Re: Obtain padded string containing number in hex form
Eric Lilja wrote:
Hello, I have an unsigned long that I need to convert to a std::string.
The unsigned long holds 32-bit checksums and sometimes the most
significant byte is 0 and in those cases the string should be zero
padded (it should always contain 8 chars) and it should display its
value in hex form without 0x in the beginning. So if the unsigned long
holds the value 0xa87d7d4 the string should contain "0a87d7d4".
I tried a combination of iomanip and stringstreams but this code
snippet still yields a string containing a decimal number (and I'm not
sure my 0-padding is working either):
std::string s;
std::stringstream ss;
ss << crc32; // crc32 is of type unsigned long
ss >> std::setw(8) >> std::hex >> s;
I guess I could read the checksum four bits at a time converting each
bit group into the corresponding hexadecimal number and gradually build
the string, but I wanted to ask you experts if there was a neater way
involving the standard library first.
I solved it using sprintf. This program shows how:
#include <cstdio>
#include <iostream>
int
main()
{
unsigned long l = 0x0a87d7d4;
char buffer[9];
// %[flags][width][.precision][modifiers]type
// type = lx = Unsigned long hexadecimal integer
// flags =none
// width = 08
std::sprintf(buffer, "%08lx", l);
std::cout << buffer << std::endl;
return 0;
}
Output:
$ ./conv.exe
0a87d7d4
But I still would like to know how to solve it using streams too, for
learning purposes.
/ E
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