1 // CodeStream.cpp A class which allows bounds-checked reading from a char array
2 //
3 // Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012
4 // Free Software Foundation, Inc.
5 //
6 // This program is free software; you can redistribute it and/or modify
7 // it under the terms of the GNU General Public License as published by
8 // the Free Software Foundation; either version 3 of the License, or
9 // (at your option) any later version.
10 //
11 // This program is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 //
16 // You should have received a copy of the GNU General Public License
17 // along with this program; if not, write to the Free Software
18 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
19
20 #include "CodeStream.h"
21 #include <iostream>
22
23 namespace gnash {
24
25 /// Read a variable length encoded 32 bit unsigned integer
26 std::uint32_t
read_V32()27 CodeStream::read_V32()
28 {
29 char data;
30
31 read(&data,1);
32 std::uint32_t result = data;
33 if (!(result & 0x00000080)) return result;
34
35 read(&data,1);
36 result = (result & 0x0000007F) | data << 7;
37 if (!(result & 0x00004000)) return result;
38
39 read(&data,1);
40 result = (result & 0x00003FFF) | data << 14;
41 if (!(result & 0x00200000)) return result;
42
43 read(&data,1);
44 result = (result & 0x001FFFFF) | data << 21;
45 if (!(result & 0x10000000)) return result;
46
47 read(&data,1);
48 return (result & 0x0FFFFFFF) | data << 28;
49
50 }
51
52 /// Read an opcode for ActionScript 3
53 std::uint8_t
read_as3op()54 CodeStream::read_as3op()
55 {
56 char data;
57 read(&data,1);
58 if(eof()){
59 return 0;
60 }
61 else{
62 return static_cast<std::uint8_t> (data);
63 }
64 }
65
66 /// Change the current position by a relative value.
67 void
seekBy(int change)68 CodeStream::seekBy(int change)
69 {
70 seekg(change,ios_base::cur);
71 }
72
73 /// Set the current position to an absolute value (relative to the start)
74 void
seekTo(unsigned int set)75 CodeStream::seekTo(unsigned int set)
76 {
77 seekg(set);
78 }
79
80 //TODO: Is there a better way to read a 24 bit signed int?
81 std::int32_t
read_S24()82 CodeStream::read_S24()
83 {
84 char buffer[3];
85 read(buffer,3);
86 uint32_t result = buffer[0] & 0xFF;
87 result |= buffer[1] & 0xFF << 8;
88 result |= buffer[2] & 0xFF << 16;
89 if (result & (1 << 23)) {
90 result |= -1 << 24;
91 }
92
93 return static_cast<std::int32_t>(result);
94 }
95
96 /// Read a signed 8-bit character.
97 int8_t
read_s8()98 CodeStream::read_s8()
99 {
100 char data;
101 read(&data,1);
102 return static_cast<int8_t> (data);
103 }
104
105 /// Read an unsigned 8-bit character.
106 std::uint8_t
read_u8()107 CodeStream::read_u8()
108 {
109 char data;
110 read(&data,1);
111 return static_cast<std::uint8_t> (data);
112 }
113
114 /// Same as read_V32(), but doesn't bother with the arithmetic for
115 /// calculating the value.
116 void
skip_V32()117 CodeStream::skip_V32()
118 {
119 // shortcut evalution is mandated as standard.
120 //TODO: Make this more efficient.
121 // if ((*mCurrent++ & 0x80) && (*mCurrent++ & 0x80) && (*mCurrent++ &0x80)
122 // && (*mCurrent++ & 0x80) && (*mCurrent++ & 0x80)){
123 // return;
124 // }
125 read_V32();
126 return;
127
128 }
129
130 } // namespace gnash
131
132