// Copyright 2016 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "PoolAlloc.h"

#ifndef _MSC_VER
#include <stdint.h>
#endif
#include <stdio.h>

#include "InitializeGlobals.h"
#include "osinclude.h"

OS_TLSIndex PoolIndex = OS_INVALID_TLS_INDEX;

bool InitializePoolIndex()
{
	assert(PoolIndex == OS_INVALID_TLS_INDEX);

	PoolIndex = OS_AllocTLSIndex();
	return PoolIndex != OS_INVALID_TLS_INDEX;
}

void FreePoolIndex()
{
	assert(PoolIndex != OS_INVALID_TLS_INDEX);

	OS_FreeTLSIndex(PoolIndex);
	PoolIndex = OS_INVALID_TLS_INDEX;
}

TPoolAllocator* GetGlobalPoolAllocator()
{
	assert(PoolIndex != OS_INVALID_TLS_INDEX);
	return static_cast<TPoolAllocator*>(OS_GetTLSValue(PoolIndex));
}

void SetGlobalPoolAllocator(TPoolAllocator* poolAllocator)
{
	assert(PoolIndex != OS_INVALID_TLS_INDEX);
	OS_SetTLSValue(PoolIndex, poolAllocator);
}

//
// Implement the functionality of the TPoolAllocator class, which
// is documented in PoolAlloc.h.
//
TPoolAllocator::TPoolAllocator(int growthIncrement, int allocationAlignment) :
	pageSize(growthIncrement),
	alignment(allocationAlignment),
	freeList(0),
	inUseList(0),
	numCalls(0),
	totalBytes(0)
{
	//
	// Don't allow page sizes we know are smaller than all common
	// OS page sizes.
	//
	if (pageSize < 4*1024)
		pageSize = 4*1024;

	//
	// A large currentPageOffset indicates a new page needs to
	// be obtained to allocate memory.
	//
	currentPageOffset = pageSize;

	//
	// Adjust alignment to be at least pointer aligned and
	// power of 2.
	//
	size_t minAlign = sizeof(void*);
	alignment &= ~(minAlign - 1);
	if (alignment < minAlign)
		alignment = minAlign;
	size_t a = 1;
	while (a < alignment)
		a <<= 1;
	alignment = a;
	alignmentMask = a - 1;

	//
	// Align header skip
	//
	headerSkip = minAlign;
	if (headerSkip < sizeof(tHeader)) {
		headerSkip = (sizeof(tHeader) + alignmentMask) & ~alignmentMask;
	}
}

TPoolAllocator::~TPoolAllocator()
{
	while (inUseList) {
		tHeader* next = inUseList->nextPage;
		inUseList->~tHeader();
		delete [] reinterpret_cast<char*>(inUseList);
		inUseList = next;
	}

	// We should not check the guard blocks
	// here, because we did it already when the block was
	// placed into the free list.
	//
	while (freeList) {
		tHeader* next = freeList->nextPage;
		delete [] reinterpret_cast<char*>(freeList);
		freeList = next;
	}
}

// Support MSVC++ 6.0
const unsigned char TAllocation::guardBlockBeginVal = 0xfb;
const unsigned char TAllocation::guardBlockEndVal   = 0xfe;
const unsigned char TAllocation::userDataFill       = 0xcd;

#ifdef GUARD_BLOCKS
	const size_t TAllocation::guardBlockSize = 16;
#else
	const size_t TAllocation::guardBlockSize = 0;
#endif

//
// Check a single guard block for damage
//
void TAllocation::checkGuardBlock(unsigned char* blockMem, unsigned char val, const char* locText) const
{
#ifdef GUARD_BLOCKS
	for (size_t x = 0; x < guardBlockSize; x++) {
		if (blockMem[x] != val) {
			char assertMsg[80];

			// We don't print the assert message.  It's here just to be helpful.
			#if defined(_MSC_VER)
				_snprintf(assertMsg, sizeof(assertMsg), "PoolAlloc: Damage %s %Iu byte allocation at 0x%p\n",
						  locText, size, data());
			#else
				snprintf(assertMsg, sizeof(assertMsg), "PoolAlloc: Damage %s %zu byte allocation at 0x%p\n",
						 locText, size, data());
			#endif
			assert(0 && "PoolAlloc: Damage in guard block");
		}
	}
#endif
}


void TPoolAllocator::push()
{
	tAllocState state = { currentPageOffset, inUseList };

	stack.push_back(state);

