[bug] - Correctly return the checked out buffer to the pool (#2732)

* Make sure to return the buffer to the pool

* update comment

* defer the return

* remove anonymous function

pkg/writers/buffered_file_writer/bufferedfilewriter.go

@@ -178,6 +178,10 @@ func (w *BufferedFileWriter) CloseForWriting() error {
 		return nil
 	}
 
+	// Return the buffer to the pool since the contents have been written to the file and
+	// the writer is transitioning to read-only mode.
+	defer w.bufPool.Put(w.buf)
+
 	if w.buf.Len() > 0 {
 		_, err := w.buf.WriteTo(w.file)
 		if err != nil {

pkg/writers/buffered_file_writer/bufferedfilewriter_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"github.com/trufflesecurity/trufflehog/v3/pkg/context"
+	"github.com/trufflesecurity/trufflehog/v3/pkg/writers/buffer"
 )
 
 func TestBufferedFileWriterNewThreshold(t *testing.T) {
@@ -506,3 +507,33 @@ func BenchmarkBufferedFileWriterWriteSmall(b *testing.B) {
 		rc.Close()
 	}
 }
+
+func TestBufferWriterCloseForWritingWithFile(t *testing.T) {
+	bufPool := buffer.NewBufferPool()
+
+	ctx := context.Background()
+	buf := bufPool.Get(ctx)
+	writer := &BufferedFileWriter{
+		threshold: 10,
+		bufPool:   bufPool,
+		buf:       buf,
+	}
+
+	// Write data exceeding the threshold to ensure a file is created.
+	data := []byte("this is a longer string exceeding the threshold")
+	_, err := writer.Write(data)
+	assert.NoError(t, err)
+
+	err = writer.CloseForWriting()
+	assert.NoError(t, err)
+	assert.Equal(t, readOnly, writer.state)
+
+	rdr, err := writer.ReadCloser()
+	assert.NoError(t, err)
+	defer rdr.Close()
+
+	// Get a buffer from the pool and check if it is the same buffer used in the writer.
+	bufFromPool := bufPool.Get(ctx)
+	assert.Same(t, buf, bufFromPool, "Buffer should be returned to the pool")
+	bufPool.Put(bufFromPool)
+}