/*+
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** 2004 April 6+
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**+
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** The author disclaims copyright to this source code.  In place of+
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** a legal notice, here is a blessing:+
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**+
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**    May you do good and not evil.+
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**    May you find forgiveness for yourself and forgive others.+
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**    May you share freely, never taking more than you give.+
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**+
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*************************************************************************+
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** $Id: btreeInt.h 1282 2008-11-13 09:31:33Z LarsPson $+
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**+
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** This file implements a external (disk-based) database using BTrees.+
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** For a detailed discussion of BTrees, refer to+
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**+
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**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:+
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**     "Sorting And Searching", pages 473-480. Addison-Wesley+
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**     Publishing Company, Reading, Massachusetts.+
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**+
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** The basic idea is that each page of the file contains N database+
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** entries and N+1 pointers to subpages.+
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**+
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**   ----------------------------------------------------------------+
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**   |  Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |+
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**   ----------------------------------------------------------------+
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**+
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** All of the keys on the page that Ptr(0) points to have values less+
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** than Key(0).  All of the keys on page Ptr(1) and its subpages have+
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** values greater than Key(0) and less than Key(1).  All of the keys+
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** on Ptr(N) and its subpages have values greater than Key(N-1).  And+
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** so forth.+
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**+
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** Finding a particular key requires reading O(log(M)) pages from the +
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** disk where M is the number of entries in the tree.+
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**+
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** In this implementation, a single file can hold one or more separate +
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** BTrees.  Each BTree is identified by the index of its root page.  The+
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** key and data for any entry are combined to form the "payload".  A+
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** fixed amount of payload can be carried directly on the database+
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** page.  If the payload is larger than the preset amount then surplus+
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** bytes are stored on overflow pages.  The payload for an entry+
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** and the preceding pointer are combined to form a "Cell".  Each +
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** page has a small header which contains the Ptr(N) pointer and other+
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** information such as the size of key and data.+
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**+
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** FORMAT DETAILS+
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**+
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** The file is divided into pages.  The first page is called page 1,+
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** the second is page 2, and so forth.  A page number of zero indicates+
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** "no such page".  The page size can be anything between 512 and 65536.+
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** Each page can be either a btree page, a freelist page or an overflow+
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** page.+
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**+
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** The first page is always a btree page.  The first 100 bytes of the first+
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** page contain a special header (the "file header") that describes the file.+
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** The format of the file header is as follows:+
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**+
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**   OFFSET   SIZE    DESCRIPTION+
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**      0      16     Header string: "SQLite format 3\000"+
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**     16       2     Page size in bytes.  +
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**     18       1     File format write version+
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**     19       1     File format read version+
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**     20       1     Bytes of unused space at the end of each page+
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**     21       1     Max embedded payload fraction+
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**     22       1     Min embedded payload fraction+
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**     23       1     Min leaf payload fraction+
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**     24       4     File change counter+
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**     28       4     Reserved for future use+
