1 //! Utilities for parsing DWARF-encoded data streams.
2 //! See http://www.dwarfstd.org,
3 //! DWARF-4 standard, Section 7 - "Data Representation"
5 // This module is used only by x86_64-pc-windows-gnu for now, but we
6 // are compiling it everywhere to avoid regressions.
13 pub struct DwarfReader {
18 struct Unaligned<T>(T);
21 pub fn new(ptr: *const u8) -> DwarfReader {
25 // DWARF streams are packed, so e.g., a u32 would not necessarily be aligned
26 // on a 4-byte boundary. This may cause problems on platforms with strict
27 // alignment requirements. By wrapping data in a "packed" struct, we are
28 // telling the backend to generate "misalignment-safe" code.
29 pub unsafe fn read<T: Copy>(&mut self) -> T {
30 let Unaligned(result) = *(self.ptr as *const Unaligned<T>);
31 self.ptr = self.ptr.add(mem::size_of::<T>());
35 // ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable
37 pub unsafe fn read_uleb128(&mut self) -> u64 {
38 let mut shift: usize = 0;
39 let mut result: u64 = 0;
42 byte = self.read::<u8>();
43 result |= ((byte & 0x7F) as u64) << shift;
52 pub unsafe fn read_sleb128(&mut self) -> i64 {
53 let mut shift: usize = 0;
54 let mut result: u64 = 0;
57 byte = self.read::<u8>();
58 result |= ((byte & 0x7F) as u64) << shift;
65 if shift < 8 * mem::size_of::<u64>() && (byte & 0x40) != 0 {
66 result |= (!0 as u64) << shift;
74 let encoded: &[u8] = &[1, 2, 3, 4, 5, 6, 7, 0xE5, 0x8E, 0x26, 0x9B, 0xF1, 0x59, 0xFF, 0xFF];
76 let mut reader = DwarfReader::new(encoded.as_ptr());
79 assert!(reader.read::<u8>() == u8::to_be(1u8));
80 assert!(reader.read::<u16>() == u16::to_be(0x0203));
81 assert!(reader.read::<u32>() == u32::to_be(0x04050607));
83 assert!(reader.read_uleb128() == 624485);
84 assert!(reader.read_sleb128() == -624485);
86 assert!(reader.read::<i8>() == i8::to_be(-1));