Use pure-Rust heic decoder

Author: gen2brain

README.md

@@ -4,9 +4,9 @@
 
 Go decoder for [HEIC Image File Format](https://en.wikipedia.org/wiki/High_Efficiency_Image_File_Format) (HEVC in HEIF).
 
-Based on [libheif](https://github.com/strukturag/libheif) and [libde265](https://github.com/strukturag/libde265) compiled to [WASM](https://en.wikipedia.org/wiki/WebAssembly) and transpiled to pure Go with [wasm2go](https://github.com/ncruces/wasm2go) (CGo-free).
+Based on the pure-Rust [heic](https://crates.io/crates/heic) decoder compiled to [WASM](https://en.wikipedia.org/wiki/WebAssembly) and transpiled to pure Go with [wasm2go](https://github.com/ncruces/wasm2go) (CGo-free).
 
-The library will first try to use a dynamic/shared library (if installed) via [purego](https://github.com/ebitengine/purego) and will fall back to the transpiled Go.
+The library will first try to use a [libheif](https://github.com/strukturag/libheif) dynamic/shared library (if installed) via [purego](https://github.com/ebitengine/purego) and will fall back to the transpiled Go.
 
 ### Build tags
 

decode.go

@@ -0,0 +1,98 @@
+package heic
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"io"
+	"sync"
+)
+
+var modPool = sync.Pool{New: func() any { return newModuleRaw() }}
+
+func decode(r io.Reader, configOnly bool) (image.Image, image.Config, error) {
+	var cfg image.Config
+
+	mod := modPool.Get().(*module)
+	defer modPool.Put(mod)
+
+	var data []byte
+	var err error
+	if configOnly {
+		data, err = io.ReadAll(io.LimitReader(r, heifMaxHeaderSize))
+	} else {
+		data, err = io.ReadAll(r)
+	}
+	if err != nil {
+		return nil, cfg, fmt.Errorf("read: %w", err)
+	}
+
+	inSize := len(data)
+
+	inPtr := mod.Xmalloc(int32(inSize))
+	if inPtr == 0 {
+		return nil, cfg, ErrMemWrite
+	}
+	defer mod.Xfree(inPtr)
+	if !mod.write(inPtr, data) {
+		return nil, cfg, ErrMemWrite
+	}
+
+	info := mod.Xmalloc(2 * 4)
+	if info == 0 {
+		return nil, cfg, ErrMemWrite
+	}
+	defer mod.Xfree(info)
+
+	cfgOnly := int32(0)
+	if configOnly {
+		cfgOnly = 1
+	}
+
+	out := mod.Xdecode(inPtr, int32(inSize), cfgOnly, info)
+
+	width := load32(mod.memory[info:])
+	height := load32(mod.memory[info+4:])
+
+	cfg.Width = int(width)
+	cfg.Height = int(height)
+	cfg.ColorModel = color.NRGBAModel
+
+	if configOnly {
+		if width == 0 {
+			return nil, image.Config{}, ErrDecode
+		}
+		return nil, cfg, nil
+	}
+
+	if out == 0 {
+		return nil, cfg, ErrDecode
+	}
+	defer mod.Xfree(out)
+
+	size := int(width) * int(height) * 4
+	pix, ok := mod.read(out, int32(size))
+	if !ok {
+		return nil, cfg, ErrMemRead
+	}
+
+	img := image.NewNRGBA(image.Rect(0, 0, int(width), int(height)))
+	copy(img.Pix, pix)
+
+	return img, cfg, nil
+}
+
+func (m *module) write(ptr int32, data []byte) bool {
+	if ptr < 0 || int(ptr)+len(data) > len(m.memory) {
+		return false
+	}
+	copy(m.memory[ptr:], data)
+	return true
+}
+
+func (m *module) read(ptr, size int32) ([]byte, bool) {
+	if ptr < 0 || size < 0 || int(ptr)+int(size) > len(m.memory) {
+		return nil, false
+	}
+	return m.memory[ptr : ptr+size : ptr+size], true
+}