static VALUE which_oneof_field(MessageHeader* self, const upb_oneofdef* o) {
// If no fields in the oneof, always nil.
if (upb_oneofdef_numfields(o) == 0) {
return Qnil;
}
// Grab the first field in the oneof so we can get its layout info to find the
// oneof_case field.
upb_oneof_iter it;
upb_oneof_begin(&it, o);
assert(!upb_oneof_done(&it));
const upb_fielddef* first_field = upb_oneof_iter_field(&it);
assert(upb_fielddef_containingoneof(first_field) != NULL);
size_t case_ofs =
self->descriptor->layout->
fields[upb_fielddef_index(first_field)].case_offset;
uint32_t oneof_case = *((uint32_t*)(Message_data(self) + case_ofs));
if (oneof_case == ONEOF_CASE_NONE) {
return Qnil;
}
// oneof_case is a field index, so find that field.
const upb_fielddef* f = upb_oneofdef_itof(o, oneof_case);
assert(f != NULL);
return ID2SYM(rb_intern(upb_fielddef_name(f)));
}
MessageLayout* create_layout(const upb_msgdef* msgdef) {
MessageLayout* layout = ALLOC(MessageLayout);
int nfields = upb_msgdef_numfields(msgdef);
upb_msg_field_iter it;
upb_msg_oneof_iter oit;
size_t off = 0;
layout->fields = ALLOC_N(MessageField, nfields);
size_t hasbit = 0;
for (upb_msg_field_begin(&it, msgdef);
!upb_msg_field_done(&it);
upb_msg_field_next(&it)) {
const upb_fielddef* field = upb_msg_iter_field(&it);
if (upb_fielddef_haspresence(field)) {
layout->fields[upb_fielddef_index(field)].hasbit = hasbit++;
} else {
layout->fields[upb_fielddef_index(field)].hasbit =
MESSAGE_FIELD_NO_HASBIT;
}
}
if (hasbit != 0) {
off += (hasbit + 8 - 1) / 8;
}
for (upb_msg_field_begin(&it, msgdef);
!upb_msg_field_done(&it);
upb_msg_field_next(&it)) {
const upb_fielddef* field = upb_msg_iter_field(&it);
size_t field_size;
if (upb_fielddef_containingoneof(field)) {
// Oneofs are handled separately below.
continue;
}
// Allocate |field_size| bytes for this field in the layout.
field_size = 0;
if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
field_size = sizeof(VALUE);
} else {
field_size = native_slot_size(upb_fielddef_type(field));
}
// Align current offset up to |size| granularity.
off = align_up_to(off, field_size);
layout->fields[upb_fielddef_index(field)].offset = off;
layout->fields[upb_fielddef_index(field)].case_offset =
MESSAGE_FIELD_NO_CASE;
off += field_size;
}
// Handle oneofs now -- we iterate over oneofs specifically and allocate only
// one slot per oneof.
//
// We assign all value slots first, then pack the 'case' fields at the end,
// since in the common case (modern 64-bit platform) these are 8 bytes and 4
// bytes respectively and we want to avoid alignment overhead.
//
// Note that we reserve 4 bytes (a uint32) per 'case' slot because the value
// space for oneof cases is conceptually as wide as field tag numbers. In
// practice, it's unlikely that a oneof would have more than e.g. 256 or 64K
// members (8 or 16 bits respectively), so conceivably we could assign
// consecutive case numbers and then pick a smaller oneof case slot size, but
// the complexity to implement this indirection is probably not worthwhile.
for (upb_msg_oneof_begin(&oit, msgdef);
!upb_msg_oneof_done(&oit);
upb_msg_oneof_next(&oit)) {
const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
upb_oneof_iter fit;
// Always allocate NATIVE_SLOT_MAX_SIZE bytes, but share the slot between
// all fields.
size_t field_size = NATIVE_SLOT_MAX_SIZE;
// Align the offset.
off = align_up_to(off, field_size);
// Assign all fields in the oneof this same offset.
for (upb_oneof_begin(&fit, oneof);
!upb_oneof_done(&fit);
upb_oneof_next(&fit)) {
const upb_fielddef* field = upb_oneof_iter_field(&fit);
layout->fields[upb_fielddef_index(field)].offset = off;
}
off += field_size;
}
// Now the case fields.
for (upb_msg_oneof_begin(&oit, msgdef);
!upb_msg_oneof_done(&oit);
upb_msg_oneof_next(&oit)) {
const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
upb_oneof_iter fit;
size_t field_size = sizeof(uint32_t);
// Align the offset.
off = (off + field_size - 1) & ~(field_size - 1);
// Assign all fields in the oneof this same offset.
