YT-19324: move YT provider to ydb/library/yql

This commit is formed by the following script: https://paste.yandex-team.ru/6f92e4b8-efc5-4d34-948b-15ee2accd7e7/text.
This commit has zero effect on all projects that depend on YQL.

The summary of changes:
- `yql/providers/yt -> ydb/library/yql/providers/yt `- the whole implementation of YT provider is moved into YDB code base for further export as a part of YT YQL plugin shared library;
- `yql/providers/stat/{expr_nodes,uploader} -> ydb/library/yql/providers/stat/{expr_nodes,uploader}` - a small interface without implementation and the description of stat expr nodes;
- `yql/core/extract_predicate/ut -> ydb/library/yql/core/extract_predicate/ut`;
- `yql/core/{ut,ut_common} -> ydb/library/yql/core/{ut,ut_common}`;
- `yql/core` is gone;
- `yql/library/url_preprocessing -> ydb/library/yql/core/url_preprocessing`.

**NB**: all new targets inside `ydb/` are under `IF (NOT CMAKE_EXPORT)` clause which disables them from open-source cmake generation and ya make build. They will be enabled in the subsequent commits.

1 files changed, 713 insertions, 0 deletions

diff --git a/contrib/libs/flatbuffers/src/reflection.cpp b/contrib/libs/flatbuffers/src/reflection.cpp
new file mode 100644
index 0000000000..2dedcb4f18
--- /dev/null
+++ b/contrib/libs/flatbuffers/src/reflection.cpp
@@ -0,0 +1,713 @@
+/*
+ * Copyright 2015 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "flatbuffers/reflection.h"
+
+#include "flatbuffers/util.h"
+
+// Helper functionality for reflection.
+
+namespace flatbuffers {
+
+int64_t GetAnyValueI(reflection::BaseType type, const uint8_t *data) {
+// clang-format off
+  #define FLATBUFFERS_GET(T) static_cast<int64_t>(ReadScalar<T>(data))
+  switch (type) {
+    case reflection::UType:
+    case reflection::Bool:
+    case reflection::UByte:  return FLATBUFFERS_GET(uint8_t);
+    case reflection::Byte:   return FLATBUFFERS_GET(int8_t);
+    case reflection::Short:  return FLATBUFFERS_GET(int16_t);
+    case reflection::UShort: return FLATBUFFERS_GET(uint16_t);
+    case reflection::Int:    return FLATBUFFERS_GET(int32_t);
+    case reflection::UInt:   return FLATBUFFERS_GET(uint32_t);
+    case reflection::Long:   return FLATBUFFERS_GET(int64_t);
+    case reflection::ULong:  return FLATBUFFERS_GET(uint64_t);
+    case reflection::Float:  return FLATBUFFERS_GET(float);
+    case reflection::Double: return FLATBUFFERS_GET(double);
+    case reflection::String: {
+      auto s = reinterpret_cast<const String *>(ReadScalar<uoffset_t>(data) +
+                                                data);
+      return s ? StringToInt(s->c_str()) : 0;
+    }
+    default: return 0;  // Tables & vectors do not make sense.
+  }
+  #undef FLATBUFFERS_GET
+  // clang-format on
+}
+
+double GetAnyValueF(reflection::BaseType type, const uint8_t *data) {
+  switch (type) {
+    case reflection::Float: return static_cast<double>(ReadScalar<float>(data));
+    case reflection::Double: return ReadScalar<double>(data);
+    case reflection::String: {
+      auto s =
+          reinterpret_cast<const String *>(ReadScalar<uoffset_t>(data) + data);
+      if (s) {
+        double d;
+        StringToNumber(s->c_str(), &d);
+        return d;
+      } else {
+        return 0.0;
+      }
+    }
+    default: return static_cast<double>(GetAnyValueI(type, data));
+  }
+}
+
+std::string GetAnyValueS(reflection::BaseType type, const uint8_t *data,
+                         const reflection::Schema *schema, int type_index) {
+  switch (type) {
+    case reflection::Float:
+    case reflection::Double: return NumToString(GetAnyValueF(type, data));
+    case reflection::String: {
+      auto s =
+          reinterpret_cast<const String *>(ReadScalar<uoffset_t>(data) + data);
+      return s ? s->c_str() : "";
+    }
+    case reflection::Obj:
+      if (schema) {
+        // Convert the table to a string. This is mostly for debugging purposes,
+        // and does NOT promise to be JSON compliant.
