Refactor code in preparation of merging with the fork in Chromium OS.

This patch is part of a bigger patch that helps merging the breakpad code
with the modified version in Chromium OS.

Specifically, this patch makes the following changes:
1. Add a MemoryRange class for encapsulating and checking read access
   to a contiguous range of memory.
2. Add a MemoryMappedFile class for mapping a file into memory for
   read-only access.
3. Refactor other source code to use MemoryMappedFile.

BUG=455
TEST=Tested the following:
1. Build on 32-bit and 64-bit Linux with gcc 4.4.3 and gcc 4.6.
2. Build on Mac OS X 10.6.8 with gcc 4.2 and clang 3.0 (with latest gmock).
3. All unit tests pass.
4. Run minidump-2-core to covnert a minidump file to a core file.
Review URL: http://breakpad.appspot.com/332001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@895 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 151 insertions, 0 deletions

diff --git a/src/common/memory_range.h b/src/common/memory_range.h
new file mode 100644
index 00000000..0c81d1ee
--- /dev/null
+++ b/src/common/memory_range.h
@@ -0,0 +1,151 @@
+// Copyright (c) 2011, Google Inc.
+// 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 Google Inc. 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.
+
+// memory_range.h: Define the google_breakpad::MemoryRange class, which
+// is a lightweight wrapper with a pointer and a length to encapsulate
+// a contiguous range of memory.
+
+#ifndef COMMON_MEMORY_RANGE_H_
+#define COMMON_MEMORY_RANGE_H_
+
+#include <stddef.h>
+
+#include "google_breakpad/common/breakpad_types.h"
+
+namespace google_breakpad {
+
+// A lightweight wrapper with a pointer and a length to encapsulate a
+// contiguous range of memory. It provides helper methods for checked
+// access of a subrange of the memory. Its implemementation does not
+// allocate memory or call into libc functions, and is thus safer to use
+// in a crashed environment.
+//
+// TODO(benchan): This class is largely based on the MMappedRange class
+// in tools/linux/md2core/minidump-2-core.cc, but generalized for use in
+// other code. Provide a variant of MemoryRange with methods for handling
+// Minidump data structures in order to replace MMappedRange in
+// minidump-2-core.cc.
+class MemoryRange {
+ public:
+  MemoryRange() : data_(NULL), length_(0) {}
+
+  MemoryRange(const void* data, size_t length) {
+    Set(data, length);
+  }
+
+  // Returns true if this memory range contains no data.
+  bool IsEmpty() const {
+    // Set() guarantees that |length_| is zero if |data_| is NULL.
+    return length_ == 0;
+  }
+
+  // Resets to an empty range.
+  void Reset() {
+    data_ = NULL;
+    length_ = 0;
+  }
+
+  // Sets this memory range to point to |data| and its length to |length|.
+  void Set(const void* data, size_t length) {
+    data_ = reinterpret_cast<const u_int8_t*>(data);
+    // Always set |length_| to zero if |data_| is NULL.
+    length_ = data ? length : 0;
+  }
+
+  // Returns true if this range covers a subrange of |sub_length| bytes
+  // at |sub_offset| bytes of this memory range, or false otherwise.
+  bool Covers(size_t sub_offset, size_t sub_length) const {
+    // The following checks verify that:
+    // 1. sub_offset is within [ 0 .. length_ - 1 ]
+    // 2. sub_offset + sub_length is within
+    //    [ sub_offset .. length_ ]
+    return sub_offset < length_ &&
+           sub_offset + sub_length >= sub_offset &&
+           sub_offset + sub_length <= length_;
+  }
+
+  // Returns a raw data pointer to a subrange of |sub_length| bytes at
+  // |sub_offset| bytes of this memory range, or NULL if the subrange
+  // is out of bounds.
+  const void* GetData(size_t sub_offset, size_t sub_length) const {
+    return Covers(sub_offset, sub_length) ? (data_ + sub_offset) : NULL;
+  }
+
+  // Same as the two-argument version of GetData() but uses sizeof(DataType)
+  // as the subrange length and returns an |DataType| pointer for convenience.
+  template <typename DataType>
+  const DataType* GetData(size_t sub_offset) const {
+    return reinterpret_cast<const DataType*>(
+        GetData(sub_offset, sizeof(DataType)));
+  }
+
+  // Returns a raw pointer to the |element_index|-th element of an array
+  // of elements of length |element_size| starting at |sub_offset| bytes
+  // of this memory range, or NULL if the element is out of bounds.
+  const void* GetArrayElement(size_t element_offset,
+                              size_t element_size,
+                              unsigned element_index) const {
+    size_t sub_offset = element_offset + element_index * element_size;
+    return GetData(sub_offset, element_size);
+  }
+
+  // Same as the three-argument version of GetArrayElement() but deduces
+  // the element size using sizeof(ElementType) and returns an |ElementType|
+  // pointer for convenience.
+  template <typename ElementType>
+  const ElementType* GetArrayElement(size_t element_offset,
+                                     unsigned element_index) const {
+    return reinterpret_cast<const ElementType*>(
+        GetArrayElement(element_offset, sizeof(ElementType), element_index));
+  }
+
+  // Returns a subrange of |sub_length| bytes at |sub_offset| bytes of
+  // this memory range, or an empty range if the subrange is out of bounds.
+  MemoryRange Subrange(size_t sub_offset, size_t sub_length) const {
+    return Covers(sub_offset, sub_length) ?
+        MemoryRange(data_ + sub_offset, sub_length) : MemoryRange();
+  }
+
+  // Returns a pointer to the beginning of this memory range.
+  const u_int8_t* data() const { return data_; }
+
+  // Returns the length, in bytes, of this memory range.
+  size_t length() const { return length_; }
+
+ private:
+  // Pointer to the beginning of this memory range.
+  const u_int8_t* data_;
+
+  // Length, in bytes, of this memory range.
+  size_t length_;
+};
+
+}  // namespace google_breakpad
+
+#endif  // COMMON_MEMORY_RANGE_H_