Re: Reading little-endian data from a file in a portable manner

Malcolm McLean wrote:
On Jul 16, 6:07 pm, Ben Bacarisse <ben.use...@xxxxxxxxx> wrote:
Malcolm McLean <malcolm.mcle...@xxxxxxxxxxxxxx> writes:

int x;
x = fgetc(fp);
x |= (fgetc(fp) << 8);
This, too can be UB if fgetc(fp) times 256 is not representable as an
int (and this is the usual case on a 16-bit machine). Again, if you use
unsigned types the problem goes away.

Except it doesn't, because on that architecture the routine will break
when you convert the unsigned to a signed.

The only way I can see of doing it is to manually apply 2s complement
conversion on an unsigned. Which isn't really acceptable.

In the grand scheme of portable data transfer, one must specify the encoding of data in the file. Can there be negative values? If so, how are they encoded? There are more than way. Pick one, then ensure that code that writes encodes properly and code that reads decodes properly.

--
Thad
.

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