Parse the fields from pdftk dump_data_fields

getfields.go

@@ -0,0 +1,83 @@
+package fillpdf
+
+import (
+	"fmt"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+// Field contains information about the fields exported from a pdf via pdftk
+type Field struct {
+	Type    string
+	Name    string
+	AltName string
+	Flags   string
+}
+
+func GetFields(formPDFFile string) ([]Field, error) {
+	formPDFFile, err := filepath.Abs(formPDFFile)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create the absolute path: %v", err)
+	}
+
+	// Check if the form file exists.
+	e, err := exists(formPDFFile)
+	if err != nil {
+		return nil, fmt.Errorf("failed to check if form PDF file exists: %v", err)
+	} else if !e {
+		return nil, fmt.Errorf("form PDF file does not exists: '%s'", formPDFFile)
+	}
+
+	// Check if the pdftk utility exists.
+	_, err = exec.LookPath("pdftk")
+	if err != nil {
+		return nil, fmt.Errorf("pdftk utility is not installed")
+	}
+
+	// Create the pdftk command line arguments.
+	args := []string{
+		formPDFFile,
+		"dump_data_fields",
+	}
+
+	output, err := runCommandWithResults("pdftk", args...)
+	if err != nil {
+		return nil, fmt.Errorf("pdftk error: %v", err)
+	}
+
+	fieldsData := strings.Split(output, "---\n")
+
+	fields := []Field{}
+	for _, f := range fieldsData {
+		lines := strings.Split(f, "\n")
+		if len(lines) <= 2 {
+			continue
+		}
+
+		field := Field{}
+
+		for _, line := range lines {
+			props := strings.SplitN(line, ": ", 2)
+
+			if len(props) != 2 {
+				continue
+			}
+
+			switch props[0] {
+			case "FieldType":
+				field.Type = strings.ToLower(props[1])
+			case "FieldName":
+				field.Name = props[1]
+			case "FieldNameAlt":
+				field.AltName = props[1]
+			case "FieldFlags":
+				field.Flags = props[1]
+			}
+		}
+
+		fields = append(fields, field)
+	}
+
+	return fields, nil
+}

sample/main.go

@@ -18,4 +18,11 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+	fields, err := fillpdf.GetFields("form.pdf")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Printf("%+v", fields)
 }

utils.go

@@ -84,3 +84,16 @@ func runCommandInPath(dir, name string, args ...string) error {
 
 	return nil
 }
+
+func runCommandWithResults(name string, args ...string) (string, error) {
+	var stderr bytes.Buffer
+	cmd := exec.Command(name, args...)
+	cmd.Stderr = &stderr
+
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf(strings.TrimSpace(stderr.String()))
+	}
+
+	return string(out), nil
+}