我需要做什么才能使Boost.Beast HTTP解析器找到主体的末尾？
我需要做什么才能使Boost.Beast HTTP解析器找到主体的末尾？
提问于 2021-03-20 17:06:31
我正在尝试使用boost::beast::http::parser解析HTTPS响应。我的解析器的定义如下：
boost::beast::http::parser<false, boost::beast::http::string_body> response_parser;异步读取的回调如下所示：
void AsyncHttpsRequest::on_response_read(const boost::system::error_code &error_code, uint32_t bytes_transferred)
{
if (bytes_transferred > 0)
{
response_parser.put(boost::asio::buffer(data_buffer, bytes_transferred), http_error_code);
std::cout << "Parser status: " << http_error_code.message() << std::endl;
std::cout << "Read " << bytes_transferred << " bytes of HTTPS response" << std::endl;
std::cout << std::string(data_buffer, bytes_transferred) << std::endl;
}
if (error_code)
{
std::cout << "Error during HTTPS response read: " << error_code.message() << std::endl;
callback(error_code, response_parser.get());
}
else
{
if (response_parser.is_done())
{
callback(error_code, response_parser.get());
}
else
{
std::cout << "Response is not yet finished, reading more" << std::endl;
read_response();
}
}
}当响应没有主体时，一切正常工作，response_parser.is_done()返回true。但是，当响应包含一个主体时，它总是返回false，即使body是完全读取的。响应还有一个Content-Length头，它与正文中的字节数相匹配，所以没有问题。
Boost docs说，如果消息的语义表明需要一个主体，并且解析了整个主体，那么response_parser.is_done()应该返回true。
当我使用Connection: keep-alive发送请求时，我被困在读取响应上，因为服务器没有什么可以发送的了，response_parser还没有完成。当我使用Connection: close时，会调用finish回调，但解析的boost::beast::http::message内部没有实体。然而，我在stdout中的日志显示，这里有body，并且它是完整的。
当从boost::beast::http::parser读取的字节数等于Content-Length时，我需要做什么才能使is_done()识别正文结束并在is_done()上返回Content-Length
回答 1
Stack Overflow用户
回答已采纳
发布于 2021-03-21 00:36:51
你的期望是对的。
背景、细节和注意事项：
你可以观察到它确实起作用：
#include <boost/beast/http.hpp>
#include <iostream>
#include <iomanip>
#include <random>
using boost::system::error_code;
namespace http = boost::beast::http;
int main() {
std::mt19937 prng { std::random_device{}() };
std::uniform_int_distribution<size_t> packet_size { 1, 372 };
std::string const response =
"HTTP/1.1 200 OK\r\n"
"Age: 207498\r\n"
"Cache-Control: max-age=604800\r\n"
"Content-Type: text/html; charset=UTF-8\r\n"
"Date: Sat, 20 Mar 2021 23:24:40 GMT\r\n"
"Etag: \"3147526947+ident\"\r\n"
"Expires: Sat, 27 Mar 2021 23:24:40 GMT\r\n"
"Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT\r\n"
"Server: ECS (bsa/EB15)\r\n"
"Vary: Accept-Encoding\r\n"
"X-Cache: HIT\r\n"
"Content-Length: 1256\r\n"
"\r\n"
"<!doctype html>\n<html>\n<head>\n <title>Example Domain</title>\n\n <meta charset=\"utf-8\" />\n <meta http-equiv=\"Content-type\" content=\"text/html; charset=utf-8\" />\n <meta name=\"viewport\" content=\"width=device-width, initial-scale=1\" />\n <style type=\"text/css\">\n body {\n background-color: #f0f0f2;\n margin: 0;\n padding: 0;\n font-family: -apple-system, system-ui, BlinkMacSystemFont, \"Segoe UI\", \"Open Sans\", \"Helvetica Neue\", Helvetica, Arial, sans-serif;\n \n }\n div {\n width: 600px;\n margin: 5em auto;\n padding: 2em;\n background-color: #fdfdff;\n border-radius: 0.5em;\n box-shadow: 2px 3px 7px 2px rgba(0,0,0,0.02);\n }\n a:link, a:visited {\n color: #38488f;\n text-decoration: none;\n }\n @media (max-width: 700px) {\n div {\n margin: 0 auto;\n width: auto;\n }\n }\n </style> \n</head>\n\n<body>\n<div>\n <h1>Example Domain</h1>\n <p>This domain is for use in illustrative examples in documents. You may use this\n domain in literature without prior coordination or asking for permission.</p>\n <p><a href=\"https://www.iana.org/domains/example\">More information...</a></p>\n</div>\n</body>\n</html>\n";
std::string const input = response + response;
std::string_view emulated_stream = input;
error_code ec;
while (not emulated_stream.empty()) {
std::cout << "== Emulated stream of " << emulated_stream.size()
<< " remaining" << std::endl;
http::parser<false, http::string_body> response_parser;
while (not (ec or response_parser.is_done() or emulated_stream.empty())) {
auto next = std::min(packet_size(prng), emulated_stream.size());
auto consumed = response_parser.put(
boost::asio::buffer(emulated_stream.data(), next), ec);
std::cout << "Consumed " << consumed << std::boolalpha
<< "\tHeaders done:" << response_parser.is_header_done()
<< "\tDone:" << response_parser.is_done()
<< "\tChunked:" << response_parser.chunked()
