Heavy refactoring, see PR #28

pkg/fileio/fileio.go

@@ -8,16 +8,20 @@ import (
 	"os"
 
 	"github.com/HikariKnight/ls-iommu/pkg/errorcheck"
+
+	"github.com/HikariKnight/quickpassthrough/internal/common"
 )
 
 /*
  * This just implements repetetive tasks I have to do with files
  */
 
-// Creates a file and appends the content to the file (ending newline must be supplied with content string)
+// AppendContent creates a file and appends the content to the file.
+// (ending newline must be supplied with content string)
 func AppendContent(content string, fileName string) {
 	// Open the file
 	f, err := os.OpenFile(fileName, os.O_CREATE|os.O_APPEND|os.O_WRONLY, os.ModePerm)
+
 	errorcheck.ErrorCheck(err, fmt.Sprintf("Error opening \"%s\" for writing", fileName))
 	defer f.Close()
 
@@ -26,7 +30,7 @@ func AppendContent(content string, fileName string) {
 	errorcheck.ErrorCheck(err, fmt.Sprintf("Error writing to %s", fileName))
 }
 
-// Reads the file and returns a stringlist with each line
+// ReadLines reads the file and returns a stringlist with each line.
 func ReadLines(fileName string) []string {
 	content, err := os.Open(fileName)
 	errorcheck.ErrorCheck(err, fmt.Sprintf("Error reading file %s", fileName))
@@ -46,10 +50,14 @@ func ReadLines(fileName string) []string {
 
 }
 
-// Reads a file and returns all the content as a string
+// ReadFile reads a file and returns all the content as a string.
 func ReadFile(fileName string) string {
 	// Read the whole file
 	content, err := os.ReadFile(fileName)
+	if errors.Is(err, os.ErrPermission) {
+		errorcheck.ErrorCheck(err, common.PermissionNotice)
+		return "" // note: unreachable due to ErrorCheck calling fatal
+	}
 	errorcheck.ErrorCheck(err, fmt.Sprintf("Failed to ReadFile on %s", fileName))
 
 	// Return all the lines as one string
@@ -57,24 +65,25 @@ func ReadFile(fileName string) string {
 
 }
 
-// Checks if a file exists and returns a bool
-func FileExist(fileName string) bool {
+// FileExist checks if a file exists and returns a bool and any error that isn't os.ErrNotExist.
+func FileExist(fileName string) (bool, error) {
 	var exist bool
 
 	// Check if the file exists
-	if _, err := os.Stat(fileName); !errors.Is(err, os.ErrNotExist) {
-		// Set the value to true
+	_, err := os.Stat(fileName)
+	switch {
+	case err == nil:
 		exist = true
-	} else {
-		// Set the value to false
+	case errors.Is(err, os.ErrNotExist):
+		// Set the value to true
 		exist = false
+		err = nil
 	}
-
 	// Return if the file exists
-	return exist
+	return exist, err
 }
 
-// Copies a FILE from source to dest
+// FileCopy copies a FILE from source to dest.
 func FileCopy(sourceFile, destFile string) {
 	// Get the file info
 	filestat, err := os.Stat(sourceFile)