fieldtypeset.go

// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tiff

import (
	"encoding/json"
	"fmt"
	"sort"
	"sync"
)

// FieldTypeSet represents a set of field types that may be in use within a file
// that uses a TIFF file structure.  This can be customized for custom file
// formats and private IFDs.
type FieldTypeSet interface {
	GetFieldType(id uint16) (FieldType, bool)
	ListFieldTypes() []uint16
	ListFieldTypeNames() []string
	Name() string
	Register(ft FieldType) bool
	Lock()
}

func NewFieldTypeSet(name string) FieldTypeSet {
	return &fieldTypeSet{
		name:  name,
		types: make(map[uint16]FieldType, 1),
	}
}

type fieldTypeSet struct {
	mu     sync.RWMutex
	locked bool
	name   string
	types  map[uint16]FieldType
}

func (fts *fieldTypeSet) GetFieldType(id uint16) (FieldType, bool) {
	fts.mu.RLock()
	ft, ok := fts.types[id]
	fts.mu.RUnlock()
	return ft, ok
}

func (fts *fieldTypeSet) ListFieldTypes() []uint16 {
	fts.mu.RLock()
	ids := make([]uint16, len(fts.types))
	i := 0
	for id := range fts.types {
		ids[i] = id
		i++
	}
	sort.Sort(uint16Slice(ids))
	fts.mu.RUnlock()
	return ids
}

func (fts *fieldTypeSet) ListFieldTypeNames() []string {
	fts.mu.RLock()
	names := make([]string, len(fts.types))
	i := 0
	for _, ft := range fts.types {
		names[i] = ft.Name()
		i++
	}
	sort.Strings(names)
	fts.mu.RUnlock()
	return names
}

func (fts *fieldTypeSet) Name() string {
	return fts.name
}

func (fts *fieldTypeSet) Register(ft FieldType) bool {
	fts.mu.Lock()
	defer fts.mu.Unlock()
	// Disallow registration if the set is locked.
	if fts.locked {
		return false
	}
	// Just overwrite field types if they already exist.  Users doing this
	// should be generally aware of what they are doing.
	fts.types[ft.ID()] = ft
	return true
}

func (fts *fieldTypeSet) Lock() {
	fts.mu.Lock()
	fts.locked = true
	fts.mu.Unlock()
}

func (fts *fieldTypeSet) MarshalJSON() ([]byte, error) {
	tmp := struct {
		Name string
	}{
		Name: fts.name,
	}
	return json.Marshal(tmp)
}

func (fts *fieldTypeSet) String() string {
	return fmt.Sprintf("<FieldTypeSet: %q>", fts.name)
}