/*
 *	PROGRAM:	JRD Access Method
 *	MODULE:		btn.cpp
 *	DESCRIPTION:	B-tree management code
 *
 *  The contents of this file are subject to the Initial
 *  Developer's Public License Version 1.0 (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.ibphoenix.com/main.nfs?a=ibphoenix&page=ibp_idpl.
 *
 *  Software distributed under the License is distributed AS IS,
 *  WITHOUT WARRANTY OF ANY KIND, either express or implied.
 *  See the License for the specific language governing rights
 *  and limitations under the License.
 *
 *  The Original Code was created by Arno Brinkman
 *  for the Firebird Open Source RDBMS project.
 *
 *  Copyright (c) 2003 Arno Brinkman and all contributors
 *  signed below.
 *
 *  All Rights Reserved.
 *  Contributor(s): ______________________________________.
 */

#include "firebird.h"			// needed for get_long
#include "memory_routines.h"	// needed for get_long

#include "../jrd/common.h"		// needed for SINT64
#include "../jrd/ods.h"
#include "../jrd/btn.h"

namespace BTreeNode {

using namespace Ods;

USHORT computePrefix(const UCHAR* prevString, USHORT prevLength, const UCHAR* string, USHORT length)
{
/**************************************
 *
 *	c o m p u t e P r e f i x
 *
 **************************************
 *
 * Functional description
 *	Compute and return prefix common
 *  to two strings.
 *
 **************************************/
	USHORT l = MIN(prevLength, length);
	if (!l) {
		return 0;
	}

	const UCHAR* p = prevString;

	while (*p == *string)
	{
		++p;
		++string;
		if (!--l) {
			break;
		}
	}
	return (p - prevString);
}


SLONG findPageInDuplicates(const btree_page* page, UCHAR* pointer,
			SLONG previousNumber, RecordNumber findRecordNumber)
{
/**************************************
 *
 *	f i n d P a g e I n D u p l i c a t e s
 *
 **************************************
 *
 * Functional description
 *	Return the first page number
 *
 **************************************/
	const bool leafPage = (page->btr_level == 0);
	const UCHAR flags = page->btr_header.pag_flags;
	//const UCHAR* endPointer = (UCHAR*)page + page->btr_length;

	IndexNode node, previousNode;
	pointer = readNode(&node, pointer, flags, leafPage);

	// Check if pointer is still valid
	//if (pointer > endPointer) {
	//	BUGCHECK(204);	// msg 204 index inconsistent
	//}

	while (true)
	{
		// loop through duplicates until
		// correct node is found.
		// If this is an end bucket marker then return
		// the previous passed page number.
		if (node.isEndBucket) {
			return previousNumber;
		}
		if (findRecordNumber <= node.recordNumber) {
			// If first record number on page is higher
			// then record number must be at the previous
			// passed page number.
			return previousNumber;
		}
		// Save current page number and fetch next node
		// for comparision.
		previousNumber = node.pageNumber;
		previousNode = node;
		pointer = BTreeNode::readNode(&node, pointer, flags, leafPage);

		// Check if pointer is still valid
		//if (pointer > endPointer) {
		//	BUGCHECK(204);	// msg 204 index inconsistent
		//}

		// We're done if end level marker is reached or this
		// isn't a equal node anymore.
		if ((node.isEndLevel) ||
			(node.length != 0) ||
			(node.prefix != (previousNode.length + previousNode.prefix)))
		{
			return previousNumber;
		}
	}
	// We never reach this point
}


USHORT getJumpNodeSize(const IndexJumpNode* jumpNode, UCHAR flags)
{
/**************************************
 *
 *	g e t J u m p N o d e S i z e
 *
 **************************************
 *
 * Functional description
 *	Return the size needed to store
 *  this node.
 *
 **************************************/
	USHORT result = 0;
	if (flags & btr_large_keys)
	{
		// Size needed for prefix
		USHORT number = jumpNode->prefix;
		if (number & 0xC000) {
			result += 3;
		}
		else if (number & 0xFF80) {
			result += 2;
		}
		else {
			result += 1;
		}