<< "\t" << ec.message() << std::endl;
if (ec == http::error::need_more)
ec.clear();
emulated_stream.remove_prefix(consumed);
}
auto res = response_parser.release();
std::cout << "== Content length " << res["Content-Length"] << " and body "
<< res.body().length() << std::endl;
std::cout << "== Headers: " << res.base() << std::endl;
}
std::cout << "== Stream depleted " << ec.message() << std::endl;
}印刷品。
== Emulated stream of 3182 remaining
Consumed 101 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 234 Headers done:true Done:false Chunked:false Success
Consumed 305 Headers done:true Done:false Chunked:false Success
Consumed 326 Headers done:true Done:false Chunked:false Success
Consumed 265 Headers done:true Done:false Chunked:false Success
Consumed 216 Headers done:true Done:false Chunked:false Success
Consumed 144 Headers done:true Done:true Chunked:false Success
== Content length 1256 and body 1256
== Headers: HTTP/1.1 200 OK
Age: 207498
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Sat, 20 Mar 2021 23:24:40 GMT
Etag: "3147526947+ident"
Expires: Sat, 27 Mar 2021 23:24:40 GMT
Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
Server: ECS (bsa/EB15)
Vary: Accept-Encoding
X-Cache: HIT
Content-Length: 1256
== Emulated stream of 1591 remaining
Consumed 204 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 0 Headers done:false Done:false Chunked:false need more
Consumed 131 Headers done:true Done:false Chunked:false Success
Consumed 355 Headers done:true Done:false Chunked:false Success
Consumed 137 Headers done:true Done:false Chunked:false Success
Consumed 139 Headers done:true Done:false Chunked:false Success
Consumed 89 Headers done:true Done:false Chunked:false Success
Consumed 87 Headers done:true Done:false Chunked:false Success
Consumed 66 Headers done:true Done:false Chunked:false Success
Consumed 355 Headers done:true Done:false Chunked:false Success
Consumed 28 Headers done:true Done:true Chunked:false Success
== Content length 1256 and body 1256
== Headers: HTTP/1.1 200 OK
Age: 207498
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Sat, 20 Mar 2021 23:24:40 GMT
Etag: "3147526947+ident"
Expires: Sat, 27 Mar 2021 23:24:40 GMT
Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
Server: ECS (bsa/EB15)
Vary: Accept-Encoding
X-Cache: HIT
Content-Length: 1256
== Stream depleted Success也许吧
- 流内容实际上不是有效的HTTP
- 您的响应根本没有内容长度标题。在本例中，在完成头文件解析后，
true的值： 根据标题的内容，解析器可能需要和文件结束通知才能知道主体的末尾在哪里。如果这个函数返回真正的put_eof，那么当输入中永远没有额外的数据时，就必须调用。 - 你的包太小了。如果您将数据包大小分布缩小到如下所示的极限，您就会看到这种效果：
std::uniform_int_distribution packet_size { 1，3 }；
这将不会导致任何内容被消耗。医生：
在某些情况下，输入缓冲区中的八进制数可能不足，以便向前推进。这是由代码
error::need_more表示的。当发生这种情况时，调用方应该将额外的字节放入缓冲区序列并再次调用put。错误代码error::need_more是特殊的。当返回此错误时，如果已更新缓冲区，则后续的put调用可能会成功。
在您的实际代码中，您将不会继续使用少量的重试，因为缓冲区只会积累并最终满足取得进展的要求。
另请参阅
奖励:简化！
好消息是，你不需要经常使用这样复杂的东西。在大多数情况下，您只需将http::read或http::async_read直接放入响应对象即可。
这将与引擎盖下的解析器一起完成整个舞蹈，而不必费心讨论细节：
boost::beast::flat_buffer buf;
boost::system::error_code ec;
for (http::response<http::string_body> res; !ec && read(pipe, buf, res, ec); res.clear()) {
std::cout << "== Content length " << res["Content-Length"] << " and body "
<< res.body().length() << std::endl;
std::cout << "== Headers: " << res.base() << std::endl;
}
std::cout << "== Stream depleted " << ec.message() << "\n" << std::endl;那是all仍有指纹：
== Content length 1256 and body 1256
== Headers: HTTP/1.1 200 OK
Age: 207498
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Sat, 20 Mar 2021 23:24:40 GMT
Etag: "3147526947+ident"
Expires: Sat, 27 Mar 2021 23:24:40 GMT
Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
Server: ECS (bsa/EB15)
Vary: Accept-Encoding
X-Cache: HIT
Content-Length: 1256
== Content length 1256 and body 2512
== Headers: HTTP/1.1 200 OK
Age: 207498
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Sat, 20 Mar 2021 23:24:40 GMT
Etag: "3147526947+ident"
Expires: Sat, 27 Mar 2021 23:24:40 GMT
Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
Server: ECS (bsa/EB15)
Vary: Accept-Encoding
X-Cache: HIT
Content-Length: 1256
== Stream depleted end of stream页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/66724298
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