;;; rocksdb/compaction.lisp --- RocksDB Compaction

 ;; RocksDB Lisp Compaction Filter API

 ;;; Commentary:

 ;; compaction filters are like custom GC rules for the database. compactions

 ;; run in the background and can be configured via the column-family-options

 ;; or compactionfilterfactory API.

 ;; ref: https://github.com/facebook/rocksdb/wiki/Compaction-Filter

 #|

 * RocksDB snapshots do not guarantee to preserve the state of the DB in the

 presence of CompactionFilter. Data seen from a snapshot might disappear after

 a table file created with a `CompactionFilter` is installed. If you use

 snapshots, think twice about whether you want to use `CompactionFilter` and

 whether you are using it in a safe way.

 * If multithreaded compaction is being used *and* a single CompactionFilter

 instance was supplied via Options::compaction_filter, CompactionFilter

 methods may be called from different threads concurrently.  The application

 must ensure that such calls are thread-safe. If the CompactionFilter was

 created by a factory, then it will only ever be used by a single thread that

 is doing the table file creation, and this call does not need to be

 thread-safe.  However, multiple filters may be in existence and operating

 concurrently.

 * The key passed to the filtering methods includes the timestamp if

 user-defined timestamps are enabled.

 * Exceptions MUST NOT propagate out of overridden functions into RocksDB,

 because RocksDB is not exception-safe. This could cause undefined behavior

 including data loss, unreported corruption, deadlocks, and more.

 |#

 ;;; Code:

 (in-package :rocksdb)

 (define-alien-type rocksdb-filter-function

   (function unsigned-char

             (* t)

             int

             c-string

             size-t

             c-string

             size-t

             (* (array unsigned-char))

             (* size-t)

             (* unsigned-char)))

 (define-alien-type rocksdb-create-compaction-filter-function

     (function (* rocksdb-compactionfilter)

               (* t)

               (* rocksdb-compactionfiltercontext)))

 (define-alien-routine rocksdb-compactionfilter-create (* rocksdb-compactionfilter)

   (state (* t))

   (destructor (* rocksdb-destructor-function))

   (filter (* rocksdb-filter-function))

   (name (* rocksdb-name-function)))

 (define-alien-routine rocksdb-compactionfilter-set-ignore-snapshots void

   (self (* rocksdb-compactionfilter)) (val unsigned-char))

 (define-alien-routine rocksdb-compactionfilter-destroy void

   (self (* rocksdb-compactionfilter)))

 ;;; Compaction Filter Context

 (define-alien-routine rocksdb-compactionfiltercontext-is-full-compaction unsigned-char

   (context (* rocksdb-compactionfiltercontext)))

 (define-alien-routine rocksdb-compactionfiltercontext-is-manual-compaction unsigned-char

   (context (* rocksdb-compactionfiltercontext)))

 ;;; Compaction Filter Factory

 (define-alien-routine rocksdb-compactionfilterfactory-create (* rocksdb-compactionfilterfactory)

   (state (* t))

   (destructor (* rocksdb-destructor-function))

   (creator (* rocksdb-create-compaction-filter-function))

   (name (* rocksdb-name-function)))

 (define-alien-routine rocksdb-compacitonfilterfactory-destroy void

   (factory (* rocksdb-compactionfilterfactory)))

 (define-alien-callable rocksdb-filter-never unsigned-char

     ((state (* t))

      (level int)

      (key (array unsigned-char))

      (key-length size-t)

      (existing-val (array unsigned-char))

      (existing-val-length size-t)

      (new-val (* (array unsigned-char)))

      (new-val-length (* size-t))

      (value-changed (* unsigned-char)))

   (declare (ignore state level key key-length existing-val existing-val-length new-val new-val-length value-changed))

   0)

 (define-alien-callable rocksdb-create-compaction-filter-never (* rocksdb-compactionfilter)

     ((state (* t))

      (context (* rocksdb-compactionfiltercontext)))

   (rocksdb-compactionfilter-create

    state

    (alien-sap (alien-callable-function 'rocksdb-destructor))

    (alien-sap (alien-callable-function 'rocksdb-filter-never))

    context))