[haiku-commits] Re: r40800 - haiku/trunk/src/add-ons/translators/raw
- From: Ingo Weinhold <ingo_weinhold@xxxxxx>
- To: haiku-commits@xxxxxxxxxxxxx
- Date: Sat, 05 Mar 2011 00:15:27 +0100
On 2011-03-04 at 13:46:38 [+0100], Ryan Leavengood <leavengood@xxxxxxxxx>
wrote:
> Given your concern over mixing status_t and ssize_t probably most of
> the methods of this class need to be changed not to assign the result
> of reading the stream to fError. So probably something like:
>
> template<class T> inline void
> operator()(T &data)
> {
> ssize_t bytesRead = fStream.Read((void *)&data, sizeof(T));
> if (bytesRead > 0) {
> if (IsSwapping())
> byte_swap(data);
> return;
> }
>
> if (bytesRead == 0)
> fError = B_ERROR;
> throw fError;
> }
Actually the correct handling, if you expect to read a certain amount of
data, is (in pseudo code):
size_t bytesExpected = ...;
ssize_t bytesRead = read bytesExpected bytes from source
if (bytesRead < 0)
bail out with error code bytesRead
if ((size_t)bytesRead != bytesExpected)
bail out with general error (or handle partial read)
handle success ...
If you also want to deal correctly with FIFOs, sockets, etc., the full
version is:
size_t bytesExpected = ...;
while (bytesExpected > 0) {
ssize_t bytesRead = read bytesExpected bytes from source
if (bytesRead < 0)
bail out with error code bytesRead
if (bytesRead == 0)
bail out with general error (or handle partial read)
bytesExpected -= bytesRead
}
handle success ...
CU, Ingo
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