feat: add json utils to pdk (#30)

* feat: add json utils to pdk

* chore: rename Json -> JSON for common go naming

* feat: update docs to include new json helpers

Author: nilslice

README.md

@@ -116,18 +116,19 @@ type Sum struct {
 //export add
 func add() int32 {
 	params := Add{}
-	err := json.Unmarshal(pdk.Input(), &params)
+	// use json input helper, which automatically unmarshals the plugin input into your struct
+	err := pdk.InputJSON(&params)
 	if err != nil {
 		pdk.SetError(err)
 		return 1
 	}
 	sum := Sum{Sum: params.A + params.B}
-	output, err := json.Marshal(sum)
+	// use json output helper, which automatically marshals your struct to the plugin output
+	output, err := pdk.OutputJSON(sum)
 	if err != nil {
 		pdk.SetError(err)
 		return 1
 	}
-	pdk.Output(output)
 	return 0
 }
 ```

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)