[thin_show_duplicates] start factoring out a chunk_stream abstraction

block-cache/block_cache.h

@@ -12,6 +12,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <vector>
+#include <iostream>
 
 //----------------------------------------------------------------
 
@@ -112,6 +113,44 @@ namespace bcache {
 			validator::ptr v_;
 		};
 
+		class auto_block {
+		public:
+			auto_block()
+				: b_(0) {
+			}
+
+			auto_block(block &b)
+			: b_(&b) {
+			}
+
+			~auto_block() {
+				put();
+			}
+
+			auto_block &operator =(block &b) {
+				put();
+				b_ = &b;
+				return *this;
+			}
+
+			void *get_data() const {
+				if (b_)
+					return b_->get_data();
+
+				throw std::runtime_error("auto_block not set");
+			}
+
+		private:
+			void put() {
+				if (b_) {
+					b_->put();
+					b_ = 0;
+				}
+			}
+
+			block *b_;
+		};
+
 		//--------------------------------
 
 		block_cache(int fd, sector_t block_size,

thin-provisioning/thin_show_duplicates.cc

@@ -38,6 +38,7 @@
 #include <boost/uuid/sha1.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/optional.hpp>
+#include <deque>
 #include <vector>
 
 using namespace base;
@@ -54,6 +55,15 @@ namespace {
 		return (n % f) == 0;
 	}
 
+	int open_file(string const &path) {
+		int fd = ::open(path.c_str(), O_RDONLY | O_DIRECT | O_EXCL, 0666);
+		if (fd < 0)
+			syscall_failed("open",
+				 "Note: you cannot run this tool with these options on live metadata.");
+
+		return fd;
+	}
+
 	block_manager<>::ptr
 	open_bm(string const &path) {
 		block_address nr_blocks = get_nr_blocks(path);
@@ -84,9 +94,97 @@ namespace {
 
 	//--------------------------------
 
-	struct data_block {
-		block_address begin, end;
-		void *data;
+	// Once we start using variable sized blocks we will find we want
+	// to examine data that crosses cache block boundaries.  So a block
+	// to be examined can be composed of multiple chunks of memory.
+
+	struct mem {
+		mem(void *b, void *e)
+			: begin(b),
+			  end(e) {
+		}
+
+		void *begin, *end;
+	};
+
+	struct chunk {
+		sector_t offset_sectors_;
+		deque<mem> mem_;
+	};
+
+	class chunk_stream {
+	public:
+		virtual ~chunk_stream() {}
+
+		virtual void rewind() = 0;
+		virtual bool advance() = 0;
+		virtual chunk const &get() const = 0;
+	};
+
+	class cache_stream : public chunk_stream {
+	public:
+		cache_stream(string const &path,
+			     block_address block_size,
+			     size_t cache_mem)
+			: block_size_(block_size),
+			  nr_blocks_(get_nr_blocks(path, block_size)),
+
+			  // hack because cache uses LRU rather than MRU
+			  cache_blocks_((cache_mem / block_size) / 2u),
+			  fd_(open_file(path)),
+			  v_(new bcache::noop_validator()),
+			  cache_(new block_cache(fd_, block_size / 512, nr_blocks_, cache_mem)),
+			  current_index_(0) {
+			load(0);
+		}
+
+		virtual void rewind() {
+			load(0);
+		}
+
+		virtual bool advance() {
+			if (current_index_ >= nr_blocks_)
+				return false;
+
+			current_index_++;
+
+			load(current_index_);
+			return true;
+		}
+
+		virtual chunk const &get() const {
+			return current_chunk_;
+		}
+
+	private:
+		void load(block_address b) {
+			current_index_ = b;
+			current_block_ = cache_->get(current_index_, 0, v_);
+
+			current_chunk_.offset_sectors_ = (b * block_size_) / 512;
+			current_chunk_.mem_.clear();
+			current_chunk_.mem_.push_back(mem(current_block_.get_data(),
+							  current_block_.get_data() + block_size_));
+		}
+
+		block_address block_size_;
+		block_address nr_blocks_;
+		block_address cache_blocks_;
+		int fd_;
+		validator::ptr v_;
+		auto_ptr<block_cache> cache_;
+
+		block_address current_index_;
+		block_cache::auto_block current_block_;
+		chunk current_chunk_;
+	};
+
+	class fixed_block_stream : public chunk_stream {
+	public:
+	};
+
+	class variable_size_stream : public chunk_stream {
+
 	};
 
 	//--------------------------------
@@ -102,16 +200,6 @@ namespace {
 		unsigned cache_mem;
 	};
 
-	int open_file(string const &path) {
-		int fd = ::open(path.c_str(), O_RDONLY | O_DIRECT | O_EXCL, 0666);
-		if (fd < 0)
-			syscall_failed("open",
-				 "Note: you cannot run this tool with these options on live metadata.");
-
-		return fd;
-	}
-
-
 	// FIXME: introduce abstraction for a stream of segments
 
 	using namespace mapping_tree_detail;
@@ -217,6 +305,10 @@ namespace {
 		}
 #endif
 
+		{
+			cache_stream(fs.data_dev, block_size, fs.cache_mem);
+		}
+
 		cerr << "path = " << fs.data_dev << "\n";
 		cerr << "block size = " << block_size << "\n";
 		block_address nr_blocks = get_nr_blocks(fs.data_dev, block_size);