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1660 lines
23 KiB
1660 lines
23 KiB
3 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<HTML
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><HEAD
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><TITLE
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>Harddisk Images based on redologs</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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REL="HOME"
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TITLE="Bochs Developers Guide"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="About the code"
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HREF="about-the-code.html"><LINK
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REL="PREVIOUS"
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TITLE="Sound Blaster 16 Emulation"
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HREF="sb16-emulation-basics.html"><LINK
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REL="NEXT"
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TITLE="How to add keymapping in a GUI client"
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HREF="add-keymapping.html"></HEAD
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><BODY
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Bochs Developers Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="sb16-emulation-basics.html"
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ACCESSKEY="P"
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>Prev</A
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 2. About the code</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="add-keymapping.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TABLE
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WIDTH="100%"></DIV
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CLASS="SECTION"
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><H1
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CLASS="SECTION"
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><A
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NAME="HARDDISK-REDOLOGS"
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>2.9. Harddisk Images based on redologs</A
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></H1
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><P
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>This section describes how the three new disk images "undoable", "growing", and "volatile" are
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implemented in Bochs 2.1 :</P
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><P
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></P
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><UL
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><LI
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><P
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>undoable -> flat file, plus growing, commitable, rollbackable redolog file</P
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></LI
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><LI
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><P
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>growing -> growing files, all previously unwritten sectors go to the end of file</P
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></LI
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><LI
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><P
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>volatile -> flat file, plus hidden growing redolog</P
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></LI
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></UL
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><P
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></P
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="AEN635"
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>2.9.1. Description</A
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></H2
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><P
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>The idea behind volatile and undoable disk images
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is to have a flat file, associated with one redolog file. </P
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><P
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>Reading a sector is done from the redolog file if it contains
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the sector, or from the flat file otherwise. </P
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><P
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>Sectors written go to the redolog,
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so flat files are opened in read only mode in this configuration.</P
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><P
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>The redolog is designed in a way so it starts as a small file
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and grows with every new sectors written to it. Previously written
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sectors are done in place. Redolog files can not shrink.</P
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><P
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>The redolog is a growing file that can be created on the fly.</P
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><P
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>Now, it turns out that if you only use a redolog without any
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flat file, you get a "growing" disk image.</P
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><P
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>So "undoable", "volatile" and "growing" harddisk images classes
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are implemented on top of a redolog class.</P
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></DIV
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="AEN644"
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>2.9.2. How redologs works ?</A
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></H2
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><P
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>At the start of a redolog file, there is a header, so Bochs can check whether
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a file is consistent.
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This header could also be checked when we implement
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automatic type and size detection.</P
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><P
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>The generic part of the header contains values like type of image, and
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spec version number.</P
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><P
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>The header also has a specific part.
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For redologs, the number
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of entries of the catalog, the extent, bitmap and disk size are stored.</P
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><P
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>In a redolog, the disk image is divided in a number of equal size "extents".
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Each extent is a collection of successive 512-bytes sectors of the disk image,
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preceeded by a n*512bytes bitmap. </P
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><P
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>the n*512bytes bitmap defines the presence (data has been written to it)
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of a specific sector in the extent, one bit for each sector.
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Therefore with a 512bytes bitmap, each extent can hold up to 4k blocks</P
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><P
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>Typically the catalog can have 256k entries.
