blobio

Documentation

Overview

Package blobio provides an SQL interface to incremental BLOB I/O.

Example

// Open the database, registering the extension.
db, err := driver.Open("file:/test.db?vfs=memdb", func(conn *sqlite3.Conn) error {
	blobio.Register(conn)
	return nil
})

if err != nil {
	log.Fatal(err)
}
defer db.Close()

_, err = db.Exec(`CREATE TABLE test (col)`)
if err != nil {
	log.Fatal(err)
}

const message = "Hello BLOB!"

// Create the BLOB.
_, err = db.Exec(`INSERT INTO test VALUES (?)`, sqlite3.ZeroBlob(len(message)))
if err != nil {
	log.Fatal(err)
}

// Write the BLOB.
_, err = db.Exec(`SELECT writeblob('main', 'test', 'col', last_insert_rowid(), 0, ?)`, message)
if err != nil {
	log.Fatal(err)
}

// Read the BLOB.
_, err = db.Exec(`SELECT openblob('main', 'test', 'col', rowid, false, ?) FROM test`,
	sqlite3.Pointer[blobio.OpenCallback](func(blob *sqlite3.Blob, _ ...sqlite3.Value) error {
		_, err = io.Copy(os.Stdout, blob)
		return err
	}))
if err != nil {
	log.Fatal(err)
}

Output:

Hello BLOB!

Index

• func Register(db *sqlite3.Conn)
• type OpenCallback

Examples

• Package

Functions

func Register

func Register(db *sqlite3.Conn)

Register registers the SQL functions:

readblob(schema, table, column, rowid, offset, n)

Reads n bytes of a blob, starting at offset.

writeblob(schema, table, column, rowid, offset, data)

Writes data into a blob, at the given offset.

openblob(schema, table, column, rowid, write, callback, args...)

Opens blobs for reading or writing. The callback is invoked for each open blob, and must be bound to an OpenCallback, using sqlite3.BindPointer or sqlite3.Pointer. The optional args will be passed to the callback, along with the sqlite3.Blob handle.

https://sqlite.org/c3ref/blob.html

Types

type OpenCallback

type OpenCallback func(*sqlite3.Blob, ...sqlite3.Value) error

OpenCallback is the type for the openblob callback.