Update //third_party/protobuf to version 3.

third_party/protobuf/ruby/ext/google/protobuf_c/storage.c

+// Protocol Buffers - Google's data interchange format
+// Copyright 2014 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "protobuf.h"
+
+#include <math.h>
+
+#include <ruby/encoding.h>
+
+// -----------------------------------------------------------------------------
+// Ruby <-> native slot management.
+// -----------------------------------------------------------------------------
+
+#define DEREF(memory, type) *(type*)(memory)
+
+size_t native_slot_size(upb_fieldtype_t type) {
+  switch (type) {
+    case UPB_TYPE_FLOAT:   return 4;
+    case UPB_TYPE_DOUBLE:  return 8;
+    case UPB_TYPE_BOOL:    return 1;
+    case UPB_TYPE_STRING:  return sizeof(VALUE);
+    case UPB_TYPE_BYTES:   return sizeof(VALUE);
+    case UPB_TYPE_MESSAGE: return sizeof(VALUE);
+    case UPB_TYPE_ENUM:    return 4;
+    case UPB_TYPE_INT32:   return 4;
+    case UPB_TYPE_INT64:   return 8;
+    case UPB_TYPE_UINT32:  return 4;
+    case UPB_TYPE_UINT64:  return 8;
+    default: return 0;
+  }
+}
+
+static bool is_ruby_num(VALUE value) {
+  return (TYPE(value) == T_FLOAT ||
+          TYPE(value) == T_FIXNUM ||
+          TYPE(value) == T_BIGNUM);
+}
+
+void native_slot_check_int_range_precision(upb_fieldtype_t type, VALUE val) {
+  if (!is_ruby_num(val)) {
+    rb_raise(rb_eTypeError, "Expected number type for integral field.");
+  }
+
+  // NUM2{INT,UINT,LL,ULL} macros do the appropriate range checks on upper
+  // bound; we just need to do precision checks (i.e., disallow rounding) and
+  // check for < 0 on unsigned types.
+  if (TYPE(val) == T_FLOAT) {
+    double dbl_val = NUM2DBL(val);
+    if (floor(dbl_val) != dbl_val) {
+      rb_raise(rb_eRangeError,
+               "Non-integral floating point value assigned to integer field.");
+    }
+  }
+  if (type == UPB_TYPE_UINT32 || type == UPB_TYPE_UINT64) {
+    if (NUM2DBL(val) < 0) {
+      rb_raise(rb_eRangeError,
+               "Assigning negative value to unsigned integer field.");
+    }
+  }
+}
+
+void native_slot_validate_string_encoding(upb_fieldtype_t type, VALUE value) {
+  bool bad_encoding = false;
+  rb_encoding* string_encoding = rb_enc_from_index(ENCODING_GET(value));
+  if (type == UPB_TYPE_STRING) {
+    bad_encoding =
+        string_encoding != kRubyStringUtf8Encoding &&
+        string_encoding != kRubyStringASCIIEncoding;
+  } else {
+    bad_encoding =
+        string_encoding != kRubyString8bitEncoding;
+  }
+  // Check that encoding is UTF-8 or ASCII (for string fields) or ASCII-8BIT
+  // (for bytes fields).
+  if (bad_encoding) {
+    rb_raise(rb_eTypeError, "Encoding for '%s' fields must be %s (was %s)",
+             (type == UPB_TYPE_STRING) ? "string" : "bytes",
+             (type == UPB_TYPE_STRING) ? "UTF-8 or ASCII" : "ASCII-8BIT",
+             rb_enc_name(string_encoding));
+  }
+}
+
+void native_slot_set(upb_fieldtype_t type, VALUE type_class,
+                     void* memory, VALUE value) {
+  native_slot_set_value_and_case(type, type_class, memory, value, NULL, 0);
+}
+
+void native_slot_set_value_and_case(upb_fieldtype_t type, VALUE type_class,
+                                    void* memory, VALUE value,
+                                    uint32_t* case_memory,
+                                    uint32_t case_number) {
+  // Note that in order to atomically change the value in memory and the case
+  // value (w.r.t. Ruby VM calls), we must set the value at |memory| only after
+  // all Ruby VM calls are complete. The case is then set at the bottom of this
+  // function.
