feat(sdk): 添加大小写不敏感的 HTTP 响应头读取方法

Sources/DuooomiBleSDK/DuooomiBleSDK+Transfer.swift

@@ -154,7 +154,7 @@ extension DuooomiBleSDK {
                 completion(.failure(DuooomiBleError.transferFailed("Format check failed: \(error.localizedDescription)")))
                 return
             }
-            guard let mime = (response as? HTTPURLResponse)?.allHeaderFields["Content-Type"] as? String else {
+            guard let mime = (response as? HTTPURLResponse)?.headerValue(caseInsensitive: "Content-Type") else {
                 completion(.failure(DuooomiBleError.unsupportedFormat("unknown")))
                 return
             }
@@ -183,7 +183,7 @@ extension DuooomiBleSDK {
             }
 
             if let http = response as? HTTPURLResponse {
-                if let lengthStr = http.allHeaderFields["Content-Length"] as? String,
+                if let lengthStr = http.headerValue(caseInsensitive: "Content-Length"),
                    let length = Int(lengthStr), length > 0 {
                     completion(.success(length))
                     return
@@ -209,7 +209,7 @@ extension DuooomiBleSDK {
                 return
             }
             if let http = response as? HTTPURLResponse,
-               let rangeHeader = http.allHeaderFields["Content-Range"] as? String,
+               let rangeHeader = http.headerValue(caseInsensitive: "Content-Range"),
                let totalStr = rangeHeader.split(separator: "/").last,
                let total = Int(totalStr), total > 0 {
                 completion(.success(total))

Sources/DuooomiBleSDK/Utils/BeijingTimeProvider.swift

@@ -69,7 +69,7 @@ final class BeijingTimeProvider {
             }
 
             if let http = resp as? HTTPURLResponse,
-               let dateHeader = (http.allHeaderFields["Date"] ?? http.allHeaderFields["date"]) as? String,
+               let dateHeader = http.headerValue(caseInsensitive: "Date"),
                let value = self.formatHTTPDateHeader(dateHeader) {
                 done(value)
                 return

Sources/DuooomiBleSDK/Utils/HTTPURLResponse+Header.swift

@@ -0,0 +1,19 @@
+import Foundation
+
+extension HTTPURLResponse {
+    /// 大小写不敏感地读取 HTTP 响应头。
+    ///
+    /// HTTP/2（RFC 7540 §8.1.2）强制把头字段名小写（如 `content-length`），而
+    /// `allHeaderFields` 的字典下标是大小写敏感精确匹配，直接用 `["Content-Length"]`
+    /// 在 HTTP/2 响应下会取不到值。系统的 `value(forHTTPHeaderField:)` 能规避，但要求
+    /// iOS 13+，本 SDK 最低支持 iOS 12，故手动遍历比较。
+    func headerValue(caseInsensitive name: String) -> String? {
+        for (key, value) in allHeaderFields {
+            if let keyStr = key as? String,
+               keyStr.caseInsensitiveCompare(name) == .orderedSame {
+                return value as? String
+            }
+        }
+        return nil
+    }
+}