+        // Also prefixes the type.
+        auto &objectdef = *schema->objects()->Get(type_index);
+        auto s = objectdef.name()->str();
+        if (objectdef.is_struct()) {
+          s += "(struct)";  // TODO: implement this as well.
+        } else {
+          auto table_field = reinterpret_cast<const Table *>(
+              ReadScalar<uoffset_t>(data) + data);
+          s += " { ";
+          auto fielddefs = objectdef.fields();
+          for (auto it = fielddefs->begin(); it != fielddefs->end(); ++it) {
+            auto &fielddef = **it;
+            if (!table_field->CheckField(fielddef.offset())) continue;
+            auto val = GetAnyFieldS(*table_field, fielddef, schema);
+            if (fielddef.type()->base_type() == reflection::String) {
+              std::string esc;
+              flatbuffers::EscapeString(val.c_str(), val.length(), &esc, true,
+                                        false);
+              val = esc;
+            }
+            s += fielddef.name()->str();
+            s += ": ";
+            s += val;
+            s += ", ";
+          }
+          s += "}";
+        }
+        return s;
+      } else {
+        return "(table)";
+      }
+    case reflection::Vector:
+      return "[(elements)]";                   // TODO: implement this as well.
+    case reflection::Union: return "(union)";  // TODO: implement this as well.
+    default: return NumToString(GetAnyValueI(type, data));
+  }
+}
+
+void SetAnyValueI(reflection::BaseType type, uint8_t *data, int64_t val) {
+// clang-format off
+  #define FLATBUFFERS_SET(T) WriteScalar(data, static_cast<T>(val))
+  switch (type) {
+    case reflection::UType:
+    case reflection::Bool:
+    case reflection::UByte:  FLATBUFFERS_SET(uint8_t ); break;
+    case reflection::Byte:   FLATBUFFERS_SET(int8_t  ); break;
+    case reflection::Short:  FLATBUFFERS_SET(int16_t ); break;
+    case reflection::UShort: FLATBUFFERS_SET(uint16_t); break;
+    case reflection::Int:    FLATBUFFERS_SET(int32_t ); break;
+    case reflection::UInt:   FLATBUFFERS_SET(uint32_t); break;
+    case reflection::Long:   FLATBUFFERS_SET(int64_t ); break;
+    case reflection::ULong:  FLATBUFFERS_SET(uint64_t); break;
+    case reflection::Float:  FLATBUFFERS_SET(float   ); break;
+    case reflection::Double: FLATBUFFERS_SET(double  ); break;
+    // TODO: support strings
+    default: break;
+  }
+  #undef FLATBUFFERS_SET
+  // clang-format on
+}
+
+void SetAnyValueF(reflection::BaseType type, uint8_t *data, double val) {
+  switch (type) {
+    case reflection::Float: WriteScalar(data, static_cast<float>(val)); break;
+    case reflection::Double: WriteScalar(data, val); break;
+    // TODO: support strings.
+    default: SetAnyValueI(type, data, static_cast<int64_t>(val)); break;
+  }
+}
+
+void SetAnyValueS(reflection::BaseType type, uint8_t *data, const char *val) {
+  switch (type) {
+    case reflection::Float:
+    case reflection::Double: {
+      double d;
+      StringToNumber(val, &d);
+      SetAnyValueF(type, data, d);
+      break;
+    }
+    // TODO: support strings.
+    default: SetAnyValueI(type, data, StringToInt(val)); break;
+  }
+}
+
+// Resize a FlatBuffer in-place by iterating through all offsets in the buffer
+// and adjusting them by "delta" if they straddle the start offset.
+// Once that is done, bytes can now be inserted/deleted safely.
