mirror of https://github.com/jlelse/GoBlog
52 lines
1.3 KiB
Go
52 lines
1.3 KiB
Go
package main
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import (
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"database/sql"
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"errors"
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"github.com/mattn/go-sqlite3"
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)
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func (db *database) shortenPath(p string) (string, error) {
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if p == "" {
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return "", errors.New("empty path")
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}
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spi, err, _ := db.sp.Do(p, func() (any, error) {
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// Check if already cached
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if spi, ok := db.spc.Get(p); ok {
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return spi.(string), nil
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}
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// Insert in case it isn't shortened yet
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_, err := db.Exec(`
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insert or rollback into shortpath (id, path)
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values (
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-- next available id (reuse skipped ids due to bug)
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(select min(id) + 1 from (select id from shortpath union all select 0) where id + 1 not in (select id from shortpath)),
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@path
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)`, sql.Named("path", p))
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if err != nil {
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if no, ok := err.(sqlite3.Error); !ok || sqlite3.ErrNo(no.ExtendedCode) != sqlite3.ErrNo(sqlite3.ErrConstraintUnique) {
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// Some other error than unique constraint violation because path is already shortened
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return nil, err
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}
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}
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// Query short path
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row, err := db.QueryRow("select printf('/s/%x', id) from shortpath where path = @path", sql.Named("path", p))
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if err != nil {
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return nil, err
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}
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var sp string
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err = row.Scan(&sp)
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if err != nil {
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return nil, err
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}
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// Cache result
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db.spc.Set(p, sp, 1)
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return sp, nil
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})
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if err != nil {
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return "", err
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}
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return spi.(string), nil
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}
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