+  switch (type) {
+    case UPB_TYPE_FLOAT:
+      if (!is_ruby_num(value)) {
+        rb_raise(rb_eTypeError, "Expected number type for float field.");
+      }
+      DEREF(memory, float) = NUM2DBL(value);
+      break;
+    case UPB_TYPE_DOUBLE:
+      if (!is_ruby_num(value)) {
+        rb_raise(rb_eTypeError, "Expected number type for double field.");
+      }
+      DEREF(memory, double) = NUM2DBL(value);
+      break;
+    case UPB_TYPE_BOOL: {
+      int8_t val = -1;
+      if (value == Qtrue) {
+        val = 1;
+      } else if (value == Qfalse) {
+        val = 0;
+      } else {
+        rb_raise(rb_eTypeError, "Invalid argument for boolean field.");
+      }
+      DEREF(memory, int8_t) = val;
+      break;
+    }
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES: {
+      if (CLASS_OF(value) != rb_cString) {
+        rb_raise(rb_eTypeError, "Invalid argument for string field.");
+      }
+      native_slot_validate_string_encoding(type, value);
+      DEREF(memory, VALUE) = value;
+      break;
+    }
+    case UPB_TYPE_MESSAGE: {
+      if (CLASS_OF(value) == CLASS_OF(Qnil)) {
+        value = Qnil;
+      } else if (CLASS_OF(value) != type_class) {
+        rb_raise(rb_eTypeError,
+                 "Invalid type %s to assign to submessage field.",
+                 rb_class2name(CLASS_OF(value)));
+      }
+      DEREF(memory, VALUE) = value;
+      break;
+    }
+    case UPB_TYPE_ENUM: {
+      int32_t int_val = 0;
+      if (!is_ruby_num(value) && TYPE(value) != T_SYMBOL) {
+        rb_raise(rb_eTypeError,
+                 "Expected number or symbol type for enum field.");
+      }
+      if (TYPE(value) == T_SYMBOL) {
+        // Ensure that the given symbol exists in the enum module.
+        VALUE lookup = rb_funcall(type_class, rb_intern("resolve"), 1, value);
+        if (lookup == Qnil) {
+          rb_raise(rb_eRangeError, "Unknown symbol value for enum field.");
+        } else {
+          int_val = NUM2INT(lookup);
+        }
+      } else {
+        native_slot_check_int_range_precision(UPB_TYPE_INT32, value);
+        int_val = NUM2INT(value);
+      }
+      DEREF(memory, int32_t) = int_val;
+      break;
+    }
+    case UPB_TYPE_INT32:
+    case UPB_TYPE_INT64:
+    case UPB_TYPE_UINT32:
+    case UPB_TYPE_UINT64:
+      native_slot_check_int_range_precision(type, value);
+      switch (type) {
+      case UPB_TYPE_INT32:
+        DEREF(memory, int32_t) = NUM2INT(value);
+        break;
+      case UPB_TYPE_INT64:
+        DEREF(memory, int64_t) = NUM2LL(value);
+        break;
+      case UPB_TYPE_UINT32:
+        DEREF(memory, uint32_t) = NUM2UINT(value);
+        break;
+      case UPB_TYPE_UINT64:
+        DEREF(memory, uint64_t) = NUM2ULL(value);
+        break;
+      default:
+        break;
+      }
+      break;
+    default:
+      break;
+  }
+
+  if (case_memory != NULL) {
+    *case_memory = case_number;
+  }
+}
+
+VALUE native_slot_get(upb_fieldtype_t type,
+                      VALUE type_class,
+                      const void* memory) {
+  switch (type) {
+    case UPB_TYPE_FLOAT:
+      return DBL2NUM(DEREF(memory, float));
+    case UPB_TYPE_DOUBLE:
+      return DBL2NUM(DEREF(memory, double));
+    case UPB_TYPE_BOOL:
