[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, 76 insertions, 0 deletions

diff --git a/vendor/github.com/ncruces/go-sqlite3/internal/util/alloc_windows.go b/vendor/github.com/ncruces/go-sqlite3/internal/util/alloc_windows.go
new file mode 100644
index 000000000..8936173b4
--- /dev/null
+++ b/vendor/github.com/ncruces/go-sqlite3/internal/util/alloc_windows.go
@@ -0,0 +1,76 @@
+//go:build !sqlite3_nosys
+
+package util
+
+import (
+	"math"
+	"reflect"
+	"unsafe"
+
+	"github.com/tetratelabs/wazero/experimental"
+	"golang.org/x/sys/windows"
+)
+
+func virtualAlloc(cap, max uint64) experimental.LinearMemory {
+	// Round up to the page size.
+	rnd := uint64(windows.Getpagesize() - 1)
+	max = (max + rnd) &^ rnd
+
+	if max > math.MaxInt {
+		// This ensures uintptr(max) overflows to a large value,
+		// and windows.VirtualAlloc returns an error.
+		max = math.MaxUint64
+	}
+
+	// Reserve max bytes of address space, to ensure we won't need to move it.
+	// This does not commit memory.
+	r, err := windows.VirtualAlloc(0, uintptr(max), windows.MEM_RESERVE, windows.PAGE_READWRITE)
+	if err != nil {
+		panic(err)
+	}
+
+	mem := virtualMemory{addr: r}
+	// SliceHeader, although deprecated, avoids a go vet warning.
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&mem.buf))
+	sh.Cap = int(max) // Not a bug.
+	sh.Data = r
+	return &mem
+}
+
+// The slice covers the entire mmapped memory:
+//   - len(buf) is the already committed memory,
+//   - cap(buf) is the reserved address space.
+type virtualMemory struct {
+	buf  []byte
+	addr uintptr
+}
+
+func (m *virtualMemory) Reallocate(size uint64) []byte {
+	com := uint64(len(m.buf))
+	res := uint64(cap(m.buf))
+	if com < size && size < res {
+		// Round up to the page size.
+		rnd := uint64(windows.Getpagesize() - 1)
+		new := (size + rnd) &^ rnd
+
+		// Commit additional memory up to new bytes.
+		_, err := windows.VirtualAlloc(m.addr, uintptr(new), windows.MEM_COMMIT, windows.PAGE_READWRITE)
+		if err != nil {
+			panic(err)
+		}
+
+		// Update committed memory.
+		m.buf = m.buf[:new]
+	}
+	// Limit returned capacity because bytes beyond
+	// len(m.buf) have not yet been committed.
+	return m.buf[:size:len(m.buf)]
+}
+
+func (m *virtualMemory) Free() {
+	err := windows.VirtualFree(m.addr, 0, windows.MEM_RELEASE)
+	if err != nil {
+		panic(err)
+	}
+	m.addr = 0
+}