src: back snapshot I/O with a std::vector sink

Author: joyeecheung

src/node_snapshotable.cc

@@ -2,6 +2,7 @@
 #include "node_snapshotable.h"
 #include <iostream>
 #include <sstream>
+#include <vector>
 #include "base_object-inl.h"
 #include "debug_utils-inl.h"
 #include "env-inl.h"
@@ -135,11 +136,10 @@ std::ostream& operator<<(std::ostream& output, const EnvSerializeInfo& i) {
   return output;
 }
 
-class FileIO {
+class SnapshotSerializerDeserializer {
  public:
-  explicit FileIO(FILE* file)
-      : f(file),
-        is_debug(per_process::enabled_debug_list.enabled(
+  SnapshotSerializerDeserializer()
+      : is_debug(per_process::enabled_debug_list.enabled(
             DebugCategory::MKSNAPSHOT)) {}
 
   template <typename... Args>
@@ -181,14 +181,14 @@ class FileIO {
     return name;
   }
 
-  FILE* f = nullptr;
   bool is_debug = false;
 };
 
-class FileReader : public FileIO {
+class SnapshotDeserializer : public SnapshotSerializerDeserializer {
  public:
-  explicit FileReader(FILE* file) : FileIO(file) {}
-  ~FileReader() {}
+  explicit SnapshotDeserializer(const std::vector<char>* s)
+      : SnapshotSerializerDeserializer(), sink(s) {}
+  ~SnapshotDeserializer() {}
 
   // Helper for reading numeric types.
   template <typename T>
@@ -233,19 +233,19 @@ class FileReader : public FileIO {
 
     CHECK_GT(length, 0);  // There should be no empty strings.
     MallocedBuffer<char> buf(length + 1);
-    size_t r = fread(buf.data, 1, length + 1, f);
-    CHECK_EQ(r, length + 1);
+    memcpy(buf.data, sink->data() + read_total, length + 1);
     std::string result(buf.data, length);  // This creates a copy of buf.data.
 
     if (is_debug) {
-      Debug("\"%s\", read %d bytes\n", result.c_str(), r);
+      Debug("\"%s\", read %zu bytes\n", result.c_str(), length + 1);
     }
 
-    read_total += r;
+    read_total += length + 1;
     return result;
   }
 
   size_t read_total = 0;
+  const std::vector<char>* sink = nullptr;
 
  private:
   // Helper for reading an array of numeric types.
@@ -258,15 +258,15 @@ class FileReader : public FileIO {
       Debug("Read<%s>()(%d-byte), count=%d: ", name.c_str(), sizeof(T), count);
     }
 
-    size_t r = fread(out, sizeof(T), count, f);
-    CHECK_EQ(r, count);
+    size_t size = sizeof(T) * count;
+    memcpy(out, sink->data() + read_total, size);
 
     if (is_debug) {
       std::string str =
           "{ " + std::to_string(out[0]) + (count > 1 ? ", ... }" : " }");
-      Debug("%s, read %d bytes\n", str.c_str(), r);
+      Debug("%s, read %zu bytes\n", str.c_str(), size);
     }
-    read_total += r;
+    read_total += size;
   }
 
   // Helper for reading numeric vectors.
@@ -300,10 +300,15 @@ class FileReader : public FileIO {
   }
 };
 
-class FileWriter : public FileIO {
+class SnapshotSerializer : public SnapshotSerializerDeserializer {
  public:
-  explicit FileWriter(FILE* file) : FileIO(file) {}
-  ~FileWriter() {}
+  SnapshotSerializer() : SnapshotSerializerDeserializer() {
+    // Currently the snapshot blob built with an empty script is around 4MB.
+    // So use that as the default sink size.
+    sink.reserve(4 * 1024 * 1024);
+  }
+  ~SnapshotSerializer() {}
+  std::vector<char> sink;
 
