win: Add and use GET_FUNCTION() and GET_FUNCTION_REQUIRED()

util/win/get_function.cc

 // Copyright 2015 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 "snapshot/minidump/minidump_string_reader.h"
+#include "util/win/get_function.h"
 
 #include "base/logging.h"
-#include "minidump/minidump_extensions.h"
+#include "base/strings/utf_string_conversions.h"
 
 namespace crashpad {
 namespace internal {
 
-bool ReadMinidumpUTF8String(FileReaderInterface* file_reader,
-                            RVA rva,
-                            std::string* string) {
-  if (rva == 0) {
-    string->clear();
-    return true;
+FARPROC GetFunctionInternal(
+    const wchar_t* library, const char* function, bool required) {
+  HMODULE module = LoadLibrary(library);
+  DPCHECK(!required || module) << "LoadLibrary " << base::UTF16ToUTF8(library);
+  if (!module) {
+    return nullptr;
   }
 
-  if (!file_reader->SeekSet(rva)) {
-    return false;
+  // Strip off any leading :: that may have come from stringifying the
+  // function’s name.
+  if (function[0] == ':' && function[1] == ':' &&
+      function[2] && function[2] != ':') {
+    function += 2;
   }
 
-  uint32_t string_size;
-  if (!file_reader->ReadExactly(&string_size, sizeof(string_size))) {
-    return false;
-  }
-
-  std::string local_string(string_size, '\0');
-  if (!file_reader->ReadExactly(&local_string[0], string_size)) {
-    return false;
-  }
-
-  string->swap(local_string);
-  return true;
+  FARPROC proc = GetProcAddress(module, function);
+  DPCHECK(!required || proc) << "GetProcAddress " << function;
+  return proc;
 }
 
 }  // namespace internal
 }  // namespace crashpad