Move tar archive parsing to C++

runtime/lib/vmservice.cc

Index: runtime/lib/vmservice.cc
diff --git a/runtime/lib/vmservice.cc b/runtime/lib/vmservice.cc
index 12aadb6831defc8db65c49e9f90837b32d061727..11380429f39844d6df05c5fad5db8bb49dc618d6 100644
--- a/runtime/lib/vmservice.cc
+++ b/runtime/lib/vmservice.cc
@@ -3,9 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap_natives.h"
-
 #include "vm/dart_api_impl.h"
+#include "vm/datastream.h"
 #include "vm/exceptions.h"
+#include "vm/growable_array.h"
 #include "vm/message.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
@@ -151,4 +152,245 @@ DEFINE_NATIVE_ENTRY(VMService_RequestAssets, 0) {
   return Service::RequestAssets();
 }
 
+
+// TODO(25041): When reading, this class copies out the filenames and contents
+// into new buffers. It does this because the lifetime of |bytes| is uncertain.
+// If |bytes| is pinned in memory, then we could instead load up
+// |filenames_| and |contents_| with pointers into |bytes| without making
+// copies.
+class TarArchive {
+ public:
+  TarArchive(uint8_t* bytes, intptr_t bytes_length)
+      : rs_(bytes, bytes_length) {}
+
+  void Read() {
+    while (HasNext()) {
+      char* filename;
+      uint8_t* data;
+      intptr_t data_length;
+      if (Next(&filename, &data, &data_length)) {
+        filenames_.Add(filename);
+        contents_.Add(data);
+        content_lengths_.Add(data_length);
+      }
+    }
+  }
+
+  char* NextFilename() {
+    return filenames_.RemoveLast();
+  }
+
+  uint8_t* NextContent() {
+    return contents_.RemoveLast();
+  }
+
+  intptr_t NextContentLength() {
+    return content_lengths_.RemoveLast();
+  }
+
+  bool HasMore() const {
+    return filenames_.length() > 0;
+  }
+
+  intptr_t Length() const { return filenames_.length(); }
+
+ private:
+  enum TarHeaderFields {
+    kTarHeaderFilenameOffset = 0,
+    kTarHeaderFilenameSize = 100,
+    kTarHeaderSizeOffset = 124,
+    kTarHeaderSizeSize = 12,
+    kTarHeaderTypeOffset = 156,
+    kTarHeaderTypeSize = 1,
+    kTarHeaderSize = 512,
+  };
+
+  enum TarType {
+    kTarAregType = '\0',
+    kTarRegType = '0',
+    kTarLnkType = '1',
+    kTarSymType = '2',
+    kTarChrType = '3',
+    kTarBlkType = '4',
+    kTarDirType = '5',
+    kTarFifoType = '6',
+    kTarContType = '7',
+    kTarXhdType = 'x',
+    kTarXglType = 'g',
+  };
+
+  bool HasNext() const {
+    return !EndOfArchive();
+  }
+
+  bool Next(char** filename, uint8_t** data, intptr_t* data_length) {
+    intptr_t startOfBlock = rs_.Position();
+    *filename = ReadFilename();
+    rs_.SetPosition(startOfBlock + kTarHeaderSizeOffset);
+    intptr_t size = ReadSize();
+    rs_.SetPosition(startOfBlock + kTarHeaderTypeOffset);
+    TarType type = ReadType();
+    SeekToNextBlock(kTarHeaderSize);
+    if ((type != kTarRegType) && (type != kTarAregType)) {
+      SkipContents(size);
+      return false;
+    }
+    ReadContents(data, size);
+    *data_length = size;
+    return true;
+  }
+
+  void SeekToNextBlock(intptr_t blockSize) {
+    intptr_t remainder = blockSize - (rs_.Position() % blockSize);
+    rs_.Advance(remainder);
+  }
+
+  uint8_t PeekByte(intptr_t i) const {
+    return *(rs_.AddressOfCurrentPosition() + i);
+  }
+
+  bool EndOfArchive() const {
+    if (rs_.PendingBytes() < (kTarHeaderSize * 2)) {
+      return true;
+    }
+    for (intptr_t i = 0; i < (kTarHeaderSize * 2); i++) {
+      if (PeekByte(i) != 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  TarType ReadType() {
+    return static_cast<TarType>(ReadStream::Raw<1, uint8_t>::Read(&rs_));
+  }
+
+  void SkipContents(intptr_t size) {
+    rs_.Advance(size);
