[refactor] Extract some test helpers for certificate verification unittests.

net/cert/internal/test_helpers.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/cert/internal/test_helpers.h"
+
+#include "base/base_paths.h"
+#include "base/files/file_util.h"
+#include "base/path_service.h"
+#include "net/cert/pem_tokenizer.h"
+
+namespace net {
+
+der::Input InputFromString(const std::string* s) {
+  return der::Input(reinterpret_cast<const uint8_t*>(s->data()), s->size());
+}
+
+::testing::AssertionResult ReadTestDataFromPemFile(
+    const std::string& file_path_ascii,
+    const PemBlockMapping* mappings,
+    size_t mappings_length) {
+  // Compute the full path, relative to the src/ directory.
+  base::FilePath src_root;
+  PathService::Get(base::DIR_SOURCE_ROOT, &src_root);
+  base::FilePath filepath = src_root.AppendASCII(file_path_ascii);
+
+  // Read the full contents of the PEM file.
+  std::string file_data;
+  if (!base::ReadFileToString(filepath, &file_data)) {
+    return ::testing::AssertionFailure() << "Couldn't read file: "
+                                         << filepath.value();
+  }
+
+  // mappings_copy is used to keep track of which mappings have already been
+  // satisfied (by nulling the |value| field). This is used to track when
+  // blocks are mulitply defined.
+  std::vector<PemBlockMapping> mappings_copy(mappings,
+                                             mappings + mappings_length);
+
+  // Build the |pem_headers| vector needed for PEMTokenzier.
+  std::vector<std::string> pem_headers;
+  for (const auto& mapping : mappings_copy) {
+    pem_headers.push_back(mapping.block_name);
+  }
+
+  PEMTokenizer pem_tokenizer(file_data, pem_headers);
+  while (pem_tokenizer.GetNext()) {
+    for (auto& mapping : mappings_copy) {
+      // Find the mapping for this block type.
+      if (pem_tokenizer.block_type() == mapping.block_name) {
+        if (!mapping.value) {
+          return ::testing::AssertionFailure()
+                 << "PEM block defined multiple times: " << mapping.block_name;
+        }
+
+        // Copy the data to the result.
+        mapping.value->assign(pem_tokenizer.data());
+
+        // Mark the mapping as having been satisfied.
+        mapping.value = nullptr;
+      }
+    }
+  }
+
+  // Ensure that all specified blocks were found.
+  for (const auto& mapping : mappings_copy) {
+    if (mapping.value) {
+      return ::testing::AssertionFailure() << "PEM block missing: "
+                                           << mapping.block_name;
+    }
+  }
+
+  return ::testing::AssertionSuccess();
+}
+
+}  // namespace net