From 84b50ef1bf07792b9e5e24b492397018ee63271c Mon Sep 17 00:00:00 2001
From: Arkadiy Tetelman <arkadiyt@gmail.com>
Date: Sun, 1 Jan 2023 08:26:21 -0800
Subject: [PATCH] Handle 10-character long proto filenames

---
 Makefile               |  2 +-
 pkg/protodump/proto.go |  5 +++--
 pkg/protodump/scan.go  | 30 +++++++++++++++++++-----------
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/Makefile b/Makefile
index 8724135..28d433f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
 build:
-	go build -o protodump cmd/protodump/main.go 
+	go build -o bin/protodump cmd/protodump/main.go
 
 fmt:
 	go fmt ./...
diff --git a/pkg/protodump/proto.go b/pkg/protodump/proto.go
index 6b51889..3395926 100644
--- a/pkg/protodump/proto.go
+++ b/pkg/protodump/proto.go
@@ -250,9 +250,10 @@ func (pd *ProtoDefinition) writeFileOptions() {
 		elemPtr := options.FieldByName(option.FieldName)
 		if !elemPtr.IsNil() {
 			elem := elemPtr.Elem()
-			if elem.Kind() == reflect.String {
+			kind := elem.Kind()
+			if kind == reflect.String {
 				pd.writeStringFileOptions(option.OptionName, elem.String())
-			} else if elem.Kind() == reflect.Bool {
+			} else if kind == reflect.Bool {
 				pd.writeBoolFileOptions(option.OptionName, elem.Bool())
 			}
 			printedOption = true
diff --git a/pkg/protodump/scan.go b/pkg/protodump/scan.go
index 9e8aba7..42c819d 100644
--- a/pkg/protodump/scan.go
+++ b/pkg/protodump/scan.go
@@ -8,13 +8,8 @@ import (
 	"google.golang.org/protobuf/encoding/protowire"
 )
 
-func ScanFile(path string) ([][]byte, error) {
-	data, err := os.ReadFile(path)
-	if err != nil {
-		return nil, fmt.Errorf("Couldn't open file: %w", err)
-	}
-	return Scan(data), nil
-}
+const scan = ".proto"
+const magicByte = 0xa
 
 func consumeBytes(data []byte, position int) int {
 	start := position
@@ -29,26 +24,39 @@ func consumeBytes(data []byte, position int) int {
 	}
 }
 
+func ScanFile(path string) ([][]byte, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("Couldn't open file: %w", err)
+	}
+	return Scan(data), nil
+}
+
 func Scan(data []byte) [][]byte {
 	results := make([][]byte, 0)
 
 	for {
-		index := bytes.Index(data, []byte(".proto"))
+		index := bytes.Index(data, []byte(scan))
 		if index == -1 {
 			break
 		}
 
 		// Look for a 0xa byte: 0 0001 010
 		//                      ^ no more bytes for varint
-		//                           ^ field 1 (file name)
+		//                        ^ field 1 (file name)
 		//                             ^ type 2 (LEN)
-		start := bytes.LastIndexByte(data[:index], 0xa)
+		start := bytes.LastIndexByte(data[:index], magicByte)
 		if start == -1 {
-			// fmt.Printf("Warn: couldn't find start to proto definition at offset:0x%s\n", strconv.FormatInt(int64(index), 16))
 			data = data[index+1:]
 			continue
 		}
 
+		// If the "<file>.proto" filename is 10 characters long then the 0xa byte we found is actually
+		// the string length and not the start of the protobuf record, so go back 1 more
+		if index-start == (magicByte-len(scan)+1) && start > 0 && data[start-1] == magicByte {
+			start -= 1
+		}
+
 		length := consumeBytes(data, start)
 		results = append(results, data[start:start+length])
 		data = data[start+length:]