[standalone] Automatically decompress gzip'd resources, including sources and script snapshots.

runtime/bin/dfe.cc

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/dfe.h"
 #include "bin/dartutils.h"
 #include "bin/error_exit.h"
 #include "bin/file.h"
 
 #include "vm/kernel.h"
@@ skipping 128 matching lines @@
   *kernel_ir_size = -1;
   void* script_file = DartUtils::OpenFile(script_uri, false);
   if (script_file != NULL) {
     const uint8_t* buffer = NULL;
     DartUtils::ReadFile(&buffer, kernel_ir_size, script_file);
     DartUtils::CloseFile(script_file);
     if (*kernel_ir_size > 0 && buffer != NULL) {
       // We need a temporary variable because SniffForMagicNumber modifies the
       // buffer pointer to skip snapshot magic number.
       const uint8_t* temp = buffer;
-      if (DartUtils::SniffForMagicNumber(&temp, kernel_ir_size) !=
+      if (DartUtils::SniffForMagicNumber(temp, *kernel_ir_size) !=

[siva, 2017/08/04 17:11:29]

Now that SniffMagicNumber does not modify the buffer pointer, the command above
can be removed and the cal could just be
if (DartUtils::SniffForMagicNumber(buffer, *kernel_ir_size)

Another aspect I don't understand is this call updates the kernel_ir_size
variable which is updated back to the caller but the magic number is not skipped
so I am not sure how the kernel reader does not run into an issue because of
that.

[rmacnak, 2017/08/07 18:18:57]

Done.
The kernel reader expects to see its magic number, unlike the snapshot reader
that expect the embedder to strip it because the embedder was the one who added
it in the first place.

           DartUtils::kKernelMagicNumber) {
         free(const_cast<uint8_t*>(buffer));
         *kernel_ir = NULL;
         *kernel_ir_size = -1;
         return false;
       } else {
         // Do not free buffer if this is a kernel file - kernel_file will be
         // backed by the same memory as the buffer and caller will own it.
         // Caller is responsible for freeing the buffer when this function
         // returns true.
         *kernel_ir = buffer;
         return true;
       }
     }
   }
   return false;
 }
 
 }  // namespace bin
 }  // namespace dart