+      return DEREF(memory, int8_t) ? Qtrue : Qfalse;
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_MESSAGE:
+      return DEREF(memory, VALUE);
+    case UPB_TYPE_ENUM: {
+      int32_t val = DEREF(memory, int32_t);
+      VALUE symbol = enum_lookup(type_class, INT2NUM(val));
+      if (symbol == Qnil) {
+        return INT2NUM(val);
+      } else {
+        return symbol;
+      }
+    }
+    case UPB_TYPE_INT32:
+      return INT2NUM(DEREF(memory, int32_t));
+    case UPB_TYPE_INT64:
+      return LL2NUM(DEREF(memory, int64_t));
+    case UPB_TYPE_UINT32:
+      return UINT2NUM(DEREF(memory, uint32_t));
+    case UPB_TYPE_UINT64:
+      return ULL2NUM(DEREF(memory, uint64_t));
+    default:
+      return Qnil;
+  }
+}
+
+void native_slot_init(upb_fieldtype_t type, void* memory) {
+  switch (type) {
+    case UPB_TYPE_FLOAT:
+      DEREF(memory, float) = 0.0;
+      break;
+    case UPB_TYPE_DOUBLE:
+      DEREF(memory, double) = 0.0;
+      break;
+    case UPB_TYPE_BOOL:
+      DEREF(memory, int8_t) = 0;
+      break;
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES:
+      DEREF(memory, VALUE) = rb_str_new2("");
+      rb_enc_associate(DEREF(memory, VALUE), (type == UPB_TYPE_BYTES) ?
+                       kRubyString8bitEncoding : kRubyStringUtf8Encoding);
+      break;
+    case UPB_TYPE_MESSAGE:
+      DEREF(memory, VALUE) = Qnil;
+      break;
+    case UPB_TYPE_ENUM:
+    case UPB_TYPE_INT32:
+      DEREF(memory, int32_t) = 0;
+      break;
+    case UPB_TYPE_INT64:
+      DEREF(memory, int64_t) = 0;
+      break;
+    case UPB_TYPE_UINT32:
+      DEREF(memory, uint32_t) = 0;
+      break;
+    case UPB_TYPE_UINT64:
+      DEREF(memory, uint64_t) = 0;
+      break;
+    default:
+      break;
+  }
+}
+
+void native_slot_mark(upb_fieldtype_t type, void* memory) {
+  switch (type) {
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_MESSAGE:
+      rb_gc_mark(DEREF(memory, VALUE));
+      break;
+    default:
+      break;
+  }
+}
+
+void native_slot_dup(upb_fieldtype_t type, void* to, void* from) {
+  memcpy(to, from, native_slot_size(type));
+}
+
+void native_slot_deep_copy(upb_fieldtype_t type, void* to, void* from) {
+  switch (type) {
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES: {
+      VALUE from_val = DEREF(from, VALUE);
+      DEREF(to, VALUE) = (from_val != Qnil) ?
+          rb_funcall(from_val, rb_intern("dup"), 0) : Qnil;
+      break;
+    }
+    case UPB_TYPE_MESSAGE: {
+      VALUE from_val = DEREF(from, VALUE);
+      DEREF(to, VALUE) = (from_val != Qnil) ?
+          Message_deep_copy(from_val) : Qnil;
+      break;
+    }
+    default:
+      memcpy(to, from, native_slot_size(type));
+  }
+}
+
+bool native_slot_eq(upb_fieldtype_t type, void* mem1, void* mem2) {
+  switch (type) {
+    case UPB_TYPE_STRING:
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_MESSAGE: {
+      VALUE val1 = DEREF(mem1, VALUE);
+      VALUE val2 = DEREF(mem2, VALUE);
+      VALUE ret = rb_funcall(val1, rb_intern("=="), 1, val2);
+      return ret == Qtrue;
+    }
+    default:
+      return !memcmp(mem1, mem2, native_slot_size(type));
+  }
+}
+
+// -----------------------------------------------------------------------------
+// Map field utilities.