		// Size needed for length
		number = jumpNode->length;
		if (number & 0xC000) {
			result += 3;
		}
		else if (number & 0xFF80) {
			result += 2;
		}
		else {
			result += 1;
		}
	}
	else
	{
		// Size needed for prefix
		result++;
		// Size needed for length
		result++;
	}
	// Size needed for offset
	// NOTE! offset can be unknown when this function is called,
	// therefor we can't use a compression method.
	result += sizeof(USHORT);
	// Size needed for data
	result += jumpNode->length;
	return result;
}


USHORT getNodeSize(const IndexNode* indexNode, UCHAR flags, bool leafNode)
{
/**************************************
 *
 *	g e t N o d e S i z e
 *
 **************************************
 *
 * Functional description
 *	Return the size needed to store
 *  this node.
 *
 **************************************/
	USHORT result = 0;
	if (flags & btr_large_keys)
	{

		// Determine flags
		UCHAR internalFlags = 0;
		if (indexNode->isEndLevel) {
			internalFlags = BTN_END_LEVEL_FLAG;
		}
		else if (indexNode->isEndBucket) {
			internalFlags = BTN_END_BUCKET_FLAG;
		}
		else if (indexNode->length == 0)
		{
			if	(indexNode->prefix == 0) {
				internalFlags = BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG;
			}
			else {
				internalFlags = BTN_ZERO_LENGTH_FLAG;
			}
		}
		else if (indexNode->length == 1) {
			internalFlags = BTN_ONE_LENGTH_FLAG;
		}

		// Store internal flags + 5 bits from number
		SINT64 number = indexNode->recordNumber.getValue();
		if (number < 0) {
			number = 0;
		}
		result++;
		// If this is a END_LEVEL marker then we're done
		if (indexNode->isEndLevel) {
			return result;
		}

		number >>= 5;
		// Get size for storing remaining bits for number
		// 5 bytes should be enough to fit remaining 34 bits of record number
		if (number & QUADCONST(0xFFF0000000)) {
			result += 5;
		}
		else if (number & QUADCONST(0xFFFFE00000)) {
			result += 4;
		}
		else if (number & QUADCONST(0xFFFFFFC000)) {
			result += 3;
		}
		else if (number & QUADCONST(0xFFFFFFFF80)) {
			result += 2;
		}
		else {
			result += 1;
		}

		if (!leafNode)
		{
			// Size needed for page number
			number = indexNode->pageNumber;
			if (number < 0) {
				number = 0;
			}

			if (number & 0xF0000000) {
				result += 5;
			}
			else if (number & 0xFFE00000) {
				result += 4;
			}
			else if (number & 0xFFFFC000) {
				result += 3;
			}
			else if (number & 0xFFFFFF80) {
				result += 2;
			}
			else {
				result += 1;
			}
		}

		if (internalFlags != BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG)
		{
			// Size needed for prefix
			number = indexNode->prefix;
			if (number & 0xFFFFC000) {
				result += 3;
			}
			else if (number & 0xFFFFFF80) {
				result += 2;
			}
			else {
				result += 1;
			}
		}

		if ((internalFlags != BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG) &&
			(internalFlags != BTN_ZERO_LENGTH_FLAG) &&
			(internalFlags != BTN_ONE_LENGTH_FLAG))
		{
			// Size needed for length
			number = indexNode->length;
			if (number & 0xFFFFC000) {
				result += 3;
			}
			else if (number & 0xFFFFFF80) {
				result += 2;
			}
			else {
				result += 1;
			}
		}

		result += indexNode->length;
	}
	else
	{
		// Size needed for prefix
		result++;
		// Size needed for length
		result++;
		// Size needed for page number
		result += sizeof(SLONG);

