mirror of
https://github.com/tursodatabase/libsql.git
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734 lines
33 KiB
C
734 lines
33 KiB
C
/*
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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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** This file implements an 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 any power of 2 between 512 and 65536.
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** Each page can be either a btree page, a freelist page, an overflow
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** page, or a pointer-map 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. (1 means 65536)
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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 (must be 64)
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** 22 1 Min embedded payload fraction (must be 32)
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** 23 1 Min leaf payload fraction (must be 32)
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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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** 40 4 Schema cookie
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** 44 4 File format of schema layer
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** 48 4 Size of page cache
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** 52 4 Largest root-page (auto/incr_vacuum)
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** 56 4 1=UTF-8 2=UTF16le 3=UTF16be
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** 60 4 User version
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** 64 4 Incremental vacuum mode
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** 68 4 Application-ID
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** 72 20 unused
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** 92 4 The version-valid-for number
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** 96 4 SQLITE_VERSION_NUMBER
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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 an 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 bits 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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** 0x81 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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/* 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) ((int)(pBt->pageSize-8))
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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 6 bytes (4 bytes for the cell itself
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** plus 2 bytes for the index to the cell in the page header). Such
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** small cells will be rare, but they are possible.
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*/
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#define MX_CELL(pBt) ((pBt->pageSize-8)/6)
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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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typedef struct CellInfo CellInfo;
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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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** 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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** An instance of this object stores information about each a single database
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** page that has been loaded into memory. The information in this object
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** is derived from the raw on-disk page content.
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**
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** As each database page is loaded into memory, the pager allocates an
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** instance of this object and zeros the first 8 bytes. (This is the
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** "extra" information associated with each page of the pager.)
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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 intKey; /* True if table b-trees. False for index b-trees */
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u8 intKeyLeaf; /* True if the leaf of an intKey table */
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Pgno pgno; /* Page number for this page */
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/* Only the first 8 bytes (above) are zeroed by pager.c when a new page
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** is allocated. All fields that follow must be initialized before use */
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u8 leaf; /* True if a leaf page */
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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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u8 max1bytePayload; /* min(maxLocal,127) */
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u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
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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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int nFree; /* Number of free bytes on the page. -1 for unknown */
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u16 nCell; /* Number of cells on this page, local and ovfl */
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u16 maskPage; /* Mask for page offset */
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u16 aiOvfl[4]; /* Insert the i-th overflow cell before the aiOvfl-th
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** non-overflow cell */
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u8 *apOvfl[4]; /* Pointers to the body of overflow cells */
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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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u8 *aDataEnd; /* One byte past the end of the entire page - not just
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** the usable space, the entire page. Used to prevent
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** corruption-induced buffer overflow. */
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u8 *aCellIdx; /* The cell index area */
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u8 *aDataOfst; /* Same as aData for leaves. aData+4 for interior */
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DbPage *pDbPage; /* Pager page handle */
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u16 (*xCellSize)(MemPage*,u8*); /* cellSizePtr method */
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void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
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};
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/*
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** A linked list of the following structures is stored at BtShared.pLock.
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** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor
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** is opened on the table with root page BtShared.iTable. Locks are removed
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** from this list when a transaction is committed or rolled back, or when
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** a btree handle is closed.
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*/
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struct BtLock {
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Btree *pBtree; /* Btree handle holding this lock */
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Pgno iTable; /* Root page of table */
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u8 eLock; /* READ_LOCK or WRITE_LOCK */
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BtLock *pNext; /* Next in BtShared.pLock list */
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};
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/* Candidate values for BtLock.eLock */
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#define READ_LOCK 1
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#define WRITE_LOCK 2
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/* A Btree handle
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**
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** 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.
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**
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** For some database files, the same underlying database cache might be
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** shared between multiple connections. In that case, each connection
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** has it own instance of 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 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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*/
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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 */
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u8 sharable; /* True if we can share pBt with another db */
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u8 locked; /* True if db currently has pBt locked */
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u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
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int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */
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int nBackup; /* Number of backup operations reading this btree */
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u32 iBDataVersion; /* Combines with pBt->pPager->iDataVersion */
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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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#ifdef SQLITE_DEBUG
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u64 nSeek; /* Calls to sqlite3BtreeMovetoUnpacked() */
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#endif
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#ifndef SQLITE_OMIT_SHARED_CACHE
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BtLock lock; /* Object used to lock page 1 */
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#endif
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};
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/*
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** Btree.inTrans may take one of the following values.
