evhttpd implementation

- *Replace usage of boost::asio with [libevent2](http://libevent.org/)*.
boost::asio is not part of C++11, so unlike other boost there is no
forwards-compatibility reason to stick with it. Together with #4738 (convert
json_spirit to UniValue), this rids Bitcoin Core of the worst offenders with
regard to compile-time slowness.

- *Replace spit-and-duct-tape http server with evhttp*. Front-end http handling
is handled by libevent, a work queue (with configurable depth and parallelism)
is used to handle application requests.

- *Wrap HTTP request in C++ class*; this makes the application code mostly
HTTP-server-neutral

- *Refactor RPC to move all http-specific code to a separate file*.
Theoreticaly this can allow building without HTTP server but with another RPC
backend, e.g. Qt's debug console (currently not implemented) or future RPC
mechanisms people may want to use.

- *HTTP dispatch mechanism*; services (e.g., RPC, REST) register which URL
paths they want to handle.

By using a proven, high-performance asynchronous networking library (also used
by Tor) and HTTP server, problems such as #5674, #5655, #344 should be avoided.

What works? bitcoind, bitcoin-cli, bitcoin-qt. Unit tests and RPC/REST tests
pass. The aim for now is everything but SSL support.

Configuration options:

- `-rpcthreads`: repurposed as "number of  work handler threads". Still
defaults to 4.

- `-rpcworkqueue`: maximum depth of work queue. When this is reached, new
requests will return a 500 Internal Error.

- `-rpctimeout`: inactivity time, in seconds, after which to disconnect a
client.

- `-debug=http`: low-level http activity logging

1 files changed, 0 insertions, 229 deletions

diff --git a/src/rpcprotocol.cpp b/src/rpcprotocol.cpp
index 2e5c913734..d83cd87f94 100644
--- a/src/rpcprotocol.cpp
+++ b/src/rpcprotocol.cpp
@@ -5,7 +5,6 @@
 
 #include "rpcprotocol.h"
 
-#include "clientversion.h"
 #include "random.h"
 #include "tinyformat.h"
 #include "util.h"
@@ -16,236 +15,8 @@
 #include <stdint.h>
 #include <fstream>
 
-#include <boost/algorithm/string.hpp>
-#include <boost/asio.hpp>
-#include <boost/asio/ssl.hpp>
-#include <boost/bind.hpp>
-#include <boost/filesystem.hpp>
-#include <boost/foreach.hpp>
-#include <boost/iostreams/concepts.hpp>
-#include <boost/iostreams/stream.hpp>
-#include <boost/shared_ptr.hpp>
-
-#include "univalue/univalue.h"
-
 using namespace std;
 
