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Documentation error

Paul Sanderson
The process for calculating a checksum text on the SQLite file format page
contains two errors.

Currently reads:

The checksum is an unsigned 32-bit integer computed as follows:

   1. Initialize the checksum to the checksum nonce value found in the
   journal header at offset 12.
   2. Initialize index X to be N-200 (where N is the size of a database
   page in bytes.
   3. Interpret the four bytes at offset X into the page as a 4-byte
   big-endian unsigned integer. Add the value of that integer to the checksum.
   4. Subtrace 200 from X.
   5. If X is greater than or equal to zero, go back to step 3.


The source states:

** This is not a real checksum. It is really just the sum of the
** random initial value (pPager->cksumInit) and every 200th byte
** of the page data, starting with byte offset (pPager->pageSize%200).
** Each byte is interpreted as an 8-bit unsigned integer.


Should read somethng like:

The checksum is an unsigned 32-bit integer computed as follows:

   1. Initialize the checksum to the checksum nonce value found in the
   journal header at offset 12.
   2. Initialize index X to be N-200 (where N is the size of a database
   page in bytes.
   3. Interpret the* byte* at offset X into the page as *an 8-bit* unsigned
   integer. Add the value of that integer to the checksum.
   4. Subtrac*t* 200 from X.
   5. If X is greater than or equal to zero, go back to step 3.




Paul
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Re: Documentation error

Richard Hipp-3
On 2/15/17, Paul Sanderson <[hidden email]> wrote:
> The process for calculating a checksum text on the SQLite file format page
> contains two errors.
>

Thanks for spotting this.  Should be fixed now.
--
D. Richard Hipp
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