/*
 *	PROGRAM:	Dynamic SQL runtime support
 *	MODULE:		hsh.cpp
 *	DESCRIPTION:	Hash table and symbol manager
 *
 * The contents of this file are subject to the Interbase 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.Inprise.com/IPL.html
 *
 * Software distributed under the License is distributed on an
 * "AS IS" basis, 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 Inprise Corporation
 * and its predecessors. Portions created by Inprise Corporation are
 * Copyright (C) Inprise Corporation.
 *
 * All Rights Reserved.
 * Contributor(s): ______________________________________.
 */

#include "firebird.h"
#include <string.h>
#include "../dsql/dsql.h"
#include "../jrd/ibase.h"
#include "../jrd/gds_proto.h"
#include "../dsql/errd_proto.h"
#include "../dsql/hsh_proto.h"
#include "../dsql/parse_proto.h"
#include "../common/classes/init.h"

using namespace Jrd;

static USHORT hash(const SCHAR*, USHORT);
static bool remove_symbol(dsql_sym**, dsql_sym*);
static bool scompare(const TEXT*, USHORT, const TEXT*, const USHORT);

namespace
{
	const int HASH_SIZE = 1021;

	class HashTable : public Firebird::Array<dsql_sym*>
	{
	public:
		explicit HashTable(MemoryPool& pool)
			: Firebird::Array<dsql_sym*>(pool)
		{
			grow(HASH_SIZE);
		}

		static void init()
		{
			LEX_dsql_init(*getDefaultMemoryPool());
		}
	};

	Firebird::InitInstance<HashTable> hash_table;
	Firebird::InitMutex<HashTable> hash_startup;
	Firebird::GlobalPtr<Firebird::RWLock> hash_sync;
}

#ifdef DEV_BUILD

#include <stdio.h>

/**

 	HSHD_debug

    @brief	Print out the hash table for debugging.



 **/
void HSHD_debug()
{
	Firebird::ReadLockGuard guard(hash_sync);

	// dump each hash table entry
	for (SSHORT h = 0; h < HASH_SIZE; h++)
	{
		for (dsql_sym* collision = hash_table()[h]; collision; collision = collision->sym_collision)
		{
			// check any homonyms first
			fprintf(stderr, "Symbol type %d: %s %p\n",
					collision->sym_type, collision->sym_string, collision->sym_dbb);
			for (dsql_sym* homptr = collision->sym_homonym; homptr; homptr = homptr->sym_homonym)
			{
				fprintf(stderr, "Homonym Symbol type %d: %s %p\n",
						homptr->sym_type, homptr->sym_string, homptr->sym_dbb);
			}
		}
	}
}
#endif


/**

 	HSHD_finish

    @brief	Remove symbols used by a particular database.
 	Don't bother to release them since their pools
 	will be released.


    @param database

 **/
void HSHD_finish(const void* database)
{
	Firebird::WriteLockGuard guard(hash_sync);

	// check each hash table entry
	for (SSHORT h = 0; h < HASH_SIZE; h++)
	{
		for (dsql_sym** collision = &hash_table()[h]; *collision;)
		{
			// check any homonyms first
			dsql_sym* chain = *collision;
			for (dsql_sym** homptr = &chain->sym_homonym; *homptr;)
			{
				dsql_sym* symbol = *homptr;
				if (symbol->sym_dbb == database)
				{
					*homptr = symbol->sym_homonym;
					symbol = symbol->sym_homonym;
				}
				else
				{
					homptr = &symbol->sym_homonym;
				}
			}

			// now, see if the root entry has to go
			if (chain->sym_dbb == database)
			{
				if (chain->sym_homonym)
				{
					chain->sym_homonym->sym_collision = chain->sym_collision;
					*collision = chain->sym_homonym;
				}
				else
				{
					*collision = chain->sym_collision;
				}
				chain = *collision;
			}
			else
			{
				collision = &chain->sym_collision;
			}
		}
	}
}


/**

 	HSHD_insert

    @brief	Insert a symbol into the hash table.


    @param symbol

 **/
void HSHD_insert(dsql_sym* symbol)
{
	const USHORT h = hash(symbol->sym_string, symbol->sym_length);
	const void* database = symbol->sym_dbb;

	fb_assert(symbol->sym_type >= SYM_statement && symbol->sym_type <= SYM_eof);

	Firebird::WriteLockGuard guard(hash_sync);

	for (dsql_sym* old = hash_table()[h]; old; old = old->sym_collision)
	{
		if ((!database || (database == old->sym_dbb)) &&
			scompare(symbol->sym_string, symbol->sym_length, old->sym_string, old->sym_length))
		{
			symbol->sym_homonym = old->sym_homonym;
			old->sym_homonym = symbol;
			return;
		}
	}

	symbol->sym_collision = hash_table()[h];
	hash_table()[h] = symbol;
}


/**

 	HSHD_lookup

    @brief	Perform a string lookup against hash table.
 	Make sure to only return a symbol of the desired type.


