String conversions

[HMS Surprise]

Greetings,

Two questions if I may.

1) I have an ascii string the represents the hex output of a string.
For instance:
"244750524d43". I need to convert this to the actual string "$GPRMC".
Is there a string utilitility for handling this kind of conversion or
do I just need to do it by shifts, subtracts, and ORs (and trial and
error)? I have misplaced my Schildt book and I remember he lists a
great variety of C string functions.

2) Could you recommend an online location that covers the cin members?

Thanx,

jh

[Alex Blekhman]

"HMS Surprise" wrote:
> Greetings,
>
> Two questions if I may.
>
> 1) I have an ascii string the represents the hex output of
> a string.
> For instance:
> "244750524d43". I need to convert this to the actual
> string "$GPRMC".
> Is there a string utilitility for handling this kind of
> conversion or
> do I just need to do it by shifts, subtracts, and ORs (and
> trial and
> error)? I have misplaced my Schildt book and I remember he
> lists a
> great variety of C string functions.

Here's working example of such conversion:

--------------------------------------
int main()
{
const char* src = "244750524d43";
char dst[16] = { 0 };

char* p = dst;

while(*src)
{
char hi = *src - '0';
++src;

if(!*src) break;

char lo = *src - '0';
++src;

*p = (hi << 4) | lo;
++p;
}

return 0;
}
--------------------------------------

> 2) Could you recommend an online location that covers the
> cin members?

"cin"
http://msdn2.microsoft.com/en-us/library/71t65ya2(VS.80).aspx

Alex

[HMS Surprise]

Thanks for posting.

I think you have the same bug I have. The code works fine for 0-9 but
the 'd' caused a problem and the output is "$GPRtC". Upper case will
be a problem too. Nonetheless your example is much cleaner than mine
so I will continue with yours, handling cases for a-f and A-F.

Thanks again,

jh

jh

[HMS Surprise]

I think this will cover most of the cases I need.....

int main()
{
const char* src = "4A4B4C232c244750524d43";

char dst[16] = { 0 };

char* p = dst;

while(*src)
{
char hi = *src - '0';
++src;

if(!*src) break;

char lo = *src;

cout << "lo" << lo;

while(1)
{

if(lo >= ' ' && lo <= '/')
{
lo -= ' ';
}
if(lo >= '0' && lo <= '9')
{
lo -= '0';
break;
}
if(lo >= 'a' && lo <= 'f')
{
lo -= 0x57;
break;
}
if(lo >= 'A' && lo <= 'F')
{
lo -= 0x37;
break;
}
}

++src;

*p = (hi << 4) | lo;
++p;
}

cout << dst << endl;
return 0;
}

[Alex Blekhman]

"HMS Surprise" wrote:
>
> I think you have the same bug I have. The code works fine
> for 0-9 but
> the 'd' caused a problem and the output is "$GPRtC". Upper
> case will
> be a problem too. Nonetheless your example is much cleaner
> than mine
> so I will continue with yours, handling cases for a-f and
> A-F.

Yes, you're right, of course. Here's correct version:

int xchtoi(int c)
{
c = toupper(c);

if(isxdigit(c))
{
if(isdigit(c))
return c - '0';

return c - 55;
}

return 0;
}

int main()
{
const char* src = "244750524d43";
char dst[16] = { 0 };

char* p = dst;

while(*src)
{
char hi = xchtoi(*src);
++src;

if(!*src) break;

char lo = xchtoi(*src);

[HMS Surprise]

Neat++ ( in more ways than 1.)

Thanks,

jh

[Ben Voigt]

"Alex Blekhman" <xf...@oohay.moc> wrote in message
news:OvWG87hS...@TK2MSFTNGP02.phx.gbl...

> "HMS Surprise" wrote:
>>
>> I think you have the same bug I have. The code works fine for 0-9 but
>> the 'd' caused a problem and the output is "$GPRtC". Upper case will
>> be a problem too. Nonetheless your example is much cleaner than mine
>> so I will continue with yours, handling cases for a-f and A-F.
>
>
> Yes, you're right, of course. Here's correct version:
>
> int xchtoi(int c)
> {
> c = toupper(c);

the toupper conversion should be moved....

>
> if(isxdigit(c))
> {
> if(isdigit(c))
> return c - '0';
>

to here.

[Alex Blekhman]

"Ben Voigt" wrote:
>> int xchtoi(int c)
>> {
>> c = toupper(c);
> the toupper conversion should be moved....
>
>>
>> if(isxdigit(c))
>> {
>> if(isdigit(c))
>> return c - '0';
>>
>
> to here.
>> return c - 55;
>> }
>>
>> return 0;
>> }

Thanks.

[Ben Voigt]

"Alex Blekhman" <xf...@oohay.moc> wrote in message

news:uJzXTn6T...@TK2MSFTNGP05.phx.gbl...

Hopefully by the time you reach that point, the compiler realizes that
having passed isxdigit and failed isdigit, c is a letter, and toupper then
optimizes to

c &= ~32;

If the compiler can't figure that out, help it along by using _toupper
instead.