/**
* Checks whether a set of offsets can be used for cstruct.
*
* Because cstruct does not support customizable offset (use struct for
* that), this function can be used to check that offsets are compatible with
* cstruct.
*
* \param field_count The number of array entries in `field_types` and `field_offsets`
* \param field_types An array of the field types.
* \param field_offsets The offsets corresponding to the types.
* \param total_size The total size of the struct in bytes.
*
* \returns True if constructing a cstruct with the same types and field offsets will
* produce the provided offsets.
*/
inline bool is_cstruct_compatible_offsets(size_t field_count,
const ndt::type *field_types, const uintptr_t *field_offsets, size_t total_size)
{
size_t offset = 0, max_alignment = 1;
for (size_t i = 0; i != field_count; ++i) {
uintptr_t field_data_alignment = field_types[i].get_data_alignment();
uintptr_t field_data_size = field_types[i].get_data_size();
offset = inc_to_alignment(offset, field_data_alignment);
if (field_offsets[i] != offset || field_data_size == 0) {
return false;
}
max_alignment = (field_data_alignment > max_alignment) ? field_data_alignment : max_alignment;
offset += field_data_size;
}
offset = inc_to_alignment(offset, max_alignment);
return total_size == offset;
}
/**
* Fills in the array of default data offsets based on the data sizes
* and alignments of the types.
*/
static void fill_default_data_offsets(intptr_t nfields, const type *field_tps, uintptr_t *out_data_offsets) {
if (nfields > 0) {
out_data_offsets[0] = 0;
size_t offs = 0;
for (intptr_t i = 1; i < nfields; ++i) {
offs += field_tps[i - 1].get_default_data_size();
offs = inc_to_alignment(offs, field_tps[i].get_data_alignment());
out_data_offsets[i] = offs;
}
}
}
