versioner: Build SymbolDatabase from version scripts

This commit adds a version script parser so that versioner can build
SymbolDatabase from version scripts.

Bug: 113263746
Test: ./bionic/tools/versioner/run_tests.py
Change-Id: Iedcfe36b51a62693668e07b86aa13592096262db
diff --git a/tools/versioner/src/SymbolFileParser.cpp b/tools/versioner/src/SymbolFileParser.cpp
new file mode 100644
index 0000000..33308d9
--- /dev/null
+++ b/tools/versioner/src/SymbolFileParser.cpp
@@ -0,0 +1,308 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#include "SymbolFileParser.h"
+
+#include "Arch.h"
+#include "CompilationType.h"
+
+#include <android-base/strings.h>
+
+#include <fstream>
+#include <ios>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <err.h>
+
+namespace {
+
+using TagList = std::vector<std::string>;
+
+struct SymbolEnt {
+  std::string name;
+  TagList tags;
+};
+
+using SymbolList = std::vector<SymbolEnt>;
+
+struct Version {
+  std::string name;
+  std::string base;
+  SymbolList symbols;
+  TagList tags;
+};
+
+class SymbolFileParser {
+ public:
+  SymbolFileParser(const std::string& path, const CompilationType& type)
+    : file_path(path),
+      compilation_type(type),
+      api_level_arch_prefix("api-level-" + to_string(type.arch) + "="),
+      intro_arch_perfix("introduced-" + to_string(type.arch) + "="),
+      file(path, std::ios_base::in),
+      curr_line_num(0) {
+  }
+
+  // Parse the version script and build a symbol map.
+  std::optional<SymbolMap> parse() {
+    if (!file) {
+      return std::nullopt;
+    }
+
+    SymbolMap symbol_map;
+    while (hasNextLine()) {
+      auto&& version = parseVersion();
+      if (!version) {
+        return std::nullopt;
+      }
+
+      if (isInArch(version->tags) && isInApi(version->tags)) {
+        for (auto&& [name, tags] : version->symbols) {
+          if (isInArch(tags) && isInApi(tags)) {
+            symbol_map[name] = getSymbolType(tags);
+          }
+        }
+      }
+    }
+    return std::make_optional(std::move(symbol_map));
+  }
+
+ private:
+  // Read a non-empty line from the input and split at the first '#' character.
+  bool hasNextLine() {
+    std::string line;
+    while (std::getline(file, line)) {
+      ++curr_line_num;
+
+      size_t hash_pos = line.find('#');
+      curr_line = android::base::Trim(line.substr(0, hash_pos));
+      if (!curr_line.empty()) {
+        if (hash_pos != std::string::npos) {
+          curr_tags = parseTags(line.substr(hash_pos + 1));
+        } else {
+          curr_tags.clear();
+        }
+        return true;
+      }
+    }
+    return false;
+  }
+
+  // Tokenize the tags after the '#' character.
+  static std::vector<std::string> parseTags(const std::string& tags_line) {
+    std::vector<std::string> tags = android::base::Split(tags_line, " \t");
+    tags.erase(std::remove(tags.begin(), tags.end(), ""), tags.end());
+    return tags;
+  }
+
+  // Parse a version scope.
+  std::optional<Version> parseVersion() {
+    size_t start_line_num = curr_line_num;
+
+    std::string::size_type lparen_pos = curr_line.find('{');
+    if (lparen_pos == std::string::npos) {
+      errx(1, "%s:%zu: error: expected '{' cannot be found in this line",
+           file_path.c_str(), curr_line_num);
+    }
+
+    // Record the version name and version tags (before hasNextLine()).
+    std::string name = android::base::Trim(curr_line.substr(0, lparen_pos));
+    TagList tags = std::move(curr_tags);
+
+    // Read symbol lines.
