1 files changed, 80 insertions, 0 deletions
diff --git a/upb_msg.c b/upb_msg.c
index 48b0472..9c03301 100644
--- a/upb_msg.c
+++ b/upb_msg.c
@@ -3,4 +3,84 @@
  *
  */
 
+#include <stdlib.h>
+#include "descriptor.h"
 #include "upb_msg.h"
+
+#define ALIGN_UP(p, t) (t + ((p - 1) & (~t - 1)))
+
+static uint32_t max(uint32_t a, uint32_t b) { return a > b ? a : b; }
+
+static int div_round_up(int numerator, int denominator) {
+  /* cf. http://stackoverflow.com/questions/17944/how-to-round-up-the-result-of-integer-division */
+  return numerator > 0 ? (numerator - 1) / denominator + 1 : 0;
+}
+
+static int compare_fields(const void *e1, const void *e2) {
+  const google_protobuf_FieldDescriptorProto *f1  = e1, *f2 = e2;
+  /* Required fields go before non-required. */
+  if(f1->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED &&
+     f2->label != GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED) {
+    return -1;
+  } else if(f1->label != GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED &&
+            f2->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED) {
+    return 1;
+  } else {
+    /* Within required and non-required field lists, list in number order. */
+    return f1->number - f2->number;
+  }
+}
+
+bool upb_msg_init(struct upb_msg *m, struct google_protobuf_DescriptorProto *d)
+{
+  /* TODO: more complete validation. */
+  if(!d->set_flags.has.field) return false;
+
+  upb_inttable_init(&m->fields_by_num, d->field->len,
+                    sizeof(struct upb_fieldsbynum_entry));
+  upb_strtable_init(&m->fields_by_name, d->field->len,
+                    sizeof(struct upb_fieldsbyname_entry));
+
+  m->fields = malloc(sizeof(struct upb_msg_field) * d->field->len);
+  m->num_fields = d->field->len;
+  m->set_flags_bytes = div_round_up(m->num_fields, 8);
+
+  /* These are incremented in the loop. */
+  m->num_required_fields = 0;
+  m->size = m->set_flags_bytes;
+
+  qsort(m->fields, d->field->len, sizeof(struct upb_msg_field), compare_fields);
+
+  size_t max_align = 0;
+
+  for(unsigned int i = 0; i < d->field->len; i++) {
+    struct upb_msg_field *f = &m->fields[i];
+    google_protobuf_FieldDescriptorProto *fd;  /* TODO */
+    struct upb_type_info *type_info = &upb_type_info[f->type];
+    f->field_index = i;
+    f->type = fd->type;
+    f->byte_offset = ALIGN_UP(m->size, type_info->align);
+    m->size = f->byte_offset + type_info->size;
+    max_align = max(max_align, type_info->align);
+    if(fd->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED)
+      m->num_required_fields++;
+
+    /* Insert into the tables.  Note that f->ref will be uninitialized, even in
+     * the tables' copies of *f, which is why we must update them separately
+     * when the references are resolved. */
+    struct upb_fieldsbynum_entry nument = {.e = {.key = fd->number}, .f = *f};
+    struct upb_fieldsbyname_entry strent = {.e = {.key = *fd->name}, .f = *f};
+    upb_inttable_insert(&m->fields_by_num, &nument.e);
+    upb_strtable_insert(&m->fields_by_name, &strent.e);
+  }
+
+  m->size = ALIGN_UP(m->size, max_align);
+  return true;
+}
+
+void upb_msg_free(struct upb_msg *m)
+{
+  upb_inttable_free(&m->fields_by_num);
+  upb_strtable_free(&m->fields_by_name);
+  free(m->fields);
+}