+// "delta" may be negative (shrinking).
+// Unless "delta" is a multiple of the largest alignment, you'll create a small
+// amount of garbage space in the buffer (usually 0..7 bytes).
+// If your FlatBuffer's root table is not the schema's root table, you should
+// pass in your root_table type as well.
+class ResizeContext {
+ public:
+  ResizeContext(const reflection::Schema &schema, uoffset_t start, int delta,
+                std::vector<uint8_t> *flatbuf,
+                const reflection::Object *root_table = nullptr)
+      : schema_(schema),
+        startptr_(vector_data(*flatbuf) + start),
+        delta_(delta),
+        buf_(*flatbuf),
+        dag_check_(flatbuf->size() / sizeof(uoffset_t), false) {
+    auto mask = static_cast<int>(sizeof(largest_scalar_t) - 1);
+    delta_ = (delta_ + mask) & ~mask;
+    if (!delta_) return;  // We can't shrink by less than largest_scalar_t.
+    // Now change all the offsets by delta_.
+    auto root = GetAnyRoot(vector_data(buf_));
+    Straddle<uoffset_t, 1>(vector_data(buf_), root, vector_data(buf_));
+    ResizeTable(root_table ? *root_table : *schema.root_table(), root);
+    // We can now add or remove bytes at start.
+    if (delta_ > 0)
+      buf_.insert(buf_.begin() + start, delta_, 0);
+    else
+      buf_.erase(buf_.begin() + start + delta_, buf_.begin() + start);
+  }
+
+  // Check if the range between first (lower address) and second straddles
+  // the insertion point. If it does, change the offset at offsetloc (of
+  // type T, with direction D).
+  template<typename T, int D>
+  void Straddle(const void *first, const void *second, void *offsetloc) {
+    if (first <= startptr_ && second >= startptr_) {
+      WriteScalar<T>(offsetloc, ReadScalar<T>(offsetloc) + delta_ * D);
+      DagCheck(offsetloc) = true;
+    }
+  }
+
+  // This returns a boolean that records if the corresponding offset location
+  // has been modified already. If so, we can't even read the corresponding
+  // offset, since it is pointing to a location that is illegal until the
+  // resize actually happens.
+  // This must be checked for every offset, since we can't know which offsets
+  // will straddle and which won't.
+  uint8_t &DagCheck(const void *offsetloc) {
+    auto dag_idx = reinterpret_cast<const uoffset_t *>(offsetloc) -
+                   reinterpret_cast<const uoffset_t *>(vector_data(buf_));
+    return dag_check_[dag_idx];
+  }
+
+  void ResizeTable(const reflection::Object &objectdef, Table *table) {
+    if (DagCheck(table)) return;  // Table already visited.
+    auto vtable = table->GetVTable();
+    // Early out: since all fields inside the table must point forwards in
+    // memory, if the insertion point is before the table we can stop here.
+    auto tableloc = reinterpret_cast<uint8_t *>(table);
+    if (startptr_ <= tableloc) {
+      // Check if insertion point is between the table and a vtable that
+      // precedes it. This can't happen in current construction code, but check
+      // just in case we ever change the way flatbuffers are built.
+      Straddle<soffset_t, -1>(vtable, table, table);
+    } else {
+      // Check each field.
+      auto fielddefs = objectdef.fields();
+      for (auto it = fielddefs->begin(); it != fielddefs->end(); ++it) {
+        auto &fielddef = **it;
+        auto base_type = fielddef.type()->base_type();
+        // Ignore scalars.
+        if (base_type <= reflection::Double) continue;
+        // Ignore fields that are not stored.
+        auto offset = table->GetOptionalFieldOffset(fielddef.offset());
+        if (!offset) continue;
+        // Ignore structs.
+        auto subobjectdef =
+            base_type == reflection::Obj
+                ? schema_.objects()->Get(fielddef.type()->index())
+                : nullptr;
+        if (subobjectdef && subobjectdef->is_struct()) continue;
+        // Get this fields' offset, and read it if safe.
+        auto offsetloc = tableloc + offset;
+        if (DagCheck(offsetloc)) continue;  // This offset already visited.
