1 // Copyright 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.
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.
11 //! Utilities for parsing DWARF-encoded data streams.
12 //! See http://www.dwarfstd.org,
13 //! DWARF-4 standard, Section 7 - "Data Representation"
15 // This module is used only by x86_64-pc-windows-gnu for now, but we
16 // are compiling it everywhere to avoid regressions.
23 pub struct DwarfReader {
28 struct Unaligned<T>(T);
31 pub fn new(ptr: *const u8) -> DwarfReader {
35 // DWARF streams are packed, so e.g. a u32 would not necessarily be aligned
36 // on a 4-byte boundary. This may cause problems on platforms with strict
37 // alignment requirements. By wrapping data in a "packed" struct, we are
38 // telling the backend to generate "misalignment-safe" code.
39 pub unsafe fn read<T: Copy>(&mut self) -> T {
40 let Unaligned(result) = *(self.ptr as *const Unaligned<T>);
41 self.ptr = self.ptr.add(mem::size_of::<T>());
45 // ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable
47 pub unsafe fn read_uleb128(&mut self) -> u64 {
48 let mut shift: usize = 0;
49 let mut result: u64 = 0;
52 byte = self.read::<u8>();
53 result |= ((byte & 0x7F) as u64) << shift;
62 pub unsafe fn read_sleb128(&mut self) -> i64 {
63 let mut shift: usize = 0;
64 let mut result: u64 = 0;
67 byte = self.read::<u8>();
68 result |= ((byte & 0x7F) as u64) << shift;
75 if shift < 8 * mem::size_of::<u64>() && (byte & 0x40) != 0 {
76 result |= (!0 as u64) << shift;
84 let encoded: &[u8] = &[1, 2, 3, 4, 5, 6, 7, 0xE5, 0x8E, 0x26, 0x9B, 0xF1, 0x59, 0xFF, 0xFF];
86 let mut reader = DwarfReader::new(encoded.as_ptr());
89 assert!(reader.read::<u8>() == u8::to_be(1u8));
90 assert!(reader.read::<u16>() == u16::to_be(0x0203));
91 assert!(reader.read::<u32>() == u32::to_be(0x04050607));
93 assert!(reader.read_uleb128() == 624485);
94 assert!(reader.read_sleb128() == -624485);
96 assert!(reader.read::<i8>() == i8::to_be(-1));