[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, 311 insertions, 0 deletions

diff --git a/vendor/github.com/ncruces/go-sqlite3/vfs/memdb/memdb.go b/vendor/github.com/ncruces/go-sqlite3/vfs/memdb/memdb.go
new file mode 100644
index 000000000..8dc57ab9c
--- /dev/null
+++ b/vendor/github.com/ncruces/go-sqlite3/vfs/memdb/memdb.go
@@ -0,0 +1,311 @@
+package memdb
+
+import (
+	"io"
+	"runtime"
+	"sync"
+	"time"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/vfs"
+)
+
+// Must be a multiple of 64K (the largest page size).
+const sectorSize = 65536
+
+type memVFS struct{}
+
+func (memVFS) Open(name string, flags vfs.OpenFlag) (vfs.File, vfs.OpenFlag, error) {
+	// For simplicity, we do not support reading or writing data
+	// across "sector" boundaries.
+	//
+	// This is not a problem for most SQLite file types:
+	// - databases, which only do page aligned reads/writes;
+	// - temp journals, as used by the sorter, which does the same:
+	//   https://github.com/sqlite/sqlite/blob/b74eb0/src/vdbesort.c#L409-L412
+	//
+	// We refuse to open all other file types,
+	// but returning OPEN_MEMORY means SQLite won't ask us to.
+	const types = vfs.OPEN_MAIN_DB |
+		vfs.OPEN_TEMP_DB |
+		vfs.OPEN_TEMP_JOURNAL
+	if flags&types == 0 {
+		return nil, flags, sqlite3.CANTOPEN
+	}
+
+	// A shared database has a name that begins with "/".
+	shared := len(name) > 1 && name[0] == '/'
+
+	var db *memDB
+	if shared {
+		name = name[1:]
+		memoryMtx.Lock()
+		defer memoryMtx.Unlock()
+		db = memoryDBs[name]
+	}
+	if db == nil {
+		if flags&vfs.OPEN_CREATE == 0 {
+			return nil, flags, sqlite3.CANTOPEN
+		}
+		db = &memDB{name: name}
+	}
+	if shared {
+		db.refs++ // +checklocksforce: memoryMtx is held
+		memoryDBs[name] = db
+	}
+
+	return &memFile{
+		memDB:    db,
+		readOnly: flags&vfs.OPEN_READONLY != 0,
+	}, flags | vfs.OPEN_MEMORY, nil
+}
+
+func (memVFS) Delete(name string, dirSync bool) error {
+	return sqlite3.IOERR_DELETE
+}
+
+func (memVFS) Access(name string, flag vfs.AccessFlag) (bool, error) {
+	return false, nil
+}
+
+func (memVFS) FullPathname(name string) (string, error) {
+	return name, nil
+}
+
+type memDB struct {
+	name string
+
+	// +checklocks:lockMtx
+	pending *memFile
+	// +checklocks:lockMtx
+	reserved *memFile
+
+	// +checklocks:dataMtx
+	data []*[sectorSize]byte
+
+	// +checklocks:dataMtx
+	size int64
+
+	// +checklocks:lockMtx
+	shared int
+
+	// +checklocks:memoryMtx
+	refs int
+
+	lockMtx sync.Mutex
+	dataMtx sync.RWMutex
+}
+
+func (m *memDB) release() {
+	memoryMtx.Lock()
+	defer memoryMtx.Unlock()
+	if m.refs--; m.refs == 0 && m == memoryDBs[m.name] {
+		delete(memoryDBs, m.name)
+	}
+}
+
+type memFile struct {
+	*memDB
+	lock     vfs.LockLevel
+	readOnly bool
+}
+
+var (
+	// Ensure these interfaces are implemented:
+	_ vfs.FileLockState = &memFile{}
+	_ vfs.FileSizeHint  = &memFile{}
+)
+
+func (m *memFile) Close() error {
+	m.release()
+	return m.Unlock(vfs.LOCK_NONE)
+}
+
+func (m *memFile) ReadAt(b []byte, off int64) (n int, err error) {
+	m.dataMtx.RLock()
+	defer m.dataMtx.RUnlock()
+
+	if off >= m.size {
+		return 0, io.EOF
+	}
+
+	base := off / sectorSize
+	rest := off % sectorSize
+	have := int64(sectorSize)
+	if base == int64(len(m.data))-1 {
+		have = modRoundUp(m.size, sectorSize)
+	}
+	n = copy(b, (*m.data[base])[rest:have])
+	if n < len(b) {
+		// Assume reads are page aligned.