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**     32       4     First freelist page+
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**     36       4     Number of freelist pages in the file+
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**     40      60     15 4-byte meta values passed to higher layers+
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**+
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** All of the integer values are big-endian (most significant byte first).+
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**+
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** The file change counter is incremented when the database is changed+
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** This counter allows other processes to know when the file has changed+
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** and thus when they need to flush their cache.+
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**+
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** The max embedded payload fraction is the amount of the total usable+
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** space in a page that can be consumed by a single cell for standard+
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** B-tree (non-LEAFDATA) tables.  A value of 255 means 100%.  The default+
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** is to limit the maximum cell size so that at least 4 cells will fit+
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** on one page.  Thus the default max embedded payload fraction is 64.+
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**+
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** If the payload for a cell is larger than the max payload, then extra+
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** payload is spilled to overflow pages.  Once an overflow page is allocated,+
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** as many bytes as possible are moved into the overflow pages without letting+
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** the cell size drop below the min embedded payload fraction.+
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**+
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** The min leaf payload fraction is like the min embedded payload fraction+
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** except that it applies to leaf nodes in a LEAFDATA tree.  The maximum+
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** payload fraction for a LEAFDATA tree is always 100% (or 255) and it+
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** not specified in the header.+
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**+
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** Each btree pages is divided into three sections:  The header, the+
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** cell pointer array, and the cell content area.  Page 1 also has a 100-byte+
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** file header that occurs before the page header.+
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**+
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**      |----------------|+
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**      | file header    |   100 bytes.  Page 1 only.+
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**      |----------------|+
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**      | page header    |   8 bytes for leaves.  12 bytes for interior nodes+
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**      |----------------|+
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**      | cell pointer   |   |  2 bytes per cell.  Sorted order.+
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**      | array          |   |  Grows downward+
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**      |                |   v+
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**      |----------------|+
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**      | unallocated    |+
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**      | space          |+
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**      |----------------|   ^  Grows upwards+
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**      | cell content   |   |  Arbitrary order interspersed with freeblocks.+
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**      | area           |   |  and free space fragments.+
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**      |----------------|+
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**+
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** The page headers looks like this:+
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**+
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**   OFFSET   SIZE     DESCRIPTION+
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**      0       1      Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf+
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**      1       2      byte offset to the first freeblock+
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**      3       2      number of cells on this page+
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**      5       2      first byte of the cell content area+
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**      7       1      number of fragmented free bytes+
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**      8       4      Right child (the Ptr(N) value).  Omitted on leaves.+
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**+
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** The flags define the format of this btree page.  The leaf flag means that+
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** this page has no children.  The zerodata flag means that this page carries+
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** only keys and no data.  The intkey flag means that the key is a integer+
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** which is stored in the key size entry of the cell header rather than in+
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** the payload area.+
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**+
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** The cell pointer array begins on the first byte after the page header.+
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** The cell pointer array contains zero or more 2-byte numbers which are+
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** offsets from the beginning of the page to the cell content in the cell+
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** content area.  The cell pointers occur in sorted order.  The system strives+
