[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/).

1 files changed, 269 insertions, 0 deletions

diff --git a/vendor/github.com/tetratelabs/wazero/internal/wasm/binary/element.go b/vendor/github.com/tetratelabs/wazero/internal/wasm/binary/element.go
new file mode 100644
index 000000000..7ab4b48eb
--- /dev/null
+++ b/vendor/github.com/tetratelabs/wazero/internal/wasm/binary/element.go
@@ -0,0 +1,269 @@
+package binary
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+
+	"github.com/tetratelabs/wazero/api"
+	"github.com/tetratelabs/wazero/internal/leb128"
+	"github.com/tetratelabs/wazero/internal/wasm"
+)
+
+func ensureElementKindFuncRef(r *bytes.Reader) error {
+	elemKind, err := r.ReadByte()
+	if err != nil {
+		return fmt.Errorf("read element prefix: %w", err)
+	}
+	if elemKind != 0x0 { // ElemKind is fixed to 0x0 now: https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#element-section
+		return fmt.Errorf("element kind must be zero but was 0x%x", elemKind)
+	}
+	return nil
+}
+
+func decodeElementInitValueVector(r *bytes.Reader) ([]wasm.Index, error) {
+	vs, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return nil, fmt.Errorf("get size of vector: %w", err)
+	}
+
+	vec := make([]wasm.Index, vs)
+	for i := range vec {
+		u32, _, err := leb128.DecodeUint32(r)
+		if err != nil {
+			return nil, fmt.Errorf("read function index: %w", err)
+		}
+
+		if u32 >= wasm.MaximumFunctionIndex {
+			return nil, fmt.Errorf("too large function index in Element init: %d", u32)
+		}
+		vec[i] = u32
+	}
+	return vec, nil
+}
+
+func decodeElementConstExprVector(r *bytes.Reader, elemType wasm.RefType, enabledFeatures api.CoreFeatures) ([]wasm.Index, error) {
+	vs, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get the size of constexpr vector: %w", err)
+	}
+	vec := make([]wasm.Index, vs)
+	for i := range vec {
+		var expr wasm.ConstantExpression
+		err := decodeConstantExpression(r, enabledFeatures, &expr)
+		if err != nil {
+			return nil, err
+		}
+		switch expr.Opcode {
+		case wasm.OpcodeRefFunc:
+			if elemType != wasm.RefTypeFuncref {
+				return nil, fmt.Errorf("element type mismatch: want %s, but constexpr has funcref", wasm.RefTypeName(elemType))
+			}
+			v, _, _ := leb128.LoadUint32(expr.Data)
+			if v >= wasm.MaximumFunctionIndex {
+				return nil, fmt.Errorf("too large function index in Element init: %d", v)
+			}
+			vec[i] = v
+		case wasm.OpcodeRefNull:
+			if elemType != expr.Data[0] {
+				return nil, fmt.Errorf("element type mismatch: want %s, but constexpr has %s",
+					wasm.RefTypeName(elemType), wasm.RefTypeName(expr.Data[0]))
+			}
+			vec[i] = wasm.ElementInitNullReference
+		case wasm.OpcodeGlobalGet:
+			i32, _, _ := leb128.LoadInt32(expr.Data)
+			// Resolving the reference type from globals is done at instantiation phase. See the comment on
+			// wasm.elementInitImportedGlobalReferenceType.
+			vec[i] = wasm.WrapGlobalIndexAsElementInit(wasm.Index(i32))
+		default:
+			return nil, fmt.Errorf("const expr must be either ref.null or ref.func but was %s", wasm.InstructionName(expr.Opcode))
+		}
+	}
+	return vec, nil
+}
+
+func decodeElementRefType(r *bytes.Reader) (ret wasm.RefType, err error) {
+	ret, err = r.ReadByte()
+	if err != nil {
+		err = fmt.Errorf("read element ref type: %w", err)
+		return
+	}
+	if ret != wasm.RefTypeFuncref && ret != wasm.RefTypeExternref {
+		return 0, errors.New("ref type must be funcref or externref for element as of WebAssembly 2.0")
+	}
+	return
+}
+
+const (
+	// The prefix is explained at https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#element-section
+
+	// elementSegmentPrefixLegacy is the legacy prefix and is only valid one before CoreFeatureBulkMemoryOperations.
+	elementSegmentPrefixLegacy = iota
+	// elementSegmentPrefixPassiveFuncrefValueVector is the passive element whose indexes are encoded as vec(varint), and reftype is fixed to funcref.
+	elementSegmentPrefixPassiveFuncrefValueVector
+	// elementSegmentPrefixActiveFuncrefValueVectorWithTableIndex is the same as elementSegmentPrefixPassiveFuncrefValueVector but active and table index is encoded.
+	elementSegmentPrefixActiveFuncrefValueVectorWithTableIndex
+	// elementSegmentPrefixDeclarativeFuncrefValueVector is the same as elementSegmentPrefixPassiveFuncrefValueVector but declarative.
+	elementSegmentPrefixDeclarativeFuncrefValueVector
+	// elementSegmentPrefixActiveFuncrefConstExprVector is active whoce reftype is fixed to funcref and indexes are encoded as vec(const_expr).
+	elementSegmentPrefixActiveFuncrefConstExprVector
+	// elementSegmentPrefixPassiveConstExprVector is passive whoce indexes are encoded as vec(const_expr), and reftype is encoded.
+	elementSegmentPrefixPassiveConstExprVector
+	// elementSegmentPrefixPassiveConstExprVector is active whoce indexes are encoded as vec(const_expr), and reftype and table index are encoded.
+	elementSegmentPrefixActiveConstExprVector
+	// elementSegmentPrefixDeclarativeConstExprVector is declarative whoce indexes are encoded as vec(const_expr), and reftype is encoded.