   // Helper for writing numeric types.
   template <typename T>
@@ -349,15 +354,15 @@ class FileWriter : public FileIO {
     size_t written_total = Write<size_t>(data.size());
     if (is_debug) {
       std::string str = ToStr(data);
-      Debug("WriteString(), length=%d: \"%s\"\n", data.size(), data.c_str());
+      Debug("WriteString(), length=%zu: \"%s\"\n", data.size(), data.c_str());
     }
 
-    size_t r = fwrite(data.c_str(), 1, data.size() + 1, f);
-    CHECK_EQ(r, data.size() + 1);
-    written_total += r;
+    // Write the null-terminated string.
+    sink.insert(sink.end(), data.c_str(), data.c_str() + data.size() + 1);
+    written_total += data.size();
 
     if (is_debug) {
-      Debug("WriteString() wrote %d bytes\n", written_total);
+      Debug("WriteString() wrote %zu bytes\n", written_total);
     }
 
     return written_total;
@@ -372,20 +377,21 @@ class FileWriter : public FileIO {
       std::string str =
           "{ " + std::to_string(data[0]) + (count > 1 ? ", ... }" : " }");
       std::string name = GetName<T>();
-      Debug("Write<%s>() (%d-byte), count=%d: %s",
+      Debug("Write<%s>() (%zu-byte), count=%zu: %s",
             name.c_str(),
             sizeof(T),
             count,
             str.c_str());
     }
 
-    size_t r = fwrite(data, sizeof(T), count, f);
-    CHECK_EQ(r, count);
+    size_t size = sizeof(T) * count;
+    const char* pos = reinterpret_cast<const char*>(data);
+    sink.insert(sink.end(), pos, pos + (sizeof(T) * count));
 
     if (is_debug) {
-      Debug(", wrote %d bytes\n", r);
+      Debug(", wrote %zu bytes\n", size);
     }
-    return r;
+    return size;
   }
 
   // Helper for writing numeric vectors.
@@ -418,19 +424,19 @@ class FileWriter : public FileIO {
 // [  4/8 bytes     ] length
 // [ |length| bytes ] contents
 template <>
-std::string FileReader::Read() {
+std::string SnapshotDeserializer::Read() {
   return ReadString();
 }
 template <>
-size_t FileWriter::Write(const std::string& data) {
+size_t SnapshotSerializer::Write(const std::string& data) {
   return WriteString(data);
 }
 
 // Layout of v8::StartupData
 // [  4/8 bytes       ] raw_size
 // [ |raw_size| bytes ] contents
 template <>
-v8::StartupData FileReader::Read() {
+v8::StartupData SnapshotDeserializer::Read() {
   Debug("Read<v8::StartupData>()\n");
 
   int raw_size = Read<int>();
@@ -445,7 +451,7 @@ v8::StartupData FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const v8::StartupData& data) {
+size_t SnapshotSerializer::Write(const v8::StartupData& data) {
   Debug("\nWrite<v8::StartupData>() size=%d\n", data.raw_size);
 
   CHECK_GT(data.raw_size, 0);  // There should be no startup data of size 0.
@@ -462,7 +468,7 @@ size_t FileWriter::Write(const v8::StartupData& data) {
 // [  4/8 bytes ]  length of module code cache
 // [    ...     ]  |length| bytes of module code cache
 template <>
-builtins::CodeCacheInfo FileReader::Read() {
+builtins::CodeCacheInfo SnapshotDeserializer::Read() {
   Debug("Read<builtins::CodeCacheInfo>()\n");
 
   builtins::CodeCacheInfo result{ReadString(), ReadVector<uint8_t>()};
@@ -475,7 +481,7 @@ builtins::CodeCacheInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const builtins::CodeCacheInfo& data) {
+size_t SnapshotSerializer::Write(const builtins::CodeCacheInfo& data) {
   Debug("\nWrite<builtins::CodeCacheInfo>() id = %s"
         ", size=%d\n",
         data.id.c_str(),
@@ -495,7 +501,7 @@ size_t FileWriter::Write(const builtins::CodeCacheInfo& data) {
 // [ 4/8 bytes ]  index in the snapshot blob, can be used with
 //                GetDataFromSnapshotOnce().
 template <>
-PropInfo FileReader::Read() {
+PropInfo SnapshotDeserializer::Read() {
   Debug("Read<PropInfo>()\n");
 
