wasm: introduce new package for host->guest buffer passing

Signed-off-by: Xe Iaso <me@xeiaso.net>

1 files changed, 53 insertions, 0 deletions

diff --git a/wasm/wasm.go b/wasm/wasm.go
new file mode 100644
index 0000000..5981c06
--- /dev/null
+++ b/wasm/wasm.go
@@ -0,0 +1,53 @@
+package wasm
+
+import (
+	"unsafe"
+
+	"github.com/tetratelabs/wazero/api"
+)
+
+type String uint64
+
+func (value String) Load(module api.Module) string {
+	return string(value.LoadBytes(module))
+}
+
+func (value String) LoadBytes(module api.Module) []byte {
+	data, ok := module.Memory().Read(uint32(value>>32), uint32(value))
+	if !ok {
+		panic("memory read out of bounds")
+	}
+	return data
+}
+
+func FromString(value string) String {
+	position := uint32(uintptr(unsafe.Pointer(unsafe.StringData(value))))
+	bytes := uint32(len(value))
+	return String(uint64(position)<<32 | uint64(bytes))
+}
+
+type Buffer uint64
+
+func (buffer Buffer) Address() uint32 {
+	return uint32(buffer >> 32)
+}
+
+func (buffer Buffer) Length() uint32 {
+	return uint32((buffer << 32) >> 32)
+}
+
+func FromSlice(value []byte) Buffer {
+	if len(value) == 0 {
+		return 0
+	}
+	ptr := uint64(uintptr(unsafe.Pointer(&value[0])))
+	return Buffer(ptr<<32 | uint64(len(value)))
+}
+
+func (buffer Buffer) Slice() []byte {
+	return unsafe.Slice((*byte)(unsafe.Pointer(uintptr(buffer.Address()))), buffer.Length())
+}
+
+func (buffer Buffer) String() string {
+	return unsafe.String((*byte)(unsafe.Pointer(uintptr(buffer.Address()))), buffer.Length())
+}