+        auto ref = offsetloc + ReadScalar<uoffset_t>(offsetloc);
+        Straddle<uoffset_t, 1>(offsetloc, ref, offsetloc);
+        // Recurse.
+        switch (base_type) {
+          case reflection::Obj: {
+            ResizeTable(*subobjectdef, reinterpret_cast<Table *>(ref));
+            break;
+          }
+          case reflection::Vector: {
+            auto elem_type = fielddef.type()->element();
+            if (elem_type != reflection::Obj && elem_type != reflection::String)
+              break;
+            auto vec = reinterpret_cast<Vector<uoffset_t> *>(ref);
+            auto elemobjectdef =
+                elem_type == reflection::Obj
+                    ? schema_.objects()->Get(fielddef.type()->index())
+                    : nullptr;
+            if (elemobjectdef && elemobjectdef->is_struct()) break;
+            for (uoffset_t i = 0; i < vec->size(); i++) {
+              auto loc = vec->Data() + i * sizeof(uoffset_t);
+              if (DagCheck(loc)) continue;  // This offset already visited.
+              auto dest = loc + vec->Get(i);
+              Straddle<uoffset_t, 1>(loc, dest, loc);
+              if (elemobjectdef)
+                ResizeTable(*elemobjectdef, reinterpret_cast<Table *>(dest));
+            }
+            break;
+          }
+          case reflection::Union: {
+            ResizeTable(GetUnionType(schema_, objectdef, fielddef, *table),
+                        reinterpret_cast<Table *>(ref));
+            break;
+          }
+          case reflection::String: break;
+          default: FLATBUFFERS_ASSERT(false);
+        }
+      }
+      // Check if the vtable offset points beyond the insertion point.
+      // Must do this last, since GetOptionalFieldOffset above still reads
+      // this value.
+      Straddle<soffset_t, -1>(table, vtable, table);
+    }
+  }
+
+ private:
+  const reflection::Schema &schema_;
+  uint8_t *startptr_;
+  int delta_;
+  std::vector<uint8_t> &buf_;
+  std::vector<uint8_t> dag_check_;
+};
+
+void SetString(const reflection::Schema &schema, const std::string &val,
+               const String *str, std::vector<uint8_t> *flatbuf,
+               const reflection::Object *root_table) {
+  auto delta = static_cast<int>(val.size()) - static_cast<int>(str->size());
+  auto str_start = static_cast<uoffset_t>(
+      reinterpret_cast<const uint8_t *>(str) - vector_data(*flatbuf));
+  auto start = str_start + static_cast<uoffset_t>(sizeof(uoffset_t));
+  if (delta) {
+    // Clear the old string, since we don't want parts of it remaining.
+    memset(vector_data(*flatbuf) + start, 0, str->size());
+    // Different size, we must expand (or contract).
+    ResizeContext(schema, start, delta, flatbuf, root_table);
+    // Set the new length.
+    WriteScalar(vector_data(*flatbuf) + str_start,
+                static_cast<uoffset_t>(val.size()));
+  }
+  // Copy new data. Safe because we created the right amount of space.
+  memcpy(vector_data(*flatbuf) + start, val.c_str(), val.size() + 1);
+}
+
+uint8_t *ResizeAnyVector(const reflection::Schema &schema, uoffset_t newsize,
+                         const VectorOfAny *vec, uoffset_t num_elems,
+                         uoffset_t elem_size, std::vector<uint8_t> *flatbuf,
+                         const reflection::Object *root_table) {
+  auto delta_elem = static_cast<int>(newsize) - static_cast<int>(num_elems);
+  auto delta_bytes = delta_elem * static_cast<int>(elem_size);
+  auto vec_start =
+      reinterpret_cast<const uint8_t *>(vec) - vector_data(*flatbuf);
+  auto start = static_cast<uoffset_t>(vec_start + sizeof(uoffset_t) +
+                                      elem_size * num_elems);
+  if (delta_bytes) {
+    if (delta_elem < 0) {
+      // Clear elements we're throwing away, since some might remain in the
+      // buffer.