+// -----------------------------------------------------------------------------
+
+const upb_msgdef* tryget_map_entry_msgdef(const upb_fielddef* field) {
+  const upb_msgdef* subdef;
+  if (upb_fielddef_label(field) != UPB_LABEL_REPEATED ||
+      upb_fielddef_type(field) != UPB_TYPE_MESSAGE) {
+    return NULL;
+  }
+  subdef = upb_fielddef_msgsubdef(field);
+  return upb_msgdef_mapentry(subdef) ? subdef : NULL;
+}
+
+const upb_msgdef *map_entry_msgdef(const upb_fielddef* field) {
+  const upb_msgdef* subdef = tryget_map_entry_msgdef(field);
+  assert(subdef);
+  return subdef;
+}
+
+bool is_map_field(const upb_fielddef *field) {
+  return tryget_map_entry_msgdef(field) != NULL;
+}
+
+const upb_fielddef* map_field_key(const upb_fielddef* field) {
+  const upb_msgdef* subdef = map_entry_msgdef(field);
+  return map_entry_key(subdef);
+}
+
+const upb_fielddef* map_field_value(const upb_fielddef* field) {
+  const upb_msgdef* subdef = map_entry_msgdef(field);
+  return map_entry_value(subdef);
+}
+
+const upb_fielddef* map_entry_key(const upb_msgdef* msgdef) {
+  const upb_fielddef* key_field = upb_msgdef_itof(msgdef, MAP_KEY_FIELD);
+  assert(key_field != NULL);
+  return key_field;
+}
+
+const upb_fielddef* map_entry_value(const upb_msgdef* msgdef) {
+  const upb_fielddef* value_field = upb_msgdef_itof(msgdef, MAP_VALUE_FIELD);
+  assert(value_field != NULL);
+  return value_field;
+}
+
+// -----------------------------------------------------------------------------
+// Memory layout management.
+// -----------------------------------------------------------------------------
+
+static size_t align_up_to(size_t offset, size_t granularity) {
+  // Granularity must be a power of two.
+  return (offset + granularity - 1) & ~(granularity - 1);
+}
+
+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);
+
+  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;
+}
+
+void free_layout(MessageLayout* layout) {
+  xfree(layout->fields);
+  upb_msgdef_unref(layout->msgdef, &layout->msgdef);
+  xfree(layout);
+}
+
+VALUE field_type_class(const upb_fielddef* field) {
+  VALUE type_class = Qnil;
+  if (upb_fielddef_type(field) == UPB_TYPE_MESSAGE) {
+    VALUE submsgdesc =
+        get_def_obj(upb_fielddef_subdef(field));
+    type_class = Descriptor_msgclass(submsgdesc);
+  } else if (upb_fielddef_type(field) == UPB_TYPE_ENUM) {
+    VALUE subenumdesc =
+        get_def_obj(upb_fielddef_subdef(field));
+    type_class = EnumDescriptor_enummodule(subenumdesc);
+  }
+  return type_class;
+}
+
+static void* slot_memory(MessageLayout* layout,
+                         const void* storage,
+                         const upb_fielddef* field) {
+  return ((uint8_t *)storage) +
+      layout->fields[upb_fielddef_index(field)].offset;
+}
+
+static uint32_t* slot_oneof_case(MessageLayout* layout,
+                                 const void* storage,
+                                 const upb_fielddef* field) {
+  return (uint32_t *)(((uint8_t *)storage) +
+      layout->fields[upb_fielddef_index(field)].case_offset);
+}
+
+
+VALUE layout_get(MessageLayout* layout,
+                 const void* storage,
+                 const upb_fielddef* field) {
+  void* memory = slot_memory(layout, storage, field);
+  uint32_t* oneof_case = slot_oneof_case(layout, storage, field);
+
+  if (upb_fielddef_containingoneof(field)) {
+    if (*oneof_case != upb_fielddef_number(field)) {
+      return Qnil;
+    }
+    return native_slot_get(upb_fielddef_type(field),