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** to keep free space after the last cell pointer so that new cells can+
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** be easily added without having to defragment the page.+
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**+
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** Cell content is stored at the very end of the page and grows toward the+
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** beginning of the page.+
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**+
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** Unused space within the cell content area is collected into a linked list of+
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** freeblocks.  Each freeblock is at least 4 bytes in size.  The byte offset+
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** to the first freeblock is given in the header.  Freeblocks occur in+
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** increasing order.  Because a freeblock must be at least 4 bytes in size,+
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** any group of 3 or fewer unused bytes in the cell content area cannot+
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** exist on the freeblock chain.  A group of 3 or fewer free bytes is called+
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** a fragment.  The total number of bytes in all fragments is recorded.+
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** in the page header at offset 7.+
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**+
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**    SIZE    DESCRIPTION+
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**      2     Byte offset of the next freeblock+
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**      2     Bytes in this freeblock+
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**+
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** Cells are of variable length.  Cells are stored in the cell content area at+
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** the end of the page.  Pointers to the cells are in the cell pointer array+
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** that immediately follows the page header.  Cells is not necessarily+
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** contiguous or in order, but cell pointers are contiguous and in order.+
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**+
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** Cell content makes use of variable length integers.  A variable+
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** length integer is 1 to 9 bytes where the lower 7 bits of each +
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** byte are used.  The integer consists of all bytes that have bit 8 set and+
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** the first byte with bit 8 clear.  The most significant byte of the integer+
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** appears first.  A variable-length integer may not be more than 9 bytes long.+
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** As a special case, all 8 bytes of the 9th byte are used as data.  This+
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** allows a 64-bit integer to be encoded in 9 bytes.+
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**+
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**    0x00                      becomes  0x00000000+
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**    0x7f                      becomes  0x0000007f+
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**    0x81 0x00                 becomes  0x00000080+
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**    0x82 0x00                 becomes  0x00000100+
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**    0x80 0x7f                 becomes  0x0000007f+
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**    0x8a 0x91 0xd1 0xac 0x78  becomes  0x12345678+
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**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081+
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**+
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** Variable length integers are used for rowids and to hold the number of+
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** bytes of key and data in a btree cell.+
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**+
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** The content of a cell looks like this:+
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**+
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**    SIZE    DESCRIPTION+
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**      4     Page number of the left child. Omitted if leaf flag is set.+
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**     var    Number of bytes of data. Omitted if the zerodata flag is set.+
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**     var    Number of bytes of key. Or the key itself if intkey flag is set.+
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**      *     Payload+
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**      4     First page of the overflow chain.  Omitted if no overflow+
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**+
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** Overflow pages form a linked list.  Each page except the last is completely+
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** filled with data (pagesize - 4 bytes).  The last page can have as little+
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** as 1 byte of data.+
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**+
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**    SIZE    DESCRIPTION+
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**      4     Page number of next overflow page+
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**      *     Data+
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**+
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** Freelist pages come in two subtypes: trunk pages and leaf pages.  The+
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** file header points to the first in a linked list of trunk page.  Each trunk+
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** page points to multiple leaf pages.  The content of a leaf page is+
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** unspecified.  A trunk page looks like this:+
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**+
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**    SIZE    DESCRIPTION+
