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//! Utilities for parsing DWARF-encoded data streams.
//! See <http://www.dwarfstd.org>,
//! DWARF-4 standard, Section 7 - "Data Representation"
// This module is used only by x86_64-pc-windows-gnu for now, but we
// are compiling it everywhere to avoid regressions.
#![allow(unused)]
#[cfg(test)]
mod tests;
pub mod eh;
use core::mem;
pub struct DwarfReader {
pub ptr: *const u8,
}
#[repr(C, packed)]
struct Unaligned<T>(T);
impl DwarfReader {
pub fn new(ptr: *const u8) -> DwarfReader {
DwarfReader { ptr }
}
// DWARF streams are packed, so e.g., a u32 would not necessarily be aligned
// on a 4-byte boundary. This may cause problems on platforms with strict
// alignment requirements. By wrapping data in a "packed" struct, we are
// telling the backend to generate "misalignment-safe" code.
pub unsafe fn read<T: Copy>(&mut self) -> T {
let Unaligned(result) = *(self.ptr as *const Unaligned<T>);
self.ptr = self.ptr.add(mem::size_of::<T>());
result
}
// ULEB128 and SLEB128 encodings are defined in Section 7.6 - "Variable
// Length Data".
pub unsafe fn read_uleb128(&mut self) -> u64 {
let mut shift: usize = 0;
let mut result: u64 = 0;
let mut byte: u8;
loop {
byte = self.read::<u8>();
result |= ((byte & 0x7F) as u64) << shift;
shift += 7;
if byte & 0x80 == 0 {
break;
}
}
result
}
pub unsafe fn read_sleb128(&mut self) -> i64 {
let mut shift: u32 = 0;
let mut result: u64 = 0;
let mut byte: u8;
loop {
byte = self.read::<u8>();
result |= ((byte & 0x7F) as u64) << shift;
shift += 7;
if byte & 0x80 == 0 {
break;
}
}
// sign-extend
if shift < u64::BITS && (byte & 0x40) != 0 {
result |= (!0 as u64) << shift;
}
result as i64
}
}
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