Add ChunkGenerator object for breaking arbitrary regions

into block- or page-sized chunks.

--HG--
extra : convert_revision : 3ebdd496f9ffc6d1fcd1847c33e98ac23f1bfe66

1 files changed, 130 insertions, 0 deletions

diff --git a/base/chunk_generator.hh b/base/chunk_generator.hh
new file mode 100644
index 000000000..83caaca88
--- /dev/null
+++ b/base/chunk_generator.hh
@@ -0,0 +1,130 @@
+/*
+ * Copyright (c) 2001-2005 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __BASE__CHUNK_GENERATOR_HH__
+#define __BASE__CHUNK_GENERATOR_HH__
+
+/**
+ * @file
+ * Declaration and inline definition of ChunkGenerator object.
+ */
+
+#include <algorithm>
+#include "base/intmath.hh"
+#include "targetarch/isa_traits.hh" // for Addr
+
+/**
+ * This class takes an arbitrary memory region (address/length pair)
+ * and generates a series of appropriately (e.g. block- or page-)
+ * aligned chunks covering the same region.
+ *
+ * Example usage:
+
+\code
+    for (ChunkGenerator gen(addr, size, chunkSize); !gen.done(); gen.next()) {
+        doSomethingChunky(gen.addr(), gen.size());
+    }
+\endcode
+ */
+class ChunkGenerator
+{
+  private:
+    /** The starting address of the current chunk. */
+    Addr curAddr;
+    /** The starting address of the next chunk (after the current one). */
+    Addr nextAddr;
+    /** The size of the current chunk (in bytes). */
+    int  curSize;
+    /** The number of bytes remaining in the region after the current chunk. */
+    int  sizeLeft;
+    /** The maximum chunk size, e.g., the cache block size or page size. */
+    const int chunkSize;
+
+  public:
+    /**
+     * Constructor.
+     * @param startAddr The starting address of the region.
+     * @param totalSize The total size of the region.
+     * @param _chunkSize The size/alignment of chunks into which
+     *    the region should be decomposed.
+     */
+    ChunkGenerator(Addr startAddr, int totalSize, int _chunkSize)
+        : chunkSize(_chunkSize)
+    {
+        // chunkSize must be a power of two
+        assert(isPowerOf2(chunkSize));
+
+        // set up initial chunk.
+        curAddr = startAddr;
+
+        // nextAddr should be *next* chunk start
+        nextAddr = roundUp(startAddr, chunkSize);
+        if (curAddr == nextAddr) {
+            // ... even if startAddr is already chunk-aligned
+            nextAddr += chunkSize;
+        }
+
+        // how many bytes are left between curAddr and the end of this chunk?
+        int left_in_chunk = nextAddr - curAddr;
+        curSize = std::min(totalSize, left_in_chunk);
+        sizeLeft = totalSize - curSize;
+    }
+
+    /** Return starting address of current chunk. */
+    Addr addr() { return curAddr; }
+    /** Return size in bytes of current chunk. */
+    int  size() { return curSize; }
+
+    /**
+     * Are we done?  That is, did the last call to next() advance
+     * past the end of the region?
+     * @return True if yes, false if more to go.
+     */
+    bool done() { return (curSize == 0); }
+
+    /**
+     * Advance generator to next chunk.
+     * @return True if successful, false if unsuccessful
+     * (because we were at the last chunk).
+     */
+    bool next()
+    {
+        if (sizeLeft == 0) {
+            curSize = 0;
+            return false;
+        }
+
+        curAddr = nextAddr;
+        curSize = std::min(sizeLeft, chunkSize);
+        sizeLeft -= curSize;
+        nextAddr += curSize;
+        return true;
+    }
+};
+
+#endif // __BASE__CHUNK_GENERATOR_HH__