On 19-12-07 11:00, C_C_Kuo@xxxxxxxxxxxxxx wrote:
I have a file which content is like below 100f1010 0f100f10 0e100e10 (The
format is ASCII text, with CRLF line terminators, which I got by typing
"file myfile" and thanks Manish and Grigoriy ). Right now I want to
transfer it to hex format each 2 chars and save it as binary file like
below:
0f 10 0f 10 original input
Ox0f 0x10 0x0f 0x10 final output
0e 10 0e 10 original input
0x0e 0x10 0x0e 0x10 final output
I expect you don't actually. Since you're probably on a little-endian
machine it's more likely that you want to turn the hexademical textual
representation "0x0f100f10" of the number 0x0f100f10 into the 4-byte
little-endian binary representation "0x10 0x0f 0x10 0x0f" of said number;
generally, turn the textual representation "12345678" of the number
0x12345678 into the "0x78 0x56 0x34 0x12" binary one.
You can just use scanf() / fwrite. An extremely simple tool to do what you
want would be:
===
#include <stdio.h>
int main(void)
{
unsigned long val;
while (scanf("%lx", &val) != EOF)
fwrite(&val, sizeof val, 1, stdout);
return 0;
}
===
(works as a filter. Ie, "./the_program <infile >outfile").
The binary output from this is native endian. If you really _do_ need to
output big-endian always stick a val = htonl(val) in between the scanf and
the fwrite: "network byte order" is big-endian.
Note by the way that libc already caches reads and therefore doing things
one character or "thing" at a time isn't particularly inefficient and since
it tends to simplify things greatly is generally preferred.
Second, note this is rather off-topic...
Rene.
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