Fantom-foundation/go-lachesis

package table

import (
    "bytes"
    "reflect"

    "github.com/ethereum/go-ethereum/ethdb"
)

// MigrateTables sets target fields to database tables.
func MigrateTables(s interface{}, db ethdb.KeyValueStore) {
    value := reflect.ValueOf(s).Elem()

    var keys uniqKeys
    defer keys.Check()

    for i := 0; i < value.NumField(); i++ {
        if prefix := value.Type().Field(i).Tag.Get("table"); prefix != "" && prefix != "-" {

            field := value.Field(i)
            var val reflect.Value
            if db != nil {
                keys.Add(prefix)
                table := New(db, []byte(prefix))
                val = reflect.ValueOf(table)
            } else {
                val = reflect.Zero(field.Type())
            }
            field.Set(val)
        }
    }
}

// MigrateCaches sets target fields to get() result.
func MigrateCaches(c interface{}, get func() interface{}) {
    value := reflect.ValueOf(c).Elem()
    for i := 0; i < value.NumField(); i++ {
        if prefix := value.Type().Field(i).Tag.Get("cache"); prefix != "" {
            field := value.Field(i)
            var cache interface{}
            if get != nil {
                cache = get()
            }
            var val reflect.Value
            if cache != nil {
                val = reflect.ValueOf(cache)
            } else {
                val = reflect.Zero(field.Type())
            }
            field.Set(val)
        }
    }
}

type uniqKeys struct {
    len  int
    keys [][]byte
}

func (u *uniqKeys) Add(s string) {
    key := []byte(s)

    if len(u.keys) == 0 || u.len > len(key) {
        u.len = len(key)
    }
    u.keys = append(u.keys, key)
}

func (u *uniqKeys) Check() {
    for i := 0; i < len(u.keys); i++ {
        for j := i + 1; j < len(u.keys); j++ {
            a := u.keys[i][:u.len]
            b := u.keys[j][:u.len]
            if bytes.Equal(a, b) {
                panic("prefixes '" + string(u.keys[i]) + "' and '" + string(u.keys[j]) + "' are the same")
            }
        }
    }
}