		result += indexNode->length;

		if ((flags & btr_all_record_number) &&
			(!leafNode ||
			(leafNode && indexNode->isEndBucket && (indexNode->length == 0))))
		{
			// Size needed for record number
			result += sizeof(SLONG);
		}
	}

	return result;
}


UCHAR* getPointerFirstNode(btree_page* page, IndexJumpInfo* jumpInfo)
{
/**************************************
 *
 *	g e t P o i n t e r F i r s t N o d e
 *
 **************************************
 *
 * Functional description
 *	Return the pointer to first data node
 *  in the bucket. When a jumpInfo is
 *  given, then pointer of first jump
 *  node is returned.
 *
 **************************************/
	if (page->btr_header.pag_flags & btr_jump_info)
	{
		if (jumpInfo)
		{
			UCHAR* pointer = reinterpret_cast<UCHAR*>(page->btr_nodes);
			return readJumpInfo(jumpInfo, pointer);
		}

		IndexJumpInfo jumpInformation;
		UCHAR* pointer = reinterpret_cast<UCHAR*>(page->btr_nodes);
		readJumpInfo(&jumpInformation, pointer);

		return reinterpret_cast<UCHAR*>(page) + jumpInformation.firstNodeOffset;
	}

	return reinterpret_cast<UCHAR*>(page->btr_nodes);
}


bool keyEquality(USHORT length, const UCHAR* data, const IndexNode* indexNode)
{
/**************************************
 *
 *	k e y E q u a l i t y
 *
 **************************************
 *
 * Functional description
 *	Check a B-tree node against a key for equality.
 *
 **************************************/

	if (length != indexNode->length + indexNode->prefix) {
		return false;
	}

	USHORT len = indexNode->length;
	if (!len) {
		return true;
	}

	return !memcmp(indexNode->data, data + indexNode->prefix, len);
}


UCHAR* nextNode(IndexNode* node, UCHAR* pointer, UCHAR flags, btree_exp** expanded_node)
{
/**************************************
 *
 *	n e x t N o d e
 *
 **************************************
 *
 * Functional description
 *	Find the next node on both the index page
 *	and its associated expanded buffer.
 *
 **************************************/

	pointer = readNode(node, pointer, flags, true);

	if (*expanded_node)
	{
		*expanded_node = (btree_exp*) ((UCHAR*) (*expanded_node)->btx_data +
			node->prefix + node->length);
	}

	return pointer;
}


UCHAR* readJumpInfo(IndexJumpInfo* jumpInfo, UCHAR* pagePointer)
{
/**************************************
 *
 *	r e a d J u m p I n f o
 *
 **************************************
 *
 * Functional description
 *	Read jump information from the page
 *  by the given pagePointer and the
 *  return the remaining position after
 *  the read.
 *
 **************************************/
	jumpInfo->firstNodeOffset = get_short(pagePointer);
	pagePointer += sizeof(USHORT);
	jumpInfo->jumpAreaSize = get_short(pagePointer);
	pagePointer += sizeof(USHORT);
	jumpInfo->jumpers = (USHORT)(*pagePointer++);
	return pagePointer;
}


UCHAR* readJumpNode(IndexJumpNode* jumpNode, UCHAR* pagePointer, UCHAR flags)
{
/**************************************
 *
 *	r e a d J u m p N o d e
 *
 **************************************
 *
 * Functional description
 *	Read a jump node from the page by the
 *  given pagePointer and the return the
 *  remaining position after the read.
 *
 **************************************/
	jumpNode->nodePointer = pagePointer;
	if (flags & btr_large_keys)
	{
		// Get prefix
		UCHAR tmp = *pagePointer++;
		jumpNode->prefix = (tmp & 0x7F);
		if (tmp & 0x80)
		{
			tmp = *pagePointer++;
			jumpNode->prefix |= (tmp & 0x7F) << 7; // We get 14 bits at this point
		}
		// Get length
		tmp = *pagePointer++;
		jumpNode->length = (tmp & 0x7F);
		if (tmp & 0x80)
		{
			tmp = *pagePointer++;
			jumpNode->length |= (tmp & 0x7F) << 7; // We get 14 bits at this point
		}
	}
	else
	{
		jumpNode->prefix = (USHORT)(*pagePointer++);
		jumpNode->length = (USHORT)(*pagePointer++);
	}
	jumpNode->offset = get_short(pagePointer);
	pagePointer += sizeof(USHORT);
	jumpNode->data = pagePointer;
	pagePointer += jumpNode->length;
	return pagePointer;
}


