1 //===-- stack_trace_compressor.h --------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef GWP_ASAN_STACK_TRACE_COMPRESSOR_
10 #define GWP_ASAN_STACK_TRACE_COMPRESSOR_
11 
12 #include <stddef.h>
13 #include <stdint.h>
14 
15 // These functions implement stack frame compression and decompression. We store
16 // the zig-zag encoded pointer difference between frame[i] and frame[i - 1] as
17 // a variable-length integer. This can reduce the memory overhead of stack
18 // traces by 50%.
19 
20 namespace gwp_asan {
21 namespace compression {
22 
23 // For the stack trace in `Unpacked` with length `UnpackedSize`, pack it into
24 // the buffer `Packed` maximum length `PackedMaxSize`. The return value is the
25 // number of bytes that were written to the output buffer.
26 size_t pack(const uintptr_t *Unpacked, size_t UnpackedSize, uint8_t *Packed,
27             size_t PackedMaxSize);
28 
29 // From the packed stack trace in `Packed` of length `PackedSize`, write the
30 // unpacked stack trace of maximum length `UnpackedMaxSize` into `Unpacked`.
31 // Returns the number of full entries unpacked, or zero on error.
32 size_t unpack(const uint8_t *Packed, size_t PackedSize, uintptr_t *Unpacked,
33               size_t UnpackedMaxSize);
34 
35 } // namespace compression
36 } // namespace gwp_asan
37 
38 #endif // GWP_ASAN_STACK_TRACE_COMPRESSOR_
39