Import relocation packer from chromium repo
Bug: 18051137
Change-Id: Ia67fa11da8247e3f86f70a8ce99e6695f2c05423
diff --git a/tools/relocation_packer/src/packer.cc b/tools/relocation_packer/src/packer.cc
new file mode 100644
index 0000000..29bec1e
--- /dev/null
+++ b/tools/relocation_packer/src/packer.cc
@@ -0,0 +1,124 @@
+// 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 "packer.h"
+
+#include <vector>
+
+#include "debug.h"
+#include "delta_encoder.h"
+#include "elf_traits.h"
+#include "leb128.h"
+#include "run_length_encoder.h"
+#include "sleb128.h"
+
+namespace relocation_packer {
+
+// Pack relative relocations into a run-length encoded packed
+// representation.
+void RelocationPacker::PackRelativeRelocations(
+ const std::vector<ELF::Rel>& relocations,
+ std::vector<uint8_t>* packed) {
+ // Run-length encode.
+ std::vector<ELF::Xword> packed_words;
+ RelocationRunLengthCodec codec;
+ codec.Encode(relocations, &packed_words);
+
+ // If insufficient data to run-length encode, do nothing.
+ if (packed_words.empty())
+ return;
+
+ // LEB128 encode, with "APR1" prefix.
+ Leb128Encoder encoder;
+ encoder.Enqueue('A');
+ encoder.Enqueue('P');
+ encoder.Enqueue('R');
+ encoder.Enqueue('1');
+ encoder.EnqueueAll(packed_words);
+
+ encoder.GetEncoding(packed);
+
+ // Pad packed to a whole number of words. This padding will decode as
+ // LEB128 zeroes. Run-length decoding ignores it because encoding
+ // embeds the pairs count in the stream itself.
+ while (packed->size() % sizeof(ELF::Word))
+ packed->push_back(0);
+}
+
+// Unpack relative relocations from a run-length encoded packed
+// representation.
+void RelocationPacker::UnpackRelativeRelocations(
+ const std::vector<uint8_t>& packed,
+ std::vector<ELF::Rel>* relocations) {
+ // LEB128 decode, after checking and stripping "APR1" prefix.
+ std::vector<ELF::Xword> packed_words;
+ Leb128Decoder decoder(packed);
+ CHECK(decoder.Dequeue() == 'A' &&
+ decoder.Dequeue() == 'P' &&
+ decoder.Dequeue() == 'R' &&
+ decoder.Dequeue() == '1');
+ decoder.DequeueAll(&packed_words);
+
+ // Run-length decode.
+ RelocationRunLengthCodec codec;
+ codec.Decode(packed_words, relocations);
+}
+
+// Pack relative relocations with addends into a delta encoded packed
+// representation.
+void RelocationPacker::PackRelativeRelocations(
+ const std::vector<ELF::Rela>& relocations,
+ std::vector<uint8_t>* packed) {
+ // Delta encode.
+ std::vector<ELF::Sxword> packed_words;
+ RelocationDeltaCodec codec;
+ codec.Encode(relocations, &packed_words);
+
+ // If insufficient data to delta encode, do nothing.
+ if (packed_words.empty())
+ return;
+
+ // Signed LEB128 encode, with "APA1" prefix. ASCII does not encode as
+ // itself under signed LEB128, so we have to treat it specially.
+ Sleb128Encoder encoder;
+ encoder.EnqueueAll(packed_words);
+ std::vector<uint8_t> encoded;
+ encoder.GetEncoding(&encoded);
+
+ packed->push_back('A');
+ packed->push_back('P');
+ packed->push_back('A');
+ packed->push_back('1');
+ packed->insert(packed->end(), encoded.begin(), encoded.end());
+
+ // Pad packed to a whole number of words. This padding will decode as
+ // signed LEB128 zeroes. Delta decoding ignores it because encoding
+ // embeds the pairs count in the stream itself.
+ while (packed->size() % sizeof(ELF::Word))
+ packed->push_back(0);
+}
+
+// Unpack relative relocations with addends from a delta encoded
+// packed representation.
+void RelocationPacker::UnpackRelativeRelocations(
+ const std::vector<uint8_t>& packed,
+ std::vector<ELF::Rela>* relocations) {
+ // Check "APA1" prefix.
+ CHECK(packed.at(0) == 'A' &&
+ packed.at(1) == 'P' &&
+ packed.at(2) == 'A' &&
+ packed.at(3) == '1');
+
+ // Signed LEB128 decode, after stripping "APA1" prefix.
+ std::vector<ELF::Sxword> packed_words;
+ std::vector<uint8_t> stripped(packed.begin() + 4, packed.end());
+ Sleb128Decoder decoder(stripped);
+ decoder.DequeueAll(&packed_words);
+
+ // Delta decode.
+ RelocationDeltaCodec codec;
+ codec.Decode(packed_words, relocations);
+}
+
+} // namespace relocation_packer