wasi preview 2 support (#4027)

* all: wasip2 support

Co-authored-by: Randy Reddig <randy.reddig@fastly.com>

src/runtime/runtime_tinygowasmp2.go

@@ -0,0 +1,76 @@
+//go:build wasip2
+
+package runtime
+
+import (
+	exit "internal/wasi/cli/v0.2.0/exit"
+	stdout "internal/wasi/cli/v0.2.0/stdout"
+	monotonicclock "internal/wasi/clocks/v0.2.0/monotonic-clock"
+	wallclock "internal/wasi/clocks/v0.2.0/wall-clock"
+	random "internal/wasi/random/v0.2.0/random"
+
+	"github.com/ydnar/wasm-tools-go/cm"
+)
+
+const putcharBufferSize = 120
+
+// Using global variables to avoid heap allocation.
+var (
+	putcharStdout        = stdout.GetStdout()
+	putcharBuffer        = [putcharBufferSize]byte{}
+	putcharPosition uint = 0
+)
+
+func putchar(c byte) {
+	putcharBuffer[putcharPosition] = c
+	putcharPosition++
+	if c == '\n' || putcharPosition >= putcharBufferSize {
+		list := cm.NewList(&putcharBuffer[0], putcharPosition)
+		putcharStdout.BlockingWriteAndFlush(list) // error return ignored; can't do anything anyways
+		putcharPosition = 0
+	}
+}
+
+func getchar() byte {
+	// dummy, TODO
+	return 0
+}
+
+func buffered() int {
+	// dummy, TODO
+	return 0
+}
+
+//go:linkname now time.now
+func now() (sec int64, nsec int32, mono int64) {
+	now := wallclock.Now()
+	sec = int64(now.Seconds)
+	nsec = int32(now.Nanoseconds)
+	mono = int64(monotonicclock.Now())
+	return
+}
+
+// Abort executes the wasm 'unreachable' instruction.
+func abort() {
+	trap()
+}
+
+//go:linkname syscall_Exit syscall.Exit
+func syscall_Exit(code int) {
+	exit.Exit(code != 0)
+}
+
+// TinyGo does not yet support any form of parallelism on WebAssembly, so these
+// can be left empty.
+
+//go:linkname procPin sync/atomic.runtime_procPin
+func procPin() {
+}
+
+//go:linkname procUnpin sync/atomic.runtime_procUnpin
+func procUnpin() {
+}
+
+func hardwareRand() (n uint64, ok bool) {
+	return random.GetRandomU64(), true
+}