+                           field_type_class(field),
+                           memory);
+  } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+    return *((VALUE *)memory);
+  } else {
+    return native_slot_get(upb_fielddef_type(field),
+                           field_type_class(field),
+                           memory);
+  }
+}
+
+static void check_repeated_field_type(VALUE val, const upb_fielddef* field) {
+  RepeatedField* self;
+  assert(upb_fielddef_label(field) == UPB_LABEL_REPEATED);
+
+  if (!RB_TYPE_P(val, T_DATA) || !RTYPEDDATA_P(val) ||
+      RTYPEDDATA_TYPE(val) != &RepeatedField_type) {
+    rb_raise(rb_eTypeError, "Expected repeated field array");
+  }
+
+  self = ruby_to_RepeatedField(val);
+  if (self->field_type != upb_fielddef_type(field)) {
+    rb_raise(rb_eTypeError, "Repeated field array has wrong element type");
+  }
+
+  if (self->field_type == UPB_TYPE_MESSAGE ||
+      self->field_type == UPB_TYPE_ENUM) {
+    if (self->field_type_class !=
+        get_def_obj(upb_fielddef_subdef(field))) {
+      rb_raise(rb_eTypeError,
+               "Repeated field array has wrong message/enum class");
+    }
+  }
+}
+
+static void check_map_field_type(VALUE val, const upb_fielddef* field) {
+  const upb_fielddef* key_field = map_field_key(field);
+  const upb_fielddef* value_field = map_field_value(field);
+  Map* self;
+
+  if (!RB_TYPE_P(val, T_DATA) || !RTYPEDDATA_P(val) ||
+      RTYPEDDATA_TYPE(val) != &Map_type) {
+    rb_raise(rb_eTypeError, "Expected Map instance");
+  }
+
+  self = ruby_to_Map(val);
+  if (self->key_type != upb_fielddef_type(key_field)) {
+    rb_raise(rb_eTypeError, "Map key type does not match field's key type");
+  }
+  if (self->value_type != upb_fielddef_type(value_field)) {
+    rb_raise(rb_eTypeError, "Map value type does not match field's value type");
+  }
+  if (upb_fielddef_type(value_field) == UPB_TYPE_MESSAGE ||
+      upb_fielddef_type(value_field) == UPB_TYPE_ENUM) {
+    if (self->value_type_class !=
+        get_def_obj(upb_fielddef_subdef(value_field))) {
+      rb_raise(rb_eTypeError,
+               "Map value type has wrong message/enum class");
+    }
+  }
+}
+
+
+void layout_set(MessageLayout* layout,
+                void* storage,
+                const upb_fielddef* field,
+                VALUE val) {
+  void* memory = slot_memory(layout, storage, field);
+  uint32_t* oneof_case = slot_oneof_case(layout, storage, field);
+
+  if (upb_fielddef_containingoneof(field)) {
+    if (val == Qnil) {
+      // Assigning nil to a oneof field clears the oneof completely.
+      *oneof_case = ONEOF_CASE_NONE;
+      memset(memory, 0, NATIVE_SLOT_MAX_SIZE);
+    } else {
+      // The transition between field types for a single oneof (union) slot is
+      // somewhat complex because we need to ensure that a GC triggered at any
+      // point by a call into the Ruby VM sees a valid state for this field and
+      // does not either go off into the weeds (following what it thinks is a
+      // VALUE but is actually a different field type) or miss an object (seeing
+      // what it thinks is a primitive field but is actually a VALUE for the new
+      // field type).
+      //
+      // In order for the transition to be safe, the oneof case slot must be in
+      // sync with the value slot whenever the Ruby VM has been called. Thus, we
+      // use native_slot_set_value_and_case(), which ensures that both the value
+      // and case number are altered atomically (w.r.t. the Ruby VM).