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**
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** 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.
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**
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** These values must match SQLITE_TXN_NONE, SQLITE_TXN_READ, and
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** SQLITE_TXN_WRITE
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*/
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#define TRANS_NONE 0
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#define TRANS_READ 1
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#define TRANS_WRITE 2
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#if TRANS_NONE!=SQLITE_TXN_NONE
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# error wrong numeric code for no-transaction
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#endif
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#if TRANS_READ!=SQLITE_TXN_READ
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# error wrong numeric code for read-transaction
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#endif
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#if TRANS_WRITE!=SQLITE_TXN_WRITE
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# error wrong numeric code for write-transaction
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#endif
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/*
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** An instance of this object represents a single database file.
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**
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** A single database file can be in use at 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
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** 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.
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**
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** Fields in this structure are accessed under the BtShared.mutex
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** mutex, except for nRef and pNext which are accessed under the
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** global SQLITE_MUTEX_STATIC_MAIN mutex. The pPager field
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** may not be modified once it is initially set as long as nRef>0.
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** The pSchema field may be set once under BtShared.mutex and
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** thereafter is unchanged as long as nRef>0.
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**
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** isPending:
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**
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** If a BtShared client fails to obtain a write-lock on a database
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** table (because there exists one or more read-locks on the table),
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** the shared-cache enters 'pending-lock' state and isPending is
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** set to true.
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**
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** The shared-cache leaves the 'pending lock' state when either of
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** the following occur:
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**
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** 1) The current writer (BtShared.pWriter) concludes its transaction, OR
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** 2) The number of locks held by other connections drops to zero.
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**
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** while in the 'pending-lock' state, no connection may start a new
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** transaction.
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**
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** This feature is included to help prevent writer-starvation.
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*/
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struct BtShared {
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Pager *pPager; /* The page cache */
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sqlite3 *db; /* Database connection currently using this Btree */
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BtCursor *pCursor; /* A list of all open cursors */
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MemPage *pPage1; /* First page of the database */
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u8 openFlags; /* Flags to sqlite3BtreeOpen() */
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#ifndef SQLITE_OMIT_AUTOVACUUM
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u8 autoVacuum; /* True if auto-vacuum is enabled */
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u8 incrVacuum; /* True if incr-vacuum is enabled */
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u8 bDoTruncate; /* True to truncate db on commit */
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#endif
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u8 inTransaction; /* Transaction state */
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u8 max1bytePayload; /* Maximum first byte of cell for a 1-byte payload */
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u8 nReserveWanted; /* Desired number of extra bytes per page */
|
|
u16 btsFlags; /* Boolean parameters. See BTS_* macros below */
|
|
u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */
|
|
u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */
|
|
u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */
|
|
u16 minLeaf; /* Minimum local payload in a LEAFDATA table */
|
|
u32 pageSize; /* Total number of bytes on a page */
|
|
u32 usableSize; /* Number of usable bytes on each page */
|
|
int nTransaction; /* Number of open transactions (read + write) */
|
|
u32 nPage; /* Number of pages in the database */
|
|
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 object */
|
|
Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */
|
|
#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 */
|
|
Btree *pWriter; /* Btree with currently open write transaction */
|
|
#endif
|
|
u8 *pTmpSpace; /* Temp space sufficient to hold a single cell */
|
|
int nPreformatSize; /* Size of last cell written by TransferRow() */
|
|
};
