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| From | Uno <Uno@example.invalid> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: looking at binary files with C |
| Date | 2011-06-12 14:47 -0600 |
| Message-ID | <95kmvoFn2bU1@mid.individual.net> (permalink) |
| References | <95j3bgFj2qU1@mid.individual.net> <1bk4crnhkt.fsf@snowball.wb.pfeifferfamily.net> |
On 06/12/2011 10:24 AM, Joe Pfeiffer wrote:
> Uno<Uno@example.invalid> writes:
>> So, why the seg fault?
>
> Let's just say this code is a prime example of why I took points of on
> student programs that had magic numbers (like 7000000 for instance) in
> the executable code.
>
There were a lot of problems with this source that needing ironing out,
and I needed to start to somehwhere. When I've got a program that
compiles, I like to have the magic numbers #defined. I haven't really
done much C on a 64-bit processor, so my ballparking seems to be wanting.
$ cc -Wall -Wextra -g hist3.c -o hist
$ ./hist
UCHAR_MAX + 1 is 256
a[0] is 217337
a[1] is 123676
a[2] is 137894
a[3] is 100155
...
a[252] is 97099
a[253] is 75547
a[254] is 113450
a[255] is 128194
Counter reached 19573713
Counter2 reached 19573712
$ cat hist3.c
#include <stdio.h>
#include <limits.h>
#define SIZE 20000000
#define SIZE2 (UCHAR_MAX+1)
int main(void)
{
int c;
long counter = 0;
long counter2 = 0;
long a[SIZE2];
long i, j;
FILE *fp;
fp = fopen("shoulder.wmv", "rb+");
printf("UCHAR_MAX + 1 is %d\n", SIZE2);
for (i = 0; i < (SIZE2); ++i) {
a[i] = 0;
}
for (j = 0; j < SIZE; ++j) {
c = fgetc(fp);
counter++;
if (c != EOF) {
a[c] = ++a[c];
} else
break;
}
for (i = 0; i < (SIZE2); ++i) {
printf("a[%ld] is %ld\n", i, a[i]);
counter2 = counter2 + a[i];
}
printf("Counter reached %ld\n", counter);
printf("Counter2 reached %ld\n", counter2);
fclose(fp);
return 0;
}
// cc -Wall -Wextra -g hist3.c -o hist
$
I needed two different SIZES, one that would be larger than the byte
count of the file to be read and another that was one greater than
UCHAR_MAX. Seems to behave. Thanks all for comments.
--
Uno
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looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 00:06 -0600
Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-12 18:41 +1200
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 00:58 -0600
Re: looking at binary files with C Barry Schwarz <schwarz45@yahoo.com> - 2011-06-12 00:05 -0700
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 01:41 -0600
Re: looking at binary files with C "Joachim Schmitz" <jojo.nospam@schmitz-digital.de> - 2011-06-12 11:44 +0200
Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 10:25 -0600
Re: looking at binary files with C Ike Naar <ike@sverige.freeshell.org> - 2011-06-12 10:26 +0000
Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-12 08:23 -0400
Re: looking at binary files with C Hans Vlems <hvlems@freenet.de> - 2011-06-13 23:48 -0700
Re: looking at binary files with C Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-23 00:55 -0700
Re: looking at binary files with C "BartC" <bc@freeuk.com> - 2011-06-12 14:26 +0100
Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 10:24 -0600
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 14:47 -0600
Re: looking at binary files with C "BartC" <bc@freeuk.com> - 2011-06-12 22:23 +0100
Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 14:29 -0700
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 16:31 -0600
Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 16:14 -0700
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 18:41 -0600
Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-12 17:42 -0400
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 17:01 -0600
Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-12 16:23 -0700
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 17:24 -0600
Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-13 11:28 +1200
Re: looking at binary files with C Geoff <geoff@invalid.invalid> - 2011-06-12 16:52 -0700
Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-13 08:51 -0700
Re: looking at binary files with C Seebs <usenet-nospam@seebs.net> - 2011-06-13 14:39 +0000
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-13 20:01 -0600
Re: looking at binary files with C Keith Thompson <kst-u@mib.org> - 2011-06-13 19:24 -0700
Re: looking at binary files with C Seebs <usenet-nospam@seebs.net> - 2011-06-14 17:02 +0000
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-16 01:32 -0600
Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-13 07:57 -0400
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-13 20:23 -0600
Re: looking at binary files with C Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-13 23:12 -0400
Re: looking at binary files with C lovecreatesbeauty <lovecreatesbeauty@gmail.com> - 2011-06-14 01:09 -0700
Re: looking at binary files with C Oliver Jackson <chexmofo@hotmail.com> - 2011-06-15 20:15 -0700
Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-12 18:41 -0600
Re: looking at binary files with C James Waldby <not@valid.invalid> - 2011-06-13 01:16 +0000
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-12 19:48 -0600
Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 12:19 +0200
Re: looking at binary files with C lovecreatesbeauty <lovecreatesbeauty@gmail.com> - 2011-06-14 03:58 -0700
Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 19:07 +0200
Re: looking at binary files with C "io_x" <a@b.c.invalid> - 2011-06-14 19:46 +0200
Re: looking at binary files with C Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-06-14 16:08 -0600
Re: looking at binary files with C Ian Collins <ian-news@hotmail.com> - 2011-06-15 08:47 +1200
Re: looking at binary files with C Hans Vlems <hvlems@freenet.de> - 2011-06-13 23:51 -0700
Re: looking at binary files with C Michael Press <rubrum@pacbell.net> - 2011-06-15 13:06 -0700
Re: looking at binary files with C Uno <Uno@example.invalid> - 2011-06-16 01:38 -0600
Re: looking at binary files with C Michael Press <rubrum@pacbell.net> - 2011-06-16 00:54 -0700
Re: looking at binary files with C James Waldby <not@valid.invalid> - 2011-06-16 16:59 +0000
Re: looking at binary files with C "J. J. Farrell" <jjf@bcs.org.uk> - 2011-06-16 18:32 +0100
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