第一次提交

service/file_detect.go

@@ -0,0 +1,35 @@
+package service
+
+import (
+	"net/http"
+	"strings"
+)
+
+// DetectFileType 根据返回的二进制内容推断 contentType + 扩展名（尽量稳定）
+func DetectFileType(data []byte) (contentType string, ext string) {
+	if len(data) == 0 {
+		return "application/octet-stream", ""
+	}
+	ct := http.DetectContentType(data)
+	switch ct {
+	case "audio/mpeg":
+		return ct, ".mp3"
+	case "audio/wave", "audio/wav", "audio/x-wav":
+		return ct, ".wav"
+	case "video/mp4":
+		return ct, ".mp4"
+	case "image/png":
+		return ct, ".png"
+	case "image/jpeg":
+		return ct, ".jpg"
+	case "application/pdf":
+		return ct, ".pdf"
+	default:
+		// 兜底：尝试从 ct 截取 subtype 作为后缀（例如 application/json）
+		if parts := strings.Split(ct, "/"); len(parts) == 2 {
+			return ct, "." + parts[1]
+		}
+		return ct, ""
+	}
+}
+