for (upb_oneof_begin(&fit, oneof);
!upb_oneof_done(&fit);
upb_oneof_next(&fit)) {
const upb_fielddef* field = upb_oneof_iter_field(&fit);
layout->fields[upb_fielddef_index(field)].case_offset = off;
}
off += field_size;
}
layout->size = off;
layout->msgdef = msgdef;
upb_msgdef_ref(layout->msgdef, &layout->msgdef);
return layout;
}
static bool upb_msglayout_init(const upb_msgdef *m,
upb_msglayout *l,
upb_msgfactory *factory) {
upb_msg_field_iter it;
upb_msg_oneof_iter oit;
size_t hasbit;
size_t submsg_count = 0;
const upb_msglayout **submsgs;
upb_msglayout_field *fields;
for (upb_msg_field_begin(&it, m);
!upb_msg_field_done(&it);
upb_msg_field_next(&it)) {
const upb_fielddef* f = upb_msg_iter_field(&it);
if (upb_fielddef_issubmsg(f)) {
submsg_count++;
}
}
memset(l, 0, sizeof(*l));
fields = upb_gmalloc(upb_msgdef_numfields(m) * sizeof(*fields));
submsgs = upb_gmalloc(submsg_count * sizeof(*submsgs));
if ((!fields && upb_msgdef_numfields(m)) ||
(!submsgs && submsg_count)) {
/* OOM. */
upb_gfree(fields);
upb_gfree(submsgs);
return false;
}
l->field_count = upb_msgdef_numfields(m);
l->fields = fields;
l->submsgs = submsgs;
/* Allocate data offsets in three stages:
*
* 1. hasbits.
* 2. regular fields.
* 3. oneof fields.
*
* OPT: There is a lot of room for optimization here to minimize the size.
*/
/* Allocate hasbits and set basic field attributes. */
submsg_count = 0;
for (upb_msg_field_begin(&it, m), hasbit = 0;
!upb_msg_field_done(&it);
upb_msg_field_next(&it)) {
const upb_fielddef* f = upb_msg_iter_field(&it);
upb_msglayout_field *field = &fields[upb_fielddef_index(f)];
field->number = upb_fielddef_number(f);
field->descriptortype = upb_fielddef_descriptortype(f);
field->label = upb_fielddef_label(f);
if (upb_fielddef_issubmsg(f)) {
const upb_msglayout *sub_layout =
upb_msgfactory_getlayout(factory, upb_fielddef_msgsubdef(f));
field->submsg_index = submsg_count++;
submsgs[field->submsg_index] = sub_layout;
}
if (upb_fielddef_haspresence(f) && !upb_fielddef_containingoneof(f)) {
field->presence = (hasbit++);
} else {
field->presence = 0;
}
}
/* Account for space used by hasbits. */
l->size = div_round_up(hasbit, 8);
/* Allocate non-oneof fields. */
for (upb_msg_field_begin(&it, m); !upb_msg_field_done(&it);
upb_msg_field_next(&it)) {
const upb_fielddef* f = upb_msg_iter_field(&it);
size_t field_size = upb_msg_fielddefsize(f);
size_t index = upb_fielddef_index(f);
if (upb_fielddef_containingoneof(f)) {
/* Oneofs are handled separately below. */
continue;
}
fields[index].offset = upb_msglayout_place(l, field_size);
}
/* Allocate oneof fields. Each oneof field consists of a uint32 for the case
* and space for the actual data. */
for (upb_msg_oneof_begin(&oit, m); !upb_msg_oneof_done(&oit);
upb_msg_oneof_next(&oit)) {
const upb_oneofdef* o = upb_msg_iter_oneof(&oit);
upb_oneof_iter fit;
size_t case_size = sizeof(uint32_t); /* Could potentially optimize this. */
size_t field_size = 0;
uint32_t case_offset;
uint32_t data_offset;
/* Calculate field size: the max of all field sizes. */
for (upb_oneof_begin(&fit, o);
!upb_oneof_done(&fit);
upb_oneof_next(&fit)) {
const upb_fielddef* f = upb_oneof_iter_field(&fit);
field_size = UPB_MAX(field_size, upb_msg_fielddefsize(f));
}
/* Align and allocate case offset. */
case_offset = upb_msglayout_place(l, case_size);
data_offset = upb_msglayout_place(l, field_size);
for (upb_oneof_begin(&fit, o);
!upb_oneof_done(&fit);
upb_oneof_next(&fit)) {
const upb_fielddef* f = upb_oneof_iter_field(&fit);
fields[upb_fielddef_index(f)].offset = data_offset;
fields[upb_fielddef_index(f)].presence = ~case_offset;
}
}
/* Size of the entire structure should be a multiple of its greatest
* alignment. TODO: track overall alignment for real? */
l->size = align_up(l->size, 8);
return true;
}