refactor flatbuffers.h and util.h so FlexBuffers do not depend on flatbuffers.h (#4331)

FlexBuffers are actually completely unrelated to FlatBuffers and can be used separately.
However, since they utilize several utility functions from flatbuffer.h, they require this header file, which creates unreasonable dependency.
By moving those utility functions to separate base header, both libraries can use same code but still be independent

include/flatbuffers/base.h

+#ifndef FLATBUFFERS_BASE_H_
+#define FLATBUFFERS_BASE_H_
+
+#include <assert.h>
+
+#ifndef ARDUINO
+#include <cstdint>
+#endif
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#ifndef ARDUINO
+#include <utility>
+#else
+#include <utility.h>
+#endif
+#include <type_traits>
+#include <vector>
+#include <set>
+#include <algorithm>
+#include <memory>
+
+#ifdef _STLPORT_VERSION
+  #define FLATBUFFERS_CPP98_STL
+#endif
+#ifndef FLATBUFFERS_CPP98_STL
+  #include <functional>
+#endif
+
+/// @cond FLATBUFFERS_INTERNAL
+#if __cplusplus <= 199711L && \
+    (!defined(_MSC_VER) || _MSC_VER < 1600) && \
+    (!defined(__GNUC__) || \
+      (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ < 40400))
+  #error A C++11 compatible compiler with support for the auto typing is \
+         required for FlatBuffers.
+  #error __cplusplus _MSC_VER __GNUC__  __GNUC_MINOR__  __GNUC_PATCHLEVEL__
+#endif
+
+#if !defined(__clang__) && \
+    defined(__GNUC__) && \
+    (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ < 40600)
+  // Backwards compatability for g++ 4.4, and 4.5 which don't have the nullptr
+  // and constexpr keywords. Note the __clang__ check is needed, because clang
+  // presents itself as an older GNUC compiler.
+  #ifndef nullptr_t
+    const class nullptr_t {
+    public:
+      template<class T> inline operator T*() const { return 0; }
+    private:
+      void operator&() const;
+    } nullptr = {};
+  #endif
+  #ifndef constexpr
+    #define constexpr const
+  #endif
+#endif
+
+// The wire format uses a little endian encoding (since that's efficient for
+// the common platforms).
+#if defined(__s390x__)
+  #define FLATBUFFERS_LITTLEENDIAN 0
+#endif // __s390x__
+#if !defined(FLATBUFFERS_LITTLEENDIAN)
+  #if defined(__GNUC__) || defined(__clang__)
+    #ifdef __BIG_ENDIAN__
+      #define FLATBUFFERS_LITTLEENDIAN 0
+    #else
+      #define FLATBUFFERS_LITTLEENDIAN 1
+    #endif // __BIG_ENDIAN__
+  #elif defined(_MSC_VER)
+    #if defined(_M_PPC)
+      #define FLATBUFFERS_LITTLEENDIAN 0
+    #else
+      #define FLATBUFFERS_LITTLEENDIAN 1
+    #endif
+  #else
+    #error Unable to determine endianness, define FLATBUFFERS_LITTLEENDIAN.
+  #endif
+#endif // !defined(FLATBUFFERS_LITTLEENDIAN)
+
+#define FLATBUFFERS_VERSION_MAJOR 1
+#define FLATBUFFERS_VERSION_MINOR 6
+#define FLATBUFFERS_VERSION_REVISION 0
+#define FLATBUFFERS_STRING_EXPAND(X) #X
+#define FLATBUFFERS_STRING(X) FLATBUFFERS_STRING_EXPAND(X)
+
+#if (!defined(_MSC_VER) || _MSC_VER > 1600) && \
+    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 407))
+  #define FLATBUFFERS_FINAL_CLASS final
+  #define FLATBUFFERS_OVERRIDE override
+#else
+  #define FLATBUFFERS_FINAL_CLASS
+  #define FLATBUFFERS_OVERRIDE
+#endif
+
+#if (!defined(_MSC_VER) || _MSC_VER >= 1900) && \
+    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 406))
+  #define FLATBUFFERS_CONSTEXPR constexpr
+#else
+  #define FLATBUFFERS_CONSTEXPR
+#endif
+
+#if defined(__GXX_EXPERIMENTAL_CXX0X__) && __GNUC__ * 10 + __GNUC_MINOR__ >= 46 || \
+    defined(_MSC_FULL_VER) && _MSC_FULL_VER >= 190023026
+  #define FLATBUFFERS_NOEXCEPT noexcept
+#else
+  #define FLATBUFFERS_NOEXCEPT
+#endif
+
+// NOTE: the FLATBUFFERS_DELETE_FUNC macro may change the access mode to
+// private, so be sure to put it at the end or reset access mode explicitly.
+#if (!defined(_MSC_VER) || _MSC_FULL_VER >= 180020827) && \
+    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 404))
+  #define FLATBUFFERS_DELETE_FUNC(func) func = delete;
+#else
+  #define FLATBUFFERS_DELETE_FUNC(func) private: func;
+#endif
+
+#if defined(_MSC_VER)
+#pragma warning(push)
+#pragma warning(disable: 4127) // C4127: conditional expression is constant
+#endif
+
+/// @endcond
+
+/// @file
+namespace flatbuffers {
+
+/// @cond FLATBUFFERS_INTERNAL
+// Our default offset / size type, 32bit on purpose on 64bit systems.
+// Also, using a consistent offset type maintains compatibility of serialized
+// offset values between 32bit and 64bit systems.
+typedef uint32_t uoffset_t;
+
+// Signed offsets for references that can go in both directions.
+typedef int32_t soffset_t;
+
+// Offset/index used in v-tables, can be changed to uint8_t in
+// format forks to save a bit of space if desired.
+typedef uint16_t voffset_t;
+
+typedef uintmax_t largest_scalar_t;
+
+// In 32bits, this evaluates to 2GB - 1
+#define FLATBUFFERS_MAX_BUFFER_SIZE ((1ULL << (sizeof(soffset_t) * 8 - 1)) - 1)
+
+// We support aligning the contents of buffers up to this size.
+#define FLATBUFFERS_MAX_ALIGNMENT 16
+
+template<typename T> T EndianScalar(T t) {
+  #if FLATBUFFERS_LITTLEENDIAN
+    return t;
+  #else
+    return EndianSwap(t);
+  #endif
+}
+
+template<typename T> T ReadScalar(const void *p) {
+  return EndianScalar(*reinterpret_cast<const T *>(p));
+}
+
+template<typename T> void WriteScalar(void *p, T t) {
+  *reinterpret_cast<T *>(p) = EndianScalar(t);
+}
+
+// Computes how many bytes you'd have to pad to be able to write an
+// "scalar_size" scalar if the buffer had grown to "buf_size" (downwards in
+// memory).
+inline size_t PaddingBytes(size_t buf_size, size_t scalar_size) {
+  return ((~buf_size) + 1) & (scalar_size - 1);
+}
+
+}
+#endif  // FLATBUFFERS_BASE_H_
\ No newline at end of file