+      auto size_clear = -delta_elem * elem_size;
+      memset(vector_data(*flatbuf) + start - size_clear, 0, size_clear);
+    }
+    ResizeContext(schema, start, delta_bytes, flatbuf, root_table);
+    WriteScalar(vector_data(*flatbuf) + vec_start, newsize);  // Length field.
+    // Set new elements to 0.. this can be overwritten by the caller.
+    if (delta_elem > 0) {
+      memset(vector_data(*flatbuf) + start, 0, delta_elem * elem_size);
+    }
+  }
+  return vector_data(*flatbuf) + start;
+}
+
+const uint8_t *AddFlatBuffer(std::vector<uint8_t> &flatbuf,
+                             const uint8_t *newbuf, size_t newlen) {
+  // Align to sizeof(uoffset_t) past sizeof(largest_scalar_t) since we're
+  // going to chop off the root offset.
+  while ((flatbuf.size() & (sizeof(uoffset_t) - 1)) ||
+         !(flatbuf.size() & (sizeof(largest_scalar_t) - 1))) {
+    flatbuf.push_back(0);
+  }
+  auto insertion_point = static_cast<uoffset_t>(flatbuf.size());
+  // Insert the entire FlatBuffer minus the root pointer.
+  flatbuf.insert(flatbuf.end(), newbuf + sizeof(uoffset_t), newbuf + newlen);
+  auto root_offset = ReadScalar<uoffset_t>(newbuf) - sizeof(uoffset_t);
+  return vector_data(flatbuf) + insertion_point + root_offset;
+}
+
+void CopyInline(FlatBufferBuilder &fbb, const reflection::Field &fielddef,
+                const Table &table, size_t align, size_t size) {
+  fbb.Align(align);
+  fbb.PushBytes(table.GetStruct<const uint8_t *>(fielddef.offset()), size);
+  fbb.TrackField(fielddef.offset(), fbb.GetSize());
+}
+
+Offset<const Table *> CopyTable(FlatBufferBuilder &fbb,
+                                const reflection::Schema &schema,
+                                const reflection::Object &objectdef,
+                                const Table &table, bool use_string_pooling) {
+  // Before we can construct the table, we have to first generate any
+  // subobjects, and collect their offsets.
+  std::vector<uoffset_t> offsets;
+  auto fielddefs = objectdef.fields();
+  for (auto it = fielddefs->begin(); it != fielddefs->end(); ++it) {
+    auto &fielddef = **it;
+    // Skip if field is not present in the source.
+    if (!table.CheckField(fielddef.offset())) continue;
+    uoffset_t offset = 0;
+    switch (fielddef.type()->base_type()) {
+      case reflection::String: {
+        offset = use_string_pooling
+                     ? fbb.CreateSharedString(GetFieldS(table, fielddef)).o
+                     : fbb.CreateString(GetFieldS(table, fielddef)).o;
+        break;
+      }
+      case reflection::Obj: {
+        auto &subobjectdef = *schema.objects()->Get(fielddef.type()->index());
+        if (!subobjectdef.is_struct()) {
+          offset = CopyTable(fbb, schema, subobjectdef,
+                             *GetFieldT(table, fielddef), use_string_pooling)
+                       .o;
+        }
+        break;
+      }
+      case reflection::Union: {
+        auto &subobjectdef = GetUnionType(schema, objectdef, fielddef, table);
+        offset = CopyTable(fbb, schema, subobjectdef,
+                           *GetFieldT(table, fielddef), use_string_pooling)
+                     .o;
+        break;
+      }
+      case reflection::Vector: {
+        auto vec =
+            table.GetPointer<const Vector<Offset<Table>> *>(fielddef.offset());
+        auto element_base_type = fielddef.type()->element();
+        auto elemobjectdef =
+            element_base_type == reflection::Obj
+                ? schema.objects()->Get(fielddef.type()->index())
+                : nullptr;
+        switch (element_base_type) {
+          case reflection::String: {
+            std::vector<Offset<const String *>> elements(vec->size());
+            auto vec_s = reinterpret_cast<const Vector<Offset<String>> *>(vec);
+            for (uoffset_t i = 0; i < vec_s->size(); i++) {
+              elements[i] = use_string_pooling
+                                ? fbb.CreateSharedString(vec_s->Get(i)).o
+                                : fbb.CreateString(vec_s->Get(i)).o;
+            }
+            offset = fbb.CreateVector(elements).o;
+            break;
+          }
+          case reflection::Obj: {
+            if (!elemobjectdef->is_struct()) {
+              std::vector<Offset<const Table *>> elements(vec->size());
+              for (uoffset_t i = 0; i < vec->size(); i++) {
+                elements[i] = CopyTable(fbb, schema, *elemobjectdef,
+                                        *vec->Get(i), use_string_pooling);
+              }
+              offset = fbb.CreateVector(elements).o;
+              break;
+            }
+          }
+            FLATBUFFERS_FALLTHROUGH();  // fall thru
+          default: {                    // Scalars and structs.
