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// Copyright 2015 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package errors
import (
"sync"
)
// LazyMultiError is a lazily-constructed MultiError.
//
// LazyMultiError is like MultiError, except that you know the ultimate size up
// front, and then you call Assign for each error encountered, and it's
// potential index. The underlying MultiError will only be allocated if one of
// the Assign'd errors is non-nil. Similarly, Get will retrieve either the
// allocated MultiError, or nil if no error was encountered.
// Build one with NewLazyMultiError.
type LazyMultiError interface {
// Assign semantically assigns the error to the given index in the MultiError.
// If the error is nil, no action is taken. Otherwise the MultiError is
// allocated to its full size (if not already), and the error assigned into
// it.
//
// Returns true iff err != nil (i.e. "was it assigned?"), so you can use this
// like:
// if !lme.Assign(i, err) {
// // stuff requiring err == nil
// }
Assign(int, error) bool
// GetOne returns the error at the given index (which may be nil)
GetOne(int) error
// Get returns the MultiError, or nil, if no non-nil error was Assign'd.
Get() error
}
type lazyMultiError struct {
sync.Mutex
size int
me MultiError
}
// NewLazyMultiError makes a new LazyMultiError of the provided size.
func NewLazyMultiError(size int) LazyMultiError {
return &lazyMultiError{size: size}
}
func (e *lazyMultiError) Assign(i int, err error) bool {
if err == nil {
return false
}
e.Lock()
defer e.Unlock()
if e.me == nil {
e.me = make(MultiError, e.size)
}
e.me[i] = err
return true
}
func (e *lazyMultiError) GetOne(i int) error {
e.Lock()
defer e.Unlock()
if e.me == nil {
return nil
}
return e.me[i]
}
func (e *lazyMultiError) Get() error {
e.Lock()
defer e.Unlock()
if e.me == nil {
return nil
}
return e.me
}