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With a 256k entries catalog and 512bytes bitmaps, the redolog can hold up to 512GiB</P
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><DIV
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CLASS="NOTE"
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><BLOCKQUOTE
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CLASS="NOTE"
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><P
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><B
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>Note: </B
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>All data is stored on images as little-endian values</P
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></BLOCKQUOTE
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></DIV
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><DIV
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CLASS="SECTION"
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><H3
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CLASS="SECTION"
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><A
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NAME="AEN654"
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>2.9.2.1. Header</A
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></H3
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><P
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>At the start of a redolog file, there is a header. This header is designed
|
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to be reusable by other disk image types.</P
|
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><P
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>The header length is 512 bytes. It contains :
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<DIV
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CLASS="TABLE"
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><A
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NAME="AEN658"
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></A
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><P
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><B
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>Table 2-7. Generic header description</B
|
||
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></P
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><TABLE
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BORDER="1"
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CLASS="CALSTABLE"
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><COL><COL><COL><COL><COL><THEAD
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><TR
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><TH
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>Start position in bytes</TH
|
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><TH
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>Length in bytes</TH
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||
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><TH
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>Data type</TH
|
||
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><TH
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>Description</TH
|
||
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><TH
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>Possible values</TH
|
||
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></TR
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></THEAD
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><TBODY
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><TR
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><TD
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> 0 </TD
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><TD
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> 32 </TD
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||
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><TD
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> string </TD
|
||
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><TD
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||
|
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> magical value </TD
|
||
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><TD
|
||
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> Bochs Virtual HD Image </TD
|
||
|
|
></TR
|
||
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><TR
|
||
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><TD
|
||
|
|
> 32 </TD
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||
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><TD
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||
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> 16 </TD
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||
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><TD
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||
|
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> string </TD
|
||
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><TD
|
||
|
|
> type of file </TD
|
||
|
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><TD
|
||
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> Redolog </TD
|
||
|
|
></TR
|
||
|
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><TR
|
||
|
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><TD
|
||
|
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> 48 </TD
|
||
|
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><TD
|
||
|
|
> 16 </TD
|
||
|
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><TD
|
||
|
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> string </TD
|
||
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|
><TD
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||
|
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> subtype of file </TD
|
||
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><TD
|
||
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> Undoable, Volatile, Growing </TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 64 </TD
|
||
|
|
><TD
|
||
|
|
> 4 </TD
|
||
|
|
><TD
|
||
|
|
> Bit32u </TD
|
||
|
|
><TD
|
||
|
|
> version of used specification </TD
|
||
|
|
><TD
|
||
|
|
> 0x00010000 </TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 68 </TD
|
||
|
|
><TD
|
||
|
|
> 4 </TD
|
||
|
|
><TD
|
||
|
|
> Bit32u </TD
|
||
|
|
><TD
|
||
|
|
> header size </TD
|
||
|
|
><TD
|
||
|
|
> 512 </TD
|
||
|
|
></TR
|
||
|
|
></TBODY
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
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>
|
||
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<DIV
|
||
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|
CLASS="TABLE"
|
||
|
|
><A
|
||
|
|
NAME="AEN699"
|
||
|
|
></A
|
||
|
|
><P
|
||
|
|
><B
|
||
|
|
>Table 2-8. Redolog specific header description</B
|
||
|
|
></P
|
||
|
|
><TABLE
|
||
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|
BORDER="1"
|
||
|
|
