System.Data.SQLite

******************************************************************************
**
** This SQLite extension implements functions that compute SHA3 hashes
** in the way described by the (U.S.) NIST FIPS 202 SHA-3 Standard.
** Two SQL functions are implemented:
**
**     sha3(X,SIZE)
**     sha3_agg(Y,SIZE)
**     sha3_query(Z,SIZE)
**
** The sha3(X) function computes the SHA3 hash of the input X, or NULL if
** X is NULL.  If inputs X is text, the UTF-8 rendering of that text is
** used to compute the hash.  If X is a BLOB, then the binary data of the
** blob is used to compute the hash.  If X is an integer or real number,
** then that number if converted into UTF-8 text and the hash is computed
** over the text.
**
** The sha3_agg(Y) function computes the SHA3 hash of all Y inputs.  Since
** order is important for the hash, it is recommended that the Y expression
** by followed by an ORDER BY clause to guarantee that the inputs occur
** in the desired order.
**
** The sha3_query(Y) function evaluates all queries in the SQL statements of Y
** and returns a hash of their results.
**
** The SIZE argument is optional.  If omitted, the SHA3-256 hash algorithm
** is used.  If SIZE is included it must be one of the integers 224, 256,
** 384, or 512, to determine SHA3 hash variant that is computed.
**
** Because the sha3_agg() and sha3_query() functions compute a hash over
** multiple values, the values are encode to use include type information.
**
** In sha3_agg(), the sequence of bytes that gets hashed for each input
** Y depends on the datatype of Y:
**
**    typeof(Y)='null'         A single "N" is hashed.  (One byte)
**
**    typeof(Y)='integer'      The data hash is the character "I" followed
**                             by an 8-byte big-endian binary of the
**                             64-bit signed integer.  (Nine bytes total.)
**
**    typeof(Y)='real'         The character "F" followed by an 8-byte
**                             big-ending binary of the double.  (Nine
**                             bytes total.)
**
**    typeof(Y)='text'         The hash is over prefix "Tnnn:" followed
**                             by the UTF8 encoding of the text.  The "nnn"
**                             in the prefix is the minimum-length decimal
**                             representation of the octet_length of the text.
**                             Notice the ":" at the end of the prefix, which
**                             is needed to separate the prefix from the
**                             content in cases where the content starts
**                             with a digit.
**
**    typeof(Y)='blob'         The hash is taken over prefix "Bnnn:" followed
**                             by the binary content of the blob.  The "nnn"
**                             in the prefix is the mimimum-length decimal
**                             representation of the byte-length of the blob.
**
** According to the rules above, all of the following SELECT statements
** should return TRUE:
**
**    SELECT sha3(1) = sha3('1');
**
**    SELECT sha3('hello') = sha3(x'68656c6c6f');
**
**    WITH a(x) AS (VALUES('xyzzy'))
**      SELECT sha3_agg(x) = sha3('T5:xyzzy')            FROM a;
**
**    WITH a(x) AS (VALUES(x'010203'))
**      SELECT sha3_agg(x) = sha3(x'42333a010203')       FROM a;
**
**    WITH a(x) AS (VALUES(0x123456))
**      SELECT sha3_agg(x) = sha3(x'490000000000123456') FROM a;
**
**    WITH a(x) AS (VALUES(100.015625))
**      SELECT sha3_agg(x) = sha3(x'464059010000000000') FROM a;
**
**    WITH a(x) AS (VALUES(NULL))
**      SELECT sha3_agg(x) = sha3('N') FROM a;
**
**
** In sha3_query(), individual column values are encoded as with
** sha3_agg(), but with the addition that a single "R" character is
** inserted at the start of each row.
**
** Note that sha3_agg() hashes rows for which Y is NULL.  Add a FILTER
** clause if NULL rows should be excluded:
**
**    SELECT sha3_agg(x ORDER BY rowid) FILTER(WHERE x NOT NULL) FROM t1;
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#include <stdarg.h>