[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/tetratelabs/wazero/cache.go

@@ -0,0 +1,116 @@
+package wazero
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	goruntime "runtime"
+	"sync"
+
+	"github.com/tetratelabs/wazero/api"
+	"github.com/tetratelabs/wazero/internal/filecache"
+	"github.com/tetratelabs/wazero/internal/version"
+	"github.com/tetratelabs/wazero/internal/wasm"
+)
+
+// CompilationCache reduces time spent compiling (Runtime.CompileModule) the same wasm module.
+//
+// # Notes
+//
+//   - This is an interface for decoupling, not third-party implementations.
+//     All implementations are in wazero.
+//   - Instances of this can be reused across multiple runtimes, if configured
+//     via RuntimeConfig.
+type CompilationCache interface{ api.Closer }
+
+// NewCompilationCache returns a new CompilationCache to be passed to RuntimeConfig.
+// This configures only in-memory cache, and doesn't persist to the file system. See wazero.NewCompilationCacheWithDir for detail.
+//
+// The returned CompilationCache can be used to share the in-memory compilation results across multiple instances of wazero.Runtime.
+func NewCompilationCache() CompilationCache {
+	return &cache{}
+}
+
+// NewCompilationCacheWithDir is like wazero.NewCompilationCache except the result also writes
+// state into the directory specified by `dirname` parameter.
+//
+// If the dirname doesn't exist, this creates it or returns an error.
+//
+// Those running wazero as a CLI or frequently restarting a process using the same wasm should
+// use this feature to reduce time waiting to compile the same module a second time.
+//
+// The contents written into dirname are wazero-version specific, meaning different versions of
+// wazero will duplicate entries for the same input wasm.
+//
+// Note: The embedder must safeguard this directory from external changes.
+func NewCompilationCacheWithDir(dirname string) (CompilationCache, error) {
+	c := &cache{}
+	err := c.ensuresFileCache(dirname, version.GetWazeroVersion())
+	return c, err
+}
+
+// cache implements Cache interface.
+type cache struct {
+	// eng is the engine for this cache. If the cache is configured, the engine is shared across multiple instances of
+	// Runtime, and its lifetime is not bound to them. Instead, the engine is alive until Cache.Close is called.
+	engs      [engineKindCount]wasm.Engine
+	fileCache filecache.Cache
+	initOnces [engineKindCount]sync.Once
+}
+
+func (c *cache) initEngine(ek engineKind, ne newEngine, ctx context.Context, features api.CoreFeatures) wasm.Engine {
+	c.initOnces[ek].Do(func() { c.engs[ek] = ne(ctx, features, c.fileCache) })
+	return c.engs[ek]
+}
+
+// Close implements the same method on the Cache interface.
+func (c *cache) Close(_ context.Context) (err error) {
+	for _, eng := range c.engs {
+		if eng != nil {
+			if err = eng.Close(); err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+func (c *cache) ensuresFileCache(dir string, wazeroVersion string) error {
+	// Resolve a potentially relative directory into an absolute one.
+	var err error
+	dir, err = filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+
+	// Ensure the user-supplied directory.
+	if err = mkdir(dir); err != nil {
+		return err
+	}
+
+	// Create a version-specific directory to avoid conflicts.
+	dirname := path.Join(dir, "wazero-"+wazeroVersion+"-"+goruntime.GOARCH+"-"+goruntime.GOOS)
+	if err = mkdir(dirname); err != nil {
+		return err
+	}
+
+	c.fileCache = filecache.New(dirname)
+	return nil
+}
+
+func mkdir(dirname string) error {
+	if st, err := os.Stat(dirname); errors.Is(err, os.ErrNotExist) {
+		// If the directory not found, create the cache dir.
+		if err = os.MkdirAll(dirname, 0o700); err != nil {
+			return fmt.Errorf("create directory %s: %v", dirname, err)
+		}
+	} else if err != nil {
+		return err
+	} else if !st.IsDir() {
+		return fmt.Errorf("%s is not dir", dirname)
+	}
+	return nil
+}