Add cache for pipes

CMakeLists.txt

@@ -99,6 +99,7 @@ string(REPLACE ";" " " CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG}")
 set(${TARGET}_SRCS
   src/config.cpp
   src/file_io.cpp
+  src/file_cache.cpp
   src/file_stream.cpp
   src/file_reader.cpp
   src/file_forward_reader.cpp

src/file_cache.cpp

@@ -0,0 +1,133 @@
+/*******************************************************************************
+
+Copyright 2015 Denis Tikhomirov
+
+This file is part of Mattext
+
+Mattext 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, either version 3 of the License, or
+(at your option) any later version.
+
+Mattext 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 Mattext.  If not, see http://www.gnu.org/licenses/.
+
+*******************************************************************************/
+
+#include <stdlib.h>
+#include "file_cache.h"
+
+void FileCache::addForward(char byte) {
+  cur = (start + len) % cache_max_len;
+  if (len == cache_max_len) {
+    incCounter(start);
+    cache[cur] = byte;
+  } else {
+    cache.push_back(byte);
+  }
+  status = Reached::End;
+  if (len < cache_max_len) {
+    ++len;
+  }
+}
+
+bool FileCache::readForward(char &byte) {
+  if ((status == Reached::End) || !len) {
+    return false;
+  }
+  incCounter(cur);
+  byte = cache[cur];
+  status = Reached::Ok;
+
+  if (cur == getEnd()) {
+    status = Reached::End;
+  }
+  return true;
+}
+
+bool FileCache::readBackward(char &byte) {
+  if ((status == Reached::Start) || !len) {
+    return false;
+  }
+  decCounter(cur);
+  byte = cache[cur];
+  status = Reached::Ok;
+
+  if (cur == start) {
+    status = Reached::Start;
+  }
+  return true;
+}
+
+inline void FileCache::incCounter(size_t &counter) {
+  ++counter;
+  if (counter >= cache_max_len) {
+    counter = 0;
+  }
+}
+
+inline void FileCache::decCounter(size_t &counter) {
+  if (counter == 0) {
+    counter = cache_max_len - 1;
+    return;
+  }
+  --counter;
+}
+
+inline size_t FileCache::getEnd() {
+  return (start + len - 1) % cache_max_len;
+}
+
+void FileCache::rewindToStart() {
+  if (!len) {
+    return;
+  }
+  cur = start;
+  status = Reached::Start;
+}
+
+void FileCache::rewindToEnd() {
+  if (!len) {
+    return;
+  }
+  cur = getEnd();
+  status = Reached::End;
+}
+
+void FileCache::offsetTo(int _offset) {
+  if (!len) {
+    return;
+  }
+  const size_t end = getEnd();
+  const size_t offset = abs(_offset);
+  size_t start_fix = 0;
+
+  if (_offset > 0) {
+    if (cur >= start) {
+      start_fix = start;
+    }
+    if ((cur - start_fix + offset) >= end) {
+      cur = end;
+      status = Reached::End;
+    } else {
+      cur = (cur + offset) % cache_max_len;
+      status = Reached::Ok;
+    }
+    return;
+  }
+  if (cur < start) {
+    start_fix = len;
+  }
+  if ((cur + start_fix - start) < offset) {
+    cur = start;
+    status = Reached::Start;
+  } else {
+    cur -= offset;
+    status = Reached::Ok;
+  }
+}

src/file_cache.h

@@ -0,0 +1,48 @@
+/*******************************************************************************
+
+Copyright 2015 Denis Tikhomirov
+
+This file is part of Mattext
+
+Mattext 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, either version 3 of the License, or
+(at your option) any later version.
+
+Mattext 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 Mattext.  If not, see http://www.gnu.org/licenses/.
+
+*******************************************************************************/
+
+#pragma once
+
+#include <vector>
+#include <stddef.h>
+
+class FileCache {
+ public:
+  void addForward(char byte);
+  bool readForward(char &byte);
+  bool readBackward(char &byte);
+  void rewindToStart();
+  void rewindToEnd();
+  void offsetTo(int offset);
+
+ private:
+  static const size_t cache_max_len = 1000000;
+  std::vector<char> cache;
+  size_t start = 0;
+  size_t len = 0;
+  size_t cur = 0;
+  enum class Reached {Start, End, Ok};
+  Reached status = Reached::End;
+
+  static inline void incCounter(size_t &counter);
+  static inline void decCounter(size_t &counter);
+  inline size_t getEnd();
+};