|
|
|
|
/*
|
|
** Allowed values for BtShared.btsFlags
|
|
*/
|
|
#define BTS_READ_ONLY 0x0001 /* Underlying file is readonly */
|
|
#define BTS_PAGESIZE_FIXED 0x0002 /* Page size can no longer be changed */
|
|
#define BTS_SECURE_DELETE 0x0004 /* PRAGMA secure_delete is enabled */
|
|
#define BTS_OVERWRITE 0x0008 /* Overwrite deleted content with zeros */
|
|
#define BTS_FAST_SECURE 0x000c /* Combination of the previous two */
|
|
#define BTS_INITIALLY_EMPTY 0x0010 /* Database was empty at trans start */
|
|
#define BTS_NO_WAL 0x0020 /* Do not open write-ahead-log files */
|
|
#define BTS_EXCLUSIVE 0x0040 /* pWriter has an exclusive lock */
|
|
#define BTS_PENDING 0x0080 /* Waiting for read-locks to clear */
|
|
|
|
/*
|
|
** 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.
|
|
*/
|
|
struct CellInfo {
|
|
i64 nKey; /* The key for INTKEY tables, or nPayload otherwise */
|
|
u8 *pPayload; /* Pointer to the start of payload */
|
|
u32 nPayload; /* Bytes of payload */
|
|
u16 nLocal; /* Amount of payload held locally, not on overflow */
|
|
u16 nSize; /* Size of the cell content on the main b-tree page */
|
|
};
|
|
|
|
/*
|
|
** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
|
|
** this will be declared corrupt. This value is calculated based on a
|
|
** maximum database size of 2^31 pages a minimum fanout of 2 for a
|
|
** root-node and 3 for all other internal nodes.
|
|
**
|
|
** If a tree that appears to be taller than this is encountered, it is
|
|
** assumed that the database is corrupt.
|
|
*/
|
|
#define BTCURSOR_MAX_DEPTH 20
|
|
|
|
/*
|
|
** 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.
|
|
**
|
|
** A single database file can be 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.
|
|
**
|
|
** skipNext meaning:
|
|
** The meaning of skipNext depends on the value of eState:
|
|
**
|
|
** eState Meaning of skipNext
|
|
** VALID skipNext is meaningless and is ignored
|
|
** INVALID skipNext is meaningless and is ignored
|
|
** SKIPNEXT sqlite3BtreeNext() is a no-op if skipNext>0 and
|
|
** sqlite3BtreePrevious() is no-op if skipNext<0.
|
|
** REQUIRESEEK restoreCursorPosition() restores the cursor to
|
|
** eState=SKIPNEXT if skipNext!=0
|
|
** FAULT skipNext holds the cursor fault error code.
|
|
*/
|
|
struct BtCursor {
|
|
u8 eState; /* One of the CURSOR_XXX constants (see below) */
|
|
u8 curFlags; /* zero or more BTCF_* flags defined below */
|
|
u8 curPagerFlags; /* Flags to send to sqlite3PagerGet() */
|
|
u8 hints; /* As configured by CursorSetHints() */
|
|
int skipNext; /* Prev() is noop if negative. Next() is noop if positive.
|
|
** Error code if eState==CURSOR_FAULT */
|
|
Btree *pBtree; /* The Btree to which this cursor belongs */
|
|
Pgno *aOverflow; /* Cache of overflow page locations */
|
|
void *pKey; /* Saved key that was cursor last known position */
|
|
/* All fields above are zeroed when the cursor is allocated. See
|
|
** sqlite3BtreeCursorZero(). Fields that follow must be manually
|
|
** initialized. */
|
|
#define BTCURSOR_FIRST_UNINIT pBt /* Name of first uninitialized field */
|
|
BtShared *pBt; /* The BtShared this cursor points to */
|
|
BtCursor *pNext; /* Forms a linked list of all cursors */
|
|
CellInfo info; /* A parse of the cell we are pointing at */
|
|
i64 nKey; /* Size of pKey, or last integer key */
|
|
Pgno pgnoRoot; /* The root page of this tree */
|
|
i8 iPage; /* Index of current page in apPage */
|
|
u8 curIntKey; /* Value of apPage[0]->intKey */
|
|
u16 ix; /* Current index for apPage[iPage] */
|
|
u16 aiIdx[BTCURSOR_MAX_DEPTH-1]; /* Current index in apPage[i] */
|
|
struct KeyInfo *pKeyInfo; /* Arg passed to comparison function */
|
|
MemPage *pPage; /* Current page */
|
|
MemPage *apPage[BTCURSOR_MAX_DEPTH-1]; /* Stack of parents of current page */
|
|
};
