From 3b9681232873029fdd983874126ba093fb611093 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Fri, 4 Sep 2015 11:28:33 +0100
Subject: [PATCH] [thin_show_dups] switch to boost::circular_buffer in the
 rolling_hash

---
 base/rolling_hash.cc |  7 ++++---
 base/rolling_hash.h  | 12 +++++-------
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/base/rolling_hash.cc b/base/rolling_hash.cc
index 8de7ac3..c780a27 100644
--- a/base/rolling_hash.cc
+++ b/base/rolling_hash.cc
@@ -10,7 +10,8 @@ using namespace std;
 rolling_hash::rolling_hash(unsigned window_size)
 	: a_(MULTIPLIER),
 	  a_to_k_minus_1_(a_),
-	  window_size_(window_size) {
+	  window_size_(window_size),
+	  buffer_(window_size) {
 
 	for (unsigned i = 1; i < window_size_ - 1; i++)
 		a_to_k_minus_1_ *= a_;
@@ -22,12 +23,12 @@ void
 rolling_hash::reset()
 {
 	// prime with zeroes
-	chars_.clear();
+	buffer_.clear();
 
 	hash_ = 0;
 	for (unsigned i = 0; i < window_size_; i++) {
 		hash_ = (hash_ * a_) + SEED;
-		chars_.push_back(0);
+		buffer_.push_back(0);
 	}
 }
 
diff --git a/base/rolling_hash.h b/base/rolling_hash.h
index c5fa44c..dff3145 100644
--- a/base/rolling_hash.h
+++ b/base/rolling_hash.h
@@ -1,7 +1,7 @@
 #ifndef BASE_ROLLING_HASH_H
 #define BASE_ROLLING_HASH_H
 
-#include <list>
+#include <boost/circular_buffer.hpp>
 #include <stdint.h>
 #include <boost/optional.hpp>
 
@@ -31,20 +31,18 @@ namespace base {
 
 	private:
 		void update_hash(uint8_t byte) {
-			hash_ -= a_to_k_minus_1_ * (chars_.front() + hash_detail::SEED);
-			chars_.pop_front();
-			chars_.push_back(byte);
+			hash_ -= a_to_k_minus_1_ * (buffer_.front() + hash_detail::SEED);
+			buffer_.push_back(byte);
 			hash_ = (hash_ * a_) + byte + hash_detail::SEED;
 		}
 
 		uint32_t a_;
 		uint32_t a_to_k_minus_1_;
 
-		// FIXME: use a ring buffer
-		std::list<uint8_t> chars_;
-
 		uint32_t hash_;
 		uint32_t window_size_;
+
+		boost::circular_buffer<uint8_t> buffer_;
 	};
 
 	class content_based_hash {