-//! Number of bytes to allocate and read at most at once in post data
-const size_t POST_READ_SIZE = 256 * 1024;
-
-/**
- * HTTP protocol
- * 
- * This ain't Apache.  We're just using HTTP header for the length field
- * and to be compatible with other JSON-RPC implementations.
- */
-
-string HTTPPost(const string& strMsg, const map<string,string>& mapRequestHeaders)
-{
-    ostringstream s;
-    s << "POST / HTTP/1.1\r\n"
-      << "User-Agent: bitcoin-json-rpc/" << FormatFullVersion() << "\r\n"
-      << "Host: 127.0.0.1\r\n"
-      << "Content-Type: application/json\r\n"
-      << "Content-Length: " << strMsg.size() << "\r\n"
-      << "Connection: close\r\n"
-      << "Accept: application/json\r\n";
-    BOOST_FOREACH(const PAIRTYPE(string, string)& item, mapRequestHeaders)
-        s << item.first << ": " << item.second << "\r\n";
-    s << "\r\n" << strMsg;
-
-    return s.str();
-}
-
-static string rfc1123Time()
-{
-    return DateTimeStrFormat("%a, %d %b %Y %H:%M:%S +0000", GetTime());
-}
-
-static const char *httpStatusDescription(int nStatus)
-{
-    switch (nStatus) {
-        case HTTP_OK: return "OK";
-        case HTTP_BAD_REQUEST: return "Bad Request";
-        case HTTP_FORBIDDEN: return "Forbidden";
-        case HTTP_NOT_FOUND: return "Not Found";
-        case HTTP_INTERNAL_SERVER_ERROR: return "Internal Server Error";
-        default: return "";
-    }
-}
-
-string HTTPError(int nStatus, bool keepalive, bool headersOnly)
-{
-    if (nStatus == HTTP_UNAUTHORIZED)
-        return strprintf("HTTP/1.0 401 Authorization Required\r\n"
-            "Date: %s\r\n"
-            "Server: bitcoin-json-rpc/%s\r\n"
-            "WWW-Authenticate: Basic realm=\"jsonrpc\"\r\n"
-            "Content-Type: text/html\r\n"
-            "Content-Length: 296\r\n"
-            "\r\n"
-            "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\"\r\n"
-            "\"http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd\">\r\n"
-            "<HTML>\r\n"
-            "<HEAD>\r\n"
-            "<TITLE>Error</TITLE>\r\n"
-            "<META HTTP-EQUIV='Content-Type' CONTENT='text/html; charset=ISO-8859-1'>\r\n"
-            "</HEAD>\r\n"
-            "<BODY><H1>401 Unauthorized.</H1></BODY>\r\n"
-            "</HTML>\r\n", rfc1123Time(), FormatFullVersion());
-
-    return HTTPReply(nStatus, httpStatusDescription(nStatus), keepalive,
-                     headersOnly, "text/plain");
-}
-
-string HTTPReplyHeader(int nStatus, bool keepalive, size_t contentLength, const char *contentType)
-{
-    return strprintf(
-            "HTTP/1.1 %d %s\r\n"
-            "Date: %s\r\n"
-            "Connection: %s\r\n"
-            "Content-Length: %u\r\n"
-            "Content-Type: %s\r\n"
-            "Server: bitcoin-json-rpc/%s\r\n"
-            "\r\n",
-        nStatus,
-        httpStatusDescription(nStatus),
-        rfc1123Time(),
-        keepalive ? "keep-alive" : "close",
-        contentLength,
-        contentType,
-        FormatFullVersion());
-}
-
-string HTTPReply(int nStatus, const string& strMsg, bool keepalive,
-                 bool headersOnly, const char *contentType)
-{
-    if (headersOnly)
-    {
-        return HTTPReplyHeader(nStatus, keepalive, 0, contentType);
-    } else {
-        return HTTPReplyHeader(nStatus, keepalive, strMsg.size(), contentType) + strMsg;
-    }
-}
-
-bool ReadHTTPRequestLine(std::basic_istream<char>& stream, int &proto,
-                         string& http_method, string& http_uri)
-{
-    string str;
-    getline(stream, str);
-
-    // HTTP request line is space-delimited
-    vector<string> vWords;
-    boost::split(vWords, str, boost::is_any_of(" "));
-    if (vWords.size() < 2)
-        return false;
-
-    // HTTP methods permitted: GET, POST
-    http_method = vWords[0];
-    if (http_method != "GET" && http_method != "POST")
-        return false;
-
-    // HTTP URI must be an absolute path, relative to current host
-    http_uri = vWords[1];
-    if (http_uri.size() == 0 || http_uri[0] != '/')
-        return false;
-
-    // parse proto, if present
-    string strProto = "";
-    if (vWords.size() > 2)
-        strProto = vWords[2];
-
-    proto = 0;
-    const char *ver = strstr(strProto.c_str(), "HTTP/1.");
-    if (ver != NULL)
-        proto = atoi(ver+7);
-
-    return true;
-}
-
-int ReadHTTPStatus(std::basic_istream<char>& stream, int &proto)
-{
-    string str;
-    getline(stream, str);
-    vector<string> vWords;
-    boost::split(vWords, str, boost::is_any_of(" "));
-    if (vWords.size() < 2)
-        return HTTP_INTERNAL_SERVER_ERROR;
-    proto = 0;
-    const char *ver = strstr(str.c_str(), "HTTP/1.");
-    if (ver != NULL)
-        proto = atoi(ver+7);
-    return atoi(vWords[1].c_str());
-}
-
-int ReadHTTPHeaders(std::basic_istream<char>& stream, map<string, string>& mapHeadersRet)
-{
-    int nLen = 0;
-    while (true)
-    {
-        string str;
-        std::getline(stream, str);
-        if (str.empty() || str == "\r")
-            break;
-        string::size_type nColon = str.find(":");
-        if (nColon != string::npos)
-        {
-            string strHeader = str.substr(0, nColon);
-            boost::trim(strHeader);
-            boost::to_lower(strHeader);
-            string strValue = str.substr(nColon+1);
-            boost::trim(strValue);
-            mapHeadersRet[strHeader] = strValue;
-            if (strHeader == "content-length")
-                nLen = atoi(strValue.c_str());
-        }
-    }
-    return nLen;
-}
-
-
-int ReadHTTPMessage(std::basic_istream<char>& stream, map<string,
-                    string>& mapHeadersRet, string& strMessageRet,
-                    int nProto, size_t max_size)
-{
-    mapHeadersRet.clear();
-    strMessageRet = "";
-
-    // Read header
-    int nLen = ReadHTTPHeaders(stream, mapHeadersRet);
-    if (nLen < 0 || (size_t)nLen > max_size)
-        return HTTP_INTERNAL_SERVER_ERROR;
-
-    // Read message
-    if (nLen > 0)
-    {
-        vector<char> vch;
-        size_t ptr = 0;
-        while (ptr < (size_t)nLen)
-        {
-            size_t bytes_to_read = std::min((size_t)nLen - ptr, POST_READ_SIZE);
-            vch.resize(ptr + bytes_to_read);
-            stream.read(&vch[ptr], bytes_to_read);
-            if (!stream) // Connection lost while reading
-                return HTTP_INTERNAL_SERVER_ERROR;
-            ptr += bytes_to_read;
-        }
-        strMessageRet = string(vch.begin(), vch.end());
-    }
-
-    string sConHdr = mapHeadersRet["connection"];
-
-    if ((sConHdr != "close") && (sConHdr != "keep-alive"))
-    {
-        if (nProto >= 1)
-            mapHeadersRet["connection"] = "keep-alive";
-        else
-            mapHeadersRet["connection"] = "close";
-    }
-
-    return HTTP_OK;
-}
-
 /**
  * JSON-RPC protocol.  Bitcoin speaks version 1.0 for maximum compatibility,
  * but uses JSON-RPC 1.1/2.0 standards for parts of the 1.0 standard that were