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// Copyright 2018 Bert Belder <bertbelder@gmail.com>
// All rights reserved. MIT License.
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include "deno.h"
#include "flatbuffer_builder.h"
#include "flatbuffers/flatbuffers.h"
namespace deno {
deno_buf FlatBufferBuilder::ExportBuf() {
uint8_t* data_ptr = GetBufferPointer();
size_t data_len = GetSize();
return allocator_.GetAndKeepBuf(data_ptr, data_len);
}
deno_buf FlatBufferBuilder::Allocator::GetAndKeepBuf(uint8_t* data_ptr,
size_t data_len) {
// The builder will typically allocate one chunk of memory with some
// default size. After that, it'll only call allocate() again if the
// initial allocation wasn't big enough, which is then immediately
// followed by deallocate() to release the buffer that was too small.
//
// Therefore we can assume that the `data_ptr` points somewhere inside
// the last allocation, and that we never have to protect earlier
// allocations from being released.
//
// Each builder gets it's own Allocator instance, so multiple builders
// can be exist at the same time without conflicts.
assert(last_alloc_ptr_ != nullptr); // Must have allocated.
assert(keep_alloc_ptr_ == nullptr); // Didn't export any buffer so far.
assert(data_ptr >= last_alloc_ptr_); // Data must be within allocation.
assert(data_ptr + data_len <= last_alloc_ptr_ + last_alloc_len_);
keep_alloc_ptr_ = last_alloc_ptr_;
deno_buf buf;
buf.alloc_ptr = last_alloc_ptr_;
buf.alloc_len = last_alloc_len_;
buf.data_ptr = data_ptr;
buf.data_len = data_len;
return buf;
}
uint8_t* FlatBufferBuilder::Allocator::allocate(size_t size) {
auto ptr = reinterpret_cast<uint8_t*>(malloc(size));
if (ptr == nullptr) {
return nullptr;
}
last_alloc_ptr_ = ptr;
last_alloc_len_ = size;
return ptr;
}
void FlatBufferBuilder::Allocator::deallocate(uint8_t* ptr, size_t size) {
if (ptr == last_alloc_ptr_) {
last_alloc_ptr_ = nullptr;
last_alloc_len_ = 0;
}
if (ptr == keep_alloc_ptr_) {
// This allocation became an exported buffer, so don't free it.
// Clearing keep_alloc_ptr_ makes it possible to export another
// buffer later (after the builder is reset with `Reset()`).
keep_alloc_ptr_ = nullptr;
return;
}
free(ptr);
}
} // namespace deno
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