Add initial prototype for the GN meta-buildsystem.

tools/gn/file_template.cc

Index: tools/gn/file_template.cc
diff --git a/tools/gn/file_template.cc b/tools/gn/file_template.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8b5d09f24006b74a400c7d700750d5651291075e
--- /dev/null
+++ b/tools/gn/file_template.cc
@@ -0,0 +1,125 @@
+// Copyright (c) 2013 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 "tools/gn/file_template.h"
+
+#include "tools/gn/filesystem_utils.h"
+
+const char FileTemplate::kSource[] = "{{source}}";
+const char FileTemplate::kSourceNamePart[] = "{{source_name_part}}";
+
+FileTemplate::FileTemplate(const Value& t, Err* err) {
+  ParseInput(t, err);
+}
+
+FileTemplate::FileTemplate(const std::vector<std::string>& t) {
+  for (size_t i = 0; i < t.size(); i++)
+    ParseOneTemplateString(t[i]);
+}
+
+FileTemplate::~FileTemplate() {
+}
+
+void FileTemplate::Apply(const Value& sources,
+                         const ParseNode* origin,
+                         std::vector<Value>* dest,
+                         Err* err) const {
+  if (!sources.VerifyTypeIs(Value::LIST, err))
+    return;
+  dest->reserve(sources.list_value().size() * templates_.container().size());
+
+  // Temporary holding place, allocate outside to re-use- buffer.
+  std::vector<std::string> string_output;
+
+  const std::vector<Value>& sources_list = sources.list_value();
+  for (size_t i = 0; i < sources_list.size(); i++) {
+    if (!sources_list[i].VerifyTypeIs(Value::STRING, err))
+      return;
+
+    ApplyString(sources_list[i].string_value(), &string_output);
+    for (size_t out_i = 0; out_i < string_output.size(); out_i++)
+      dest->push_back(Value(origin, string_output[i]));
+  }
+}
+
+void FileTemplate::ApplyString(const std::string& str,
+                               std::vector<std::string>* output) const {
+  // Compute all substitutions needed so we can just do substitutions below.
+  // We skip the LITERAL one since that varies each time.
+  std::string subst[Subrange::NUM_TYPES];
+  if (types_required_[Subrange::SOURCE])
+    subst[Subrange::SOURCE] = str;
+  if (types_required_[Subrange::NAME_PART])
+    subst[Subrange::NAME_PART] = FindFilenameNoExtension(&str).as_string();
+
+  output->resize(templates_.container().size());
+  for (size_t template_i = 0;
+       template_i < templates_.container().size(); template_i++) {
+    const Template& t = templates_[template_i];
+    (*output)[template_i].clear();
+    for (size_t subrange_i = 0; subrange_i < t.container().size();
+         subrange_i++) {
+      if (t[subrange_i].type == Subrange::LITERAL)
+        (*output)[template_i].append(t[subrange_i].literal);
+      else
+        (*output)[template_i].append(subst[t[subrange_i].type]);
+    }
+  }
+}
+
+void FileTemplate::ParseInput(const Value& value, Err* err) {
+  switch (value.type()) {
+    case Value::STRING:
+      ParseOneTemplateString(value.string_value());
+      break;
+    case Value::LIST:
+      for (size_t i = 0; i < value.list_value().size(); i++) {
+        if (!value.list_value()[i].VerifyTypeIs(Value::STRING, err))
+          return;
+        ParseOneTemplateString(value.list_value()[i].string_value());
+      }
+      break;
+    default:
+      *err = Err(value, "File template must be a string or list.",
+                 "A sarcastic comment about your skills goes here.");
+  }
+}
+
+void FileTemplate::ParseOneTemplateString(const std::string& str) {
+  templates_.container().resize(templates_.container().size() + 1);
+  Template& t = templates_[templates_.container().size() - 1];
+
+  size_t cur = 0;
+  while (true) {
+    size_t next = str.find("{{", cur);
+
+    // Pick up everything from the previous spot to here as a literal.
+    if (next == std::string::npos) {
+      if (cur != str.size())
+        t.container().push_back(Subrange(Subrange::LITERAL, str.substr(cur)));
+      break;
+    } else if (next > cur) {
+      t.container().push_back(
+          Subrange(Subrange::LITERAL, str.substr(cur, next - cur)));
+    }
+
+    // Decode the template param.
+    if (str.compare(next, arraysize(kSource) - 1, kSource) == 0) {
+      t.container().push_back(Subrange(Subrange::SOURCE));
+      types_required_[Subrange::SOURCE] = true;
+      cur = next + arraysize(kSource) - 1;
+    } else if (str.compare(next, arraysize(kSourceNamePart) - 1,
+                           kSourceNamePart) == 0) {
+      t.container().push_back(Subrange(Subrange::NAME_PART));
+      types_required_[Subrange::NAME_PART] = true;
+      cur = next + arraysize(kSourceNamePart) - 1;
+    } else {
+      // If it's not a match, treat it like a one-char literal (this will be
+      // rare, so it's not worth the bother to add to the previous literal) so
+      // we can keep going.
+      t.container().push_back(Subrange(Subrange::LITERAL, "{"));
+      cur = next + 1;
+    }
+  }
+}