include/flatbuffers/flatbuffers.h

@@ -17,154 +17,9 @@
 #ifndef FLATBUFFERS_H_
 #define FLATBUFFERS_H_
 
-#include <assert.h>
+#include "flatbuffers/base.h"
 
-#ifndef ARDUINO
-#include <cstdint>
-#endif
-#include <cstddef>
-#include <cstdlib>
-#include <cstring>
-#include <string>
-#ifndef ARDUINO
-#include <utility>
-#else
-#include <utility.h>
-#endif
-#include <type_traits>
-#include <vector>
-#include <set>
-#include <algorithm>
-#include <memory>
-
-#ifdef _STLPORT_VERSION
-  #define FLATBUFFERS_CPP98_STL
-#endif
-#ifndef FLATBUFFERS_CPP98_STL
-  #include <functional>
-#endif
-
-/// @cond FLATBUFFERS_INTERNAL
-#if __cplusplus <= 199711L && \
-    (!defined(_MSC_VER) || _MSC_VER < 1600) && \
-    (!defined(__GNUC__) || \
-      (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ < 40400))
-  #error A C++11 compatible compiler with support for the auto typing is \
-         required for FlatBuffers.
-  #error __cplusplus _MSC_VER __GNUC__  __GNUC_MINOR__  __GNUC_PATCHLEVEL__
-#endif
-
-#if !defined(__clang__) && \
-    defined(__GNUC__) && \
-    (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ < 40600)
-  // Backwards compatability for g++ 4.4, and 4.5 which don't have the nullptr
-  // and constexpr keywords. Note the __clang__ check is needed, because clang
-  // presents itself as an older GNUC compiler.
-  #ifndef nullptr_t
-    const class nullptr_t {
-    public:
-      template<class T> inline operator T*() const { return 0; }
-    private:
-      void operator&() const;
-    } nullptr = {};
-  #endif
-  #ifndef constexpr
-    #define constexpr const
-  #endif
-#endif
-
-// The wire format uses a little endian encoding (since that's efficient for
-// the common platforms).
-#if defined(__s390x__)
-  #define FLATBUFFERS_LITTLEENDIAN 0
-#endif // __s390x__
-#if !defined(FLATBUFFERS_LITTLEENDIAN)
-  #if defined(__GNUC__) || defined(__clang__)
-    #ifdef __BIG_ENDIAN__
-      #define FLATBUFFERS_LITTLEENDIAN 0
-    #else
-      #define FLATBUFFERS_LITTLEENDIAN 1
-    #endif // __BIG_ENDIAN__
-  #elif defined(_MSC_VER)
-    #if defined(_M_PPC)
-      #define FLATBUFFERS_LITTLEENDIAN 0
-    #else
-      #define FLATBUFFERS_LITTLEENDIAN 1
-    #endif
-  #else
-    #error Unable to determine endianness, define FLATBUFFERS_LITTLEENDIAN.
-  #endif
-#endif // !defined(FLATBUFFERS_LITTLEENDIAN)
-
-#define FLATBUFFERS_VERSION_MAJOR 1
-#define FLATBUFFERS_VERSION_MINOR 6
-#define FLATBUFFERS_VERSION_REVISION 0
-#define FLATBUFFERS_STRING_EXPAND(X) #X
-#define FLATBUFFERS_STRING(X) FLATBUFFERS_STRING_EXPAND(X)
-
-#if (!defined(_MSC_VER) || _MSC_VER > 1600) && \
-    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 407))
-  #define FLATBUFFERS_FINAL_CLASS final
-  #define FLATBUFFERS_OVERRIDE override
-#else
-  #define FLATBUFFERS_FINAL_CLASS
-  #define FLATBUFFERS_OVERRIDE
-#endif
-
-#if (!defined(_MSC_VER) || _MSC_VER >= 1900) && \
-    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 406))
-  #define FLATBUFFERS_CONSTEXPR constexpr
-#else
-  #define FLATBUFFERS_CONSTEXPR
-#endif
-
-#if defined(__GXX_EXPERIMENTAL_CXX0X__) && __GNUC__ * 10 + __GNUC_MINOR__ >= 46 || \
-    defined(_MSC_FULL_VER) && _MSC_FULL_VER >= 190023026
