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// midipak implements compressing and appending MIDI flles
// to a midipak file.
package midipak
import (
"context"
"database/sql"
)
// Encoder compresses each of the input files,
// and is expected to be goroutine safe.
type Encoder interface {
EncodeAll(src, dst []byte) []byte
}
// File stores the name and data of a file.
type File struct {
Name string
Data []byte
}
// Create initializes a new midipak.
func Create(ctx context.Context, db *sql.DB) error {
sqlStmt := "CREATE TABLE files (name TEXT PRIMARY KEY, sz INTEGER NOT NULL, data BLOB);"
_, err := db.ExecContext(ctx, sqlStmt)
return err
}
// Pack appends the files to the midipak, after being compressed
// with the provided encoder. Attempting to pack files that already
// exist is an error.
func Pack(ctx context.Context, db *sql.DB, enc Encoder, files []File) error {
tx, err := db.BeginTx(ctx, nil)
if err != nil {
return err
}
stmt, err := tx.Prepare("INSERT INTO files(name, sz, data) VALUES (?, ?, ?)")
if err != nil {
return err
}
defer stmt.Close()
for _, file := range files {
sz := len(file.Data)
_, err = stmt.Exec(file.Name, sz, enc.EncodeAll(file.Data, make([]byte, 0, sz)))
if err != nil {
return err
}
}
return tx.Commit()
}
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