+            auto element_size = GetTypeSize(element_base_type);
+            if (elemobjectdef && elemobjectdef->is_struct())
+              element_size = elemobjectdef->bytesize();
+            fbb.StartVector(vec->size(), element_size);
+            fbb.PushBytes(vec->Data(), element_size * vec->size());
+            offset = fbb.EndVector(vec->size());
+            break;
+          }
+        }
+        break;
+      }
+      default:  // Scalars.
+        break;
+    }
+    if (offset) { offsets.push_back(offset); }
+  }
+  // Now we can build the actual table from either offsets or scalar data.
+  auto start = objectdef.is_struct() ? fbb.StartStruct(objectdef.minalign())
+                                     : fbb.StartTable();
+  size_t offset_idx = 0;
+  for (auto it = fielddefs->begin(); it != fielddefs->end(); ++it) {
+    auto &fielddef = **it;
+    if (!table.CheckField(fielddef.offset())) continue;
+    auto base_type = fielddef.type()->base_type();
+    switch (base_type) {
+      case reflection::Obj: {
+        auto &subobjectdef = *schema.objects()->Get(fielddef.type()->index());
+        if (subobjectdef.is_struct()) {
+          CopyInline(fbb, fielddef, table, subobjectdef.minalign(),
+                     subobjectdef.bytesize());
+          break;
+        }
+      }
+        FLATBUFFERS_FALLTHROUGH();  // fall thru
+      case reflection::Union:
+      case reflection::String:
+      case reflection::Vector:
+        fbb.AddOffset(fielddef.offset(), Offset<void>(offsets[offset_idx++]));
+        break;
+      default: {  // Scalars.
+        auto size = GetTypeSize(base_type);
+        CopyInline(fbb, fielddef, table, size, size);
+        break;
+      }
+    }
+  }
+  FLATBUFFERS_ASSERT(offset_idx == offsets.size());
+  if (objectdef.is_struct()) {
+    fbb.ClearOffsets();
+    return fbb.EndStruct();
+  } else {
+    return fbb.EndTable(start);
+  }
+}
+
+bool VerifyStruct(flatbuffers::Verifier &v,
+                  const flatbuffers::Table &parent_table,
+                  voffset_t field_offset, const reflection::Object &obj,
+                  bool required) {
+  auto offset = parent_table.GetOptionalFieldOffset(field_offset);
+  if (required && !offset) { return false; }
+
+  return !offset || v.Verify(reinterpret_cast<const uint8_t *>(&parent_table),
+                             offset, obj.bytesize());
+}
+
+bool VerifyVectorOfStructs(flatbuffers::Verifier &v,
+                           const flatbuffers::Table &parent_table,
+                           voffset_t field_offset,
+                           const reflection::Object &obj, bool required) {
+  auto p = parent_table.GetPointer<const uint8_t *>(field_offset);
+  if (required && !p) { return false; }
+
+  return !p || v.VerifyVectorOrString(p, obj.bytesize());
+}
+
+// forward declare to resolve cyclic deps between VerifyObject and VerifyVector
+bool VerifyObject(flatbuffers::Verifier &v, const reflection::Schema &schema,
+                  const reflection::Object &obj,
+                  const flatbuffers::Table *table, bool required);
+
+bool VerifyUnion(flatbuffers::Verifier &v, const reflection::Schema &schema,
+                 uint8_t utype, const uint8_t *elem,
+                 const reflection::Field &union_field) {
+  if (!utype) return true;  // Not present.
