| // 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. |
| |
| // Pack relative relocations into a more compact form. |
| // |
| // |
| // For relative relocations without addends (32 bit platforms) |
| // ----------------------------------------------------------- |
| // |
| // Applies two packing strategies. The first is run-length encoding, which |
| // turns a large set of relative relocations into a much smaller set |
| // of delta-count pairs, prefixed with a two-word header comprising the |
| // count of pairs and the initial relocation offset. The second is LEB128 |
| // encoding, which compresses the result of run-length encoding. |
| // |
| // Once packed, data is prefixed by an identifier that allows for any later |
| // versioning of packing strategies. |
| // |
| // A complete packed stream of relocations without addends might look |
| // something like: |
| // |
| // "APR1" pairs init_offset count1 delta1 count2 delta2 ... |
| // 41505231 f2b003 b08ac716 e001 04 01 10 ... |
| // |
| // |
| // For relative relocations with addends (64 bit platforms) |
| // -------------------------------------------------------- |
| // |
| // Applies two packing strategies. The first is delta encoding, which |
| // turns a large set of relative relocations into a smaller set |
| // of offset and addend delta pairs, prefixed with a header indicating the |
| // count of pairs. The second is signed LEB128 encoding, which compacts |
| // the result of delta encoding. |
| // |
| // Once packed, data is prefixed by an identifier that allows for any later |
| // versioning of packing strategies. |
| // |
| // A complete packed stream might look something like: |
| // |
| // "APA1" pairs offset_d1 addend_d1 offset_d2 addend_d2 ... |
| // 41505232 f2b018 04 28 08 9f01 ... |
| |
| #ifndef TOOLS_RELOCATION_PACKER_SRC_PACKER_H_ |
| #define TOOLS_RELOCATION_PACKER_SRC_PACKER_H_ |
| |
| #include <stdint.h> |
| #include <vector> |
| |
| #include "elf.h" |
| #include "elf_traits.h" |
| |
| namespace relocation_packer { |
| |
| // A RelocationPacker packs vectors of relative relocations into more |
| // compact forms, and unpacks them to reproduce the pre-packed data. |
| class RelocationPacker { |
| public: |
| // Pack relative relocations into a more compact form. |
| // |relocations| is a vector of relative relocation structs. |
| // |packed| is the vector of packed bytes into which relocations are packed. |
| static void PackRelativeRelocations(const std::vector<ELF::Rel>& relocations, |
| std::vector<uint8_t>* packed); |
| static void PackRelativeRelocations(const std::vector<ELF::Rela>& relocations, |
| std::vector<uint8_t>* packed); |
| |
| // Unpack relative relocations from their more compact form. |
| // |packed| is the vector of packed relocations. |
| // |relocations| is a vector of unpacked relative relocation structs. |
| static void UnpackRelativeRelocations(const std::vector<uint8_t>& packed, |
| std::vector<ELF::Rel>* relocations); |
| static void UnpackRelativeRelocations(const std::vector<uint8_t>& packed, |
| std::vector<ELF::Rela>* relocations); |
| }; |
| |
| } // namespace relocation_packer |
| |
| #endif // TOOLS_RELOCATION_PACKER_SRC_PACKER_H_ |