Add epoll and do more release readiness changes

This change also pays off some of the remaining technical debt with
stdio, file descriptors, and memory managemnt polyfills.

net/http/http.h

@@ -95,6 +95,7 @@ int GetHttpMethod(const char *, size_t);
 int ParseHttpRequest(struct HttpRequest *, const char *, size_t);
 int NegotiateHttpRequest(int, const char *, uint32_t *, char *, uint32_t *,
                          uint32_t *, bool, long double);
+long ParseContentLength(const struct HttpRequest *, const char *);
 char *FormatHttpDateTime(char[hasatleast 30], struct tm *);
 bool ParseHttpRange(const char *, size_t, long, long *, long *);
 unsigned ParseHttpVersion(const char *, size_t);

net/http/parsecontentlength.c

@@ -0,0 +1,35 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ This program is free software; you can redistribute it and/or modify         │
+│ it under the terms of the GNU General Public License as published by         │
+│ the Free Software Foundation; version 2 of the License.                      │
+│                                                                              │
+│ This program is distributed in the hope that it will be useful, but          │
+│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
+│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
+│ General Public License for more details.                                     │
+│                                                                              │
+│ You should have received a copy of the GNU General Public License            │
+│ along with this program; if not, write to the Free Software                  │
+│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
+│ 02110-1301 USA                                                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/str/str.h"
+#include "net/http/http.h"
+
+long ParseContentLength(const struct HttpRequest *req, const char *p) {
+  long i, r, n = 0;
+  for (i = req->headers[kHttpContentLength].a;
+       i < req->headers[kHttpContentLength].b; ++i) {
+    if (isdigit(p[i])) {
+      if (!__builtin_mul_overflow(n, 10, &r) &&
+          !__builtin_add_overflow(r, p[i] - '0', &r)) {
+        n = r;
+      }
+    }
+  }
+  return n;
+}

net/http/parsehttprequest.c

@@ -114,12 +114,12 @@ int ParseHttpRequest(struct HttpRequest *req, const char *p, size_t n) {
       case LF2:
         if (c == '\n') {
           req->length = i + 1;
-          return 0;
+          return i + 1;
         }
         return ebadmsg();
       default:
         unreachable;
     }
   }
-  return ebadmsg();
+  return 0;
 }