feat: add json utils to pdk

example/countvowels/std_main.go

@@ -4,6 +4,7 @@
 package main
 
 import (
+	// "fmt"
 	"strconv"
 
 	"github.com/extism/go-pdk"
@@ -13,10 +14,45 @@ import (
 // `_start` via WASI. So, `main` functions should contain the plugin behavior, that the host will
 // invoke by explicitly calling `_start`.
 func main() {
-	countVowels()
+	count_vowels()
+	count_vowels_typed()
+	count_vowels_json_output()
 }
 
-func countVowels() int32 {
+type CountVowelsInput struct {
+	Input string `json:"input"`
+}
+
+type CountVowelsOuptut struct {
+	Count  int    `json:"count"`
+	Total  int    `json:"total"`
+	Vowels string `json:"vowels"`
+}
+
+//export count_vowels_typed
+func count_vowels_typed() int32 {
+	var input CountVowelsInput
+	if err := pdk.InputJson(&input); err != nil {
+		pdk.SetError(err)
+		return -1
+	}
+
+	pdk.OutputString(input.Input)
+	return 0
+}
+
+//export count_vowels_json_output
+func count_vowels_json_output() int32 {
+	output := CountVowelsOuptut{Count: 42, Total: 2.1e7, Vowels: "aAeEiIoOuUyY"}
+	err := pdk.OutputJson(output)
+	if err != nil {
+		pdk.SetError(err)
+		return -1
+	}
+	return 0
+}
+
+func count_vowels() int32 {
 	input := pdk.Input()
 
 	count := 0

example/countvowels/tiny_main.go

@@ -9,6 +9,39 @@ import (
 	"github.com/extism/go-pdk"
 )
 
+type CountVowelsInput struct {
+	Input string `json:"input"`
+}
+
+type CountVowelsOuptut struct {
+	Count  int    `json:"count"`
+	Total  int    `json:"total"`
+	Vowels string `json:"vowels"`
+}
+
+//export count_vowels_typed
+func count_vowels_typed() int32 {
+	var input CountVowelsInput
+	if err := pdk.InputJson(&input); err != nil {
+		pdk.SetError(err)
+		return -1
+	}
+
+	pdk.OutputString(input.Input)
+	return 0
+}
+
+//export count_vowels_json_output
+func count_vowels_json_output() int32 {
+	output := CountVowelsOuptut{Count: 42, Total: 2.1e7, Vowels: "aAeEiIoOuUyY"}
+	err := pdk.OutputJson(output)
+	if err != nil {
+		pdk.SetError(err)
+		return -1
+	}
+	return 0
+}
+
 //export count_vowels
 func count_vowels() int32 {
 	input := pdk.Input()

extism_pdk.go

@@ -77,6 +77,25 @@ func Input() []byte {
 	return loadInput()
 }
 
+func JsonFrom(offset uint64, v any) error {
+	mem := FindMemory(offset)
+	return json.Unmarshal(mem.ReadBytes(), v)
+}
+
+func InputJson(v any) error {
+	return json.Unmarshal(Input(), v)
+}
+
+func OutputJson(v any) error {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return err
+	}
+
+	OutputMemory(AllocateBytes(b))
+	return nil
+}
+
 func Allocate(length int) Memory {
 	clength := uint64(length)
 	offset := extism_alloc(clength)