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**      4     Page number of next trunk page+
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**      4     Number of leaf pointers on this page+
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**      *     zero or more pages numbers of leaves+
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*/+
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#include "sqliteInt.h"+
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#include "pager.h"+
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#include "btree.h"+
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#include "os.h"+
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#include <assert.h>+
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+
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/* Round up a number to the next larger multiple of 8.  This is used+
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** to force 8-byte alignment on 64-bit architectures.+
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*/+
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#define ROUND8(x)   ((x+7)&~7)+
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+
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+
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/* The following value is the maximum cell size assuming a maximum page+
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** size give above.+
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*/+
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#define MX_CELL_SIZE(pBt)  (pBt->pageSize-8)+
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+
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/* The maximum number of cells on a single page of the database.  This+
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** assumes a minimum cell size of 3 bytes.  Such small cells will be+
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** exceedingly rare, but they are possible.+
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*/+
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#define MX_CELL(pBt) ((pBt->pageSize-8)/3)+
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+
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/* Forward declarations */+
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typedef struct MemPage MemPage;+
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typedef struct BtLock BtLock;+
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+
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/*+
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** This is a magic string that appears at the beginning of every+
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** SQLite database in order to identify the file as a real database.+
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**+
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** You can change this value at compile-time by specifying a+
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** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The+
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** header must be exactly 16 bytes including the zero-terminator so+
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** the string itself should be 15 characters long.  If you change+
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** the header, then your custom library will not be able to read +
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** databases generated by the standard tools and the standard tools+
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** will not be able to read databases created by your custom library.+
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*/+
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#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */+
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#  define SQLITE_FILE_HEADER "SQLite format 3"+
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#endif+
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+
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/*+
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** Page type flags.  An ORed combination of these flags appear as the+
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** first byte of on-disk image of every BTree page.+
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*/+
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#define PTF_INTKEY    0x01+
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#define PTF_ZERODATA  0x02+
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#define PTF_LEAFDATA  0x04+
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#define PTF_LEAF      0x08+
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+
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/*+
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** As each page of the file is loaded into memory, an instance of the following+
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** structure is appended and initialized to zero.  This structure stores+
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** information about the page that is decoded from the raw file page.+
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**+
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** The pParent field points back to the parent page.  This allows us to+
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** walk up the BTree from any leaf to the root.  Care must be taken to+
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** unref() the parent page pointer when this page is no longer referenced.+
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** The pageDestructor() routine handles that chore.+
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**+
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** Access to all fields of this structure is controlled by the mutex+
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** stored in MemPage.pBt->mutex.+
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*/+
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struct MemPage {+
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  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */+
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  u8 idxShift;         /* True if Cell indices have changed */+
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  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */+
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  u8 intKey;           /* True if intkey flag is set */+
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  u8 leaf;             /* True if leaf flag is set */+