CLASS="CALSTABLE"
|
||
|
|
><COL><COL><COL><COL><COL><THEAD
|
||
|
|
><TR
|
||
|
|
><TH
|
||
|
|
>Start position in bytes</TH
|
||
|
|
><TH
|
||
|
|
>Length in bytes</TH
|
||
|
|
><TH
|
||
|
|
>Data type</TH
|
||
|
|
><TH
|
||
|
|
>Description</TH
|
||
|
|
><TD
|
||
|
|
> </TD
|
||
|
|
></TR
|
||
|
|
></THEAD
|
||
|
|
><TBODY
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 72 </TD
|
||
|
|
><TD
|
||
|
|
> 4 </TD
|
||
|
|
><TD
|
||
|
|
> Bit32u </TD
|
||
|
|
><TD
|
||
|
|
> number of entries in the catalog </TD
|
||
|
|
><TD
|
||
|
|
> </TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 76 </TD
|
||
|
|
><TD
|
||
|
|
> 4 </TD
|
||
|
|
><TD
|
||
|
|
> Bit32u </TD
|
||
|
|
><TD
|
||
|
|
> bitmap size in bytes </TD
|
||
|
|
><TD
|
||
|
|
> </TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 80 </TD
|
||
|
|
><TD
|
||
|
|
> 4 </TD
|
||
|
|
><TD
|
||
|
|
> Bit32u </TD
|
||
|
|
><TD
|
||
|
|
> extent size in bytes</TD
|
||
|
|
><TD
|
||
|
|
> </TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
> 84 </TD
|
||
|
|
><TD
|
||
|
|
> 8 </TD
|
||
|
|
><TD
|
||
|
|
> Bit64u </TD
|
||
|
|
><TD
|
||
|
|
> disk size in bytes </TD
|
||
|
|
><TD
|
||
|
|
> </TD
|
||
|
|
></TR
|
||
|
|
></TBODY
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
|
|
></P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN729"
|
||
|
|
>2.9.2.2. Catalog</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
>Immediately following the header, there is a catalog containing
|
||
|
|
the position number (in extents) where each extent is located in the file.</P
|
||
|
|
><P
|
||
|
|
>Each position is a Bit32u entity.</P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN733"
|
||
|
|
>2.9.2.3. Extent</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
> <IMG
|
||
|
|
SRC="../images/undercon.png"></P
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H2
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN737"
|
||
|
|
>2.9.3. Parameters</A
|
||
|
|
></H2
|
||
|
|
><P
|
||
|
|
>The following tables shows what parameters are used when creating redologs or creating "growing" images :
|
||
|
|
<DIV
|
||
|
|
CLASS="TABLE"
|
||
|
|
><A
|
||
|
|
NAME="AEN740"
|
||
|
|
></A
|
||
|
|
><P
|
||
|
|
><B
|
||
|
|
>Table 2-9. How number of entries in the catalog and number of blocks by extents are computed</B
|
||
|
|
></P
|
||
|
|
><TABLE
|
||
|
|
BORDER="1"
|
||
|
|
CLASS="CALSTABLE"
|
||
|
|
><COL><COL><COL><COL><COL><THEAD
|
||
|
|
><TR
|
||
|
|
><TH
|
||
|
|
>Catalog entries</TH
|
||
|
|
><TH
|
||
|
|
>Catalog size(KiB)</TH
|
||
|
|
><TH
|
||
|
|
>Bitmap size (B)</TH
|
||
|
|
><TH
|
||
|
|
>Extent size (KiB)</TH
|
||
|
|
><TH
|
||
|
|
>Disk Max Size</TH
|
||
|
|
></TR
|
||
|
|
></THEAD
|
||
|
|
><TBODY
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>2</TD
|
||
|
|
><TD
|
||
|
|
>1</TD
|
||
|
|
><TD
|
||
|
|
>4</TD
|
||
|
|
><TD
|
||
|
|
>2MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>2</TD
|
||
|
|
><TD
|
||
|
|
>2</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>4MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>1k</TD
|
||
|
|
><TD
|
||
|
|
>4</TD
|
||
|
|
><TD
|
||
|
|
>2</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>8MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>1k</TD
|
||
|
|
><TD
|
||
|
|
>4</TD
|
||
|
|
><TD
|
||
|
|
>4</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>16MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>2k</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>4</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>32MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>2k</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>64MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>4k</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>8</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>128MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>4k</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>256MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>8k</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>16</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>512MiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>8k</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>1GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>16k</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>32</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>2GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>16k</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>4GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>32k</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>64</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>8GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>32k</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>16GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>64k</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>128</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>32GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>64k</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>64GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>128k</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>256</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>128GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>128k</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>256GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>256k</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>512</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>512GiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>256k</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>1TiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>512k</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>1024</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>2TiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>512k</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>8192</TD
|
||
|
|
><TD
|
||
|
|
>4TiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>1024k</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>2048</TD
|
||
|
|
><TD
|
||
|
|
>8192</TD
|
||
|
|
><TD
|
||
|
|
>8TiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>1024k</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>16384</TD
|
||
|
|
><TD
|
||
|
|
>16TiB</TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
>2048k</TD
|
||
|
|
><TD
|
||
|
|
>8192</TD
|
||
|
|
><TD
|
||
|
|
>4096</TD
|
||
|
|
><TD
|
||
|
|
>16384</TD
|
||
|
|
><TD
|
||
|
|
>32TiB</TD
|
||
|
|
></TR
|
||
|
|
></TBODY
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
|
|
></P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H2
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN901"
|
||
|
|
>2.9.4. Redolog class description</A
|
||
|
|
></H2
|
||
|
|
><P
|
||
|
|
>The class <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_t();</I
|
||
|
|
></SPAN
|
||
|
|
> implements the necessary
|
||
|
|
methods to create, open, close, read and write data to a redolog.