   PropInfo result;
@@ -512,7 +518,7 @@ PropInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const PropInfo& data) {
+size_t SnapshotSerializer::Write(const PropInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("Write<PropInfo>() %s\n", str.c_str());
@@ -535,7 +541,7 @@ size_t FileWriter::Write(const PropInfo& data) {
 // [   ...     ]  snapshot indices of each element in
 //                native_execution_async_resources
 template <>
-AsyncHooks::SerializeInfo FileReader::Read() {
+AsyncHooks::SerializeInfo SnapshotDeserializer::Read() {
   Debug("Read<AsyncHooks::SerializeInfo>()\n");
 
   AsyncHooks::SerializeInfo result;
@@ -553,7 +559,7 @@ AsyncHooks::SerializeInfo FileReader::Read() {
   return result;
 }
 template <>
-size_t FileWriter::Write(const AsyncHooks::SerializeInfo& data) {
+size_t SnapshotSerializer::Write(const AsyncHooks::SerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("Write<AsyncHooks::SerializeInfo>() %s\n", str.c_str());
@@ -573,7 +579,7 @@ size_t FileWriter::Write(const AsyncHooks::SerializeInfo& data) {
 // Layout of TickInfo::SerializeInfo
 // [ 4/8 bytes ]  snapshot index of fields
 template <>
-TickInfo::SerializeInfo FileReader::Read() {
+TickInfo::SerializeInfo SnapshotDeserializer::Read() {
   Debug("Read<TickInfo::SerializeInfo>()\n");
 
   TickInfo::SerializeInfo result;
@@ -588,7 +594,7 @@ TickInfo::SerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const TickInfo::SerializeInfo& data) {
+size_t SnapshotSerializer::Write(const TickInfo::SerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("Write<TickInfo::SerializeInfo>() %s\n", str.c_str());
@@ -603,7 +609,7 @@ size_t FileWriter::Write(const TickInfo::SerializeInfo& data) {
 // Layout of TickInfo::SerializeInfo
 // [ 4/8 bytes ]  snapshot index of fields
 template <>
-ImmediateInfo::SerializeInfo FileReader::Read() {
+ImmediateInfo::SerializeInfo SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT,
                      "Read<ImmediateInfo::SerializeInfo>()\n");
 
@@ -617,7 +623,7 @@ ImmediateInfo::SerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const ImmediateInfo::SerializeInfo& data) {
+size_t SnapshotSerializer::Write(const ImmediateInfo::SerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("Write<ImmediateInfo::SerializeInfo>() %s\n", str.c_str());
@@ -635,7 +641,7 @@ size_t FileWriter::Write(const ImmediateInfo::SerializeInfo& data) {
 // [ 4/8 bytes ]  snapshot index of milestones
 // [ 4/8 bytes ]  snapshot index of observers
 template <>
-performance::PerformanceState::SerializeInfo FileReader::Read() {
+performance::PerformanceState::SerializeInfo SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT,
                      "Read<PerformanceState::SerializeInfo>()\n");
 
@@ -651,7 +657,7 @@ performance::PerformanceState::SerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(
+size_t SnapshotSerializer::Write(
     const performance::PerformanceState::SerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
@@ -673,7 +679,7 @@ size_t FileWriter::Write(
 // [ 4/8 bytes ]  length of template_values vector
 // [    ...    ]  |length| of PropInfo data
 template <>
-IsolateDataSerializeInfo FileReader::Read() {
+IsolateDataSerializeInfo SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT,
                      "Read<IsolateDataSerializeInfo>()\n");
 
