90 lines
2.1 KiB
Go
90 lines
2.1 KiB
Go
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package level
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import (
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"encoding/json"
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"fmt"
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"git.kirsle.net/apps/doodle/render"
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)
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// Types of chunks.
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const (
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MapType int = iota
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GridType
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)
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// Chunk holds a single portion of the pixel canvas.
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type Chunk struct {
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Type int // map vs. 2D array.
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Accessor
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}
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// JSONChunk holds a lightweight (interface-free) copy of the Chunk for
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// unmarshalling JSON files from disk.
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type JSONChunk struct {
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Type int `json:"type"`
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Data json.RawMessage `json:"data"`
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}
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// Accessor provides a high-level API to interact with absolute pixel coordinates
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// while abstracting away the details of how they're stored.
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type Accessor interface {
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Inflate(*Palette) error
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Iter() <-chan Pixel
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IterViewport(viewport render.Rect) <-chan Pixel
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Get(render.Point) (*Swatch, error)
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Set(render.Point, *Swatch) error
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Delete(render.Point) error
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Len() int
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MarshalJSON() ([]byte, error)
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UnmarshalJSON([]byte) error
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}
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// NewChunk creates a new chunk.
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func NewChunk() *Chunk {
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return &Chunk{
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Type: MapType,
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Accessor: NewMapAccessor(),
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}
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}
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// Usage returns the percent of free space vs. allocated pixels in the chunk.
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func (c *Chunk) Usage(size int) float64 {
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return float64(c.Len()) / float64(size)
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}
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// MarshalJSON writes the chunk to JSON.
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func (c *Chunk) MarshalJSON() ([]byte, error) {
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data, err := c.Accessor.MarshalJSON()
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if err != nil {
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return []byte{}, err
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}
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generic := &JSONChunk{
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Type: c.Type,
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Data: data,
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}
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b, err := json.Marshal(generic)
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return b, err
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}
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// UnmarshalJSON loads the chunk from JSON and uses the correct accessor to
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// parse the inner details.
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func (c *Chunk) UnmarshalJSON(b []byte) error {
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// Parse it generically so we can hand off the inner "data" object to the
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// right accessor for unmarshalling.
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generic := &JSONChunk{}
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err := json.Unmarshal(b, generic)
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if err != nil {
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return fmt.Errorf("Chunk.UnmarshalJSON: failed to unmarshal into generic JSONChunk type: %s", err)
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}
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switch c.Type {
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case MapType:
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c.Accessor = NewMapAccessor()
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return c.Accessor.UnmarshalJSON(generic.Data)
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default:
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return fmt.Errorf("Chunk.UnmarshalJSON: unsupported chunk type '%d'", c.Type)
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}
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}
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