|
||
|
|
Managment of header catalog and sector bitmaps is done internally
|
||
|
|
by the class.</P
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN905"
|
||
|
|
>2.9.4.1. Constants</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><TABLE
|
||
|
|
BORDER="0"
|
||
|
|
BGCOLOR="#E0E0E0"
|
||
|
|
WIDTH="100%"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
><PRE
|
||
|
|
CLASS="SCREEN"
|
||
|
|
>#define STANDARD_HEADER_MAGIC "Bochs Virtual HD Image"
|
||
|
|
#define STANDARD_HEADER_VERSION (0x00010000)
|
||
|
|
#define STANDARD_HEADER_SIZE (512)</PRE
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
>
|
||
|
|
These constants are used in the generic part of the header.</P
|
||
|
|
><P
|
||
|
|
><TABLE
|
||
|
|
BORDER="0"
|
||
|
|
BGCOLOR="#E0E0E0"
|
||
|
|
WIDTH="100%"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
><PRE
|
||
|
|
CLASS="SCREEN"
|
||
|
|
>#define REDOLOG_TYPE "Redolog"
|
||
|
|
#define REDOLOG_SUBTYPE_UNDOABLE "Undoable"
|
||
|
|
#define REDOLOG_SUBTYPE_VOLATILE "Volatile"
|
||
|
|
#define REDOLOG_SUBTYPE_GROWING "Growing"</PRE
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
>
|
||
|
|
These constants are used in the specific part of the header.</P
|
||
|
|
><P
|
||
|
|
><TABLE
|
||
|
|
BORDER="0"
|
||
|
|
BGCOLOR="#E0E0E0"
|
||
|
|
WIDTH="100%"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
><PRE
|
||
|
|
CLASS="SCREEN"
|
||
|
|
>#define REDOLOG_PAGE_NOT_ALLOCATED (0xffffffff)</PRE
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
>
|
||
|
|
This constant is used in the catalog for an unwritten extent.</P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN913"
|
||
|
|
>2.9.4.2. Methods</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_t();</I
|
||
|
|
></SPAN
|
||
|
|
> instanciates a new redolog.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int make_header (const char* type, Bit64u size);</I
|
||
|
|
></SPAN
|
||
|
|
> creates a header
|
||
|
|
structure in memory, and sets its <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>type</I
|
||
|
|
></SPAN
|
||
|
|
> and parameters based on the
|
||
|
|
disk image <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
>. Returns 0.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int create (const char* filename, const char* type, Bit64u size);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
creates a new empty redolog file, with header and catalog, named <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>filename</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
of type <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>type</I
|
||
|
|
></SPAN
|
||
|
|
> for a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
> bytes image.
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int create (int filedes, const char* type, Bit64u size);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
creates a new empty redolog file, with header and catalog, in a previously
|
||
|
|
opened file described by <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>filedes</I
|
||
|
|
></SPAN
|
||
|
|
>, of type <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>type</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
for a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
> bytes image.
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int open (const char* filename, const char* type, Bit64u size);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
opens a redolog file named <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>filename</I
|
||
|
|
></SPAN
|
||
|
|
>, and checks
|
||
|
|
for consistency of header values against a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>type</I
|
||
|
|
></SPAN
|
||
|
|
> and
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>void close ();</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
closes a redolog file.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>off_t lseek (off_t offset, int whence);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
seeks at logical data offset <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>offset</I
|
||
|
|
></SPAN
|
||
|
|
> in a redolog.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>offset</I
|
||
|
|
></SPAN
|
||
|
|
> must be a multiple of 512.
