Add ElfWriter::GetStream().

This will be used for writing the OatHeader which is
currently oddly written through the .text stream.

Also move the error delaying output stream out of the
ElfBuilder<> to its own file and move all output stream
files to compiler/linker/.

Change-Id: I00db4e33ed80ac4757ec459946c7b5ae014a3a2e
diff --git a/compiler/linker/vector_output_stream.h b/compiler/linker/vector_output_stream.h
new file mode 100644
index 0000000..3210143
--- /dev/null
+++ b/compiler/linker/vector_output_stream.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef ART_COMPILER_LINKER_VECTOR_OUTPUT_STREAM_H_
+#define ART_COMPILER_LINKER_VECTOR_OUTPUT_STREAM_H_
+
+#include "output_stream.h"
+
+#include <string>
+#include <string.h>
+#include <vector>
+
+namespace art {
+
+class VectorOutputStream FINAL : public OutputStream {
+ public:
+  VectorOutputStream(const std::string& location, std::vector<uint8_t>* vector);
+
+  ~VectorOutputStream() OVERRIDE {}
+
+  bool WriteFully(const void* buffer, size_t byte_count) OVERRIDE {
+    if (static_cast<size_t>(offset_) == vector_->size()) {
+      const uint8_t* start = reinterpret_cast<const uint8_t*>(buffer);
+      vector_->insert(vector_->end(), &start[0], &start[byte_count]);
+      offset_ += byte_count;
+    } else {
+      off_t new_offset = offset_ + byte_count;
+      EnsureCapacity(new_offset);
+      memcpy(&(*vector_)[offset_], buffer, byte_count);
+      offset_ = new_offset;
+    }
+    return true;
+  }
+
+  off_t Seek(off_t offset, Whence whence) OVERRIDE;
+
+  bool Flush() OVERRIDE {
+    return true;
+  }
+
+ private:
+  void EnsureCapacity(off_t new_offset) {
+    if (new_offset > static_cast<off_t>(vector_->size())) {
+      vector_->resize(new_offset);
+    }
+  }
+
+  off_t offset_;
+  std::vector<uint8_t>* const vector_;
+
+  DISALLOW_COPY_AND_ASSIGN(VectorOutputStream);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_LINKER_VECTOR_OUTPUT_STREAM_H_