Introduce MinidumpWritable, its dependencies, and their tests

minidump/minidump_writable.cc

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "minidump/minidump_writable.h"
+
+#include "base/logging.h"
+#include "util/numeric/safe_assignment.h"
+
+namespace {
+
+const size_t kMaximumAlignment = 16;
+
+}  // namespace
+
+namespace crashpad {
+namespace internal {
+
+bool MinidumpWritable::WriteEverything(FileWriterInterface* file_writer) {
+  DCHECK_EQ(state_, kStateMutable);
+
+  if (!Freeze()) {
+    return false;
+  }
+
+  DCHECK_EQ(state_, kStateFrozen);
+
+  off_t offset = 0;
+  std::vector<MinidumpWritable*> write_sequence;
+  size_t size = WillWriteAtOffset(kPhaseEarly, &offset, &write_sequence);
+  if (size == kInvalidSize) {
+    return false;
+  }
+
+  offset += size;
+  if (WillWriteAtOffset(kPhaseLate, &offset, &write_sequence) == kInvalidSize) {
+    return false;
+  }
+
+  DCHECK_EQ(state_, kStateWritable);
+  DCHECK_EQ(write_sequence.front(), this);
+
+  for (MinidumpWritable* writable : write_sequence) {
+    if (!writable->WritePaddingAndObject(file_writer)) {
+      return false;
+    }
+  }
+
+  DCHECK_EQ(state_, kStateWritten);
+
+  return true;
+}
+
+void MinidumpWritable::RegisterRVA(RVA* rva) {
+  DCHECK_LE(state_, kStateFrozen);
+
+  registered_rvas_.push_back(rva);
+}
+
+void MinidumpWritable::RegisterLocationDescriptor(
+    MINIDUMP_LOCATION_DESCRIPTOR* location_descriptor) {
+  DCHECK_LE(state_, kStateFrozen);
+
+  registered_location_descriptors_.push_back(location_descriptor);
+}
+
+const size_t MinidumpWritable::kInvalidSize =
+    std::numeric_limits<size_t>::max();
+
+MinidumpWritable::MinidumpWritable()
+    : registered_rvas_(),
+      registered_location_descriptors_(),
+      leading_pad_bytes_(0),
+      state_(kStateMutable) {
+}
+
+MinidumpWritable::~MinidumpWritable() {
+}
+
+bool MinidumpWritable::Freeze() {
+  DCHECK_EQ(state_, kStateMutable);
+  state_ = kStateFrozen;
+
+  std::vector<MinidumpWritable*> children = Children();
+  for (MinidumpWritable* child : children) {
+    if (!child->Freeze()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+size_t MinidumpWritable::Alignment() {
+  DCHECK_GE(state_, kStateFrozen);
+
+  return 4;
+}
+
+std::vector<MinidumpWritable*> MinidumpWritable::Children() {
+  DCHECK_GE(state_, kStateFrozen);
+
+  return std::vector<MinidumpWritable*>();
+}
+
+MinidumpWritable::Phase MinidumpWritable::WritePhase() {
+  return kPhaseEarly;
+}
+
+size_t MinidumpWritable::WillWriteAtOffset(
+    Phase phase,
+    off_t* offset,
+    std::vector<MinidumpWritable*>* write_sequence) {
+  off_t local_offset = *offset;
+  CHECK_GE(local_offset, 0);
+
+  size_t leading_pad_bytes_this_phase;
+  size_t size;
+  if (phase == WritePhase()) {
+    DCHECK_EQ(state_, kStateFrozen);
+
+    // Add this object to the sequence of MinidumpWritable objects to be
+    // written.
+    write_sequence->push_back(this);
+
+    size = SizeOfObject();
+
+    if (size > 0) {
+      // Honor this object’s request to be aligned to a specific byte boundary.
+      // Once the alignment is corrected, this object knows exactly what file
+      // offset it will be written at.
+      size_t alignment = Alignment();
+      CHECK_LE(alignment, kMaximumAlignment);
+
+      leading_pad_bytes_this_phase =
+          (alignment - (local_offset % alignment)) % alignment;
+      local_offset += leading_pad_bytes_this_phase;
+      *offset = local_offset;
+    } else {
+      // If the object is size 0, alignment is of no concern.
+      leading_pad_bytes_this_phase = 0;
+    }
+    leading_pad_bytes_ = leading_pad_bytes_this_phase;
+
+    // Now that the file offset that this object will be written at is known,
+    // let the subclass implementation know in case it’s interested.
+    if (!WillWriteAtOffsetImpl(local_offset)) {
+      return kInvalidSize;
+    }
+
+    // Populate the RVA fileds in other objects that have registered to point to

