gemini-search

A simple search engine for Geminispace
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sqlite3_opt_preupdate_hook.go (3240B)

      1 // Copyright (C) 2019 G.J.R. Timmer <gjr.timmer@gmail.com>.
      2 // Copyright (C) 2018 segment.com <friends@segment.com>
      3 //
      4 // Use of this source code is governed by an MIT-style
      5 // license that can be found in the LICENSE file.
      6 
      7 //go:build sqlite_preupdate_hook
      8 // +build sqlite_preupdate_hook
      9 
     10 package sqlite3
     11 
     12 /*
     13 #cgo CFLAGS: -DSQLITE_ENABLE_PREUPDATE_HOOK
     14 #cgo LDFLAGS: -lm
     15 
     16 #ifndef USE_LIBSQLITE3
     17 #include "sqlite3-binding.h"
     18 #else
     19 #include <sqlite3.h>
     20 #endif
     21 #include <stdlib.h>
     22 #include <string.h>
     23 
     24 void preUpdateHookTrampoline(void*, sqlite3 *, int, char *, char *, sqlite3_int64, sqlite3_int64);
     25 */
     26 import "C"
     27 import (
     28 	"errors"
     29 	"unsafe"
     30 )
     31 
     32 // RegisterPreUpdateHook sets the pre-update hook for a connection.
     33 //
     34 // The callback is passed a SQLitePreUpdateData struct with the data for
     35 // the update, as well as methods for fetching copies of impacted data.
     36 //
     37 // If there is an existing preupdate hook for this connection, it will be
     38 // removed. If callback is nil the existing hook (if any) will be removed
     39 // without creating a new one.
     40 func (c *SQLiteConn) RegisterPreUpdateHook(callback func(SQLitePreUpdateData)) {
     41 	if callback == nil {
     42 		C.sqlite3_preupdate_hook(c.db, nil, nil)
     43 	} else {
     44 		C.sqlite3_preupdate_hook(c.db, (*[0]byte)(unsafe.Pointer(C.preUpdateHookTrampoline)), unsafe.Pointer(newHandle(c, callback)))
     45 	}
     46 }
     47 
     48 // Depth returns the source path of the write, see sqlite3_preupdate_depth()
     49 func (d *SQLitePreUpdateData) Depth() int {
     50 	return int(C.sqlite3_preupdate_depth(d.Conn.db))
     51 }
     52 
     53 // Count returns the number of columns in the row
     54 func (d *SQLitePreUpdateData) Count() int {
     55 	return int(C.sqlite3_preupdate_count(d.Conn.db))
     56 }
     57 
     58 func (d *SQLitePreUpdateData) row(dest []any, new bool) error {
     59 	for i := 0; i < d.Count() && i < len(dest); i++ {
     60 		var val *C.sqlite3_value
     61 		var src any
     62 
     63 		// Initially I tried making this just a function pointer argument, but
     64 		// it's absurdly complicated to pass C function pointers.
     65 		if new {
     66 			C.sqlite3_preupdate_new(d.Conn.db, C.int(i), &val)
     67 		} else {
     68 			C.sqlite3_preupdate_old(d.Conn.db, C.int(i), &val)
     69 		}
     70 
     71 		switch C.sqlite3_value_type(val) {
     72 		case C.SQLITE_INTEGER:
     73 			src = int64(C.sqlite3_value_int64(val))
     74 		case C.SQLITE_FLOAT:
     75 			src = float64(C.sqlite3_value_double(val))
     76 		case C.SQLITE_BLOB:
     77 			len := C.sqlite3_value_bytes(val)
     78 			blobptr := C.sqlite3_value_blob(val)
     79 			src = C.GoBytes(blobptr, len)
     80 		case C.SQLITE_TEXT:
     81 			len := C.sqlite3_value_bytes(val)
     82 			cstrptr := unsafe.Pointer(C.sqlite3_value_text(val))
     83 			src = C.GoBytes(cstrptr, len)
     84 		case C.SQLITE_NULL:
     85 			src = nil
     86 		}
     87 
     88 		err := convertAssign(&dest[i], src)
     89 		if err != nil {
     90 			return err
     91 		}
     92 	}
     93 
     94 	return nil
     95 }
     96 
     97 // Old populates dest with the row data to be replaced. This works similar to
     98 // database/sql's Rows.Scan()
     99 func (d *SQLitePreUpdateData) Old(dest ...any) error {
    100 	if d.Op == SQLITE_INSERT {
    101 		return errors.New("There is no old row for INSERT operations")
    102 	}
    103 	return d.row(dest, false)
    104 }
    105 
    106 // New populates dest with the replacement row data. This works similar to
    107 // database/sql's Rows.Scan()
    108 func (d *SQLitePreUpdateData) New(dest ...any) error {
    109 	if d.Op == SQLITE_DELETE {
    110 		return errors.New("There is no new row for DELETE operations")
    111 	}
    112 	return d.row(dest, true)
    113 }