@@ -688,7 +694,7 @@ IsolateDataSerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const IsolateDataSerializeInfo& data) {
+size_t SnapshotSerializer::Write(const IsolateDataSerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("Write<IsolateDataSerializeInfo>() %s\n", str.c_str());
@@ -702,7 +708,7 @@ size_t FileWriter::Write(const IsolateDataSerializeInfo& data) {
 }
 
 template <>
-RealmSerializeInfo FileReader::Read() {
+RealmSerializeInfo SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT, "Read<RealmSerializeInfo>()\n");
   RealmSerializeInfo result;
   result.builtins = ReadVector<std::string>();
@@ -713,7 +719,7 @@ RealmSerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const RealmSerializeInfo& data) {
+size_t SnapshotSerializer::Write(const RealmSerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("\nWrite<RealmSerializeInfo>() %s\n", str.c_str());
@@ -730,7 +736,7 @@ size_t FileWriter::Write(const RealmSerializeInfo& data) {
 }
 
 template <>
-EnvSerializeInfo FileReader::Read() {
+EnvSerializeInfo SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT, "Read<EnvSerializeInfo>()\n");
   EnvSerializeInfo result;
   result.async_hooks = Read<AsyncHooks::SerializeInfo>();
@@ -747,7 +753,7 @@ EnvSerializeInfo FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const EnvSerializeInfo& data) {
+size_t SnapshotSerializer::Write(const EnvSerializeInfo& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("\nWrite<EnvSerializeInfo>() %s\n", str.c_str());
@@ -780,7 +786,7 @@ size_t FileWriter::Write(const EnvSerializeInfo& data) {
 // [    ...    ]  |length| bytes of node platform
 // [  4 bytes  ]  v8 cache version tag
 template <>
-SnapshotMetadata FileReader::Read() {
+SnapshotMetadata SnapshotDeserializer::Read() {
   per_process::Debug(DebugCategory::MKSNAPSHOT, "Read<SnapshotMetadata>()\n");
 
   SnapshotMetadata result;
@@ -798,7 +804,7 @@ SnapshotMetadata FileReader::Read() {
 }
 
 template <>
-size_t FileWriter::Write(const SnapshotMetadata& data) {
+size_t SnapshotSerializer::Write(const SnapshotMetadata& data) {
   if (is_debug) {
     std::string str = ToStr(data);
     Debug("\nWrite<SnapshotMetadata>() %s\n", str.c_str());
@@ -833,7 +839,7 @@ size_t FileWriter::Write(const SnapshotMetadata& data) {
 // [    ...       ]  code_cache
 
 void SnapshotData::ToBlob(FILE* out) const {
-  FileWriter w(out);
+  SnapshotSerializer w;
   w.Debug("SnapshotData::ToBlob()\n");
 
   size_t written_total = 0;
@@ -850,11 +856,24 @@ void SnapshotData::ToBlob(FILE* out) const {
   written_total += w.Write<EnvSerializeInfo>(env_info);
   w.Debug("Write code_cache\n");
   written_total += w.WriteVector<builtins::CodeCacheInfo>(code_cache);
+  size_t num_written = fwrite(w.sink.data(), w.sink.size(), 1, out);
+  CHECK_EQ(num_written, 1);
   w.Debug("SnapshotData::ToBlob() Wrote %d bytes\n", written_total);
 }
 
 bool SnapshotData::FromBlob(SnapshotData* out, FILE* in) {
-  FileReader r(in);
+  CHECK_EQ(ftell(in), 0);
+  int err = fseek(in, 0, SEEK_END);
+  CHECK_EQ(err, 0);
+  size_t size = ftell(in);
+  err = fseek(in, 0, SEEK_SET);
+  CHECK_EQ(err, 0);
+
+  std::vector<char> sink(size);
+  size_t num_read = fread(sink.data(), size, 1, in);
+  CHECK_EQ(num_read, 1);
+
+  SnapshotDeserializer r(&sink);
   r.Debug("SnapshotData::FromBlob()\n");
 
   DCHECK_EQ(out->data_ownership, SnapshotData::DataOwnership::kOwned);