Re: Comment on trim string function please

swengineer001@xxxxxxxxx <swengineer001@xxxxxxxxx> wrote:
Just looking for a few eyes on this code other than my own.

void TrimCString(char *str)
{
// Trim whitespace from beginning:

I guess I would trim from the end first since then you have less
copying to do afterwards.

size_t i = 0;
size_t j;

while(isspace(str[i]))

isspace() expects an int and not a char as it's argument.

{
i++;
}
if(i > 0)
{
for(j = 0; i < strlen(str); j++, i++)
{
str[j] = str[i];
}
str[j] = '\0';
}

An alternative would be to use memmove() here, so you don't
have to do it byte by byte. Also callling strlen() each time
through the loop is a bit of a waste of time - it doesn't
change and can be replaced by a check if str[i] is '\0'.

// Trim whitespace from end:
i = strlen(str) - 1;

Careful: This could set 'i' to -1 (if the string consistet of white
space only) and then the rest won't work anymore.

while(isspace(str[i]))
{
i--;
}

if(i < (strlen(str) - 1))
{
str[i + 1] = '\0';
}
}

Here's an alternative version using pointers (and trying to
minimize the number of calls of strlen()):

void
TrimCString( char *str )
{
char *p,
*q;

/* Check that we've got something that looks like a string */

if ( ! str || ! * str )
return;

/* Trim from end */

for ( p = str + strlen( str ) - 1; p != str && isspace( ( int ) *p ); p-- )
/* empty */ ;

if ( p == str ) /* only white space in string */
{
*str = '\0';
return;
}

*++p = '\0';

/* Trim from start */

for ( q = str; isspace( ( int ) *q ); q++ )
/* empty */ ;

if ( q != str )
memmove( str, q, p - q + 1 );
}
Regards, Jens
--
\ Jens Thoms Toerring ___ jt@xxxxxxxxxxx
\__________________________ http://toerring.de
.

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