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1 | // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
11 | #[inline] | |
12 | pub fn write_to_vec(vec: &mut Vec<u8>, position: &mut usize, byte: u8) { | |
13 | if *position == vec.len() { | |
14 | vec.push(byte); | |
15 | } else { | |
16 | vec[*position] = byte; | |
17 | } | |
18 | ||
19 | *position += 1; | |
20 | } | |
21 | ||
22 | pub fn write_unsigned_leb128(out: &mut Vec<u8>, start_position: usize, mut value: u64) -> usize { | |
23 | let mut position = start_position; | |
24 | loop { | |
25 | let mut byte = (value & 0x7F) as u8; | |
26 | value >>= 7; | |
27 | if value != 0 { | |
28 | byte |= 0x80; | |
29 | } | |
30 | ||
31 | write_to_vec(out, &mut position, byte); | |
32 | ||
33 | if value == 0 { | |
34 | break; | |
35 | } | |
36 | } | |
37 | ||
38 | return position - start_position; | |
39 | } | |
40 | ||
c30ab7b3 | 41 | #[inline] |
9cc50fc6 SL |
42 | pub fn read_unsigned_leb128(data: &[u8], start_position: usize) -> (u64, usize) { |
43 | let mut result = 0; | |
44 | let mut shift = 0; | |
45 | let mut position = start_position; | |
46 | loop { | |
47 | let byte = data[position]; | |
48 | position += 1; | |
49 | result |= ((byte & 0x7F) as u64) << shift; | |
50 | if (byte & 0x80) == 0 { | |
51 | break; | |
52 | } | |
53 | shift += 7; | |
54 | } | |
55 | ||
56 | (result, position - start_position) | |
57 | } | |
58 | ||
59 | ||
60 | pub fn write_signed_leb128(out: &mut Vec<u8>, start_position: usize, mut value: i64) -> usize { | |
61 | let mut position = start_position; | |
62 | ||
63 | loop { | |
64 | let mut byte = (value as u8) & 0x7f; | |
65 | value >>= 7; | |
66 | let more = !((((value == 0) && ((byte & 0x40) == 0)) || | |
67 | ((value == -1) && ((byte & 0x40) != 0)))); | |
68 | if more { | |
69 | byte |= 0x80; // Mark this byte to show that more bytes will follow. | |
70 | } | |
71 | ||
72 | write_to_vec(out, &mut position, byte); | |
73 | ||
74 | if !more { | |
75 | break; | |
76 | } | |
77 | } | |
78 | ||
79 | return position - start_position; | |
80 | } | |
81 | ||
c30ab7b3 | 82 | #[inline] |
9cc50fc6 SL |
83 | pub fn read_signed_leb128(data: &[u8], start_position: usize) -> (i64, usize) { |
84 | let mut result = 0; | |
85 | let mut shift = 0; | |
86 | let mut position = start_position; | |
87 | let mut byte; | |
88 | ||
89 | loop { | |
90 | byte = data[position]; | |
91 | position += 1; | |
92 | result |= ((byte & 0x7F) as i64) << shift; | |
93 | shift += 7; | |
94 | ||
95 | if (byte & 0x80) == 0 { | |
96 | break; | |
97 | } | |
98 | } | |
99 | ||
100 | if (shift < 64) && ((byte & 0x40) != 0) { | |
101 | // sign extend | |
102 | result |= -(1i64 << shift); | |
103 | } | |
104 | ||
105 | (result, position - start_position) | |
106 | } | |
107 | ||
108 | #[test] | |
109 | fn test_unsigned_leb128() { | |
110 | let mut stream = Vec::with_capacity(10000); | |
111 | ||
112 | for x in 0..62 { | |
113 | let pos = stream.len(); | |
114 | let bytes_written = write_unsigned_leb128(&mut stream, pos, 3 << x); | |
115 | assert_eq!(stream.len(), pos + bytes_written); | |
116 | } | |
117 | ||
118 | let mut position = 0; | |
119 | for x in 0..62 { | |
120 | let expected = 3 << x; | |
121 | let (actual, bytes_read) = read_unsigned_leb128(&stream, position); | |
122 | assert_eq!(expected, actual); | |
123 | position += bytes_read; | |
124 | } | |
125 | assert_eq!(stream.len(), position); | |
126 | } | |
127 | ||
128 | #[test] | |
129 | fn test_signed_leb128() { | |
130 | let mut values = Vec::new(); | |
131 | ||
132 | let mut i = -500; | |
133 | while i < 500 { | |
134 | values.push(i * 123457i64); | |
135 | i += 1; | |
136 | } | |
137 | ||
138 | let mut stream = Vec::new(); | |
139 | ||
140 | for &x in &values { | |
141 | let pos = stream.len(); | |
142 | let bytes_written = write_signed_leb128(&mut stream, pos, x); | |
143 | assert_eq!(stream.len(), pos + bytes_written); | |
144 | } | |
145 | ||
146 | let mut pos = 0; | |
147 | for &x in &values { | |
148 | let (value, bytes_read) = read_signed_leb128(&mut stream, pos); | |
149 | pos += bytes_read; | |
150 | assert_eq!(x, value); | |
151 | } | |
152 | assert_eq!(pos, stream.len()); | |
153 | } |