iovector.cxx

// Cosmos
#include <cosmos/error/RuntimeError.hxx>
#include <cosmos/io/iovector.hxx>
 
namespace cosmos {
 
static_assert(sizeof(struct iovec_const) == sizeof(struct iovec),
                "size mismatch between iovec_const vs. struct iovec in system headers");
 
template <typename MEMORY_REGION>
bool IOVector<MEMORY_REGION>::update(size_t processed_bytes) {
        // there's two approaches to update an io vector after partial
        // read/write operations:
        // a) removing completely processed entry from the begin of the
        //    vector and update partially processed ones
        // b) only updating pointer and length information but keeping
        //    the entry in the vector.
        // For b) the erase operation on the front of the vector is
        // somewhat expensive. For a) the re-entry into the kernel is
        // somewhat expensive, since the first entries processed will
        // potentially be finished already. For b) the advantage is that even
        // a fixed size std::array would be possible to use.  Currently we
        // follow b).
        bool vec_finished = true;
 
        for (auto &entry: *this) {
                processed_bytes -= entry.update(processed_bytes);
 
                if (!entry.finished()) {
                        vec_finished = false;
                        break;
                }
        }
 
        if (processed_bytes != 0) {
                cosmos_throw (RuntimeError("inconsistency while updating IOVector"));
        }
 
        return vec_finished;
}
 
template class IOVector<InputMemoryRegion>;
template class IOVector<OutputMemoryRegion>;
 
} // end ns