+      native_slot_set_value_and_case(
+          upb_fielddef_type(field), field_type_class(field),
+          memory, val,
+          oneof_case, upb_fielddef_number(field));
+    }
+  } else if (is_map_field(field)) {
+    check_map_field_type(val, field);
+    DEREF(memory, VALUE) = val;
+  } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+    check_repeated_field_type(val, field);
+    DEREF(memory, VALUE) = val;
+  } else {
+    native_slot_set(upb_fielddef_type(field), field_type_class(field),
+                    memory, val);
+  }
+}
+
+void layout_init(MessageLayout* layout,
+                 void* storage) {
+  upb_msg_field_iter it;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+    void* memory = slot_memory(layout, storage, field);
+    uint32_t* oneof_case = slot_oneof_case(layout, storage, field);
+
+    if (upb_fielddef_containingoneof(field)) {
+      memset(memory, 0, NATIVE_SLOT_MAX_SIZE);
+      *oneof_case = ONEOF_CASE_NONE;
+    } else if (is_map_field(field)) {
+      VALUE map = Qnil;
+
+      const upb_fielddef* key_field = map_field_key(field);
+      const upb_fielddef* value_field = map_field_value(field);
+      VALUE type_class = field_type_class(value_field);
+
+      if (type_class != Qnil) {
+        VALUE args[3] = {
+          fieldtype_to_ruby(upb_fielddef_type(key_field)),
+          fieldtype_to_ruby(upb_fielddef_type(value_field)),
+          type_class,
+        };
+        map = rb_class_new_instance(3, args, cMap);
+      } else {
+        VALUE args[2] = {
+          fieldtype_to_ruby(upb_fielddef_type(key_field)),
+          fieldtype_to_ruby(upb_fielddef_type(value_field)),
+        };
+        map = rb_class_new_instance(2, args, cMap);
+      }
+
+      DEREF(memory, VALUE) = map;
+    } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+      VALUE ary = Qnil;
+
+      VALUE type_class = field_type_class(field);
+
+      if (type_class != Qnil) {
+        VALUE args[2] = {
+          fieldtype_to_ruby(upb_fielddef_type(field)),
+          type_class,
+        };
+        ary = rb_class_new_instance(2, args, cRepeatedField);
+      } else {
+        VALUE args[1] = { fieldtype_to_ruby(upb_fielddef_type(field)) };
+        ary = rb_class_new_instance(1, args, cRepeatedField);
+      }
+
+      DEREF(memory, VALUE) = ary;
+    } else {
+      native_slot_init(upb_fielddef_type(field), memory);
+    }
+  }
+}
+
+void layout_mark(MessageLayout* layout, void* storage) {
+  upb_msg_field_iter it;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+    void* memory = slot_memory(layout, storage, field);
+    uint32_t* oneof_case = slot_oneof_case(layout, storage, field);
+
+    if (upb_fielddef_containingoneof(field)) {
+      if (*oneof_case == upb_fielddef_number(field)) {
+        native_slot_mark(upb_fielddef_type(field), memory);
+      }
+    } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+      rb_gc_mark(DEREF(memory, VALUE));
+    } else {
+      native_slot_mark(upb_fielddef_type(field), memory);
+    }
+  }
+}
+
+void layout_dup(MessageLayout* layout, void* to, void* from) {
+  upb_msg_field_iter it;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+
+    void* to_memory = slot_memory(layout, to, field);
+    uint32_t* to_oneof_case = slot_oneof_case(layout, to, field);
+    void* from_memory = slot_memory(layout, from, field);
+    uint32_t* from_oneof_case = slot_oneof_case(layout, from, field);
+
+    if (upb_fielddef_containingoneof(field)) {
+      if (*from_oneof_case == upb_fielddef_number(field)) {
+        *to_oneof_case = *from_oneof_case;
+        native_slot_dup(upb_fielddef_type(field), to_memory, from_memory);
+      }
+    } else if (is_map_field(field)) {