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  u8 zeroData;         /* True if table stores keys only */+
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  u8 leafData;         /* True if tables stores data on leaves only */+
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  u8 hasData;          /* True if this page stores data */+
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  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */+
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  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */+
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  u16 maxLocal;        /* Copy of BtShared.maxLocal or BtShared.maxLeaf */+
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  u16 minLocal;        /* Copy of BtShared.minLocal or BtShared.minLeaf */+
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  u16 cellOffset;      /* Index in aData of first cell pointer */+
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  u16 idxParent;       /* Index in parent of this node */+
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  u16 nFree;           /* Number of free bytes on the page */+
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  u16 nCell;           /* Number of cells on this page, local and ovfl */+
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  struct _OvflCell {   /* Cells that will not fit on aData[] */+
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    u8 *pCell;          /* Pointers to the body of the overflow cell */+
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    u16 idx;            /* Insert this cell before idx-th non-overflow cell */+
−
  } aOvfl[5];+
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  BtShared *pBt;       /* Pointer to BtShared that this page is part of */+
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  u8 *aData;           /* Pointer to disk image of the page data */+
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  DbPage *pDbPage;     /* Pager page handle */+
−
  Pgno pgno;           /* Page number for this page */+
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  MemPage *pParent;    /* The parent of this page.  NULL for root */+
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};+
−
+
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/*+
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** The in-memory image of a disk page has the auxiliary information appended+
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** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold+
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** that extra information.+
−
*/+
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#define EXTRA_SIZE sizeof(MemPage)+
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+
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/* A Btree handle+
−
**+
−
** A database connection contains a pointer to an instance of+
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** this object for every database file that it has open.  This structure+
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** is opaque to the database connection.  The database connection cannot+
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** see the internals of this structure and only deals with pointers to+
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** this structure.+
−
**+
−
** For some database files, the same underlying database cache might be +
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** shared between multiple connections.  In that case, each contection+
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** has it own pointer to this object.  But each instance of this object+
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** points to the same BtShared object.  The database cache and the+
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** schema associated with the database file are all contained within+
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** the BtShared object.+
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**+
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** All fields in this structure are accessed under sqlite3.mutex.+
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** The pBt pointer itself may not be changed while there exists cursors +
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** in the referenced BtShared that point back to this Btree since those+
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** cursors have to do go through this Btree to find their BtShared and+
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** they often do so without holding sqlite3.mutex.+
−
*/+
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struct Btree {+
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  sqlite3 *db;       /* The database connection holding this btree */+
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  BtShared *pBt;     /* Sharable content of this btree */+
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  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */+
−
  u8 sharable;       /* True if we can share pBt with another db */+
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  u8 locked;         /* True if db currently has pBt locked */+
−
  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */+
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  Btree *pNext;      /* List of other sharable Btrees from the same db */+
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  Btree *pPrev;      /* Back pointer of the same list */+
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};+
−
+
−
/*+
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** Btree.inTrans may take one of the following values.+
−
**+
−
** If the shared-data extension is enabled, there may be multiple users+
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** of the Btree structure. At most one of these may open a write transaction,+
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** but any number may have active read transactions.+
−
*/+
−
#define TRANS_NONE  0+
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#define TRANS_READ  1+
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#define TRANS_WRITE 2+
−
+
−
/*+
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** An instance of this object represents a single database file.+
−
** +
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** A single database file can be in use as the same time by two+
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** or more database connections.  When two or more connections are+
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** sharing the same database file, each connection has it own+
−
