1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
6 #define V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
7 
8 #include "src/base/logging.h"
9 #include "src/utils.h"
10 
11 namespace v8 {
12 namespace internal {
13 
14 
15 /**
16  * Source to read snapshot and builtins files from.
17  *
18  * Note: Memory ownership remains with callee.
19  */
20 class SnapshotByteSource final {
21  public:
SnapshotByteSource(const char * data,int length)22   SnapshotByteSource(const char* data, int length)
23       : data_(reinterpret_cast<const byte*>(data)),
24         length_(length),
25         position_(0) {}
26 
SnapshotByteSource(Vector<const byte> payload)27   explicit SnapshotByteSource(Vector<const byte> payload)
28       : data_(payload.start()), length_(payload.length()), position_(0) {}
29 
~SnapshotByteSource()30   ~SnapshotByteSource() {}
31 
HasMore()32   bool HasMore() { return position_ < length_; }
33 
Get()34   byte Get() {
35     DCHECK(position_ < length_);
36     return data_[position_++];
37   }
38 
Advance(int by)39   void Advance(int by) { position_ += by; }
40 
41   void CopyRaw(byte* to, int number_of_bytes);
42 
GetInt()43   inline int GetInt() {
44     // This way of decoding variable-length encoded integers does not
45     // suffer from branch mispredictions.
46     DCHECK(position_ + 3 < length_);
47     uint32_t answer = data_[position_];
48     answer |= data_[position_ + 1] << 8;
49     answer |= data_[position_ + 2] << 16;
50     answer |= data_[position_ + 3] << 24;
51     int bytes = (answer & 3) + 1;
52     Advance(bytes);
53     uint32_t mask = 0xffffffffu;
54     mask >>= 32 - (bytes << 3);
55     answer &= mask;
56     answer >>= 2;
57     return answer;
58   }
59 
60   // Returns length.
61   int GetBlob(const byte** data);
62 
position()63   int position() { return position_; }
64 
65  private:
66   const byte* data_;
67   int length_;
68   int position_;
69 
70   DISALLOW_COPY_AND_ASSIGN(SnapshotByteSource);
71 };
72 
73 
74 /**
75  * Sink to write snapshot files to.
76  *
77  * Subclasses must implement actual storage or i/o.
78  */
79 class SnapshotByteSink {
80  public:
SnapshotByteSink()81   SnapshotByteSink() {}
SnapshotByteSink(int initial_size)82   explicit SnapshotByteSink(int initial_size) : data_(initial_size) {}
83 
~SnapshotByteSink()84   ~SnapshotByteSink() {}
85 
Put(byte b,const char * description)86   void Put(byte b, const char* description) { data_.Add(b); }
87 
PutSection(int b,const char * description)88   void PutSection(int b, const char* description) {
89     DCHECK_LE(b, kMaxUInt8);
90     Put(static_cast<byte>(b), description);
91   }
92 
93   void PutInt(uintptr_t integer, const char* description);
94   void PutRaw(const byte* data, int number_of_bytes, const char* description);
Position()95   int Position() { return data_.length(); }
96 
data()97   const List<byte>& data() const { return data_; }
98 
99  private:
100   List<byte> data_;
101 };
102 
103 }  // namespace internal
104 }  // namespace v8
105 
106 #endif  // V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
107