Always use signed leb128 decoder

  Relocation packer no longer encodes relocation tables
  using unsigned leb128: https://android-review.googlesource.com/147745

Bug: http://b/18051137
Change-Id: I620b7188e5f3dd9d5123431aa1fc7feca76be607

1 files changed, 58 insertions, 0 deletions

diff --git a/linker/linker_sleb128.h b/linker/linker_sleb128.h
new file mode 100644
index 0000000..a34916f
--- /dev/null
+++ b/linker/linker_sleb128.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LINKER_SLEB128_H
+#define _LINKER_SLEB128_H
+
+#include <stdint.h>
+
+// Helper classes for decoding LEB128, used in packed relocation data.
+// http://en.wikipedia.org/wiki/LEB128
+
+class sleb128_decoder {
+ public:
+  sleb128_decoder(const uint8_t* buffer, size_t count)
+      : current_(buffer), end_(buffer+count) { }
+
+  size_t pop_front() {
+    size_t value = 0;
+    static const size_t size = CHAR_BIT * sizeof(value);
+
+    size_t shift = 0;
+    uint8_t byte;
+
+    do {
+      if (current_ >= end_) {
+        __libc_fatal("sleb128_decoder ran out of bounds");
+      }
+      byte = *current_++;
+      value |= (static_cast<size_t>(byte & 127) << shift);
+      shift += 7;
+    } while (byte & 128);
+
+    if (shift < size && (byte & 64)) {
+      value |= -(static_cast<size_t>(1) << shift);
+    }
+
+    return value;
+  }
+
+ private:
+  const uint8_t* current_;
+  const uint8_t* const end_;
+};
+
+#endif // __LINKER_SLEB128_H