+	elementSegmentPrefixDeclarativeConstExprVector
+)
+
+func decodeElementSegment(r *bytes.Reader, enabledFeatures api.CoreFeatures, ret *wasm.ElementSegment) error {
+	prefix, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return fmt.Errorf("read element prefix: %w", err)
+	}
+
+	if prefix != elementSegmentPrefixLegacy {
+		if err := enabledFeatures.RequireEnabled(api.CoreFeatureBulkMemoryOperations); err != nil {
+			return fmt.Errorf("non-zero prefix for element segment is invalid as %w", err)
+		}
+	}
+
+	// Encoding depends on the prefix and described at https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#element-section
+	switch prefix {
+	case elementSegmentPrefixLegacy:
+		// Legacy prefix which is WebAssembly 1.0 compatible.
+		err = decodeConstantExpression(r, enabledFeatures, &ret.OffsetExpr)
+		if err != nil {
+			return fmt.Errorf("read expr for offset: %w", err)
+		}
+
+		ret.Init, err = decodeElementInitValueVector(r)
+		if err != nil {
+			return err
+		}
+
+		ret.Mode = wasm.ElementModeActive
+		ret.Type = wasm.RefTypeFuncref
+		return nil
+	case elementSegmentPrefixPassiveFuncrefValueVector:
+		// Prefix 1 requires funcref.
+		if err = ensureElementKindFuncRef(r); err != nil {
+			return err
+		}
+
+		ret.Init, err = decodeElementInitValueVector(r)
+		if err != nil {
+			return err
+		}
+		ret.Mode = wasm.ElementModePassive
+		ret.Type = wasm.RefTypeFuncref
+		return nil
+	case elementSegmentPrefixActiveFuncrefValueVectorWithTableIndex:
+		ret.TableIndex, _, err = leb128.DecodeUint32(r)
+		if err != nil {
+			return fmt.Errorf("get size of vector: %w", err)
+		}
+
+		if ret.TableIndex != 0 {
+			if err := enabledFeatures.RequireEnabled(api.CoreFeatureReferenceTypes); err != nil {
+				return fmt.Errorf("table index must be zero but was %d: %w", ret.TableIndex, err)
+			}
+		}
+
+		err := decodeConstantExpression(r, enabledFeatures, &ret.OffsetExpr)
+		if err != nil {
+			return fmt.Errorf("read expr for offset: %w", err)
+		}
+
+		// Prefix 2 requires funcref.
+		if err = ensureElementKindFuncRef(r); err != nil {
+			return err
+		}
+
+		ret.Init, err = decodeElementInitValueVector(r)
+		if err != nil {
+			return err
+		}
+
+		ret.Mode = wasm.ElementModeActive
+		ret.Type = wasm.RefTypeFuncref
+		return nil
+	case elementSegmentPrefixDeclarativeFuncrefValueVector:
+		// Prefix 3 requires funcref.
+		if err = ensureElementKindFuncRef(r); err != nil {
+			return err
+		}
+		ret.Init, err = decodeElementInitValueVector(r)
+		if err != nil {
+			return err
+		}
+		ret.Type = wasm.RefTypeFuncref
+		ret.Mode = wasm.ElementModeDeclarative
+		return nil
+	case elementSegmentPrefixActiveFuncrefConstExprVector:
+		err := decodeConstantExpression(r, enabledFeatures, &ret.OffsetExpr)
+		if err != nil {
+			return fmt.Errorf("read expr for offset: %w", err)
+		}
+
+		ret.Init, err = decodeElementConstExprVector(r, wasm.RefTypeFuncref, enabledFeatures)
+		if err != nil {
+			return err
+		}
+		ret.Mode = wasm.ElementModeActive
+		ret.Type = wasm.RefTypeFuncref
+		return nil
+	case elementSegmentPrefixPassiveConstExprVector:
+		ret.Type, err = decodeElementRefType(r)
+		if err != nil {
+			return err
+		}
+		ret.Init, err = decodeElementConstExprVector(r, ret.Type, enabledFeatures)
+		if err != nil {
+			return err
+		}
+		ret.Mode = wasm.ElementModePassive
+		return nil
+	case elementSegmentPrefixActiveConstExprVector:
+		ret.TableIndex, _, err = leb128.DecodeUint32(r)
+		if err != nil {
+			return fmt.Errorf("get size of vector: %w", err)
+		}
+
+		if ret.TableIndex != 0 {
+			if err := enabledFeatures.RequireEnabled(api.CoreFeatureReferenceTypes); err != nil {
+				return fmt.Errorf("table index must be zero but was %d: %w", ret.TableIndex, err)
+			}
+		}
+		err := decodeConstantExpression(r, enabledFeatures, &ret.OffsetExpr)
+		if err != nil {
+			return fmt.Errorf("read expr for offset: %w", err)
+		}
+
+		ret.Type, err = decodeElementRefType(r)
+		if err != nil {
+			return err
+		}
+
+		ret.Init, err = decodeElementConstExprVector(r, ret.Type, enabledFeatures)
+		if err != nil {
+			return err
+		}
+
+		ret.Mode = wasm.ElementModeActive
+		return nil
+	case elementSegmentPrefixDeclarativeConstExprVector:
+		ret.Type, err = decodeElementRefType(r)
+		if err != nil {
+			return err
+		}
+		ret.Init, err = decodeElementConstExprVector(r, ret.Type, enabledFeatures)
+		if err != nil {
+			return err
+		}
+
+		ret.Mode = wasm.ElementModeDeclarative
+		return nil
+	default:
+		return fmt.Errorf("invalid element segment prefix: 0x%x", prefix)
+	}
+}