.char( "0x"..c ), it's just evil – you concatenate lots of strings and then trigger the automatic conversion to numbers. Much better to just specify the base when explicitly converting.)
The resulting string should be exactly what went into the hex-dumper, no matter the encoding.
If you cannot correctly display the result, your viewer will also be unable to display the original input. If you used different viewers for the original input and the resulting output (e.g. a text editor and a terminal), try writing the output to a file instead and looking at it with the same viewer you used for the original input, then the two should be exactly the same.
Getting viewers that assume different encodings (e.g. one of the "old" 8-bit code pages or one of the many versions of Unicode) to display the same thing will require conversion between different formats, which tends to be quite complicated or even impossible. As you did not mention what encodings are involved (nor any other information like OS or programs used that might hint at the likely encodings), this could be just about anything, so it's impossible to say anything more specific on that.
You actually have a couple of problems:
First, make sure you know the meaning of the term character encoding, and that you know the difference between characters and bytes. A popular post on the topic is The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)
Then, what encoding was used for the bytes you just received? You need to know this, otherwise you don't know what byte 234 means. For example it could be ISO-8859-1, in which case it is U+00EA, the character ê.
The characters 0 to 31 are control characters (eg. 0 is NUL). Use a lookup table for these.
Then, displaying the characters on the terminal is the hard part. There is no platform-independent way to display ê on the terminal. It may well be impossible with the standard print function. If you can't figure this step out you can search for a question dealing specifically with how to print Unicode text from Lua.
I'm currently having a very strange issue. I'm running into the "float imprecision problem" when defining a number as an NSString. Here is an excerpt from my JSON file, which I am reading from my iOS application:
{"id":"804760","addtime":"1398886836","symbol":"UG","exchange":"NAS(USA)","shares":"71.00","cost":"0","in_price":"32.64","price":28.78,"rchange":-0.72,"rchange_p":-2.44,"a_open":"28.72","volume":"8K","a_low":"28.54","a_high":"29.44","pettm":"23.40","ps":"8.60","pb":"8.40","gain_p":"-11.83%","gain":-274.06,"comments":""}
I read this into an NSMutableArray, and then I want to display individual pieces of information. The code I use to do this is as follows:
label.text = [NSString stringWithFormat:#"%#",(NSString *)json[indexPath.section][#"detail"][indexPath.row][#"price"]];
However, I'm getting the floating point precision error where there's a ton of extra decimal places that were not there in the original JSON output. This confuses me, because I specified the data type as NSString, so even though the string consists of all numbers and decimal points, shouldn't it still be treated as such?
What I am not understanding correctly, and why is this happening? By the way, the error is also resolved if I add quotation marks when creating the JSON output, such as "a_high":"\"29.44\"". I would prefer not to do this though.
,"in_price":"32.64","price":28.78,"rchange":-0.72, -- do you notice something different about "price" vs "in_price"? "in_price" has a string value, "price" has a numeric value, as does "rchange". The numerics will translate into an NSNumber, not an NSString.
As already pointed out in the topic, I got the following error:
Character #\u009C cannot be represented in the character set CHARSET:CP1252
trying to print out a string given back by drakma:http-request, as far as I understand the error-code the problem is that the windows-encoding (CP1252) does not support this character.
Therefore to be able to process it, I might/must convert the whole string.
My question is what package/library does support converting strings to certain character-sets efficiently?
An alike question is this one, but just ignoring the error would not help in my case.
Drakma already does the job of "converting strings": after all, when it reads from some random webserver, it just gets a stream of bytes. It then has to convert that to a lisp string. You probably want to bind *drakma-default-external-format* to something else, although I can't remember off-hand what the allowable values are. Maybe something like :utf-8?
I'm using FitNesse to test web service responses using check to compare the expected to the actual response.
In some cases the check is failing and I can't see what the differences are between the expected and the actual that is causing it to fail.
Here's a screenshot from what it's telling me in a specific instance (of many similar instances):
Feel free to point out the obvious; it's probably staring at me in the face and I'm looking so hard I can't see it!
I would check that the expected and actual strings are both written with the same text encoding. I've seen this error plenty of times when the text comparing failed due to a comma or apostrophe being written in different encodes.
It is possible that your string contains extra spaces in the actual value. FitNesse, being html based, will not respect leading or trailing spaces. It might not handle any extra spaces inside the actual either. So this can cause the result to be different, but not visibly so.
See if you can add some debug messages that would help you see the extra spaces, or at least count the number of characters in both strings.
This question doesn't specify whether Slim or Fit are being used, or which Slim server/plugin if using Slim, but I found the following to be true for me using FitNesse release 20130530 and fitSharp release 2.2:
Non-ASCII characters and { apostrophes / single quote characters } in input arguments/parameters that are strings are HTML encoded. The values in my FitNesse test tables are HTML encoded, but only the required syntax characters and (double) quotes; not the non-ASCII characters (and FitNesse doesn't seem to have any problems storing those values).
EOL characters in the input arguments that are strings consist of a linefeed character only
I imagine that because I'm using .NET, EOLs in my return values consist of carriage return and linefeed characters.
Because of [1], I'm HTML-encoding non-ASCII characters (but not the HTML syntax characters or quotes). Because of [2] and [3], I'm now removing carriage return characters from my fixture return values. Both changes seem to have resolved this issue for me and expected and actual values are now reported as being the same.
Whitespace has troubled me often. The resulting HTML just collapses whitespace, but the compare in code does not.
I now use a fixture to make differences more explicit to me. Example usage: http://fhoeben.github.io/hsac-fitnesse-fixtures/examples-results/HsacExamples.SlimTests.UtilityFixtures.CompareFixtureTest.html
Newer versions of FitNesse (since 20151230) do a diff on the expected and actual result values. Has that helped you at all?