|
||
|
|
Only SEEK_SET is supported for <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>whence</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
Returns -1 if a problem occured, or the current logical offset in
|
||
|
|
the redolog.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t read (void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
reads <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data of the redolog, from current logical offset,
|
||
|
|
and copies it into <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes read, that can be 0 if the data
|
||
|
|
has not previously be written to the redolog.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t write (const void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
writes <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data from <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
to the redolog, at current logical offset.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes written.</P
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H2
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN953"
|
||
|
|
>2.9.5. Disk image classes description</A
|
||
|
|
></H2
|
||
|
|
><P
|
||
|
|
>"volatile" and "undoable" disk images are easily implemented
|
||
|
|
by instanciating a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>default_image_t</I
|
||
|
|
></SPAN
|
||
|
|
> object (flat image)
|
||
|
|
and a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_t</I
|
||
|
|
></SPAN
|
||
|
|
> object (redolog).</P
|
||
|
|
><P
|
||
|
|
>"growing" disk images only instanciates a <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_t</I
|
||
|
|
></SPAN
|
||
|
|
> object.</P
|
||
|
|
><P
|
||
|
|
>Classe names are <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>undoable_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>, <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>volatile_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
and <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>growing_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>.</P
|
||
|
|
><P
|
||
|
|
>When using these disk images, the underlying data structure and layout
|
||
|
|
is completely
|
||
|
|
hidden to the caller. Then, all offset and size values are "logical" values,
|
||
|
|
as if the disk was a flat file.</P
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN965"
|
||
|
|
>2.9.5.1. Constants</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><TABLE
|
||
|
|
BORDER="0"
|
||
|
|
BGCOLOR="#E0E0E0"
|
||
|
|
WIDTH="100%"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
><PRE
|
||
|
|
CLASS="SCREEN"
|
||
|
|
>#define UNDOABLE_REDOLOG_EXTENSION ".redolog"
|
||
|
|
#define UNDOABLE_REDOLOG_EXTENSION_LENGTH (strlen(UNDOABLE_REDOLOG_EXTENSION))
|
||
|
|
#define VOLATILE_REDOLOG_EXTENSION ".XXXXXX"
|
||
|
|
#define VOLATILE_REDOLOG_EXTENSION_LENGTH (strlen(VOLATILE_REDOLOG_EXTENSION))</PRE
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
>
|
||
|
|
These constants are used when building redolog file names</P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN969"
|
||
|
|
>2.9.5.2. undoable_image_t methods</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>undoable_image_t(Bit64u size, const char* redolog_name);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
instanciates a new <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>undoable_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
object. This disk image logical length is <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
> bytes and
|
||
|
|
the redolog filename is <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_name</I
|
||
|
|
></SPAN
|
||
|
|
>. </P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int open (const char* pathname);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
opens the flat disk image <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>pathname</I
|
||
|
|
></SPAN
|
||
|
|
>,
|
||
|
|
as an undoable disk image. The associated redolog will
|
||
|
|
be named <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>pathname</I
|
||
|
|
></SPAN
|
||
|
|
> with a
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>UNDOABLE_REDOLOG_EXTENSION</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
suffix, unless set in the constructor.
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>void close ();</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
closes the flat image and its redolog.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>off_t lseek (off_t offset, int whence);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
seeks at logical data position <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>offset</I
|
||
|
|
></SPAN
|
||
|
|
> in
|
||
|
|
the undoable disk image.
|
||
|
|
Only SEEK_SET is supported for <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>whence</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
Returns -1 if a problem occured, or the current logical
|
||
|
|
offset in the undoable disk image.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t read (void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
reads <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data
|
||
|
|
from the undoable disk image, from current logical offset,
|
||
|
|
and copies it into <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes read.
|
||
|
|
Data will be read from the redolog if it has
|
||
|
|
been previously written or from the flat image
|
||
|
|
otherwise.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t write (const void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
writes <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data from <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
to the undoable disk image, at current logical offset.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes written.
|
||
|
|
Data will always be written to the redolog.</P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN997"
|
||
|
|
>2.9.5.3. volatile_image_t methods</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>volatile_image_t(Bit64u size, const char* redolog_name);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
instanciates a new <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>volatile_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
object. This disk image logical length is <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
> bytes and
|
||
|
|
the redolog filename is <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>redolog_name</I
|
||
|
|
></SPAN
|
||
|
|
> plus a
|
||
|
|
random suffix. </P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int open (const char* pathname);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
opens the flat disk image <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>pathname</I
|
||
|
|
></SPAN
|
||
|
|
>,
|
||
|
|
as a volatile disk image. The associated redolog will
|
||
|
|
be named <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>pathname</I
|
||
|
|
></SPAN
|
||
|
|
> with a
|
||
|
|
random suffix, unless set in the constructor.