+  auto fb_enum = schema.enums()->Get(union_field.type()->index());
+  if (utype >= fb_enum->values()->size()) return false;
+  auto elem_type = fb_enum->values()->Get(utype)->union_type();
+  switch (elem_type->base_type()) {
+    case reflection::Obj: {
+      auto elem_obj = schema.objects()->Get(elem_type->index());
+      if (elem_obj->is_struct()) {
+        return v.VerifyFromPointer(elem, elem_obj->bytesize());
+      } else {
+        return VerifyObject(v, schema, *elem_obj,
+                            reinterpret_cast<const flatbuffers::Table *>(elem),
+                            true);
+      }
+    }
+    case reflection::String:
+      return v.VerifyString(
+          reinterpret_cast<const flatbuffers::String *>(elem));
+    default: return false;
+  }
+}
+
+bool VerifyVector(flatbuffers::Verifier &v, const reflection::Schema &schema,
+                  const flatbuffers::Table &table,
+                  const reflection::Field &vec_field) {
+  FLATBUFFERS_ASSERT(vec_field.type()->base_type() == reflection::Vector);
+  if (!table.VerifyField<uoffset_t>(v, vec_field.offset())) return false;
+
+  switch (vec_field.type()->element()) {
+    case reflection::UType:
+      return v.VerifyVector(flatbuffers::GetFieldV<uint8_t>(table, vec_field));
+    case reflection::Bool:
+    case reflection::Byte:
+    case reflection::UByte:
+      return v.VerifyVector(flatbuffers::GetFieldV<int8_t>(table, vec_field));
+    case reflection::Short:
+    case reflection::UShort:
+      return v.VerifyVector(flatbuffers::GetFieldV<int16_t>(table, vec_field));
+    case reflection::Int:
+    case reflection::UInt:
+      return v.VerifyVector(flatbuffers::GetFieldV<int32_t>(table, vec_field));
+    case reflection::Long:
+    case reflection::ULong:
+      return v.VerifyVector(flatbuffers::GetFieldV<int64_t>(table, vec_field));
+    case reflection::Float:
+      return v.VerifyVector(flatbuffers::GetFieldV<float>(table, vec_field));
+    case reflection::Double:
+      return v.VerifyVector(flatbuffers::GetFieldV<double>(table, vec_field));
+    case reflection::String: {
+      auto vec_string =
+          flatbuffers::GetFieldV<flatbuffers::Offset<flatbuffers::String>>(
+              table, vec_field);
+      if (v.VerifyVector(vec_string) && v.VerifyVectorOfStrings(vec_string)) {
+        return true;
+      } else {
+        return false;
+      }
+    }
+    case reflection::Obj: {
+      auto obj = schema.objects()->Get(vec_field.type()->index());
+      if (obj->is_struct()) {
+        return VerifyVectorOfStructs(v, table, vec_field.offset(), *obj,
+                                     vec_field.required());
+      } else {
+        auto vec =
+            flatbuffers::GetFieldV<flatbuffers::Offset<flatbuffers::Table>>(
+                table, vec_field);
+        if (!v.VerifyVector(vec)) return false;
+        if (!vec) return true;
+        for (uoffset_t j = 0; j < vec->size(); j++) {
+          if (!VerifyObject(v, schema, *obj, vec->Get(j), true)) {
+            return false;
+          }
+        }
+        return true;
+      }
+    }
+    case reflection::Union: {
+      auto vec = flatbuffers::GetFieldV<flatbuffers::Offset<uint8_t>>(
+          table, vec_field);
+      if (!v.VerifyVector(vec)) return false;
+      if (!vec) return true;
+      auto type_vec = table.GetPointer<Vector<uint8_t> *>(vec_field.offset() -
+                                                          sizeof(voffset_t));
+      if (!v.VerifyVector(type_vec)) return false;
+      for (uoffset_t j = 0; j < vec->size(); j++) {
+        //  get union type from the prev field
+        auto utype = type_vec->Get(j);
