From 813c483a312e1b1b4fa5a02234009ec546a0cc8c Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Sat, 23 May 2020 23:33:57 +0300
Subject: Add putback depth char_scanner template parameter

---
 libbutl/char-scanner.ixx | 52 +++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 27 deletions(-)

(limited to 'libbutl/char-scanner.ixx')

diff --git a/libbutl/char-scanner.ixx b/libbutl/char-scanner.ixx
index 7e9c4b0..57aefc2 100644
--- a/libbutl/char-scanner.ixx
+++ b/libbutl/char-scanner.ixx
@@ -3,36 +3,33 @@
 
 namespace butl
 {
-  template <typename V>
-  inline char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline char_scanner<V, N>::
   char_scanner (std::istream& is, bool crlf, std::uint64_t l, std::uint64_t p)
       : char_scanner (is, validator_type (), crlf, l, p)
   {
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   peek (std::string& what) -> xchar
   {
     return peek (&what);
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   peek () -> xchar
   {
     return peek (nullptr /* what */);
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   get (std::string* what) -> xchar
   {
-    if (unget_)
-    {
-      unget_ = false;
-      return ungetc_;
-    }
+    if (ungetn_ != 0)
+      return ungetb_[--ungetn_];
     else
     {
       xchar c (peek (what));
@@ -41,33 +38,34 @@ namespace butl
     }
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   get (std::string& what) -> xchar
   {
     return get (&what);
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   get () -> xchar
   {
     return get (nullptr /* what */);
   }
 
-  template <typename V>
-  inline void char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline void char_scanner<V, N>::
   unget (const xchar& c)
   {
     // Because iostream::unget cannot work once eos is reached, we have to
     // provide our own implementation.
     //
-    unget_ = true;
-    ungetc_ = c;
+    assert (ungetn_ != N); // Make sure the buffer is not filled.
+
+    ungetb_[ungetn_++] = c;
   }
 
-  template <typename V>
-  inline auto char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline auto char_scanner<V, N>::
   peek_ () -> int_type
   {
     if (gptr_ != egptr_)
@@ -86,8 +84,8 @@ namespace butl
     return r;
   }
 
-  template <typename V>
-  inline void char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline void char_scanner<V, N>::
   get_ ()
   {
     int_type c;
@@ -106,8 +104,8 @@ namespace butl
       save_->push_back (static_cast<char_type> (c));
   }
 
-  template <typename V>
-  inline std::uint64_t char_scanner<V>::
+  template <typename V, std::size_t N>
+  inline std::uint64_t char_scanner<V, N>::
   pos_ () const
   {
     return buf_ != nullptr ? buf_->tellg () : 0;
-- 
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