From 15481872dd1f28c83f214f8e65406bbea3ec0530 Mon Sep 17 00:00:00 2001
From: Christine Dodrill <me@christine.website>
Date: Mon, 6 Aug 2018 18:04:11 -0700
Subject: [PATCH] go

---
 cmd/land/go.go      | 134 ++++++++++++++++++++++++++++++++++++++++++++
 cmd/land/process.go |   3 +
 2 files changed, 137 insertions(+)
 create mode 100644 cmd/land/go.go

diff --git a/cmd/land/go.go b/cmd/land/go.go
new file mode 100644
index 0000000..6e64f34
--- /dev/null
+++ b/cmd/land/go.go
@@ -0,0 +1,134 @@
+package main
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"os"
+	"time"
+)
+
+func (p *Process) getInt32(addr int32) int32 {
+	mem := p.vm.Memory()[addr : addr+4]
+
+	var result int32
+	err := binary.Read(bytes.NewReader(mem), binary.LittleEndian, &result)
+	if err != nil {
+		panic(err)
+	}
+
+	return result
+}
+
+func (p *Process) setInt32(addr int32, val int32) {
+	data := make([]byte, 4)
+	buf := bytes.NewBuffer(data)
+	err := binary.Write(buf, binary.LittleEndian, val)
+	if err != nil {
+		panic(err)
+	}
+
+	_, err := p.writeMem(addr, data)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (p *Process) getInt64(addr int32) int64 {
+	mem := p.vm.Memory()[addr : addr+8]
+
+	var result int64
+	err := binary.Read(bytes.NewReader(mem), binary.LittleEndian, &result)
+	if err != nil {
+		panic(err)
+	}
+
+	return result
+}
+
+func (p *Process) setInt64(addr int32, val int64) {
+	data := make([]byte, 8)
+	buf := bytes.NewBuffer(data)
+	err := binary.Write(buf, binary.LittleEndian, val)
+	if err != nil {
+		panic(err)
+	}
+
+	_, err := p.writeMem(addr, data)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// goRuntimeWasmExit implements the go runtime function runtime.wasmExit. It uses
+// the Go abi.
+//
+// This has the effective type of:
+//
+//     func (p *Process) goRuntimeWasmExit(code int32)
+func (p *Process) goRuntimeWasmExit(sp int32) {
+	exitCode := p.getInt32(sp + 8)
+	os.Exit(int(exitCode))
+}
+
+// goRuntimeWasmWrite wraps the write function.
+//
+// This has the effective type of:
+//
+//     func (p *Process) goRuntimeWasmWrite(fd int64, ptr int64, n int32)
+func (p *Process) goRuntimeWasmWrite(sp int32) {
+	fd := p.getInt64(sp + 8)
+	ptr := p.getInt64(sp + 16)
+	n := p.getInt32(sp + 24)
+
+	result := p.write(int32(fd), int32(ptr), n)
+	// TODO: write result to wasmWrite?
+	_ = result
+}
+
+// goRuntimeNanotime implements the go runtime function runtime.nanotime. It uses
+// the Go abi.
+//
+// This has the effective type of:
+//
+//     func (p *Process) goRuntimeNanotime() int64
+func (p *Process) goRuntimeNanotime(sp int32) {
+	p.setInt64(sp+8, int64(time.Now().UnixNano()))
+}
+
+// goRuntimeWalltime implements the go runtime function runtime.walltime. It uses
+// the Go abi.
+//
+// This has the effective type of:
+//
+//     func (p *Process) goRuntimeWalltime() (int64, int32)
+func (p *Process) goRuntimeWalltime(sp int32) {
+	now := time.Now()
+	p.setInt64(sp+8, now.Unix())
+	p.setInt32(sp+16, int32(now.Nanosecond()))
+}
+
+// goRuntimeScheduleCallback implements the go runtime function runtime.scheduleCallback.
+// It uses the Go abi and is not implemented yet.
+func (p *Process) goRuntimeScheduleCallback(sp int32) {
+	p.setInt32(sp+16, -1)
+}
+
+func (p *Process) goRuntimeClearScheduledCallback(sp int32) {}
+
+// goLoadSlice loads a Go slice out of wasm memory. It uses the the Go abi.
+func (p *Process) goLoadSlice(sp int32) []byte {
+	arr := p.getInt64(sp)
+	len := p.getInt64(sp + 8)
+	return p.vm.Memory()[arr : arr+len]
+}
+
+func (p *Process) goRuntimeGetRandomData(sp int32) {
+	data := p.goLoadSlice(sp + 8)
+	_, err := rand.Read(data)
+	if err != nil {
+		panic(err)
+	}
+
+	p.writeMem(sp+8, data)
+}
diff --git a/cmd/land/process.go b/cmd/land/process.go
index 6a2b2b2..c395fe4 100644
--- a/cmd/land/process.go
+++ b/cmd/land/process.go
@@ -25,6 +25,9 @@ type Process struct {
 	fs    afero.Fs
 	files []afero.File
 	name  string
+
+	// go runtime cruft
+	goRuntimeValues []interface{}
 }
 
 // NewProcess constructs a new webassembly process based on the input webassembly module as a reader.