feat: prevent log allocation unless needed

env.go

@@ -120,6 +120,17 @@ func extismHTTPRequest(request, body extismPointer) extismPointer
 //go:wasmimport extism:host/env http_status_code
 func extismHTTPStatusCode() int32
 
+// extismGetLogLevel returns the current log level set in the Extism runtime.
+//
+//go:wasmimport extism:host/env get_log_level
+func extismGetLogLevel() int32
+
+// extismLogTrace logs a "trace" string to the host from the previously-written UTF-8 string written to `offset`.
+// Note that the memory at `offset` can be immediately freed because it is immediately logged.
+//
+//go:wasmimport extism:host/env log_trace
+func extismLogTrace(offset extismPointer)
+
 // extismLogInfo logs an "info" string to the host from the previously-written UTF-8 string written to `offset`.
 // Note that the memory at `offset` can be immediately freed because it is immediately logged.
 //

example/countvowels/tiny_main.go

@@ -95,6 +95,7 @@ func countVowels() int32 {
 	}
 
 	output := `{"count": ` + strconv.Itoa(count) + `, "config": "` + thing + `", "a": "` + string(varA) + `"}`
+	pdk.Log(pdk.LogWarn, "WE GOT LOGS: "+output)
 	mem := pdk.AllocateString(output)
 
 	// zero-copy output to host

extism_pdk.go

@@ -15,11 +15,11 @@ type Memory struct {
 type LogLevel int
 
 const (
-	LogInfo LogLevel = iota
+	LogTrace LogLevel = iota
 	LogDebug
+	LogInfo
 	LogWarn
 	LogError
-	LogTrace
 )
 
 func load(offset extismPointer, buf []byte) {
@@ -217,13 +217,24 @@ func LogMemory(level LogLevel, memory Memory) {
 	}
 }
 
-// Log logs the provided UTF-8 string `s` on the host using the provided log `level`.
-func Log(level LogLevel, s string) {
-	mem := AllocateString(s)
-	// TODO: coordinate replacement of call to free based on SDK alignment
-	// defer mem.Free()
-
-	LogMemory(level, mem)
+// Log logs a message at the specified log level, but only if the current log level is high enough.
+func Log(level LogLevel, message string) {
+	currentLevel := LogLevel(extismGetLogLevel())
+	if currentLevel <= level {
+		mem := AllocateString(message)
+		switch level {
+		case LogInfo:
+			extismLogInfo(mem.offset)
+		case LogDebug:
+			extismLogDebug(mem.offset)
+		case LogWarn:
+			extismLogWarn(mem.offset)
+		case LogError:
+			extismLogError(mem.offset)
+		case LogTrace:
+			extismLogTrace(mem.offset)
+		}
+	}
 }
 
 // GetVar returns the byte slice (if any) associated with `key`.