    @param database
    @param string
    @param length
    @param type
    @param parser_version

 **/
dsql_sym* HSHD_lookup(const void* database,
					  const TEXT* string,
					  SSHORT length,
					  SYM_TYPE type,
					  USHORT parser_version)
{
	hash_startup.init();

	const USHORT h = hash(string, length);

	Firebird::ReadLockGuard guard(hash_sync);

	for (dsql_sym* symbol = hash_table()[h]; symbol; symbol = symbol->sym_collision)
	{
		if ((database == symbol->sym_dbb) &&
			scompare(string, length, symbol->sym_string, symbol->sym_length))
		{
			// Search for a symbol of the proper type
			while (symbol && symbol->sym_type != type)
			{
				symbol = symbol->sym_homonym;
			}

			// If the symbol found was not part of the list of keywords for the
			// client connecting, then assume nothing was found

			if (symbol)
			{
				if (parser_version < symbol->sym_version && type == SYM_keyword)
				{
					return NULL;
				}
			}
			return symbol;
		}
	}

	return NULL;
}


/**

 	HSHD_remove

    @brief	Remove a symbol from the hash table.


    @param symbol

 **/
void HSHD_remove(dsql_sym* symbol)
{
	Firebird::WriteLockGuard guard(hash_sync);

	const USHORT h = hash(symbol->sym_string, symbol->sym_length);

	for (dsql_sym** collision = &hash_table()[h]; *collision; collision = &(*collision)->sym_collision)
	{
		if (remove_symbol(collision, symbol))
		{
			return;
		}
	}

	ERRD_error("HSHD_remove failed");
}


/**

 HSHD_set_flag

    @brief      Set a flag in all similar objects in a chain.
       This is used primarily to mark relations
       as deleted.   The object must have the same name and
       type, but not the same database, and must belong to
       some database.   Later access to such an object by
       another user or thread should result in that object's
       being refreshed.   Note that even if the name and ID
	   both match, it may still not represent an exact match.
	   This is because there's no way at present for DSQL to tell
	   if two databases as represented in DSQL are attachments to
	   the same physical database.


    @param database
    @param string
    @param length
    @param type
    @param flag

 **/
void HSHD_set_flag(const void* database,
				   const TEXT* string,
				   SSHORT length,
				   SYM_TYPE type,
				   SSHORT flag)
{
	// as of now, there's no work to do if there is no database or if
	// the type is not a relation

	if (!database || type != SYM_relation)
		return;

	const USHORT h = hash(string, length);

	Firebird::WriteLockGuard guard(hash_sync);

	for (dsql_sym* symbol = hash_table()[h]; symbol; symbol = symbol->sym_collision)
	{
		if (symbol->sym_dbb && (database != symbol->sym_dbb) &&
			scompare(string, length, symbol->sym_string, symbol->sym_length))
		{
			// the symbol name matches and it's from a different database

			for (dsql_sym* homonym = symbol; homonym; homonym = homonym->sym_homonym)
			{
				if (homonym->sym_type == type)
				{
					// the homonym is of the correct type

					// the next check is for the same relation ID,
					// which indicates that it MAY be the same relation
					fb_assert(type == SYM_relation);

					dsql_rel* sym_rel = (dsql_rel*) homonym->sym_object;
					sym_rel->rel_flags |= flag;
				}
			}
		}
	}
}


/**

 	hash

    @brief	Returns the hash function of a string.


    @param
    @param

 **/
static USHORT hash(const SCHAR* string, USHORT length)
{
	ULONG value = 0;

	while (length--)
	{
		UCHAR c = *string++;
		value = (value << 1) + c;
	}

	return value % HASH_SIZE;
}


/**

 	remove_symbol

    @brief	Given the address of a collision,
 	remove a symbol from the collision
 	and homonym linked lists.


    @param collision
    @param symbol

 **/
static bool remove_symbol(dsql_sym** collision, dsql_sym* symbol)
{
	if (symbol == *collision)
	{
	    dsql_sym* homonym = symbol->sym_homonym;
		if (homonym != NULL)
		{
			homonym->sym_collision = symbol->sym_collision;
			*collision = homonym;
		}
		else
		{
			*collision = symbol->sym_collision;
		}

		return true;
	}

	for (dsql_sym** ptr = &(*collision)->sym_homonym; *ptr; ptr = &(*ptr)->sym_homonym)
	{
		if (symbol == *ptr)
		{
			*ptr = symbol->sym_homonym;
			return true;
		}
	}

	return false;
}


/**

 	scompare

    @brief	Compare two symbolic strings
 	The character set for these strings is either ASCII or
 	Unicode in UTF format.
 	Symbols are case-significant - so no uppercase operation
 	is performed.


    @param string1
    @param length1
    @param string2
    @param length2

 **/
static bool scompare(const TEXT* string1,
					 USHORT length1,
					 const TEXT* string2,
					 const USHORT length2)
{

	if (length1 != length2)
		return false;

	while (length1--)
	{
		if ((*string1++) != (*string2++))
			return false;
	}

	return true;
}