UCHAR* writeJumpInfo(btree_page* page, const IndexJumpInfo* jumpInfo)
{
/**************************************
 *
 *	w r i t e J u m p I n f o
 *
 **************************************
 *
 * Functional description
 *	Write jump information to the page by the
 *  given pointer.
 *
 **************************************/
	UCHAR* pointer = reinterpret_cast<UCHAR*>(page->btr_nodes);
	put_short(pointer, jumpInfo->firstNodeOffset);
	pointer += sizeof(USHORT);
	put_short(pointer, jumpInfo->jumpAreaSize);
	pointer += sizeof(USHORT);
	*pointer++ = (UCHAR) jumpInfo->jumpers;
	return pointer;
}


UCHAR* writeJumpNode(IndexJumpNode* jumpNode, UCHAR* pagePointer, UCHAR flags)
{
/**************************************
 *
 *	w r i t e J u m p N o d e
 *
 **************************************
 *
 * Functional description
 *	Write jump information to the page by the
 *  given pointer.
 *
 **************************************/
	jumpNode->nodePointer = pagePointer;
	if (flags & btr_large_keys)
	{
		// Write prefix, maximum 14 bits
		USHORT number = jumpNode->prefix;
		UCHAR tmp = (number & 0x7F);
		number >>= 7;
		if (number > 0) {
			tmp |= 0x80;
		}
		*pagePointer++ = tmp;
		if (tmp & 0x80)
		{
			tmp = (number & 0x7F);
			*pagePointer++ = tmp;
		}

		// Write length, maximum 14 bits
		number = jumpNode->length;
		tmp = (number & 0x7F);
		number >>= 7;
		if (number > 0) {
			tmp |= 0x80;
		}
		*pagePointer++ = tmp;
		if (tmp & 0x80)
		{
			tmp = (number & 0x7F);
			*pagePointer++ = tmp;
		}
	}
	else
	{
		*pagePointer++ = (UCHAR) jumpNode->prefix;
		*pagePointer++ = (UCHAR) jumpNode->length;
	}
	put_short(pagePointer, jumpNode->offset);
	pagePointer += sizeof(USHORT);
	memmove(pagePointer, jumpNode->data, jumpNode->length);
	pagePointer += jumpNode->length;
	return pagePointer;
}


UCHAR* writeNode(IndexNode* indexNode, UCHAR* pagePointer, UCHAR flags, bool leafNode, bool withData)
{
/**************************************
 *
 *	w r i t e N o d e
 *
 **************************************
 *
 * Functional description
 *	Write a leaf/page node to the page by the
 *  given page_pointer.
 *
 **************************************/
	indexNode->nodePointer = pagePointer;
	if (flags & btr_large_keys)
	{

		// AB: 2004-02-22
		// To allow as much as compression possible we
		// store numbers per 7 bit and the 8-th bit tell us
		// if we need to go on reading or we're done.
		// Also for duplicate node entries (length and prefix
		// are zero) we don't store the length and prefix
		// information. This will save at least 2 bytes per node.

		if (!withData)
		{
			// First move data so we can't override it.
			// For older structure node was always the same, but length
			// from new structure depends on the values.
			const USHORT offset = getNodeSize(indexNode, flags, leafNode) - indexNode->length;
			pagePointer += offset; // set pointer to right position
			memmove(pagePointer, indexNode->data, indexNode->length);
			pagePointer -= offset; // restore pointer to original position
		}

