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;;                                                                 ;;

;;  QUEUE.INC                                                      ;;

;;                                                                 ;;

;;  Buffer queue management for Menuet OS TCP/IP Stack             ;;

;;                                                                 ;;

;;  Version 0.3  29 August 2002                                    ;;

;;                                                                 ;;

;;  Copyright 2002 Mike Hibbett, mikeh@oceanfree.net               ;;

;;                                                                 ;;

;;  See file COPYING for details                                   ;;

;;                                                                 ;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;*******************************************************************

;   Interface

;

;       queueInit   Configures the queues to empty

;       dequeue     Removes a buffer pointer from a queue

;       queue       Inserts a buffer pointer into a queue

;       freeBuff    Adds the buffer pointer to the list of free buffers

;       queueSize   Returns the number of entries in a queue

;

;      The various defines for queue names can be found in stack.inc

;

;*******************************************************************

;***************************************************************************

;   Function

;      freeBuff

;

;   Description

;       Adds a buffer number to the beginning of the free list.

;       buffer number in eax  ( ms word zeroed )

;       all other registers preserved

;        This always works, so no error returned

;***************************************************************************

freeBuff:

    push    ebx

    push    ecx

    mov     ebx, EMPTY_QUEUE

    shl     ebx, 1

    add     ebx, queues

    cli     ; Ensure that another process does not interfer

    movzx   ecx, word [ebx]

    mov     [ebx], ax

    shl     eax, 1

    add     eax, queueList

    mov     [eax], cx

    sti

    pop     ecx

    pop     ebx

    ret

;***************************************************************************

;   Function

;      queueSize

;

;   Description

;       Counts the number of entries in a queue

;       queue number in ebx ( ms word zeroed )

;       Queue size returned in eax

;    This always works, so no error returned

;***************************************************************************

queueSize:

    xor     eax, eax

    shl     ebx, 1

    add     ebx, queues

    movzx   ecx, word [ebx]

    cmp     cx, NO_BUFFER

    je      qs_exit

qs_001:

    inc     eax

    shl     ecx, 1

    add     ecx, queueList

    movzx   ecx, word [ecx]

    cmp     cx, NO_BUFFER

    je      qs_exit

    jmp     qs_001

qs_exit:

    ret

;***************************************************************************

;   Function

;      queue

;

;   Description

;       Adds a buffer number to the *end* of a queue

;       This is quite quick because these queues will be short

;       queue number in eax ( ms word zeroed )

;       buffer number in ebx  ( ms word zeroed )

;       all other registers preserved

;        This always works, so no error returned

;***************************************************************************

queue:

    push    ebx

    shl     ebx, 1

    add     ebx, queueList        ; eax now holds address of queue entry

    mov     [ebx], word NO_BUFFER    ; This buffer will be the last

    cli

    shl     eax, 1

    add     eax, queues            ; eax now holds address of queue

    movzx   ebx, word [eax]

    cmp     bx, NO_BUFFER

    jne     qu_001

    pop     ebx

    ; The list is empty, so add this to the head

    mov     [eax], bx

    jmp     qu_exit

qu_001:

    ; Find the last entry

    shl     ebx, 1

    add     ebx, queueList

    mov     eax, ebx

    movzx   ebx, word [ebx]

    cmp     bx, NO_BUFFER

    jne     qu_001

    mov     ebx, eax

    pop     eax

    mov     [ebx], ax

qu_exit:

    sti

    ret

;***************************************************************************

;   Function

;      dequeue

;

;   Description

;       removes a buffer number from the head of a queue

;       This is fast, as it unlinks the first entry in the list

;       queue number in eax ( ms word zeroed )

;       buffer number returned in eax ( ms word zeroed )

;       all other registers preserved

;

;***************************************************************************

dequeue:

    push    ebx

    shl     eax, 1

    add     eax, queues            ; eax now holds address of queue

    mov     ebx, eax

    cli

    movzx   eax, word [eax]

    cmp     ax, NO_BUFFER

    je      dq_exit

    push    eax

    shl     eax, 1

    add     eax, queueList        ; eax now holds address of queue entry

    mov     ax, [eax]

    mov     [ebx], ax

    pop     eax

dq_exit:

    sti

    pop     ebx

    ret

;***************************************************************************

;   Function

;      queueInit

;

;   Description

;       Initialises the queues to empty, and creates the free queue

;       list.

;

;***************************************************************************

queueInit:

    mov     esi, queues

    mov     ecx, NUMQUEUES

    mov     ax, NO_BUFFER

qi001:

    mov     [esi], ax

    inc     esi

    inc     esi

    loop    qi001

    mov     esi, queues + ( 2 * EMPTY_QUEUE )

    ; Initialise empty queue list

    xor     ax, ax

    mov     [esi], ax

    mov     ecx, NUMQUEUEENTRIES - 1

    mov     esi, queueList

qi002:

    inc     ax

    mov     [esi], ax

    inc     esi

    inc     esi

    loop    qi002

    mov     ax, NO_BUFFER

    mov     [esi], ax

    ret