Share bounded regular file read mechanics

profile.go

@@ -3,7 +3,6 @@ package configkit
 import (
 	"bytes"
 	"errors"
-	"io"
 	"io/fs"
 	"os"
 	"path/filepath"
@@ -122,41 +121,9 @@ func readProfileFile(root *os.Root, relative, sourceID string, remaining int64)
 	if limit < 0 {
 		limit = 0
 	}
-	preflight, err := root.Stat(relative)
-	if err != nil {
-		value := classifySourceError(err, sourceID)
-		return nil, &value
-	}
-	if !preflight.Mode().IsRegular() {
-		value := sourceDiagnostic(CodeSourceNotRegular, sourceID, "source is not a regular file")
-		return nil, &value
-	}
-	file, err := root.Open(relative)
-	if err != nil {
-		value := classifySourceError(err, sourceID)
-		return nil, &value
-	}
-	defer func() { _ = file.Close() }()
-	info, err := file.Stat()
-	if err != nil {
-		value := classifySourceError(err, sourceID)
-		return nil, &value
-	}
-	if !info.Mode().IsRegular() {
-		value := sourceDiagnostic(CodeSourceNotRegular, sourceID, "source is not a regular file")
-		return nil, &value
-	}
-	if info.Size() > limit {
-		value := importDiagnostic(CodeProfileLimitExceeded, "selected profile exceeds a source or aggregate byte limit", &Location{SourceID: sourceID})
-		return nil, &value
-	}
-	data, err := io.ReadAll(io.LimitReader(file, limit+1))
-	if err != nil {
-		value := classifySourceError(err, sourceID)
-		return nil, &value
-	}
-	if int64(len(data)) > limit {
-		value := importDiagnostic(CodeProfileLimitExceeded, "selected profile exceeds a source or aggregate byte limit", &Location{SourceID: sourceID})
+	data, failure := readRegularFile(relative, root.Stat, root.Open, limit)
+	if failure != nil {
+		value := sourceReadDiagnostic(failure, sourceID, CodeProfileLimitExceeded, "selected profile exceeds a source or aggregate byte limit")
 		return nil, &value
 	}
 	return data, nil