		// Internal flags
		UCHAR internalFlags = 0;
		if (indexNode->isEndLevel) {
			internalFlags = BTN_END_LEVEL_FLAG;
		}
		else if (indexNode->isEndBucket) {
			internalFlags = BTN_END_BUCKET_FLAG;
		}
		else if (indexNode->length == 0)
		{
			if (indexNode->prefix == 0) {
				internalFlags = BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG;
			}
			else {
				internalFlags = BTN_ZERO_LENGTH_FLAG;
			}
		}
		else if (indexNode->length == 1) {
			internalFlags = BTN_ONE_LENGTH_FLAG;
		}

		SINT64 number = indexNode->recordNumber.getValue();
		if (number < 0) {
			number = 0;
		}
		// Store internal flags + 6 bits from number
		UCHAR tmp = internalFlags;
		*pagePointer++ = ((tmp << 5) | (number & 0x1F));

		if (indexNode->isEndLevel) {
			return pagePointer;
		}

		// Store remaining bits from number
		number >>= 5;
		tmp = (number & 0x7F);
		number >>= 7; //12
		if (number == 0) {
			*pagePointer++ = tmp;
		}
		else
		{
			*pagePointer++ = tmp | 0x80;
			tmp = (number & 0x7F);
			number >>= 7; //19
			if (number == 0) {
				*pagePointer++ = tmp;
			}
			else
			{
				*pagePointer++ = tmp | 0x80;
				tmp = (number & 0x7F);
				number >>= 7; //26
				if (number == 0) {
					*pagePointer++ = tmp;
				}
				else
				{
					*pagePointer++ = tmp | 0x80;
					tmp = (number & 0x7F);
					number >>= 7; //33
					if (number == 0) {
						*pagePointer++ = tmp;
					}
					else
					{
						*pagePointer++ = tmp | 0x80;
						tmp = (number & 0x7F);
						number >>= 7; //40
						if (number == 0) {
							*pagePointer++ = tmp;
						}
/*
			Enable this if you need more bits in record number
						else
						{
							*pagePointer++ = tmp | 0x80;
							tmp = (number & 0x7F);
							number >>= 7; //47
							if (number == 0) {
								*pagePointer++ = tmp;
							}
							else
							{
								*pagePointer++ = tmp | 0x80;
								tmp = (number & 0x7F);
								number >>= 7; //54
								if (number == 0) {
									*pagePointer++ = tmp;
								}
								else
								{
									*pagePointer++ = tmp | 0x80;
									tmp = (number & 0x7F);
									number >>= 7; //61
									if (number == 0) {
										*pagePointer++ = tmp;
									}
									else {
										// ....
									}
								}
							}
						}
*/
					}
				}
			}
		}

		if (!leafNode)
		{
			// Store page number for non-leaf pages
			number = indexNode->pageNumber;
			if (number < 0) {
				number = 0;
			}
			tmp = (number & 0x7F);
			number >>= 7;
			if (number > 0) {
				tmp |= 0x80;
			}
			*pagePointer++ = tmp;
			if (number > 0)
			{
				tmp = (number & 0x7F);
				number >>= 7; //14
				if (number > 0) {
					tmp |= 0x80;
				}
				*pagePointer++ = tmp;
				if (number > 0)
				{
					tmp = (number & 0x7F);
					number >>= 7; //21
					if (number > 0) {
						tmp |= 0x80;
					}
					*pagePointer++ = tmp;
					if (number > 0)
					{
						tmp = (number & 0x7F);
						number >>= 7; //28
						if (number > 0) {
							tmp |= 0x80;
						}
						*pagePointer++ = tmp;
						if (number > 0)
						{
							tmp = (number & 0x0F);
							number >>= 7; //35
							*pagePointer++ = tmp;
						}
					}
				}
			}
		}

