-- File DBSegmentPrivate.mesa
-- Last edited by:
  -- MBrown on December 16, 1982 3:08 pm
  -- Cattell on July 16, 1982 10:42 am

DIRECTORY
  DBCommon USING [DBPage, NullDBPage, softwareCompatibilityVersion],
  DBStoragePagetags USING[Free, AMap],
  DBStorageTID USING[TID];

DBSegmentPrivate: DEFINITIONS = BEGIN
  DBPage: TYPE = DBCommon.DBPage;
  NullDBPage: DBPage = DBCommon.NullDBPage;
  TID: TYPE = DBStorageTID.TID;

  StrBody: TYPE = MACHINE DEPENDENT RECORD [
    length: CARDINAL _ 0, maxLength: CARDINAL _ StrMaxLength,
    text: PACKED ARRAY [0..StrMaxLength) OF CHAR _ TRASH];
  StrMaxLength: CARDINAL = 64;
    -- If I could write StringBody[StrMaxLength], or even TEXT[StrMaxLength], I would!

  -- Definition of persistent segment-related objects

  -- The record types below are necessarily MACHINE DEPENDENT since their
  --representation must not change with different versions of the compiler (because
  --instances of these types will persist in the database).


  SegmentHeadPage: TYPE = MACHINE DEPENDENT RECORD[
    tag: [0..377B] _ DBStoragePagetags.AMap,
      -- Page type, on all pages in the system.
    unused: [0..377B] _ 0,
      -- On tuple pages, the count of allocated slots on the page.
    softwareCompatibilityVersion: CARDINAL _ DBCommon.softwareCompatibilityVersion,
      -- Version of DB software that initially produced this segment.
    seal: LONG CARDINAL _ Seal,
    name: StrBody _ [],
    segmentID: DBPage,
      -- Address of this page in DB.
    allocator: RECORD [
      firstPageInBlock: DBPage,
        -- Pointer to first in a block of consecutive free pages in this segment, or NullDBPage
        --to indicate no block.
      nPagesInBlock: CARDINAL,
        -- Count of number of pages in block.
      pagesPerExtent: CARDINAL,
        -- Number of pages to allocate from end of file when page allocator is empty.
      freeList: DBPage _ NullDBPage
        --  Pointer to first in a list of free pages in this segment, or NullDBPage to
        --indicate no list.  Format of FreeListPages is defined below.
      ],
    index1: TID _ TRASH,
    index2: TID _ TRASH
    ];

  Seal: LONG CARDINAL = 16177213452B; --exp(gamma)
  
  -- Format of a page on a segment free list.
  FreeListPage: TYPE = MACHINE DEPENDENT RECORD[
    tag: [0..377B] _ DBStoragePagetags.Free,
      -- Page type (DBStoragePagetags).
    unused: [0..377B] _ 0,
    next: DBCommon.DBPage,
      -- Pointer to next in a list of free pages in this segment, or NullDBPage.
    nPagesInBlock: CARDINAL _ 1
      -- Number of consecutive free pages that this page represents.
  ];--FreeListPage


END.--DBSegmentPrivate


CHANGE LOG

Created by MBrown on June 2, 1980  9:37 AM
-- By splitting defs out of SegmentImpl.mesa

Changed by MBrown on June 10, 1980  9:02 PM
-- TID is now from DBStorageTID.

Changed by MBrown on August 22, 1980  11:35 AM
-- Made NCachePages = 512.

Changed by MBrown on December 8, 1980  1:57 PM
-- Changed AMapPage to allow segment page allocator to represent a block of pages (expected to
--be the end of a file that we're extending), and extended free list format to allow blocks
--to be represented there, too.

Changed by MBrown on February 26, 1981  9:35 PM
-- Use DBFile.File, not UserPineDefs.File.  InlineDefs -> Inline.

Changed by Cattell on May 24, 1982 9:48 am
-- Make FileHandle into REF.  Default value of FileHandle is NIL in InternalQuantumObject.