[Robert Sesek, 2014/08/01 14:38:04]

nit: fields

+    // this one. Typically, a parent object will have registered to point to its
+    // children, but this can also occur where no parent-child relationship
+    // exists.
+    if (!registered_rvas_.empty() ||
+        !registered_location_descriptors_.empty()) {
+      RVA local_rva;
+      if (!AssignIfInRange(&local_rva, local_offset)) {
+        LOG(ERROR) << "offset " << local_offset << " out of range";
+        return kInvalidSize;
+      }
+
+      for (RVA* rva : registered_rvas_) {
+        *rva = local_rva;
+      }
+
+      if (!registered_location_descriptors_.empty()) {
+        typeof(registered_location_descriptors_[0]->DataSize) local_size;
+        if (!AssignIfInRange(&local_size, size)) {
+          LOG(ERROR) << "size " << size << " out of range";
+          return kInvalidSize;
+        }
+
+        for (MINIDUMP_LOCATION_DESCRIPTOR* location_descriptor :
+             registered_location_descriptors_) {

[Robert Sesek, 2014/08/01 14:38:04]

nit: indent 4 more, or are we just letting clang-format rule here?

[Mark Mentovai, 2014/08/01 16:09:34]

rsesek wrote:
I’ll fix cases like this where clang-format clearly did a less-good thing.

+          location_descriptor->DataSize = local_size;
+          location_descriptor->Rva = local_rva;
+        }
+      }
+    }
+
+    // This object is now considered writable. However, RVA fields that it
+    // registered to have populated may not yet be populated, because this

[Robert Sesek, 2014/08/01 14:38:04]

This sentence is hard to parse.

+    // method may not yet have been called on the objects that this object’s RVA
+    // fields point to. Once WillWriteAtOffset has completed running for both
+    // phases on an entire tree, all RVA fields within that tree will be
+    // populated.
+    state_ = kStateWritable;
+  } else {
+    if (phase == kPhaseEarly) {
+      DCHECK_EQ(state_, kStateFrozen);
+    } else {
+      DCHECK_EQ(state_, kStateWritable);
+    }
+
+    size = 0;
+    leading_pad_bytes_this_phase = 0;
+  }
+
+  // Loop over children regardless of whether this object itself will write
+  // during this phase. An object’s children are not required to be written
+  // during the same phase as their parent.
+  std::vector<MinidumpWritable*> children = Children();
+  for (MinidumpWritable* child : children) {
+    auto unaligned_child_offset = local_offset + size;

[Robert Sesek, 2014/08/01 14:38:03]

This use of auto seems out of place IMO.

[Mark Mentovai, 2014/08/01 16:09:34]

rsesek wrote:
It’s unfortunately necessary because we’re dealing with distinct types, size_t
and off_t, and we don’t know here which one has a greater range. I’ll add a
comment.

+    off_t child_offset;
+    if (!AssignIfInRange(&child_offset, unaligned_child_offset)) {
+      LOG(ERROR) << "offset " << unaligned_child_offset << " out of range";
+      return kInvalidSize;
+    }
+
+    size_t child_size =
+        child->WillWriteAtOffset(phase, &child_offset, write_sequence);
+    if (child_size == kInvalidSize) {
+      return kInvalidSize;
+    }
+
+    size += child_size;
+  }
+
+  return leading_pad_bytes_this_phase + size;
+}
+
+bool MinidumpWritable::WillWriteAtOffsetImpl(off_t offset) {
+  return true;
+}
+
+bool MinidumpWritable::WritePaddingAndObject(FileWriterInterface* file_writer) {
+  DCHECK_EQ(state_, kStateWritable);
+
+  // The number of elements in kZeroes must be at least one less than the
+  // maximum Alignment() ever encountered.
+  const uint8_t kZeroes[kMaximumAlignment - 1] = {};
+  DCHECK_LE(leading_pad_bytes_, arraysize(kZeroes));
+
+  if (leading_pad_bytes_) {
+    if (!file_writer->Write(&kZeroes, leading_pad_bytes_)) {
+      return false;
+    }
+  }
+
+  if (!WriteObject(file_writer)) {
+    return false;
+  }
+
+  state_ = kStateWritten;
+  return true;
+}
+
+}  // namespace internal
+}  // namespace crashpad