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/* Managed memory allocator.

* Author: Steffen Vogel <post@steffenvogel.de>

* SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University

* SPDX-License-Identifier: Apache-2.0

#include <cstdlib>

#include <strings.h>

#include <sys/mman.h>

#include <sys/resource.h>

#include <sys/time.h>

#include <sys/types.h>

#include <unistd.h>

#include <villas/exceptions.hpp>

#include <villas/log.hpp>

#include <villas/node/memory.hpp>

#include <villas/utils.hpp>

using namespace villas;

using namespace villas::node;

using namespace villas::utils;

using namespace villas::node::memory;

static struct Allocation *managed_alloc(size_t len, size_t alignment,

struct Type *m) {

// Simple first-fit allocation

struct Block *first = (struct Block *)m->_vd;

struct Block *block;

for (block = first; block != nullptr; block = block->next) {

if (block->used)

continue;

char *cptr = reinterpret_cast<char *>(block) + sizeof(struct Block);

size_t avail = block->length;

uintptr_t uptr = (uintptr_t)cptr;

/* Check alignment first; leave a gap at start of block to assure

* alignment if necessary */

uintptr_t rem = uptr % alignment;

uintptr_t gap = 0;

if (rem != 0) {

gap = alignment - rem;

if (gap > avail)

continue; // Next aligned address isn't in this block anymore

cptr += gap;

avail -= gap;

}

if (avail >= len) {

if (gap > sizeof(struct Block)) {

/* The alignment gap is big enough to fit another block.

* The original block descriptor is already at the correct

* position, so we just change its len and create a new block

* descriptor for the actual block we're handling. */

block->length = gap - sizeof(struct Block);

struct Block *newblock =

reinterpret_cast<struct Block *>(cptr - sizeof(struct Block));

newblock->prev = block;

newblock->next = block->next;

block->next = newblock;

newblock->used = false;

newblock->length = len;

block = newblock;

} else {

/* The gap is too small to fit another block descriptor, so we

* must account for the gap length in the block length. */

block->length = len + gap;

}

if (avail > len + sizeof(struct Block)) {

// Imperfect fit, so create another block for the remaining part

struct Block *newblock = reinterpret_cast<struct Block *>(cptr + len);

newblock->prev = block;

newblock->next = block->next;

block->next = newblock;

if (newblock->next)

newblock->next->prev = newblock;

newblock->used = false;

newblock->length = avail - len - sizeof(struct Block);

} else {

/* If this block was larger than the requested length, but only

* by less than sizeof(struct Block), we may have wasted

* memory by previous assignments to block->length. */

block->length = avail;

}

block->used = true;

auto *ma = new struct Allocation;

if (!ma)

throw MemoryAllocationError();

ma->address = cptr;

ma->type = m;

ma->alignment = alignment;

ma->length = len;

ma->managed.block = block;

return ma;

}

// No suitable block found

return nullptr;

}

static int managed_free(struct Allocation *ma, struct Type *m) {

struct Block *block = ma->managed.block;

// Try to merge it with neighbouring free blocks

if (block->prev && !block->prev->used && block->next && !block->next->used) {

// Special case first: both previous and next block are unused

block->prev->length +=

block->length + block->next->length + 2 * sizeof(struct Block);

block->prev->next = block->next->next;

if (block->next->next)

block->next->next->prev = block->prev;

} else if (block->prev && !block->prev->used) {

block->prev->length += block->length + sizeof(struct Block);

block->prev->next = block->next;

if (block->next)

block->next->prev = block->prev;

} else if (block->next && !block->next->used) {

block->length += block->next->length + sizeof(struct Block);

block->next = block->next->next;

if (block->next)

block->next->prev = block;

} else {

// no neighbouring free block, so just mark it as free

block->used = false;

}

return 0;

}

struct Type *villas::node::memory::managed(void *ptr, size_t len) {

struct Type *mt = (struct Type *)ptr;

struct Block *mb;

char *cptr = (char *)ptr;

if (len < sizeof(struct Type) + sizeof(struct Block)) {

auto logger = Log::get("memory:managed");

logger->info("Passed region is too small");

return nullptr;

}

// Initialize type

mt->name = "managed";

mt->flags = 0;

mt->alloc = managed_alloc;

mt->free = managed_free;

mt->alignment = 1;

cptr += ALIGN(sizeof(struct Type), sizeof(void *));

// Initialize first free memory block

mb = reinterpret_cast<struct Block *>(cptr);

mb->prev = nullptr;

mb->next = nullptr;

mb->used = false;

cptr += ALIGN(sizeof(struct Block), sizeof(void *));

mb->length = len - (cptr - (char *)ptr);

mt->_vd = (void *)mb;

return mt;

}

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