Familiarity : Trimming leading and trailing spaces from a string...

Blake Miller

We can strip leading and trailing spaces from a string….

            int len = strlen((LPSTR)wName);
            while( \*((LPSTR)wName + len - 1) == ' ')
            {
            \*((LPSTR)wName + len - 1) = '\\0';
            len = strlen((LPSTR)wName);
            }                                                                                              

            firstNonSpace=((LPSTR)wName);
            while(\*firstNonSpace != '\\0' && isspace(\*firstNonSpace))    
            {          
                ++firstNonSpace;     
            }     
            len = strlen(firstNonSpace)+1;               
            strcpy((LPSTR)wName, firstNonSpace);

Or just call… MSDN: “Removes all leading and trailing spaces from a string.”

PathRemoveBlanks(wName);

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

Jorgen Andersson

You should probably add your context, as PathRemoveBlanks is a shell utility function, while most people here use dotnet where String.Trim would suffice.

Light moves faster than sound. That is why some people appear bright, until you hear them speak. List of common misconceptions

Jecc

I'm no good at Big O notation, but that's some kind of amortized N⁵, isn't it?

Blake Miller

1. This code was COPIED to 3 different places - they didn't bother to make a function out of all of it. That is probably the worst error, because now if this 'new' code has bugs, you have to modify three places instead of one. 2. It 'excessively' calculates the length of the string. I think I am being kind here when I say that. 3. 'Familiarity' was my joke - there is already a function in Windows to do this.

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

Jamercee

Not sure if you are joking, or looking for a serious answer. The code you posted makes WAY too many passes through the source string. If you're looking for maximum performance, you can get this down to just a single pass thusly:

LPSTR* nxt = wName;

// find 1st non-whitespace char
while(*nxt && isspace(*nxt))
nxt++;

// if nothing but whitespace
if (!*np) {
wName = '\0';
return wName;
}

// save position of 1st non-whitespace
LPSTR* start = nxt;

// now find last non-whitespace character
// before end of line

LPSTR* last_no_ws = nxt;
while(*nxt) {
if (!isspace(*nxt))
last_no_ws = nxt;
nxt++;
}

// how long is our non-whitespace string?
int len = (last_no_ws - start) + 1;

// move the string to beginning of wName
memmove(wName, start, len);
wName[len] = '\0';

return wName;

You could even save the 'memove' at the end by just modifying the wName string in place (add null after last_no_ws), then return the reference to 'start'. :)

Martin0815

Changes: 1. Clear defined end of first loop cutting trailing spaces 2. No undefined behavior of strcpy with overlapping memory areas 3. No unnecessary strlen calls 4. Unified way to test for whitespaces via isspace 5. No warnings because of signed/unsigned conflicts (int <-> unsigned int strlen(...))

LPSTR myStrTrim(LPSTR pszString)
{
LPSTR pszLastChar = pszString + strlen(pszString) - 1;
while (pszLastChar >= pszString && isspace(*pszLastChar))
*pszLastChar-- = '\0';

LPSTR pszFirstChar = pszString;
while(pszFirstChar < pszLastChar && isspace(\*pszFirstChar))
    ++pszFirstChar;

memmove(pszString, pszFirstChar, pszLastChar-pszFirstChar+1);

return pszString;

}

Chris Boss

One of the best languages for string manipulation is PowerBasic. You can use it to write 32 bit DLL's callable from other languages. To trim leading spaces: LTRIM$(AnyStringVar) To trim any character from left: LTRIM$(AnyStringVar, SomeCharacter) To trim any of multiple characters from left: LTRIM$(AnyStringVar, ANY SomeCharacters) To trim trailing edge spaces: RTRIM$(AnyStringVar) To trim any trailing character: RTRIM$(AnyStringVar,SomeCharacter) To trim any of multiple trailing characters: RTRIM$(AnyStringVar, ANY SomeCharacters) Trim both leading and trailing spaces: TRIM$(AnyStringVar) Trim any character leading or trailing: TRIM$(AnyStringVar, SomeCharacter) Trim any of multiple characters leading and trailing: TRIM$(AnyStringvar, ANY SomeCharacters) PowerBasic supports pointers too ! PowerBasic has many other powerful string functions (both ANSI and UNICODE) such as: ACODE$ - Translate a Unicode string into an ANSI string. BIN$ - Return a string with the binary (base 2) representation of a value. BITS$ - Copies string contents without modification. BUILD$ - Concatenate multiple strings with high efficiency. CHOOSE$ - Return one of several values, based upon the value of an index. CHR$ - Convert one or more character codes into ASCII character(s). CHR$$ - Convert one or more character codes into Unicode character(s). CHRBYTES - Determine the size of a single character in a string variable. ChrToOem$ - Translates a string of ANSI/WIDE characters to OEM byte characters. ChrToUtf8$ - Translates a string of ANSI/WIDE characters to UTF-8 byte characters. CLIP$ - Deletes characters from a string. CLSID$ - Return a 16-byte (128-bit) GUID string containing a CLSID. CSET - Center a string within the space of another string or UDT. CSET$ - Return a string containing a centered (padded) string. DEC$ - Convert an integral value to a decimal string. EXTRACT$ - Return up to the first occurrence of a specified character. FORMAT$ - Return a string containing formatted numeric data. GUID$ - Return a 16-byte (128-bit) Globally Unique Identifier GUID. GUIDTXT$ - Return a 38-byte human-readable GUID/UUID string. HEX$ - Hexadecimal (base 16) string representation of an argument. INSTR - Search a string for the first occurrence of a character or string. JOIN$ - Return a string consisting of all of the strings in a string array. LCASE$ - Return a lowercase version of a string argument. LEFT$ - Return the left

Blake Miller

This is great. I was just posting the orginal code because of the three reasons I listed. 1. Should be a function - REGARDLESS. 2 - It's inefficient on multiple levels. 3. MS already has the 'tried and true' function to call anyways. I like to see that others do not consider what I posted to be optimal in ANY case, so that is comforting :)

I need a 32 bit unsigned value just to hold the number of coding WTF I see in a day …

RafagaX

Blake Miller wrote:

if this 'new' code has bugs, you have to modify three places instead of one.

Or you can create a function with this code and replace the code in the other 3 (and modify just one). :)

CEO at: - Rafaga Systems - Para Facturas - Modern Components for the moment...

Brady Kelly

Blake Miller wrote:

2. It 'excessively' calculates the length of the string.

And just as excessively casts wName to LPSTR.

Julien Villers

Is that supposed to be a (long) joke or is it just stupid spam?

'I'm French! Why do you think I've got this outrrrrageous accent?' Monty Python and the Holy Grail

Lost User

I feel your pain - points to your signature.