+    SeekToNextBlock(kTarHeaderSize);
+  }
+
+  intptr_t ReadCString(char** s, intptr_t length) {
+    intptr_t to_read = Utils::Minimum(length, rs_.PendingBytes());
+    char* result = new char[to_read + 1];
+    strncpy(result,
+            reinterpret_cast<const char*>(rs_.AddressOfCurrentPosition()),
+            to_read);
+    result[to_read] = '\0';
+    rs_.SetPosition(rs_.Position() + to_read);
+    *s = result;
+    return to_read;
+  }
+
+  intptr_t ReadSize() {
+    char* octalSize;
+    unsigned int size;
+
+    ReadCString(&octalSize, kTarHeaderSizeSize);
+    int result = sscanf(octalSize, "%o", &size);
+    delete[] octalSize;
+
+    if (result != 1) {
+      return 0;
+    }
+    return size;
+  }
+
+  char* ReadFilename() {
+    char* result;
+    intptr_t result_length = ReadCString(&result, kTarHeaderFilenameSize);
+    if (result[0] == '/') {
+      return result;
+    }
+    char* fixed_result = new char[result_length + 2];  // '/' + '\0'.
+    fixed_result[0] = '/';
+    strncpy(&fixed_result[1], result, result_length);
+    fixed_result[result_length + 1] = '\0';
+    delete[] result;
+    return fixed_result;
+  }
+
+  void ReadContents(uint8_t** data, intptr_t size) {
+    uint8_t* result = new uint8_t[size];
+    rs_.ReadBytes(result, size);
+    SeekToNextBlock(kTarHeaderSize);
+    *data = result;
+  }
+
+  ReadStream rs_;
+  GrowableArray<char*> filenames_;
+  GrowableArray<uint8_t*> contents_;
+  GrowableArray<intptr_t> content_lengths_;
+
+  DISALLOW_COPY_AND_ASSIGN(TarArchive);
+};
+
+
+static void ContentsFinalizer(void* isolate_callback_data,
+                              Dart_WeakPersistentHandle handle,
+                              void* peer) {
+  uint8_t* data = reinterpret_cast<uint8_t*>(peer);
+  delete[] data;
+}
+
+
+static void FilenameFinalizer(void* peer) {
+  char* filename = reinterpret_cast<char*>(peer);
+  delete[] filename;
+}
+
+
+DEFINE_NATIVE_ENTRY(VMService_DecodeAssets, 1) {
+  GET_NON_NULL_NATIVE_ARGUMENT(TypedData, data, arguments->NativeArgAt(0));
+  Api::Scope scope(thread);
+
+  Dart_Handle data_handle = Api::NewHandle(thread->isolate(), data.raw());
+
+  Dart_TypedData_Type typ;
+  void* bytes;
+  intptr_t length;
+  Dart_Handle err = Dart_TypedDataAcquireData(
+      data_handle, &typ, &bytes, &length);
+  ASSERT(!Dart_IsError(err));
+
+  TarArchive archive(reinterpret_cast<uint8_t*>(bytes), length);
+  archive.Read();
+
+  err = Dart_TypedDataReleaseData(data_handle);
+  ASSERT(!Dart_IsError(err));
+
+  intptr_t archive_size = archive.Length();
+
+  const Array& result_list = Array::Handle(thread->zone(),
+    Array::New(2 * archive_size));
+
+  intptr_t idx = 0;
+  while (archive.HasMore()) {
+    char* filename = archive.NextFilename();
+    uint8_t* contents = archive.NextContent();
+    intptr_t contents_length = archive.NextContentLength();
+
+    Dart_Handle dart_filename = Dart_NewExternalLatin1String(
+        reinterpret_cast<uint8_t*>(filename),
+        strlen(filename),
+        filename,
+        FilenameFinalizer);
+    ASSERT(!Dart_IsError(dart_filename));
+
+    Dart_Handle dart_contents = Dart_NewExternalTypedData(
+        Dart_TypedData_kUint8, contents, contents_length);
+    ASSERT(!Dart_IsError(dart_contents));
+    Dart_NewWeakPersistentHandle(
+        dart_contents, contents, contents_length, ContentsFinalizer);
+
+    result_list.SetAt(idx, Api::UnwrapStringHandle(
+        thread->zone(), dart_filename));
+    result_list.SetAt(idx + 1, Api::UnwrapExternalTypedDataHandle(
+        thread->zone(), dart_contents));
+    idx += 2;
+  }
+
+  return result_list.raw();
+}
+
 }  // namespace dart