+		return 0, io.ErrNoProgress
+	}
+	return n, nil
+}
+
+func (m *memFile) WriteAt(b []byte, off int64) (n int, err error) {
+	m.dataMtx.Lock()
+	defer m.dataMtx.Unlock()
+
+	base := off / sectorSize
+	rest := off % sectorSize
+	for base >= int64(len(m.data)) {
+		m.data = append(m.data, new([sectorSize]byte))
+	}
+	n = copy((*m.data[base])[rest:], b)
+	if n < len(b) {
+		// Assume writes are page aligned.
+		return n, io.ErrShortWrite
+	}
+	if size := off + int64(len(b)); size > m.size {
+		m.size = size
+	}
+	return n, nil
+}
+
+func (m *memFile) Truncate(size int64) error {
+	m.dataMtx.Lock()
+	defer m.dataMtx.Unlock()
+	return m.truncate(size)
+}
+
+// +checklocks:m.dataMtx
+func (m *memFile) truncate(size int64) error {
+	if size < m.size {
+		base := size / sectorSize
+		rest := size % sectorSize
+		if rest != 0 {
+			clear((*m.data[base])[rest:])
+		}
+	}
+	sectors := divRoundUp(size, sectorSize)
+	for sectors > int64(len(m.data)) {
+		m.data = append(m.data, new([sectorSize]byte))
+	}
+	clear(m.data[sectors:])
+	m.data = m.data[:sectors]
+	m.size = size
+	return nil
+}
+
+func (m *memFile) Sync(flag vfs.SyncFlag) error {
+	return nil
+}
+
+func (m *memFile) Size() (int64, error) {
+	m.dataMtx.RLock()
+	defer m.dataMtx.RUnlock()
+	return m.size, nil
+}
+
+const spinWait = 25 * time.Microsecond
+
+func (m *memFile) Lock(lock vfs.LockLevel) error {
+	if m.lock >= lock {
+		return nil
+	}
+
+	if m.readOnly && lock >= vfs.LOCK_RESERVED {
+		return sqlite3.IOERR_LOCK
+	}
+
+	m.lockMtx.Lock()
+	defer m.lockMtx.Unlock()
+
+	switch lock {
+	case vfs.LOCK_SHARED:
+		if m.pending != nil {
+			return sqlite3.BUSY
+		}
+		m.shared++
+
+	case vfs.LOCK_RESERVED:
+		if m.reserved != nil {
+			return sqlite3.BUSY
+		}
+		m.reserved = m
+
+	case vfs.LOCK_EXCLUSIVE:
+		if m.lock < vfs.LOCK_PENDING {
+			if m.pending != nil {
+				return sqlite3.BUSY
+			}
+			m.lock = vfs.LOCK_PENDING
+			m.pending = m
+		}
+
+		for before := time.Now(); m.shared > 1; {
+			if time.Since(before) > spinWait {
+				return sqlite3.BUSY
+			}
+			m.lockMtx.Unlock()
+			runtime.Gosched()
+			m.lockMtx.Lock()
+		}
+	}
+
+	m.lock = lock
+	return nil
+}
+
+func (m *memFile) Unlock(lock vfs.LockLevel) error {
+	if m.lock <= lock {
+		return nil
+	}
+
+	m.lockMtx.Lock()
+	defer m.lockMtx.Unlock()
+
+	if m.pending == m {
+		m.pending = nil
+	}
+	if m.reserved == m {
+		m.reserved = nil
+	}
+	if lock < vfs.LOCK_SHARED {
+		m.shared--
+	}
+	m.lock = lock
+	return nil
+}
+
+func (m *memFile) CheckReservedLock() (bool, error) {
+	if m.lock >= vfs.LOCK_RESERVED {
+		return true, nil
+	}
+	m.lockMtx.Lock()
+	defer m.lockMtx.Unlock()
+	return m.reserved != nil, nil
+}
+
+func (m *memFile) SectorSize() int {
+	return sectorSize
+}
+
+func (m *memFile) DeviceCharacteristics() vfs.DeviceCharacteristic {
+	return vfs.IOCAP_ATOMIC |
+		vfs.IOCAP_SEQUENTIAL |
+		vfs.IOCAP_SAFE_APPEND |
+		vfs.IOCAP_POWERSAFE_OVERWRITE
+}
+
+func (m *memFile) SizeHint(size int64) error {
+	m.dataMtx.Lock()
+	defer m.dataMtx.Unlock()
+	if size > m.size {
+		return m.truncate(size)
+	}
+	return nil
+}
+
+func (m *memFile) LockState() vfs.LockLevel {
+	return m.lock
+}
+
+func divRoundUp(a, b int64) int64 {
+	return (a + b - 1) / b
+}
+
+func modRoundUp(a, b int64) int64 {
+	return b - (b-a%b)%b
+}