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>void close ();</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
closes the flat image and its redolog.
|
||
|
|
The redolog is deleted/lost after close is called.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>off_t lseek (off_t offset, int whence);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
seeks at logical data position <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>offset</I
|
||
|
|
></SPAN
|
||
|
|
> in
|
||
|
|
the volatile disk image.
|
||
|
|
Only SEEK_SET is supported for <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>whence</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
Returns -1 if a problem occured, or the current logical offset in
|
||
|
|
the volatile disk image.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t read (void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
reads <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data
|
||
|
|
from the volatile disk image, from current logical offset,
|
||
|
|
and copies it into <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes read.
|
||
|
|
Data will be read from the redolog if it has
|
||
|
|
been previously written or from the flat image
|
||
|
|
otherwise.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t write (const void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
writes <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data from <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
to the volatile disk image, at current logical offset.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes written.
|
||
|
|
Data will always be written to the redolog.</P
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECTION"
|
||
|
|
><H3
|
||
|
|
CLASS="SECTION"
|
||
|
|
><A
|
||
|
|
NAME="AEN1024"
|
||
|
|
>2.9.5.4. growing_image_t methods</A
|
||
|
|
></H3
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>growing_image_t(Bit64u size);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
instanciates a new <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>growing_image_t</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
object. This disk image logical length is <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>size</I
|
||
|
|
></SPAN
|
||
|
|
> bytes.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>int open (const char* pathname);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
opens the growing disk image <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>pathname</I
|
||
|
|
></SPAN
|
||
|
|
>,
|
||
|
|
Returns 0 for OK or -1 if a problem occured.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>void close ();</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
closes the growing disk image.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>off_t lseek (off_t offset, int whence);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
seeks at logical data position <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>offset</I
|
||
|
|
></SPAN
|
||
|
|
> in
|
||
|
|
the growable disk image.
|
||
|
|
Only SEEK_SET is supported for <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>whence</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
Returns -1 if a problem occured, or the current logical offset in
|
||
|
|
the grwoing image.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t read (void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
reads <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data
|
||
|
|
from the growing disk image, from current logical offset,
|
||
|
|
and copies it into <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes read.
|
||
|
|
The buffer will be filled with null bytes if data
|
||
|
|
has not been previously written to the growing image.</P
|
||
|
|
><P
|
||
|
|
><SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>ssize_t write (const void* buf, size_t count);</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
writes <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> bytes of data from <SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>buf</I
|
||
|
|
></SPAN
|
||
|
|
>
|
||
|
|
to the growing disk image, at current logical offset.
|
||
|
|
<SPAN
|
||
|
|
CLASS="emphasis"
|
||
|
|
><I
|
||
|
|
CLASS="EMPHASIS"
|
||
|
|
>count</I
|
||
|
|
></SPAN
|
||
|
|
> must be 512.
|
||
|
|
Returns the number of bytes written.</P
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="NAVFOOTER"
|
||
|
|
><HR
|
||
|
|
ALIGN="LEFT"
|
||
|
|
WIDTH="100%"><TABLE
|
||
|
|
SUMMARY="Footer navigation table"
|
||
|
|
WIDTH="100%"
|
||
|
|
BORDER="0"
|
||
|
|
CELLPADDING="0"
|
||
|
|
CELLSPACING="0"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="sb16-emulation-basics.html"
|
||
|
|
ACCESSKEY="P"
|
||
|
|
>Prev</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="index.html"
|
||
|
|
ACCESSKEY="H"
|
||
|
|
>Home</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="add-keymapping.html"
|
||
|
|
ACCESSKEY="N"
|
||
|
|
>Next</A
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
>Sound Blaster 16 Emulation</TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="about-the-code.html"
|
||
|
|
ACCESSKEY="U"
|
||
|
|
>Up</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
>How to add keymapping in a GUI client</TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
|
|
></BODY
|
||
|
|
></HTML
|
||
|
|
>
|