Revert "basic_parser: remove skip_ usage"

This reverts commit aefc564.

Author: ashtum

include/boost/beast/http/basic_parser.hpp

@@ -78,6 +78,7 @@ class basic_parser
     std::uint64_t len0_ = 0;                // content length if known
     std::unique_ptr<char[]> buf_;           // temp storage
     std::size_t buf_len_ = 0;               // size of buf_
+    std::size_t skip_ = 0;                  // resume search here
     std::uint32_t header_limit_ = 8192;     // max header size
     unsigned short status_ = 0;             // response status
     state state_ = state::nothing_yet;      // initial state

include/boost/beast/http/impl/basic_parser.ipp

@@ -164,6 +164,7 @@ loop:
         parse_chunk_header(p, n, ec);
         if(ec)
             goto done;
+        BOOST_ASSERT(! skip_);
         if(state_ != state::trailer_fields)
             break;
         n = static_cast<std::size_t>(p1 - p);
@@ -590,7 +591,7 @@ parse_chunk_header(char const*& in,
     auto p = in;
     auto const pend = p + n;
 
-    if(n < 2)
+    if(n < skip_ + 2)
     {
         BOOST_BEAST_ASSIGN_EC(ec, error::need_more);
         return;
@@ -607,14 +608,17 @@ parse_chunk_header(char const*& in,
         }
     }
 
-    auto const eol = find_eol(p, pend, ec);
+    auto const eol = find_eol(p + skip_, pend, ec);
     if(ec)
         return;
     if(! eol)
     {
         BOOST_BEAST_ASSIGN_EC(ec, error::need_more);
+        if(p != pend)
+            skip_ = pend - p - 1;
         return;
     }
+    skip_ = static_cast<std::size_t>(eol - p - 2);
 
     std::uint64_t size;
     if(! parse_hex(p, size))
@@ -647,6 +651,7 @@ parse_chunk_header(char const*& in,
         return;
 
     len_ = size;
+    skip_ = 0;
     in = eol;
     f_ |= flagExpectCRLF;
     if(size != 0)