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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "mojo/public/cpp/bindings/lib/validation_context.h"
      6 
      7 #include <stddef.h>
      8 #include <stdint.h>
      9 
     10 #include "base/logging.h"
     11 #include "mojo/public/cpp/bindings/lib/serialization_util.h"
     12 #include "mojo/public/cpp/bindings/message.h"
     13 #include "mojo/public/cpp/system/handle.h"
     14 
     15 namespace mojo {
     16 namespace internal {
     17 
     18 ValidationContext::ValidationContext(const void* data,
     19                                      size_t data_num_bytes,
     20                                      size_t num_handles,
     21                                      Message* message,
     22                                      const base::StringPiece& description)
     23     : message_(message),
     24       description_(description),
     25       data_begin_(reinterpret_cast<uintptr_t>(data)),
     26       data_end_(data_begin_ + data_num_bytes),
     27       handle_begin_(0),
     28       handle_end_(static_cast<uint32_t>(num_handles)) {
     29   if (data_end_ < data_begin_) {
     30     // The calculation of |data_end_| overflowed.
     31     // It shouldn't happen but if it does, set the range to empty so
     32     // IsValidRange() and ClaimMemory() always fail.
     33     NOTREACHED();
     34     data_end_ = data_begin_;
     35   }
     36   if (handle_end_ < num_handles) {
     37     // Assigning |num_handles| to |handle_end_| overflowed.
     38     // It shouldn't happen but if it does, set the handle index range to empty.
     39     NOTREACHED();
     40     handle_end_ = 0;
     41   }
     42 }
     43 
     44 ValidationContext::~ValidationContext() {
     45 }
     46 
     47 bool ValidationContext::ClaimMemory(const void* position, uint32_t num_bytes) {
     48   uintptr_t begin = reinterpret_cast<uintptr_t>(position);
     49   uintptr_t end = begin + num_bytes;
     50 
     51   if (!InternalIsValidRange(begin, end))
     52     return false;
     53 
     54   data_begin_ = end;
     55   return true;
     56 }
     57 
     58 bool ValidationContext::ClaimHandle(const Handle_Data& encoded_handle) {
     59   uint32_t index = encoded_handle.value;
     60   if (index == kEncodedInvalidHandleValue)
     61     return true;
     62 
     63   if (index < handle_begin_ || index >= handle_end_)
     64     return false;
     65 
     66   // |index| + 1 shouldn't overflow, because |index| is not the max value of
     67   // uint32_t (it is less than |handle_end_|).
     68   handle_begin_ = index + 1;
     69   return true;
     70 }
     71 
     72 bool ValidationContext::IsValidRange(const void* position,
     73                                      uint32_t num_bytes) const {
     74   uintptr_t begin = reinterpret_cast<uintptr_t>(position);
     75   uintptr_t end = begin + num_bytes;
     76 
     77   return InternalIsValidRange(begin, end);
     78 }
     79 
     80 bool ValidationContext::InternalIsValidRange(uintptr_t begin,
     81                                              uintptr_t end) const {
     82   return end > begin && begin >= data_begin_ && end <= data_end_;
     83 }
     84 
     85 }  // namespace internal
     86 }  // namespace mojo
     87