⟦a0501b680⟧

E3 Source Code



-- Copyright 1988, 1992 Verdix Corporation

------------------------------------------------------------------------------
-- User interface to the mailbox data structures and subprograms
--
-- Provides backward compatibility with earlier releases of VADS.
--
-- The interface to ALL the low kernel services is now provided in
-- ada_krn_i.a. Types used by these services is defined in ada_krn_defs.a.
--
-- This package simply layers upon the mailbox data structures and
-- subprograms found in ada_krn_defs.a and ada_krn_i.a.
--
-- Differences from earlier releases:
--  [1] The intr_flag and intr_status are only applicable to the
--      VADS_MICRO RTS.
--  [2] For the delete() service, if the conditional_delete_flag is TRUE,
--      the mailbox might not be deleted even though no tasks are
--      waiting to read. This caveat isn't applicable to the VADS_MICRO RTS.
--  [3] For mailbox write, only the DO_NOT_WAIT option is supported.
--      Earlier releases also supported timed and WAIT_FOREVER
--\x09\x09write options.
------------------------------------------------------------------------------
with System;
--with Ada_Krn_Defs;
--with Ada_Krn_I;
package V_I_Mbox is

    pragma Suppress (All_Checks);
    pragma Suppress (Exception_Tables);
    pragma Not_Elaborated;

    type Intr_Status_T is new Ada_Krn_Defs.Intr_Status_T;
--    DISABLE_INTR_STATUS\x09: constant intr_status_t :=
--\x09\x09intr_status_t(ada_krn_defs.DISABLE_INTR_STATUS);
    function Disable_Intr_Status return Intr_Status_T;
    pragma Inline_Only (Disable_Intr_Status);

    -- Predefined wait_time values
    Wait_Forever : constant Duration := -1.0;
    Do_Not_Wait : constant Duration := 0.0;

    --------------------------------------------------------------------------
    -- "read_write" function parameter types
    --------------------------------------------------------------------------
    type Access_T is (Read_A, Write_A);
    for Access_T use (Read_A => 1, Write_A => 2);
    for Access_T'Size use Integer'Size;

    --------------------------------------------------------------------------
    -- The following types are used to define the mailbox data structure
    --------------------------------------------------------------------------

    type Mbox_Record_T is new Ada_Krn_Defs.Mailbox_T;
    type A_Mbox_T is new Ada_Krn_Defs.A_Mailbox_T;

    --------------------------------------------------------------------------
    -- Create a new mailbox. A mailbox consists of n fixed length slots.
    -- The slot_len parameter specifies the length in units of
    -- system.storage_unit (normally bytes).
    --
    -- Normally, a mailbox's critical region is protected by a
    -- semaphore.
    --
    -- However, if the intr_flag is TRUE, then,
    -- its critical region is protected by disabling interrupts. This
    -- allows the mailbox to be accessed from an ISR.
    --
    -- STORAGE_ERROR exception is raised if not enough memory for mailbox.
    --
    -- Use of the intr_flag and intr_status fields is only applicable
    -- to the VADS_MICRO.
    --------------------------------------------------------------------------
    function Create (Slots_Cnt : Positive;
                     Slot_Len : Natural;
                     Intr_Flag : Boolean := False;
                     Intr_Status : Intr_Status_T := Disable_Intr_Status)
                    return A_Mbox_T;
    pragma Inline_Only (Create);

    --------------------------------------------------------------------------
    -- Deletes a previously created mailbox. Returns TRUE if mailbox
    -- was successfully deleted.
    --
    -- If conditional_delete_flag parameter is TRUE, then, mailbox
    -- is not deleted if any of the following are TRUE:
    --  - task is waiting to read/write
    --  - unread messages
    -- Otherwise, mailbox is always deleted, and tasks waiting to read/write
    -- are resumed.
    --
    -- Note: if the conditional_delete_flag is TRUE, the mailbox might not
    -- be deleted even though no tasks are waiting to read. This caveat isn't
    -- applicable to the VADS_MICRO.
    --------------------------------------------------------------------------
    function Delete (Mbox : A_Mbox_T; Conditional_Delete_Flag : Boolean)
                    return Boolean;
    pragma Inline_Only (Delete);

    --------------------------------------------------------------------------
    -- Reads/writes a message from/to a mailbox. The access_type parameter
    -- indicates the type of access. Returns TRUE if message was
    -- successfully read/written.
    --
    -- If no message is available for reading, or if no slot is available
    -- for writing, then, returns according to the wait_time parameter:
    --  < 0.0           - returns when message was successfully read/written.
    --                    This may necessitate suspension of current task
    --                    until another task does mailbox write/read.
    --  = 0.0           - returns FALSE immediately if unable to do
    --                    mailbox operation
    --  > 0.0           - if the mailbox operation cannot be completed
    --                    within "wait_time" amount of time, returns FALSE.
    --
    -- Note: returns FALSE for any wait_time, if mailbox was deleted.
    --
    -- For mailbox write, only the DO_NOT_WAIT option is supported.
    -- In earlier releases, also supported timed and WAIT_FOREVER
    -- write options.
    --------------------------------------------------------------------------
    function Read_Write (Access_Type : Access_T;
                         Mbox : A_Mbox_T;
                         Msg_Addr : System.Address;
                         Msg_Len : Natural;
                         Wait_Time : Duration) return Boolean;
    pragma Inline_Only (Read_Write);

    --------------------------------------------------------------------------
    -- Returns number of unread messages in mailbox
    --------------------------------------------------------------------------
    function Get_Message_Count (Mbox : A_Mbox_T) return Natural;
    pragma Inline_Only (Get_Message_Count);
end V_I_Mbox;
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⟦a0501b680⟧ Ada Source

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E3 Source Code

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