Index: tools/relocation_packer/src/delta_encoder.cc |
diff --git a/tools/relocation_packer/src/delta_encoder.cc b/tools/relocation_packer/src/delta_encoder.cc |
new file mode 100644 |
index 0000000000000000000000000000000000000000..69cc91a51174953203d71d96f62af4cf72ce0e0d |
--- /dev/null |
+++ b/tools/relocation_packer/src/delta_encoder.cc |
@@ -0,0 +1,72 @@ |
+// Copyright 2014 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#include "delta_encoder.h" |
+ |
+#include <vector> |
+ |
+#include "debug.h" |
+#include "elf_traits.h" |
+ |
+namespace relocation_packer { |
+ |
+// Encode relative relocations with addends into a delta encoded (packed) |
+// representation. Represented as simple r_offset and r_addend delta pairs, |
+// with an implicit neutral element at the start. |
+void RelocationDeltaCodec::Encode(const std::vector<ELF::Rela>& relocations, |
+ std::vector<ELF::Sxword>* packed) { |
+ // One relocation is sufficient for delta encoding. |
+ if (relocations.size() < 1) |
+ return; |
+ |
+ // Start with the element count, then append the delta pairs. |
+ packed->push_back(relocations.size()); |
+ |
+ ELF::Addr offset = 0; |
+ ELF::Sxword addend = 0; |
+ |
+ for (size_t i = 0; i < relocations.size(); ++i) { |
+ const ELF::Rela* relocation = &relocations[i]; |
+ CHECK(ELF_R_TYPE(relocation->r_info) == ELF::kRelativeRelocationCode); |
+ |
+ packed->push_back(relocation->r_offset - offset); |
+ offset = relocation->r_offset; |
+ packed->push_back(relocation->r_addend - addend); |
+ addend = relocation->r_addend; |
+ } |
+} |
+ |
+// Decode relative relocations with addends from a delta encoded (packed) |
+// representation. |
+void RelocationDeltaCodec::Decode(const std::vector<ELF::Sxword>& packed, |
+ std::vector<ELF::Rela>* relocations) { |
+ // We need at least one packed pair after the packed pair count to be |
+ // able to unpack. |
+ if (packed.size() < 3) |
+ return; |
+ |
+ // Ensure that the packed data offers enough pairs. There may be zero |
+ // padding on it that we ignore. |
+ CHECK(static_cast<size_t>(packed[0]) <= (packed.size() - 1) >> 1); |
+ |
+ ELF::Addr offset = 0; |
+ ELF::Sxword addend = 0; |
+ |
+ // The first packed vector element is the pairs count. Start uncondensing |
+ // pairs at the second, and finish at the end of the pairs data. |
+ const size_t pairs_count = packed[0]; |
+ for (size_t i = 1; i < 1 + (pairs_count << 1); i += 2) { |
+ offset += packed[i]; |
+ addend += packed[i + 1]; |
+ |
+ // Generate a relocation for this offset and addend pair. |
+ ELF::Rela relocation; |
+ relocation.r_offset = offset; |
+ relocation.r_info = ELF_R_INFO(0, ELF::kRelativeRelocationCode); |
+ relocation.r_addend = addend; |
+ relocations->push_back(relocation); |
+ } |
+} |
+ |
+} // namespace relocation_packer |