add DepsLog, a new data structure for dependency information

DepsLog is a compact serialization of dependency information.
It can be used to replace depfiles for faster loading.

1 files changed, 149 insertions, 0 deletions

diff --git a/src/deps_log.cc b/src/deps_log.cc
new file mode 100644
index 0000000..ca7fd4b
--- /dev/null
+++ b/src/deps_log.cc
@@ -0,0 +1,149 @@
+// 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.
+
+#include "deps_log.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+
+#include "graph.h"
+#include "state.h"
+#include "util.h"
+
+bool DepsLog::OpenForWrite(const string& path, string* err) {
+  file_ = fopen(path.c_str(), "ab");
+  if (!file_) {
+    *err = strerror(errno);
+    return false;
+  }
+  SetCloseOnExec(fileno(file_));
+
+  // Opening a file in append mode doesn't set the file pointer to the file's
+  // end on Windows. Do that explicitly.
+  fseek(file_, 0, SEEK_END);
+
+  /* XXX
+  if (ftell(log_file_) == 0) {
+    if (fprintf(log_file_, kFileSignature, kCurrentVersion) < 0) {
+      *err = strerror(errno);
+      return false;
+    }
+  }
+  */
+
+  return true;
+}
+
+bool DepsLog::RecordDeps(Node* node, TimeStamp mtime,
+                         const vector<Node*>& nodes) {
+  // Assign ids to all nodes that are missing one.
+  if (node->id() < 0)
+    RecordId(node);
+  for (vector<Node*>::const_iterator i = nodes.begin();
+       i != nodes.end(); ++i) {
+    if ((*i)->id() < 0)
+      RecordId(*i);
+  }
+
+  uint16_t size = 4 * (1 + 1 + nodes.size());
+  size |= 0x8000;  // Deps record: set high bit.
+  fwrite(&size, 2, 1, file_);
+  int id = node->id();
+  fwrite(&id, 4, 1, file_);
+  int timestamp = node->mtime();
+  fwrite(&timestamp, 4, 1, file_);
+  for (vector<Node*>::const_iterator i = nodes.begin();
+       i != nodes.end(); ++i) {
+    id = node->id();
+    fwrite(&id, 4, 1, file_);
+  }
+
+  return true;
+}
+
+void DepsLog::Close() {
+  fclose(file_);
+  file_ = NULL;
+}
+
+bool DepsLog::Load(const string& path, State* state, string* err) {
+  char buf[32 << 10];
+  FILE* f = fopen(path.c_str(), "rb");
+  if (!f) {
+    *err = strerror(errno);
+    return false;
+  }
+
+  int id = 0;
+  for (;;) {
+    uint16_t size;
+    if (fread(&size, 2, 1, f) < 1)
+      break;
+    bool is_deps = (size >> 15) != 0;
+    size = size & 0x7FFF;
+
+    if (fread(buf, size, 1, f) < 1)
+      break;
+
+    if (is_deps) {
+      assert(size % 4 == 0);
+      int* deps_data = reinterpret_cast<int*>(buf);
+      int out_id = deps_data[0];
+      int mtime = deps_data[1];
+      deps_data += 2;
+      int deps_count = (size / 4) - 2;
+
+      Deps* deps = new Deps;
+      deps->mtime = mtime;
+      deps->node_count = deps_count;
+      deps->nodes = new Node*[deps_count];
+      for (int i = 0; i < deps_count; ++i) {
+        assert(deps_data[i] < (int)nodes_.size());
+        assert(nodes_[deps_data[i]]);
+        deps->nodes[i] = nodes_[deps_data[i]];
+      }
+
+      if (out_id >= (int)deps_.size())
+        deps_.resize(out_id + 1);
+      if (deps_[out_id])
+        delete deps_[out_id];
+      deps_[out_id] = deps;
+    } else {
+      StringPiece path(buf, size);
+      Node* node = state->GetNode(path);
+      assert(node->id() < 0);
+      node->set_id(id);
+      ++id;
+    }
+  }
+  if (ferror(f)) {
+    *err = strerror(ferror(f));
+    return false;
+  }
+  fclose(f);
+  return true;
+}
+
+bool DepsLog::RecordId(Node* node) {
+  uint16_t size = node->path().size();
+  fwrite(&size, 2, 1, file_);
+  fwrite(node->path().data(), node->path().size(), 1, file_);
+
+  node->set_id(nodes_.size());
+  nodes_.push_back(node);
+
+  return true;
+}