	//
	// Indicate there is no current page to allocate from.
	//
	currentPageOffset = pageSize;
}

//
// Do a mass-deallocation of all the individual allocations
// that have occurred since the last push(), or since the
// last pop(), or since the object's creation.
//
// The deallocated pages are saved for future allocations.
//
void TPoolAllocator::pop()
{
	if (stack.size() < 1)
		return;

	tHeader* page = stack.back().page;
	currentPageOffset = stack.back().offset;

	while (inUseList != page) {
		// invoke destructor to free allocation list
		inUseList->~tHeader();

		tHeader* nextInUse = inUseList->nextPage;
		if (inUseList->pageCount > 1)
			delete [] reinterpret_cast<char*>(inUseList);
		else {
			inUseList->nextPage = freeList;
			freeList = inUseList;
		}
		inUseList = nextInUse;
	}

	stack.pop_back();
}

//
// Do a mass-deallocation of all the individual allocations
// that have occurred.
//
void TPoolAllocator::popAll()
{
	while (stack.size() > 0)
		pop();
}

void* TPoolAllocator::allocate(size_t numBytes)
{
	//
	// Just keep some interesting statistics.
	//
	++numCalls;
	totalBytes += numBytes;

	// If we are using guard blocks, all allocations are bracketed by
	// them: [guardblock][allocation][guardblock].  numBytes is how
	// much memory the caller asked for.  allocationSize is the total
	// size including guard blocks.  In release build,
	// guardBlockSize=0 and this all gets optimized away.
	size_t allocationSize = TAllocation::allocationSize(numBytes);
	// Detect integer overflow.
	if (allocationSize < numBytes)
		return 0;

	//
	// Do the allocation, most likely case first, for efficiency.
	// This step could be moved to be inline sometime.
	//
	if (allocationSize <= pageSize - currentPageOffset) {
		//
		// Safe to allocate from currentPageOffset.
		//
		unsigned char* memory = reinterpret_cast<unsigned char *>(inUseList) + currentPageOffset;
		currentPageOffset += allocationSize;
		currentPageOffset = (currentPageOffset + alignmentMask) & ~alignmentMask;

		return initializeAllocation(inUseList, memory, numBytes);
	}

	if (allocationSize > pageSize - headerSkip) {
		//
		// Do a multi-page allocation.  Don't mix these with the others.
		// The OS is efficient and allocating and free-ing multiple pages.
		//
		size_t numBytesToAlloc = allocationSize + headerSkip;
		// Detect integer overflow.
		if (numBytesToAlloc < allocationSize)
			return 0;

		tHeader* memory = reinterpret_cast<tHeader*>(::new char[numBytesToAlloc]);
		if (memory == 0)
			return 0;

		// Use placement-new to initialize header
		new(memory) tHeader(inUseList, (numBytesToAlloc + pageSize - 1) / pageSize);
		inUseList = memory;

		currentPageOffset = pageSize;  // make next allocation come from a new page

		// No guard blocks for multi-page allocations (yet)
		return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(memory) + headerSkip);
	}

	//
	// Need a simple page to allocate from.
	//
	tHeader* memory;
	if (freeList) {
		memory = freeList;
		freeList = freeList->nextPage;
	} else {
		memory = reinterpret_cast<tHeader*>(::new char[pageSize]);
		if (memory == 0)
			return 0;
	}

	// Use placement-new to initialize header
	new(memory) tHeader(inUseList, 1);
	inUseList = memory;

	unsigned char* ret = reinterpret_cast<unsigned char *>(inUseList) + headerSkip;
	currentPageOffset = (headerSkip + allocationSize + alignmentMask) & ~alignmentMask;

	return initializeAllocation(inUseList, ret, numBytes);
}


//
// Check all allocations in a list for damage by calling check on each.
//
void TAllocation::checkAllocList() const
{
	for (const TAllocation* alloc = this; alloc != 0; alloc = alloc->prevAlloc)
		alloc->check();
}