** private Btree object for the file and each of those Btrees points+
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** to this one BtShared object.  BtShared.nRef is the number of+
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** connections currently sharing this database file.+
−
**+
−
** Fields in this structure are accessed under the BtShared.mutex+
−
** mutex, except for nRef and pNext which are accessed under the+
−
** global SQLITE_MUTEX_STATIC_MASTER mutex.  The pPager field+
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** may not be modified once it is initially set as long as nRef>0.+
−
** The pSchema field may be set once under BtShared.mutex and+
−
** thereafter is unchanged as long as nRef>0.+
−
*/+
−
struct BtShared {+
−
  Pager *pPager;        /* The page cache */+
−
  sqlite3 *db;          /* Database connection currently using this Btree */+
−
  BtCursor *pCursor;    /* A list of all open cursors */+
−
  MemPage *pPage1;      /* First page of the database */+
−
  u8 inStmt;            /* True if we are in a statement subtransaction */+
−
  u8 readOnly;          /* True if the underlying file is readonly */+
−
  u8 maxEmbedFrac;      /* Maximum payload as % of total page size */+
−
  u8 minEmbedFrac;      /* Minimum payload as % of total page size */+
−
  u8 minLeafFrac;       /* Minimum leaf payload as % of total page size */+
−
  u8 pageSizeFixed;     /* True if the page size can no longer be changed */+
−
#ifndef SQLITE_OMIT_AUTOVACUUM+
−
  u8 autoVacuum;        /* True if auto-vacuum is enabled */+
−
  u8 incrVacuum;        /* True if incr-vacuum is enabled */+
−
  Pgno nTrunc;          /* Non-zero if the db will be truncated (incr vacuum) */+
−
#endif+
−
  u16 pageSize;         /* Total number of bytes on a page */+
−
  u16 usableSize;       /* Number of usable bytes on each page */+
−
  int maxLocal;         /* Maximum local payload in non-LEAFDATA tables */+
−
  int minLocal;         /* Minimum local payload in non-LEAFDATA tables */+
−
  int maxLeaf;          /* Maximum local payload in a LEAFDATA table */+
−
  int minLeaf;          /* Minimum local payload in a LEAFDATA table */+
−
  u8 inTransaction;     /* Transaction state */+
−
  int nTransaction;     /* Number of open transactions (read + write) */+
−
  void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */+
−
  void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */+
−
  sqlite3_mutex *mutex; /* Non-recursive mutex required to access this struct */+
−
  BusyHandler busyHdr;  /* The busy handler for this btree */+
−
#ifndef SQLITE_OMIT_SHARED_CACHE+
−
  int nRef;             /* Number of references to this structure */+
−
  BtShared *pNext;      /* Next on a list of sharable BtShared structs */+
−
  BtLock *pLock;        /* List of locks held on this shared-btree struct */+
−
#endif+
−
};+
−
+
−
/*+
−
** An instance of the following structure is used to hold information+
−
** about a cell.  The parseCellPtr() function fills in this structure+
−
** based on information extract from the raw disk page.+
−
*/+
−
typedef struct CellInfo CellInfo;+
−
struct CellInfo {+
−
  u8 *pCell;     /* Pointer to the start of cell content */+
−
  i64 nKey;      /* The key for INTKEY tables, or number of bytes in key */+
−
  u32 nData;     /* Number of bytes of data */+
−
  u32 nPayload;  /* Total amount of payload */+
−
  u16 nHeader;   /* Size of the cell content header in bytes */+
−
  u16 nLocal;    /* Amount of payload held locally */+
−
  u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */+
−
  u16 nSize;     /* Size of the cell content on the main b-tree page */+
−
};+
−
+
−
/*+
−
** A cursor is a pointer to a particular entry within a particular+
−
** b-tree within a database file.+
−
**+
−
** The entry is identified by its MemPage and the index in+
−
** MemPage.aCell[] of the entry.+
−
**+
−
** When a single database file can shared by two more database connections,+
−
** but cursors cannot be shared.  Each cursor is associated with a+
−
** particular database connection identified BtCursor.pBtree.db.+
−
**+
−
** Fields in this structure are accessed under the BtShared.mutex+
−
** found at self->pBt->mutex. +
−
*/+
−
struct BtCursor {+
−
  Btree *pBtree;            /* The Btree to which this cursor belongs */+
−
  BtShared *pBt;            /* The BtShared this cursor points to */+
−
  BtCursor *pNext, *pPrev;  /* Forms a linked list of all cursors */+
−
  int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */+
−
  void *pArg;               /* First arg to xCompare() */+
−
  Pgno pgnoRoot;            /* The root page of this tree */+
−
  MemPage *pPage;           /* Page that contains the entry */+
−
  int idx;                  /* Index of the entry in pPage->aCell[] */+
−
  CellInfo info;            /* A parse of the cell we are pointing at */+
−
  u8 wrFlag;                /* True if writable */+
−
  u8 eState;                /* One of the CURSOR_XXX constants (see below) */+
−
  void *pKey;      /* Saved key that was cursor's last known position */+
−
  i64 nKey;        /* Size of pKey, or last integer key */+
−
  int skip;        /* (skip<0) -> Prev() is a no-op. (skip>0) -> Next() is */+
−
#ifndef SQLITE_OMIT_INCRBLOB+
−
  u8 isIncrblobHandle;      /* True if this cursor is an incr. io handle */+
−
  Pgno *aOverflow;          /* Cache of overflow page locations */+
−
#endif+
−
};+
−
+
−
/*+
−
** Potential values for BtCursor.eState.+
−
**+
−
** CURSOR_VALID:+
−
**   Cursor points to a valid entry. getPayload() etc. may be called.+
−
**+
−
** CURSOR_INVALID:+
−
**   Cursor does not point to a valid entry. This can happen (for example) +
−
**   because the table is empty or because BtreeCursorFirst() has not been+
−
**   called.+
−
**+
−
** CURSOR_REQUIRESEEK:+
−
**   The table that this cursor was opened on still exists, but has been +
−
**   modified since the cursor was last used. The cursor position is saved+
−
**   in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in +
−
**   this state, restoreOrClearCursorPosition() can be called to attempt to+
−
**   seek the cursor to the saved position.+
−
**+
−
** CURSOR_FAULT:+
−
**   A unrecoverable error (an I/O error or a malloc failure) has occurred+
−
**   on a different connection that shares the BtShared cache with this+
−
**   cursor.  The error has left the cache in an inconsistent state.+
−
**   Do nothing else with this cursor.  Any attempt to use the cursor+
−
**   should return the error code stored in BtCursor.skip+
−
*/+
−
#define CURSOR_INVALID           0+
−
#define CURSOR_VALID             1+
−
#define CURSOR_REQUIRESEEK       2+
−
#define CURSOR_FAULT             3+
−
+
−
/*+
−
** The TRACE macro will print high-level status information about the+
−
** btree operation when the global variable sqlite3_btree_trace is+
−
** enabled.+
−
