Hello all,
need to read a 321bit value from a file into a 64 bit variable (either
float or int). in addition, the endianness of the run-time platform
could differ from the endianness of the value - let's assume it's known
at runtime whether the endianness is the same or different. any ideas?
TIA,
andrey
--
comp.lang.c.mod erated - moderation address: cl**@plethora.n et -- you must
have an appropriate newsgroups line in your header for your mail to be seen,
or the newsgroup name in square brackets in the subject line. Sorry. 4 3590 ae****@yahoo.co m wrote: need to read a 32 bit value from a file into a 64 bit variable (either float or int). in addition, the endianness of the run-time platform could differ from the endianness of the value - let's assume it's known at runtime whether the endianness is the same or different. any ideas?
Assume your value is 1,500,000,000.
int i = 1500000000; /* 32-bits wide ints */
fprintf(fp, "%i\n", i);
then, on the other system,
int i; /* 64-bits wide ints */
fscanf(fp, "%i\n", &i);
or
float f;
fscanf(fp, "%f\n", &f);
On Sun, 26 Jun 2005 09:57:52 +0000, ae5880 wrote: Hello all,
need to read a 321bit value from a file into a 64 bit variable (either float or int). in addition, the endianness of the run-time platform could differ from the endianness of the value - let's assume it's known at runtime whether the endianness is the same or different. any ideas?
If the file representation of the 32-bit value doesn't change between
run-time platforms then you don't need to worry how the machine represents
it in memory. Just don't use any techniques that make any assumptions
about byte-position - eg. use bit shifting if you have to interpret the
32-bit value in the file as 4 separate bytes.
--
comp.lang.c.mod erated - moderation address: cl**@plethora.n et -- you must
have an appropriate newsgroups line in your header for your mail to be seen,
or the newsgroup name in square brackets in the subject line. Sorry.
In comp.lang.c.mod erated ae****@yahoo.co m wrote: need to read a 321bit value from a file into a 64 bit variable (either float or int). in addition, the endianness of the run-time platform could differ from the endianness of the value - let's assume it's known at runtime whether the endianness is the same or different. any ideas?
Read it byte-wise, cast each byte to the result type, shift it to the
right position, and logical-or it all together.
[And please don't cross-post between an open and a moderated group; or
if you think you have to, at least reduce the F'up2 to a single group.
Thank you]
--
Hans-Bernhard Broeker (br*****@physik .rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.
--
comp.lang.c.mod erated - moderation address: cl**@plethora.n et -- you must
have an appropriate newsgroups line in your header for your mail to be seen,
or the newsgroup name in square brackets in the subject line. Sorry. ae****@yahoo.co m wrote: need to read a 321bit value from a file into a 64 bit variable (either float or int). in addition, the endianness of the run-time platform could differ from the endianness of the value - let's assume it's known at runtime whether the endianness is the same or different. any ideas?
You have to know the endianness of the source file.
Assuming it's big-endian and your PC has 8-bit chars:
long long read_64(FILE *fp)
{
unsigned long long var;
var = getc(fp); var <<= 8;
var |= getc(fp); var <<= 8;
var |= getc(fp); var <<= 8;
var |= getc(fp);
if (feof(fp))
return ERROR_READING_F ILE;
return var;
}
Of course there are 1001 (at least) other ways to write
this function.
--
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