working commit

vendor/github.com/tetratelabs/wabin/wasm/memory.go

@@ -0,0 +1,45 @@
+package wasm
+
+import (
+	"fmt"
+)
+
+const (
+	// MemoryPageSize is the unit of memory length in WebAssembly,
+	// and is defined as 2^16 = 65536.
+	// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#memory-instances%E2%91%A0
+	MemoryPageSize = uint32(65536)
+	// MemoryPageSizeInBits satisfies the relation: "1 << MemoryPageSizeInBits == MemoryPageSize".
+	MemoryPageSizeInBits = 16
+)
+
+// MemoryPagesToBytesNum converts the given pages into the number of bytes contained in these pages.
+func MemoryPagesToBytesNum(pages uint32) (bytesNum uint64) {
+	return uint64(pages) << MemoryPageSizeInBits
+}
+
+// PagesToUnitOfBytes converts the pages to a human-readable form similar to what's specified. Ex. 1 -> "64Ki"
+//
+// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#memory-instances%E2%91%A0
+func PagesToUnitOfBytes(pages uint32) string {
+	k := pages * 64
+	if k < 1024 {
+		return fmt.Sprintf("%d Ki", k)
+	}
+	m := k / 1024
+	if m < 1024 {
+		return fmt.Sprintf("%d Mi", m)
+	}
+	g := m / 1024
+	if g < 1024 {
+		return fmt.Sprintf("%d Gi", g)
+	}
+	return fmt.Sprintf("%d Ti", g/1024)
+}
+
+// Below are raw functions used to implement the api.Memory API:
+
+// memoryBytesNumToPages converts the given number of bytes into the number of pages.
+func memoryBytesNumToPages(bytesNum uint64) (pages uint32) {
+	return uint32(bytesNum >> MemoryPageSizeInBits)
+}