*/+
−
#if SQLITE_TEST+
−
# define TRACE(X)   if( sqlite3_btree_trace ){ printf X; fflush(stdout); }+
−
#else+
−
# define TRACE(X)+
−
#endif+
−
+
−
/*+
−
** Routines to read and write variable-length integers.  These used to+
−
** be defined locally, but now we use the varint routines in the util.c+
−
** file.+
−
*/+
−
#define getVarint    sqlite3GetVarint+
−
#define getVarint32(A,B)  ((*B=*(A))<=0x7f?1:sqlite3GetVarint32(A,B))+
−
#define putVarint    sqlite3PutVarint+
−
+
−
/* The database page the PENDING_BYTE occupies. This page is never used.+
−
** TODO: This macro is very similary to PAGER_MJ_PGNO() in pager.c. They+
−
** should possibly be consolidated (presumably in pager.h).+
−
**+
−
** If disk I/O is omitted (meaning that the database is stored purely+
−
** in memory) then there is no pending byte.+
−
*/+
−
#ifdef SQLITE_OMIT_DISKIO+
−
# define PENDING_BYTE_PAGE(pBt)  0x7fffffff+
−
#else+
−
# define PENDING_BYTE_PAGE(pBt) ((PENDING_BYTE/(pBt)->pageSize)+1)+
−
#endif+
−
+
−
/*+
−
** A linked list of the following structures is stored at BtShared.pLock.+
−
** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor +
−
** is opened on the table with root page BtShared.iTable. Locks are removed+
−
** from this list when a transaction is committed or rolled back, or when+
−
** a btree handle is closed.+
−
*/+
−
struct BtLock {+
−
  Btree *pBtree;        /* Btree handle holding this lock */+
−
  Pgno iTable;          /* Root page of table */+
−
  u8 eLock;             /* READ_LOCK or WRITE_LOCK */+
−
  BtLock *pNext;        /* Next in BtShared.pLock list */+
−
};+
−
+
−
/* Candidate values for BtLock.eLock */+
−
#define READ_LOCK     1+
−
#define WRITE_LOCK    2+
−
+
−
/*+
−
** These macros define the location of the pointer-map entry for a +
−
** database page. The first argument to each is the number of usable+
−
** bytes on each page of the database (often 1024). The second is the+
−
** page number to look up in the pointer map.+
−
**+
−
** PTRMAP_PAGENO returns the database page number of the pointer-map+
−
** page that stores the required pointer. PTRMAP_PTROFFSET returns+
−
** the offset of the requested map entry.+
−
**+
−
** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,+
−
** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be+
−
** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements+
−
** this test.+
−
*/+
−
#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)+
−
#define PTRMAP_PTROFFSET(pBt, pgno) (5*(pgno-ptrmapPageno(pBt, pgno)-1))+
−
#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))+
−
+
−
/*+
−
** The pointer map is a lookup table that identifies the parent page for+
−
** each child page in the database file.  The parent page is the page that+
−
** contains a pointer to the child.  Every page in the database contains+
−
** 0 or 1 parent pages.  (In this context 'database page' refers+
−
** to any page that is not part of the pointer map itself.)  Each pointer map+
−
** entry consists of a single byte 'type' and a 4 byte parent page number.+
−
** The PTRMAP_XXX identifiers below are the valid types.+
−
**+
−
** The purpose of the pointer map is to facility moving pages from one+
−
** position in the file to another as part of autovacuum.  When a page+
−
** is moved, the pointer in its parent must be updated to point to the+
−
** new location.  The pointer map is used to locate the parent page quickly.+
−
**+
−
** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not+
−
**                  used in this case.+
−
**+
−
** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number +
−
**                  is not used in this case.+
−
**+
−
** PTRMAP_OVERFLOW1: The database page is the first page in a list of +
−
**                   overflow pages. The page number identifies the page that+
−
**                   contains the cell with a pointer to this overflow page.+
−
**+
−
** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of+
−
**                   overflow pages. The page-number identifies the previous+
−
**                   page in the overflow page list.+
−
**+
−
** PTRMAP_BTREE: The database page is a non-root btree page. The page number+
−
**               identifies the parent page in the btree.+
−
*/+
−
#define PTRMAP_ROOTPAGE 1+
−
#define PTRMAP_FREEPAGE 2+
−
#define PTRMAP_OVERFLOW1 3+
−
#define PTRMAP_OVERFLOW2 4+
−
#define PTRMAP_BTREE 5+
−
+
−
/* A bunch of assert() statements to check the transaction state variables+
−
** of handle p (type Btree*) are internally consistent.+
−
*/+
−
#define btreeIntegrity(p) \+
−
  assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \+
−
  assert( p->pBt->inTransaction>=p->inTrans ); +
−
+
−
+
−
/*+
−
** The ISAUTOVACUUM macro is used within balance_nonroot() to determine+
−
** if the database supports auto-vacuum or not. Because it is used+
−
** within an expression that is an argument to another macro +
−
** (sqliteMallocRaw), it is not possible to use conditional compilation.+
−
** So, this macro is defined instead.+
−
*/+
−
#ifndef SQLITE_OMIT_AUTOVACUUM+
−
#define ISAUTOVACUUM (pBt->autoVacuum)+
−
#else+
−
#define ISAUTOVACUUM 0+
−
#endif+
−
+
−
+
−
/*+
−
** This structure is passed around through all the sanity checking routines+
−
** in order to keep track of some global state information.+
−
*/+
−
typedef struct IntegrityCk IntegrityCk;+
−
struct IntegrityCk {+
−
  BtShared *pBt;    /* The tree being checked out */+
−
  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */+
−
  int nPage;        /* Number of pages in the database */+
−
  int *anRef;       /* Number of times each page is referenced */+
−
  int mxErr;        /* Stop accumulating errors when this reaches zero */+
−
  char *zErrMsg;    /* An error message.  NULL if no errors seen. */+
−
  int nErr;         /* Number of messages written to zErrMsg so far */+
−
};+
−
+
−
/*+
−
** Read or write a two- and four-byte big-endian integer values.+
−
*/+
−
#define get2byte(x)   ((x)[0]<<8 | (x)[1])+
−
#define put2byte(p,v) ((p)[0] = (v)>>8, (p)[1] = (v))+
−
#define get4byte sqlite3Get4byte+
−
#define put4byte sqlite3Put4byte+
−
+
−
/*+
−
** Internal routines that should be accessed by the btree layer only.+
−
*/+
−
int sqlite3BtreeGetPage(BtShared*, Pgno, MemPage**, int);+
−
int sqlite3BtreeInitPage(MemPage *pPage, MemPage *pParent);+
−
void sqlite3BtreeParseCellPtr(MemPage*, u8*, CellInfo*);+
−
void sqlite3BtreeParseCell(MemPage*, int, CellInfo*);+
−
#ifdef SQLITE_TEST+
−
u8 *sqlite3BtreeFindCell(MemPage *pPage, int iCell);+
−
#endif+
−
int sqlite3BtreeRestoreOrClearCursorPosition(BtCursor *pCur);+
−
void sqlite3BtreeGetTempCursor(BtCursor *pCur, BtCursor *pTempCur);+
−
void sqlite3BtreeReleaseTempCursor(BtCursor *pCur);+
−
int sqlite3BtreeIsRootPage(MemPage *pPage);+
−
void sqlite3BtreeMoveToParent(BtCursor *pCur);+
−