|
|
|
|
/*
|
|
** Legal values for BtCursor.curFlags
|
|
*/
|
|
#define BTCF_WriteFlag 0x01 /* True if a write cursor */
|
|
#define BTCF_ValidNKey 0x02 /* True if info.nKey is valid */
|
|
#define BTCF_ValidOvfl 0x04 /* True if aOverflow is valid */
|
|
#define BTCF_AtLast 0x08 /* Cursor is pointing to the last entry */
|
|
#define BTCF_Incrblob 0x10 /* True if an incremental I/O handle */
|
|
#define BTCF_Multiple 0x20 /* Maybe another cursor on the same btree */
|
|
#define BTCF_Pinned 0x40 /* Cursor is busy and cannot be moved */
|
|
|
|
/*
|
|
** Potential values for BtCursor.eState.
|
|
**
|
|
** 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_VALID:
|
|
** Cursor points to a valid entry. getPayload() etc. may be called.
|
|
**
|
|
** CURSOR_SKIPNEXT:
|
|
** Cursor is valid except that the Cursor.skipNext field is non-zero
|
|
** indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious()
|
|
** operation should be a no-op.
|
|
**
|
|
** 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, restoreCursorPosition() can be called to attempt to
|
|
** seek the cursor to the saved position.
|
|
**
|
|
** CURSOR_FAULT:
|
|
** An 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.skipNext
|
|
*/
|
|
#define CURSOR_VALID 0
|
|
#define CURSOR_INVALID 1
|
|
#define CURSOR_SKIPNEXT 2
|
|
#define CURSOR_REQUIRESEEK 3
|
|
#define CURSOR_FAULT 4
|
|
|
|
/*
|
|
** The database page the PENDING_BYTE occupies. This page is never used.
|
|
*/
|
|
#define PENDING_BYTE_PAGE(pBt) ((Pgno)((PENDING_BYTE/((pBt)->pageSize))+1))
|
|
|
|
/*
|
|
** 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(pgptrmap, pgno) (5*(pgno-pgptrmap-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) (pBt->autoVacuum)
|
|
#else
|
|
#define ISAUTOVACUUM(pBt) 0
|
|
#endif
|
|
|
|
|
|
/*
|
|
** This structure is passed around through all the PRAGMA integrity_check
|
|
** checking routines in order to keep track of some global state information.
|
|
**
|
|
** The aRef[] array is allocated so that there is 1 bit for each page in
|
|
** the database. As the integrity-check proceeds, for each page used in
|
|
** the database the corresponding bit is set. This allows integrity-check to
|
|
** detect pages that are used twice and orphaned pages (both of which
|
|
** indicate corruption).
|
|
*/
|
|
typedef struct IntegrityCk IntegrityCk;
|
|
struct IntegrityCk {
|
|
BtShared *pBt; /* The tree being checked out */
|
|
Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
|
|
u8 *aPgRef; /* 1 bit per page in the db (see above) */
|
|
Pgno nCkPage; /* Pages in the database. 0 for partial check */
|
|
int mxErr; /* Stop accumulating errors when this reaches zero */
|
|
int nErr; /* Number of messages written to zErrMsg so far */
|
|
int rc; /* SQLITE_OK, SQLITE_NOMEM, or SQLITE_INTERRUPT */
|
|
u32 nStep; /* Number of steps into the integrity_check process */
|
|
const char *zPfx; /* Error message prefix */
|
|
Pgno v0; /* Value for first %u substitution in zPfx (root page) */
|
|
Pgno v1; /* Value for second %u substitution in zPfx (current pg) */
|
|
int v2; /* Value for third %d substitution in zPfx */
|
|
StrAccum errMsg; /* Accumulate the error message text here */
|
|
u32 *heap; /* Min-heap used for analyzing cell coverage */
|
|
sqlite3 *db; /* Database connection running the check */
|
|
};
|
|
|
|
/*
|
|
** Routines to 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] = (u8)((v)>>8), (p)[1] = (u8)(v))
|
|
#define get4byte sqlite3Get4byte
|
|
#define put4byte sqlite3Put4byte
|
|
|
|
/*
|
|
** get2byteAligned(), unlike get2byte(), requires that its argument point to a
|
|
** two-byte aligned address. get2byteAligned() is only used for accessing the
|
|
** cell addresses in a btree header.
|
|
*/
|
|
#if SQLITE_BYTEORDER==4321
|
|
# define get2byteAligned(x) (*(u16*)(x))
|
|
#elif SQLITE_BYTEORDER==1234 && GCC_VERSION>=4008000
|
|
# define get2byteAligned(x) __builtin_bswap16(*(u16*)(x))
|
|
#elif SQLITE_BYTEORDER==1234 && MSVC_VERSION>=1300
|
|
# define get2byteAligned(x) _byteswap_ushort(*(u16*)(x))
|
|
#else
|
|
# define get2byteAligned(x) ((x)[0]<<8 | (x)[1])
|
|
#endif
|