/*++

Copyright (c) 1997  Microsoft Corporation

Module Name:    ThreadPool.c

Abstract:

    Work queue management functions.

--*/

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <httpext.h>
#include "threadpool.h"


//
// Structure to create simple linked list
//

typedef struct {
	EXTENSION_CONTROL_BLOCK *pECB;	    // Data for list entry
	DWORD dwNextEntry;			        // Pointer to next entry
} ECB_QUEUE_ENTRY;


//
// Array that is a simple linked list
//

ECB_QUEUE_ENTRY ECBqueue[WORK_QUEUE_ENTRIES];


//
// Index of next ECBqueue entry to use, and last Entry in use.
//

DWORD dwCurrentEntry, dwLastEntry;


//
// Flag to indicate that there are no other entries in the ECBqueue
//

BOOL fQueueEmpty;


BOOL 
InitThreadPool(
    void
)
/*++
Purpose:

    Initialize our thread pool.

--*/
{
	DWORD i;
	DWORD dwThreadID;

    //
    // Create Semaphore in nonsignaled state
    //

    if ( (hWorkSem = CreateSemaphore( NULL, 0, 0x7fffffff, NULL )) == NULL ) {
		return FALSE;
    }

	InitializeCriticalSection( &csQueueLock );

	fQueueEmpty = TRUE;

    //
	// Create Pool Threads
    //

	for ( i = 0; i < POOL_THREADS; i++ ) {
		if ( CreateThread( 
                NULL, 
                0, 
                WorkerFunction, 
                (LPVOID) i, 
                0, 
                &dwThreadID
                ) == NULL ) {
			return FALSE;
        }
	}

    //
	// Clear work queue
    //

	ZeroMemory( ECBqueue, WORK_QUEUE_ENTRIES * sizeof (ECB_QUEUE_ENTRY) );


	return TRUE;
}


BOOL 
AddWorkQueueEntry(
    IN EXTENSION_CONTROL_BLOCK * pECB
)
/*++

Purpose:

    Add single work unit to the queue

Arguments:

    pECB - pointer to the extension control block

Returns:
    
    TRUE if the unit was successfully queued
    FALSE if queue is full

--*/
{
	DWORD i;

	for ( i = 0; i < WORK_QUEUE_ENTRIES; i++ ) {
		if ( ECBqueue[i].pECB == NULL ) {
			if ( fQueueEmpty ) {
				dwCurrentEntry = i;
				fQueueEmpty = FALSE;
            } else {
				ECBqueue[dwLastEntry].dwNextEntry = i;
            }

			ECBqueue[i].pECB = pECB;
			dwLastEntry = i;

			return TRUE;
		}
	}

	// If no NULL queue entry found, indicate failure
	return FALSE;
}

BOOL 
GetWorkQueueEntry(
    OUT EXTENSION_CONTROL_BLOCK ** ppECB
)
/*++

Purpose:

Arguments:

Returns:

--*/
{
    if ( (*ppECB = ECBqueue[dwCurrentEntry].pECB) == NULL ) {
		return FALSE;
    } else {
		ECBqueue[dwCurrentEntry].pECB = NULL;
		if (dwCurrentEntry == dwLastEntry)	// If this is only pending item

			fQueueEmpty = TRUE;
		else
			dwCurrentEntry = ECBqueue[dwCurrentEntry].dwNextEntry;
	}

	return TRUE;
}