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Commit | Line | Data |
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c1a9b12d | 1 | //! Utilities for parsing DWARF-encoded data streams. |
9fa01778 | 2 | //! See <http://www.dwarfstd.org>, |
c1a9b12d SL |
3 | //! DWARF-4 standard, Section 7 - "Data Representation" |
4 | ||
5 | // This module is used only by x86_64-pc-windows-gnu for now, but we | |
6 | // are compiling it everywhere to avoid regressions. | |
7 | #![allow(unused)] | |
8 | ||
416331ca XL |
9 | #[cfg(test)] |
10 | mod tests; | |
11 | ||
c1a9b12d SL |
12 | pub mod eh; |
13 | ||
c1a9b12d SL |
14 | use core::mem; |
15 | ||
16 | pub struct DwarfReader { | |
3157f602 | 17 | pub ptr: *const u8, |
c1a9b12d SL |
18 | } |
19 | ||
dfeec247 | 20 | #[repr(C, packed)] |
c1a9b12d SL |
21 | struct Unaligned<T>(T); |
22 | ||
23 | impl DwarfReader { | |
3157f602 | 24 | pub fn new(ptr: *const u8) -> DwarfReader { |
a1dfa0c6 | 25 | DwarfReader { ptr } |
c1a9b12d SL |
26 | } |
27 | ||
0731742a | 28 | // DWARF streams are packed, so e.g., a u32 would not necessarily be aligned |
c1a9b12d SL |
29 | // on a 4-byte boundary. This may cause problems on platforms with strict |
30 | // alignment requirements. By wrapping data in a "packed" struct, we are | |
31 | // telling the backend to generate "misalignment-safe" code. | |
3157f602 | 32 | pub unsafe fn read<T: Copy>(&mut self) -> T { |
c1a9b12d | 33 | let Unaligned(result) = *(self.ptr as *const Unaligned<T>); |
b7449926 | 34 | self.ptr = self.ptr.add(mem::size_of::<T>()); |
c1a9b12d SL |
35 | result |
36 | } | |
37 | ||
38 | // ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable | |
39 | // Length Data". | |
40 | pub unsafe fn read_uleb128(&mut self) -> u64 { | |
3157f602 XL |
41 | let mut shift: usize = 0; |
42 | let mut result: u64 = 0; | |
43 | let mut byte: u8; | |
c1a9b12d SL |
44 | loop { |
45 | byte = self.read::<u8>(); | |
46 | result |= ((byte & 0x7F) as u64) << shift; | |
47 | shift += 7; | |
48 | if byte & 0x80 == 0 { | |
49 | break; | |
50 | } | |
51 | } | |
52 | result | |
53 | } | |
54 | ||
55 | pub unsafe fn read_sleb128(&mut self) -> i64 { | |
1b1a35ee | 56 | let mut shift: u32 = 0; |
3157f602 XL |
57 | let mut result: u64 = 0; |
58 | let mut byte: u8; | |
c1a9b12d SL |
59 | loop { |
60 | byte = self.read::<u8>(); | |
61 | result |= ((byte & 0x7F) as u64) << shift; | |
62 | shift += 7; | |
63 | if byte & 0x80 == 0 { | |
64 | break; | |
65 | } | |
66 | } | |
67 | // sign-extend | |
1b1a35ee | 68 | if shift < u64::BITS && (byte & 0x40) != 0 { |
c1a9b12d SL |
69 | result |= (!0 as u64) << shift; |
70 | } | |
71 | result as i64 | |
72 | } | |
73 | } |