Spaces:
Running
Running
| """内存结果共用的 HTTP 下载响应，适用于图像字节和 JSON。""" | |
| import hashlib | |
| import secrets | |
| from email.utils import formatdate | |
| from fastapi import Request | |
| from fastapi.responses import FileResponse, Response | |
| class ResultFileResponse(FileResponse): | |
| """文件响应结束时释放既有下载租约，包括 416 和连接中断路径。""" | |
| async def __call__(self, scope, receive, send): | |
| """发送文件并保证后台租约释放动作只执行一次。 | |
| Args: | |
| scope: ASGI 请求上下文。 | |
| receive: ASGI 请求消息接收函数。 | |
| send: ASGI 响应消息发送函数。 | |
| """ | |
| release = self.background | |
| self.background = None | |
| if scope["method"] == "HEAD": | |
| # Range 只用于 GET；HEAD 应提供完整结果的长度和校验信息。 | |
| scope = {**scope, "headers": [(name, value) for name, value in scope["headers"] | |
| if name.lower() != b"range"]} | |
| try: | |
| await super().__call__(scope, receive, send) | |
| finally: | |
| # FileResponse 的范围错误会提前返回，不会运行通常的 background。 | |
| if release is not None: | |
| await release() | |
| def result_bytes_response(request: Request, content: bytes, media_type: str, | |
| modified_at: float) -> Response: | |
| """返回带校验信息、范围读取和 HEAD 支持的不可变结果。 | |
| Args: | |
| request: 当前 GET 或 HEAD 请求。 | |
| content: 已在任务清理锁内读出的完整结果，发送期间不再依赖文件。 | |
| media_type: 结果的 MIME 类型。 | |
| modified_at: 任务完成时间，作为稳定的 Last-Modified。 | |
| Returns: | |
| 完整结果、206 范围结果或 416 越界响应；HEAD 始终不含响应体。 | |
| """ | |
| size = len(content) | |
| etag = '"' + hashlib.sha256(content).hexdigest() + '"' | |
| modified = formatdate(modified_at, usegmt=True) | |
| headers = { | |
| "ETag": etag, | |
| "Last-Modified": modified, | |
| "Accept-Ranges": "bytes", | |
| "Cache-Control": "private, max-age=300", | |
| "Referrer-Policy": "no-referrer", | |
| "X-Content-Type-Options": "nosniff", | |
| "Access-Control-Allow-Origin": "*", | |
| "Access-Control-Expose-Headers": ( | |
| "Content-Length, Content-Range, Accept-Ranges, ETag, Last-Modified" | |
| ), | |
| } | |
| status_code = 200 | |
| range_header = request.headers.get("range") | |
| # If-Range 不匹配时发送完整的新结果，避免把两个版本拼成一个文件。 | |
| if (request.method == "GET" and range_header | |
| and request.headers.get("if-range", etag) in {etag, modified}): | |
| try: | |
| unit, ranges_text = range_header.split("=", 1) | |
| ranges = [] | |
| if unit.strip() != "bytes" or len(ranges_text.split(",")) > 100: | |
| raise ValueError("Unsupported range") | |
| for part in ranges_text.split(","): | |
| start_text, end_text = part.strip().split("-", 1) | |
| if not start_text: | |
| suffix = int(end_text) | |
| if suffix <= 0: | |
| raise ValueError("Empty suffix") | |
| start, end = max(0, size - suffix), size - 1 | |
| else: | |
| start = int(start_text) | |
| end = min(int(end_text), size - 1) if end_text else size - 1 | |
| if start < 0 or start > end or start >= size: | |
| raise ValueError("Unsatisfiable range") | |
| ranges.append((start, end)) | |
| except ValueError: | |
| headers["Content-Range"] = f"bytes */{size}" | |
| return Response(status_code=416, headers=headers) | |
| status_code = 206 | |
| if len(ranges) == 1: | |
| start, end = ranges[0] | |
| headers["Content-Range"] = f"bytes {start}-{end}/{size}" | |
| content = content[start:end + 1] | |
| else: | |
| boundary = secrets.token_hex(16) | |
| content = b"".join( | |
| (f"--{boundary}\r\nContent-Type: {media_type}\r\n" | |
| f"Content-Range: bytes {start}-{end}/{size}\r\n\r\n").encode() | |
| + content[start:end + 1] + b"\r\n" for start, end in ranges | |
| ) + f"--{boundary}--\r\n".encode() | |
| media_type = f"multipart/byteranges; boundary={boundary}" | |
| headers["Content-Length"] = str(len(content)) | |
| return Response(b"" if request.method == "HEAD" else content, | |
| status_code=status_code, media_type=media_type, headers=headers) | |