		if (internalFlags != BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG)
		{
			// Write prefix, maximum 14 bits
			number = indexNode->prefix;
			tmp = (number & 0x7F);
			number >>= 7;
			if (number > 0) {
				tmp |= 0x80;
			}
			*pagePointer++ = tmp;
			if (number > 0)
			{
				tmp = (number & 0x7F);
				*pagePointer++ = tmp;
			}
		}

		if ((internalFlags != BTN_ZERO_PREFIX_ZERO_LENGTH_FLAG) &&
			(internalFlags != BTN_ZERO_LENGTH_FLAG) &&
			(internalFlags != BTN_ONE_LENGTH_FLAG))
		{
			// Write length, maximum 14 bits
			number = indexNode->length;
			tmp = (number & 0x7F);
			number >>= 7;
			if (number > 0) {
				tmp |= 0x80;
			}
			*pagePointer++ = tmp;
			if (number > 0)
			{
				tmp = (number & 0x7F);
				*pagePointer++ = tmp;
			}
		}

		// Store data
		if (withData) {
			memcpy(pagePointer, indexNode->data, indexNode->length);
		}
		pagePointer += indexNode->length;
	}
	else
	{
		// Write prefix
		*pagePointer++ = (UCHAR)indexNode->prefix;
		// Write length
		*pagePointer++ = (UCHAR)indexNode->length;

		if (indexNode->isEndLevel) {
			put_long(pagePointer, END_LEVEL);
		}
		else if (indexNode->isEndBucket) {
			put_long(pagePointer, END_BUCKET);
		}
		else
		{
			if (leafNode) {
				// Write record number
				put_long(pagePointer, indexNode->recordNumber.getValue());
			}
			else {
				// Write page number
				put_long(pagePointer, indexNode->pageNumber);
			}
		}
		pagePointer += sizeof(SLONG);

		if (withData)
		{
			USHORT size = indexNode->length;
			const UCHAR* ptr = indexNode->data;
			while (size)
			{
				*pagePointer++ = *ptr++;
				size--;
			}
		}
		else {
			pagePointer += indexNode->length;
		}

		if ((flags & btr_all_record_number) &&
			(!leafNode ||
			(leafNode && indexNode->isEndBucket && (indexNode->length == 0))))
		{
			// Write record number
			put_long(pagePointer, indexNode->recordNumber.getValue());
			pagePointer += sizeof(SLONG);
		}
	}

	return pagePointer;
}


void setEndBucket(IndexNode* indexNode) //, bool leafNode)
{
/**************************************
 *
 *	s e t E n d B u c k e t
 *
 **************************************
 *
 * Functional description
 *
 **************************************/
	indexNode->isEndBucket = true;
	indexNode->isEndLevel = false;
}


void setEndLevel(IndexNode* indexNode) //, bool leafNode)
{
/**************************************
 *
 *	s e t E n d L e v e l
 *
 **************************************
 *
 * Functional description
 *
 **************************************/
	indexNode->isEndBucket = false;
	indexNode->isEndLevel = true;
	indexNode->prefix = 0;
	indexNode->length = 0;
	indexNode->pageNumber = 0;
	indexNode->recordNumber.setValue(0);
}


void setNode(IndexNode* indexNode, USHORT prefix, USHORT length,
			RecordNumber recordNumber, SLONG pageNumber,
			bool isEndBucket, bool isEndLevel)
{
/**************************************
 *
 *	s e t N o d e
 *
 **************************************
 *
 * Functional description
 *
 **************************************/
	indexNode->isEndBucket = isEndBucket;
	indexNode->isEndLevel = isEndLevel;
	indexNode->prefix = prefix;
	indexNode->length = length;
	indexNode->recordNumber = recordNumber;
	indexNode->pageNumber = pageNumber;
}


} // namespace BTreeNode