-  #define FLATBUFFERS_NOEXCEPT noexcept
-#else
-  #define FLATBUFFERS_NOEXCEPT
-#endif
-
-// NOTE: the FLATBUFFERS_DELETE_FUNC macro may change the access mode to
-// private, so be sure to put it at the end or reset access mode explicitly.
-#if (!defined(_MSC_VER) || _MSC_FULL_VER >= 180020827) && \
-    (!defined(__GNUC__) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 404))
-  #define FLATBUFFERS_DELETE_FUNC(func) func = delete;
-#else
-  #define FLATBUFFERS_DELETE_FUNC(func) private: func;
-#endif
-
-#if defined(_MSC_VER)
-#pragma warning(push)
-#pragma warning(disable: 4127) // C4127: conditional expression is constant
-#endif
-
-/// @endcond
-
-/// @file
 namespace flatbuffers {
-
-/// @cond FLATBUFFERS_INTERNAL
-// Our default offset / size type, 32bit on purpose on 64bit systems.
-// Also, using a consistent offset type maintains compatibility of serialized
-// offset values between 32bit and 64bit systems.
-typedef uint32_t uoffset_t;
-
-// Signed offsets for references that can go in both directions.
-typedef int32_t soffset_t;
-
-// Offset/index used in v-tables, can be changed to uint8_t in
-// format forks to save a bit of space if desired.
-typedef uint16_t voffset_t;
-
-typedef uintmax_t largest_scalar_t;
-
-// In 32bits, this evaluates to 2GB - 1
-#define FLATBUFFERS_MAX_BUFFER_SIZE ((1ULL << (sizeof(soffset_t) * 8 - 1)) - 1)
-
-// We support aligning the contents of buffers up to this size.
-#define FLATBUFFERS_MAX_ALIGNMENT 16
-
 // Wrapper for uoffset_t to allow safe template specialization.
 // Value is allowed to be 0 to indicate a null object (see e.g. AddOffset).
 template<typename T> struct Offset {
@@ -214,22 +69,6 @@ template<typename T> T EndianSwap(T t) {
   }
 }
 
-template<typename T> T EndianScalar(T t) {
-  #if FLATBUFFERS_LITTLEENDIAN
-    return t;
-  #else
-    return EndianSwap(t);
-  #endif
-}
-
-template<typename T> T ReadScalar(const void *p) {
-  return EndianScalar(*reinterpret_cast<const T *>(p));
-}
-
-template<typename T> void WriteScalar(void *p, T t) {
-  *reinterpret_cast<T *>(p) = EndianScalar(t);
-}
-
 template<typename T> size_t AlignOf() {
   #ifdef _MSC_VER
     return __alignof(T);
@@ -800,13 +639,6 @@ inline voffset_t FieldIndexToOffset(voffset_t field_id) {
   return static_cast<voffset_t>((field_id + fixed_fields) * sizeof(voffset_t));
 }
 
-// Computes how many bytes you'd have to pad to be able to write an
-// "scalar_size" scalar if the buffer had grown to "buf_size" (downwards in
-// memory).
-inline size_t PaddingBytes(size_t buf_size, size_t scalar_size) {
-  return ((~buf_size) + 1) & (scalar_size - 1);
-}
-
 template <typename T> const T* data(const std::vector<T> &v) {
   return v.empty() ? nullptr : &v.front();
 }

include/flatbuffers/flexbuffers.h

@@ -19,7 +19,6 @@
 
 #include <map>
 // We use the basic binary writing functions from the regular FlatBuffers.
-#include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/util.h"
 
 #ifdef _MSC_VER

include/flatbuffers/util.h

@@ -40,7 +40,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 
-#include "flatbuffers/flatbuffers.h"
+#include "flatbuffers/base.h"
 
 
 namespace flatbuffers {