+    SymbolList symbols;
+    bool global_scope = true;
+    bool cpp_scope = false;
+    while (hasNextLine()) {
+      size_t rparen_pos = curr_line.find('}');
+      if (rparen_pos != std::string::npos) {
+        size_t semicolon_pos = curr_line.find(';', rparen_pos + 1);
+        if (semicolon_pos == std::string::npos) {
+          errx(1, "%s:%zu: error: the line that ends a scope must end with ';'",
+               file_path.c_str(), curr_line_num);
+        }
+
+        if (cpp_scope) {
+          cpp_scope = false;
+          continue;
+        }
+
+        std::string base = android::base::Trim(
+          curr_line.substr(rparen_pos + 1, semicolon_pos - 1));
+
+        return std::make_optional(Version{std::move(name), std::move(base),
+                                          std::move(symbols), std::move(tags)});
+      }
+
+      if (android::base::StartsWith(curr_line, R"(extern "C++" {)")) {
+        cpp_scope = true;
+        continue;
+      }
+
+      if (cpp_scope) {
+        continue;
+      }
+
+      size_t colon_pos = curr_line.find(':');
+      if (colon_pos != std::string::npos) {
+        std::string visibility =
+          android::base::Trim(curr_line.substr(0, colon_pos));
+
+        if (visibility == "global") {
+          global_scope = true;
+        } else if (visibility == "local") {
+          global_scope = false;
+        } else {
+          errx(1, "%s:%zu: error: unknown version visibility: %s",
+               file_path.c_str(), curr_line_num, visibility.c_str());
+        }
+        continue;
+      }
+
+      if (global_scope) {
+        size_t semicolon_pos = curr_line.find(';');
+        if (semicolon_pos == std::string::npos) {
+          errx(1, "%s:%zu: error: symbol name line must end with ';'",
+               file_path.c_str(), curr_line_num);
+        }
+
+        std::string symbol_name =
+          android::base::Trim(curr_line.substr(0, semicolon_pos));
+
+        size_t asterisk_pos = symbol_name.find('*');
+        if (asterisk_pos != std::string::npos) {
+          errx(1, "%s:%zu: error: global symbol name must not have wildcards",
+               file_path.c_str(), curr_line_num);
+        }
+
+        symbols.push_back(SymbolEnt{std::move(symbol_name),
+                                    std::move(curr_tags)});
+      }
+    }
+
+    errx(1, "%s:%zu: error: scope started from %zu must be closed before EOF",
+         file_path.c_str(), curr_line_num, start_line_num);
+  }
+
+  static NdkSymbolType getSymbolType(const TagList& tags) {
+    for (auto&& tag : tags) {
+      if (tag == "var") {
+        return NdkSymbolType::variable;
+      }
+    }
+    return NdkSymbolType::function;
+  }
+
+  // isInArch() returns true if there is a matching arch-specific tag or there
+  // are no arch-specific tags.
+  bool isInArch(const TagList& tags) const {
+    bool has_arch_tags = false;
+    for (auto&& tag : tags) {
+      std::optional<Arch> arch = arch_from_string(tag);
+      if (!arch) {
+        continue;
+      }
+      if (*arch == compilation_type.arch) {
+        return true;
+      }
+      has_arch_tags = true;
+    }
+    return !has_arch_tags;
+  }
+
+  // isInApi() returns true if the specified API level is equal to the
+  // api-level tag, or the specified API level is greater than or equal to the
+  // introduced tag, or there are no api-level or introduced tags.
+  bool isInApi(const TagList& tags) const {
+    bool api_level_arch = false;
+    bool intro_arch = false;
+    std::string api_level;
+    std::string intro;
+
+    for (const std::string& tag : tags) {
+      // Check api-level tags.
+      if (android::base::StartsWith(tag, "api-level=") && !api_level_arch) {
+        api_level = tag;
+        continue;
+      }
+      if (android::base::StartsWith(tag, api_level_arch_prefix)) {
+        api_level = tag;
+        api_level_arch = true;
+        continue;
+      }
+
+      // Check introduced tags.
+      if (android::base::StartsWith(tag, "introduced=") && !intro_arch) {
+        intro = tag;
+        continue;
+      }
+      if (android::base::StartsWith(tag, intro_arch_perfix)) {
+        intro = tag;
+        intro_arch = true;
+        continue;
+      }
+
+      if (tag == "future") {
+        return compilation_type.api_level == future_api;
+      }
+    }
+
+    if (intro.empty() && api_level.empty()) {
+      return true;
+    }
+
+    if (!api_level.empty()) {
+      // If an api-level tag is specified, it must be an exact match (mainly
+      // for versioner unit tests).
+      return compilation_type.api_level == decodeApiLevelValue(api_level);
+    }
+
+    return compilation_type.api_level >= decodeApiLevelValue(intro);
+  }
+
+  // Extract and decode the integer API level from api-level or introduced tags.
+  static int decodeApiLevelValue(const std::string& tag) {
+    std::string api_level = tag.substr(tag.find('=') + 1);
+    auto it = api_codename_map.find(api_level);
+    if (it != api_codename_map.end()) {
+      return it->second;
+    }
+    return std::stoi(api_level);
+  }
+
+ private:
+  const std::string& file_path;
+  const CompilationType& compilation_type;
+  const std::string api_level_arch_prefix;
+  const std::string intro_arch_perfix;
+
+  std::ifstream file;
+  std::string curr_line;
+  std::vector<std::string> curr_tags;
+  size_t curr_line_num;
+};
+
+}  // anonymous namespace
+
+
+std::optional<SymbolMap> parseSymbolFile(const std::string& file_path,
+                                         const CompilationType& type) {
+  SymbolFileParser parser(file_path, type);
+  return parser.parse();
+}