+      DEREF(to_memory, VALUE) = Map_dup(DEREF(from_memory, VALUE));
+    } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+      DEREF(to_memory, VALUE) = RepeatedField_dup(DEREF(from_memory, VALUE));
+    } else {
+      native_slot_dup(upb_fielddef_type(field), to_memory, from_memory);
+    }
+  }
+}
+
+void layout_deep_copy(MessageLayout* layout, void* to, void* from) {
+  upb_msg_field_iter it;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+
+    void* to_memory = slot_memory(layout, to, field);
+    uint32_t* to_oneof_case = slot_oneof_case(layout, to, field);
+    void* from_memory = slot_memory(layout, from, field);
+    uint32_t* from_oneof_case = slot_oneof_case(layout, from, field);
+
+    if (upb_fielddef_containingoneof(field)) {
+      if (*from_oneof_case == upb_fielddef_number(field)) {
+        *to_oneof_case = *from_oneof_case;
+        native_slot_deep_copy(upb_fielddef_type(field), to_memory, from_memory);
+      }
+    } else if (is_map_field(field)) {
+      DEREF(to_memory, VALUE) =
+          Map_deep_copy(DEREF(from_memory, VALUE));
+    } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+      DEREF(to_memory, VALUE) =
+          RepeatedField_deep_copy(DEREF(from_memory, VALUE));
+    } else {
+      native_slot_deep_copy(upb_fielddef_type(field), to_memory, from_memory);
+    }
+  }
+}
+
+VALUE layout_eq(MessageLayout* layout, void* msg1, void* msg2) {
+  upb_msg_field_iter it;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+
+    void* msg1_memory = slot_memory(layout, msg1, field);
+    uint32_t* msg1_oneof_case = slot_oneof_case(layout, msg1, field);
+    void* msg2_memory = slot_memory(layout, msg2, field);
+    uint32_t* msg2_oneof_case = slot_oneof_case(layout, msg2, field);
+
+    if (upb_fielddef_containingoneof(field)) {
+      if (*msg1_oneof_case != *msg2_oneof_case ||
+          (*msg1_oneof_case == upb_fielddef_number(field) &&
+           !native_slot_eq(upb_fielddef_type(field),
+                           msg1_memory,
+                           msg2_memory))) {
+        return Qfalse;
+      }
+    } else if (is_map_field(field)) {
+      if (!Map_eq(DEREF(msg1_memory, VALUE),
+                  DEREF(msg2_memory, VALUE))) {
+        return Qfalse;
+      }
+    } else if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
+      if (!RepeatedField_eq(DEREF(msg1_memory, VALUE),
+                            DEREF(msg2_memory, VALUE))) {
+        return Qfalse;
+      }
+    } else {
+      if (!native_slot_eq(upb_fielddef_type(field),
+                          msg1_memory, msg2_memory)) {
+        return Qfalse;
+      }
+    }
+  }
+  return Qtrue;
+}
+
+VALUE layout_hash(MessageLayout* layout, void* storage) {
+  upb_msg_field_iter it;
+  st_index_t h = rb_hash_start(0);
+  VALUE hash_sym = rb_intern("hash");
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+    VALUE field_val = layout_get(layout, storage, field);
+    h = rb_hash_uint(h, NUM2LONG(rb_funcall(field_val, hash_sym, 0)));
+  }
+  h = rb_hash_end(h);
+
+  return INT2FIX(h);
+}
+
+VALUE layout_inspect(MessageLayout* layout, void* storage) {
+  VALUE str = rb_str_new2("");
+
+  upb_msg_field_iter it;
+  bool first = true;
+  for (upb_msg_field_begin(&it, layout->msgdef);
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* field = upb_msg_iter_field(&it);
+    VALUE field_val = layout_get(layout, storage, field);
+
+    if (!first) {
+      str = rb_str_cat2(str, ", ");
+    } else {
+      first = false;
+    }
+    str = rb_str_cat2(str, upb_fielddef_name(field));
+    str = rb_str_cat2(str, ": ");
+
+    str = rb_str_append(str, rb_funcall(field_val, rb_intern("inspect"), 0));
+  }
+
+  return str;
+}