| // Copyright 2012 Google Inc. 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. |
| |
| #ifndef NINJA_DEPS_LOG_H_ |
| #define NINJA_DEPS_LOG_H_ |
| |
| #include <string> |
| #include <vector> |
| |
| #include <stdio.h> |
| |
| #include "load_status.h" |
| #include "timestamp.h" |
| |
| struct Node; |
| struct State; |
| |
| /// As build commands run they can output extra dependency information |
| /// (e.g. header dependencies for C source) dynamically. DepsLog collects |
| /// that information at build time and uses it for subsequent builds. |
| /// |
| /// The on-disk format is based on two primary design constraints: |
| /// - it must be written to as a stream (during the build, which may be |
| /// interrupted); |
| /// - it can be read all at once on startup. (Alternative designs, where |
| /// it contains indexing information, were considered and discarded as |
| /// too complicated to implement; if the file is small than reading it |
| /// fully on startup is acceptable.) |
| /// Here are some stats from the Windows Chrome dependency files, to |
| /// help guide the design space. The total text in the files sums to |
| /// 90mb so some compression is warranted to keep load-time fast. |
| /// There's about 10k files worth of dependencies that reference about |
| /// 40k total paths totalling 2mb of unique strings. |
| /// |
| /// Based on these stats, here's the current design. |
| /// The file is structured as version header followed by a sequence of records. |
| /// Each record is either a path string or a dependency list. |
| /// Numbering the path strings in file order gives them dense integer ids. |
| /// A dependency list maps an output id to a list of input ids. |
| /// |
| /// Concretely, a record is: |
| /// four bytes record length, high bit indicates record type |
| /// (but max record sizes are capped at 512kB) |
| /// path records contain the string name of the path, followed by up to 3 |
| /// padding bytes to align on 4 byte boundaries, followed by the |
| /// one's complement of the expected index of the record (to detect |
| /// concurrent writes of multiple ninja processes to the log). |
| /// dependency records are an array of 4-byte integers |
| /// [output path id, |
| /// output path mtime (lower 4 bytes), output path mtime (upper 4 bytes), |
| /// input path id, input path id...] |
| /// (The mtime is compared against the on-disk output path mtime |
| /// to verify the stored data is up-to-date.) |
| /// If two records reference the same output the latter one in the file |
| /// wins, allowing updates to just be appended to the file. A separate |
| /// repacking step can run occasionally to remove dead records. |
| struct DepsLog { |
| DepsLog() : needs_recompaction_(false), file_(NULL) {} |
| ~DepsLog(); |
| |
| // Writing (build-time) interface. |
| bool OpenForWrite(const std::string& path, std::string* err); |
| bool RecordDeps(Node* node, TimeStamp mtime, const std::vector<Node*>& nodes); |
| bool RecordDeps(Node* node, TimeStamp mtime, int node_count, Node** nodes); |
| void Close(); |
| |
| // Reading (startup-time) interface. |
| struct Deps { |
| Deps(int64_t mtime, int node_count) |
| : mtime(mtime), node_count(node_count), nodes(new Node*[node_count]) {} |
| ~Deps() { delete [] nodes; } |
| TimeStamp mtime; |
| int node_count; |
| Node** nodes; |
| }; |
| LoadStatus Load(const std::string& path, State* state, std::string* err); |
| Deps* GetDeps(Node* node); |
| |
| /// Rewrite the known log entries, throwing away old data. |
| bool Recompact(const std::string& path, std::string* err); |
| |
| /// Returns if the deps entry for a node is still reachable from the manifest. |
| /// |
| /// The deps log can contain deps entries for files that were built in the |
| /// past but are no longer part of the manifest. This function returns if |
| /// this is the case for a given node. This function is slow, don't call |
| /// it from code that runs on every build. |
| bool IsDepsEntryLiveFor(Node* node); |
| |
| /// Used for tests. |
| const std::vector<Node*>& nodes() const { return nodes_; } |
| const std::vector<Deps*>& deps() const { return deps_; } |
| |
| private: |
| // Updates the in-memory representation. Takes ownership of |deps|. |
| // Returns true if a prior deps record was deleted. |
| bool UpdateDeps(int out_id, Deps* deps); |
| // Write a node name record, assigning it an id. |
| bool RecordId(Node* node); |
| |
| /// Should be called before using file_. When false is returned, errno will |
| /// be set. |
| bool OpenForWriteIfNeeded(); |
| |
| bool needs_recompaction_; |
| FILE* file_; |
| std::string file_path_; |
| |
| /// Maps id -> Node. |
| std::vector<Node*> nodes_; |
| /// Maps id -> deps of that id. |
| std::vector<Deps*> deps_; |
| |
| friend struct DepsLogTest; |
| }; |
| |
| #endif // NINJA_DEPS_LOG_H_ |