[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/internal/wasm/binary/names.go

@@ -0,0 +1,151 @@
+package binary
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"github.com/tetratelabs/wazero/internal/leb128"
+	"github.com/tetratelabs/wazero/internal/wasm"
+)
+
+const (
+	// subsectionIDModuleName contains only the module name.
+	subsectionIDModuleName = uint8(0)
+	// subsectionIDFunctionNames is a map of indices to function names, in ascending order by function index
+	subsectionIDFunctionNames = uint8(1)
+	// subsectionIDLocalNames contain a map of function indices to a map of local indices to their names, in ascending
+	// order by function and local index
+	subsectionIDLocalNames = uint8(2)
+)
+
+// decodeNameSection deserializes the data associated with the "name" key in SectionIDCustom according to the
+// standard:
+//
+// * ModuleName decode from subsection 0
+// * FunctionNames decode from subsection 1
+// * LocalNames decode from subsection 2
+//
+// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#binary-namesec
+func decodeNameSection(r *bytes.Reader, limit uint64) (result *wasm.NameSection, err error) {
+	// TODO: add leb128 functions that work on []byte and offset. While using a reader allows us to reuse reader-based
+	// leb128 functions, it is less efficient, causes untestable code and in some cases more complex vs plain []byte.
+	result = &wasm.NameSection{}
+
+	// subsectionID is decoded if known, and skipped if not
+	var subsectionID uint8
+	// subsectionSize is the length to skip when the subsectionID is unknown
+	var subsectionSize uint32
+	var bytesRead uint64
+	for limit > 0 {
+		if subsectionID, err = r.ReadByte(); err != nil {
+			if err == io.EOF {
+				return result, nil
+			}
+			// TODO: untestable as this can't fail for a reason beside EOF reading a byte from a buffer
+			return nil, fmt.Errorf("failed to read a subsection ID: %w", err)
+		}
+		limit--
+
+		if subsectionSize, bytesRead, err = leb128.DecodeUint32(r); err != nil {
+			return nil, fmt.Errorf("failed to read the size of subsection[%d]: %w", subsectionID, err)
+		}
+		limit -= bytesRead
+
+		switch subsectionID {
+		case subsectionIDModuleName:
+			if result.ModuleName, _, err = decodeUTF8(r, "module name"); err != nil {
+				return nil, err
+			}
+		case subsectionIDFunctionNames:
+			if result.FunctionNames, err = decodeFunctionNames(r); err != nil {
+				return nil, err
+			}
+		case subsectionIDLocalNames:
+			if result.LocalNames, err = decodeLocalNames(r); err != nil {
+				return nil, err
+			}
+		default: // Skip other subsections.
+			// Note: Not Seek because it doesn't err when given an offset past EOF. Rather, it leads to undefined state.
+			if _, err = io.CopyN(io.Discard, r, int64(subsectionSize)); err != nil {
+				return nil, fmt.Errorf("failed to skip subsection[%d]: %w", subsectionID, err)
+			}
+		}
+		limit -= uint64(subsectionSize)
+	}
+	return
+}
+
+func decodeFunctionNames(r *bytes.Reader) (wasm.NameMap, error) {
+	functionCount, err := decodeFunctionCount(r, subsectionIDFunctionNames)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make(wasm.NameMap, functionCount)
+	for i := uint32(0); i < functionCount; i++ {
+		functionIndex, err := decodeFunctionIndex(r, subsectionIDFunctionNames)
+		if err != nil {
+			return nil, err
+		}
+
+		name, _, err := decodeUTF8(r, "function[%d] name", functionIndex)
+		if err != nil {
+			return nil, err
+		}
+		result[i] = wasm.NameAssoc{Index: functionIndex, Name: name}
+	}
+	return result, nil
+}
+
+func decodeLocalNames(r *bytes.Reader) (wasm.IndirectNameMap, error) {
+	functionCount, err := decodeFunctionCount(r, subsectionIDLocalNames)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make(wasm.IndirectNameMap, functionCount)
+	for i := uint32(0); i < functionCount; i++ {
+		functionIndex, err := decodeFunctionIndex(r, subsectionIDLocalNames)
+		if err != nil {
+			return nil, err
+		}
+
+		localCount, _, err := leb128.DecodeUint32(r)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read the local count for function[%d]: %w", functionIndex, err)
+		}
+
+		locals := make(wasm.NameMap, localCount)
+		for j := uint32(0); j < localCount; j++ {
+			localIndex, _, err := leb128.DecodeUint32(r)
+			if err != nil {
+				return nil, fmt.Errorf("failed to read a local index of function[%d]: %w", functionIndex, err)
+			}
+
+			name, _, err := decodeUTF8(r, "function[%d] local[%d] name", functionIndex, localIndex)
+			if err != nil {
+				return nil, err
+			}
+			locals[j] = wasm.NameAssoc{Index: localIndex, Name: name}
+		}
+		result[i] = wasm.NameMapAssoc{Index: functionIndex, NameMap: locals}
+	}
+	return result, nil
+}
+
+func decodeFunctionIndex(r *bytes.Reader, subsectionID uint8) (uint32, error) {
+	functionIndex, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return 0, fmt.Errorf("failed to read a function index in subsection[%d]: %w", subsectionID, err)
+	}
+	return functionIndex, nil
+}
+
+func decodeFunctionCount(r *bytes.Reader, subsectionID uint8) (uint32, error) {
+	functionCount, _, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return 0, fmt.Errorf("failed to read the function count of subsection[%d]: %w", subsectionID, err)
+	}
+	return functionCount, nil
+}