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// Copyright 2018 the Deno authors. All rights reserved. MIT license.
#ifndef FLATBUFFER_BUILDER_H_
#define FLATBUFFER_BUILDER_H_
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include "deno.h"
#include "flatbuffers/flatbuffers.h"
namespace deno {
// Wrap the default FlatBufferBuilder class, because the default one can't give
// us a pointer to the output buffer that we own. Nominally,
// FlatBufferBuilder::Release() should do that, but it returns some
// smart-pointer-like object (DetachedBuffer) that frees the buffer when it goes
// out of scope.
//
// This wrapper adds the `ExportBuf` method that returns a deno_buf, which
// is really not owned at all -- the caller is responsible for releasing the
// allocation with free().
//
// The alternative allocator also uses malloc()/free(), rather than
// new/delete[], so that the exported buffer can be later be converted to an
// ArrayBuffer; the (default) V8 ArrayBuffer allocator also uses free().
class FlatBufferBuilder : public flatbuffers::FlatBufferBuilder {
static const size_t kDefaultInitialSize = 1024;
class Allocator : public flatbuffers::Allocator {
uint8_t* keep_alloc_ptr_ = nullptr;
uint8_t* last_alloc_ptr_ = nullptr;
size_t last_alloc_len_ = 0;
public:
deno_buf GetAndKeepBuf(uint8_t* data_ptr, size_t data_len);
protected:
virtual uint8_t* allocate(size_t size);
virtual void deallocate(uint8_t* ptr, size_t size);
};
Allocator allocator_;
public:
explicit FlatBufferBuilder(size_t initial_size = kDefaultInitialSize)
: flatbuffers::FlatBufferBuilder(initial_size, &allocator_) {}
// Export the finalized flatbuffer as a deno_buf structure. The caller takes
// ownership of the underlying memory allocation, which must be released with
// free().
// Afer calling ExportBuf() the FlatBufferBuilder should no longer be used;
// However it can be used again once it is reset with the Reset() method.
deno_buf ExportBuf();
// Don't use these.
flatbuffers::DetachedBuffer Release() = delete;
flatbuffers::DetachedBuffer ReleaseBufferPointer() = delete;
};
} // namespace deno
#endif // FLATBUFFER_BUILDER_H_
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