+        auto elem = vec->Get(j);
+        if (!VerifyUnion(v, schema, utype, elem, vec_field)) return false;
+      }
+      return true;
+    }
+    case reflection::Vector:
+    case reflection::None:
+    default: FLATBUFFERS_ASSERT(false); return false;
+  }
+}
+
+bool VerifyObject(flatbuffers::Verifier &v, const reflection::Schema &schema,
+                  const reflection::Object &obj,
+                  const flatbuffers::Table *table, bool required) {
+  if (!table) return !required;
+  if (!table->VerifyTableStart(v)) return false;
+  for (uoffset_t i = 0; i < obj.fields()->size(); i++) {
+    auto field_def = obj.fields()->Get(i);
+    switch (field_def->type()->base_type()) {
+      case reflection::None: FLATBUFFERS_ASSERT(false); break;
+      case reflection::UType:
+        if (!table->VerifyField<uint8_t>(v, field_def->offset())) return false;
+        break;
+      case reflection::Bool:
+      case reflection::Byte:
+      case reflection::UByte:
+        if (!table->VerifyField<int8_t>(v, field_def->offset())) return false;
+        break;
+      case reflection::Short:
+      case reflection::UShort:
+        if (!table->VerifyField<int16_t>(v, field_def->offset())) return false;
+        break;
+      case reflection::Int:
+      case reflection::UInt:
+        if (!table->VerifyField<int32_t>(v, field_def->offset())) return false;
+        break;
+      case reflection::Long:
+      case reflection::ULong:
+        if (!table->VerifyField<int64_t>(v, field_def->offset())) return false;
+        break;
+      case reflection::Float:
+        if (!table->VerifyField<float>(v, field_def->offset())) return false;
+        break;
+      case reflection::Double:
+        if (!table->VerifyField<double>(v, field_def->offset())) return false;
+        break;
+      case reflection::String:
+        if (!table->VerifyField<uoffset_t>(v, field_def->offset()) ||
+            !v.VerifyString(flatbuffers::GetFieldS(*table, *field_def))) {
+          return false;
+        }
+        break;
+      case reflection::Vector:
+        if (!VerifyVector(v, schema, *table, *field_def)) return false;
+        break;
+      case reflection::Obj: {
+        auto child_obj = schema.objects()->Get(field_def->type()->index());
+        if (child_obj->is_struct()) {
+          if (!VerifyStruct(v, *table, field_def->offset(), *child_obj,
+                            field_def->required())) {
+            return false;
+          }
+        } else {
+          if (!VerifyObject(v, schema, *child_obj,
+                            flatbuffers::GetFieldT(*table, *field_def),
+                            field_def->required())) {
+            return false;
+          }
+        }
+        break;
+      }
+      case reflection::Union: {
+        //  get union type from the prev field
+        voffset_t utype_offset = field_def->offset() - sizeof(voffset_t);
+        auto utype = table->GetField<uint8_t>(utype_offset, 0);
+        auto uval = reinterpret_cast<const uint8_t *>(
+            flatbuffers::GetFieldT(*table, *field_def));
+        if (!VerifyUnion(v, schema, utype, uval, *field_def)) { return false; }
+        break;
+      }
+      default: FLATBUFFERS_ASSERT(false); break;
+    }
+  }
+
+  if (!v.EndTable()) return false;
+
+  return true;
+}
+
+bool Verify(const reflection::Schema &schema, const reflection::Object &root,
+            const uint8_t *buf, size_t length, uoffset_t max_depth /*= 64*/,
+            uoffset_t max_tables /*= 1000000*/) {
+  Verifier v(buf, length, max_depth, max_tables);
+  return VerifyObject(v, schema, root, flatbuffers::GetAnyRoot(buf), true);
+}
+
+}  // namespace flatbuffers