//
// Copyright 2011,2014 Ettus Research LLC
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include <uhd/transport/buffer_pool.hpp>
#include <uhd/transport/zero_copy.hpp>
#include <boost/shared_array.hpp>
#include <vector>

using namespace uhd::transport;

//! pad the byte count to a multiple of alignment
static size_t pad_to_boundary(const size_t bytes, const size_t alignment)
{
    return bytes + (alignment - bytes) % alignment;
}

buffer_pool::~buffer_pool(void)
{
    /* NOP */
}

/***********************************************************************
 * Buffer pool implementation
 **********************************************************************/
class buffer_pool_impl : public buffer_pool
{
public:
    buffer_pool_impl(const std::vector<ptr_type>& ptrs, boost::shared_array<char> mem)
        : _ptrs(ptrs), _mem(mem)
    {
        /* NOP */
    }

    ptr_type at(const size_t index) const
    {
        return _ptrs.at(index);
    }

    size_t size(void) const
    {
        return _ptrs.size();
    }

private:
    std::vector<ptr_type> _ptrs;
    boost::shared_array<char> _mem;
};

/***********************************************************************
 * Buffer pool factor function
 **********************************************************************/
buffer_pool::sptr buffer_pool::make(
    const size_t num_buffs, const size_t buff_size, const size_t alignment)
{
    // 1) pad the buffer size to be a multiple of alignment
    // 2) pad the overall memory size for room after alignment
    // 3) allocate the memory in one block of sufficient size
    const size_t padded_buff_size = pad_to_boundary(buff_size, alignment);
    boost::shared_array<char> mem(new char[padded_buff_size * num_buffs + alignment - 1]);

    // Fill a vector with boundary-aligned points in the memory
    const size_t mem_start = pad_to_boundary(size_t(mem.get()), alignment);
    std::vector<ptr_type> ptrs(num_buffs);
    for (size_t i = 0; i < num_buffs; i++) {
        ptrs[i] = ptr_type(mem_start + padded_buff_size * i);
    }

    // Create a new buffer pool implementation with:
    // - the pre-computed pointers, and
    // - the reference to allocated memory.
    return sptr(new buffer_pool_impl(ptrs, mem));
}
