Merge #55

55: feat(memory) Add the `Memory.Grow` method r=Hywan a=Hywan

Fix #52.

This method can be used to grow the memory by a number of pages (65kb each).

Co-authored-by: Ivan Enderlin <ivan.enderlin@hoa-project.net>

wasmer/bridge.go

@@ -324,6 +324,13 @@ func cWasmerMemoryDataLength(memory *cWasmerMemoryT) cUint32T {
 	))
 }
 
+func cWasmerMemoryGrow(memory *cWasmerMemoryT, numberOfPages cUint32T) cWasmerResultT {
+	return (cWasmerResultT)(C.wasmer_memory_grow(
+		(*C.wasmer_memory_t)(memory),
+		(C.uint32_t)(numberOfPages),
+	))
+}
+
 func cWasmerModuleDeserialize(module **cWasmerModuleT, serializedModule *cWasmerSerializedModuleT) cWasmerResultT {
 	return (cWasmerResultT)(C.wasmer_module_deserialize(
 		(**C.wasmer_module_t)(unsafe.Pointer(module)),

wasmer/memory.go

@@ -1,10 +1,29 @@
 package wasmer
 
 import (
+	"fmt"
 	"reflect"
 	"unsafe"
 )
 
+// MemoryError represents any kind of errors related to a WebAssembly memory. It
+// is returned by `Memory` functions only.
+type MemoryError struct {
+	// Error message.
+	message string
+}
+
+// NewMemoryError constructs a new `MemoryError`.
+func NewMemoryError(message string) *MemoryError {
+	return &MemoryError{message}
+}
+
+// `MemoryError` is an actual error. The `Error` function returns
+// the error message.
+func (error *MemoryError) Error() string {
+	return error.message
+}
+
 // Memory represents an exported memory of a WebAssembly instance. To read
 // and write data, please see the `Data` function.
 type Memory struct {
@@ -35,3 +54,23 @@ func (memory *Memory) Data() []byte {
 
 	return *(*[]byte)(unsafe.Pointer(&header))
 }
+
+// Grow the memory by a number of pages (65kb each).
+func (memory *Memory) Grow(numberOfPages uint32) error {
+	var growResult = cWasmerMemoryGrow(memory.memory, cUint32T(numberOfPages))
+
+	if growResult != cWasmerOk {
+		var lastError, err = GetLastError()
+		var errorMessage = "Failed to grow the memory:\n    %s"
+
+		if err != nil {
+			errorMessage = fmt.Sprintf(errorMessage, "(unknown details)")
+		} else {
+			errorMessage = fmt.Sprintf(errorMessage, lastError)
+		}
+
+		return NewMemoryError(errorMessage)
+	}
+
+	return nil
+}

wasmer/test/memory_test.go

@@ -72,3 +72,31 @@ func TestMemoryDataReadWrite(t *testing.T) {
 
 	assert.Equal(t, "Aello, World!", string(memory3[pointer:pointer+13]))
 }
+
+func TestMemoryGrow(t *testing.T) {
+	instance, _ := wasm.NewInstance(GetBytes())
+	defer instance.Close()
+
+	memory := instance.Memory
+	oldMemoryLength := memory.Length()
+
+	assert.Equal(t, uint32(1114112), oldMemoryLength)
+
+	err := memory.Grow(1)
+
+	assert.NoError(t, err)
+
+	memoryLength := memory.Length()
+
+	assert.Equal(t, uint32(1179648), memoryLength)
+	assert.Equal(t, uint32(65536), memoryLength-oldMemoryLength)
+}
+
+func TestMemoryGrowTooMuch(t *testing.T) {
+	instance, _ := wasm.NewInstance(GetBytes())
+	defer instance.Close()
+
+	err := instance.Memory.Grow(100000)
+
+	assert.EqualError(t, err, "Failed to grow the memory:\n    Grow Error: Failed to add pages because would exceed maximum number of pages. Left: 17, Right: 100000, Pages added: 100017")
+}