1 files changed, 107 insertions, 0 deletions
diff --git a/Source/WTF/wtf/LEBDecoder.h b/Source/WTF/wtf/LEBDecoder.h
new file mode 100644
index 000000000..e14a52796
--- /dev/null
+++ b/Source/WTF/wtf/LEBDecoder.h
@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2016 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include "Compiler.h"
+#include <algorithm>
+
+// This file contains a bunch of helper functions for decoding LEB numbers.
+// See https://en.wikipedia.org/wiki/LEB128 for more information about the
+// LEB format.
+
+namespace WTF { namespace LEBDecoder {
+
+template<typename T>
+inline bool WARN_UNUSED_RETURN decodeUInt(const uint8_t* bytes, size_t length, size_t& offset, T& result)
+{
+    const size_t numBits = sizeof(T) * CHAR_BIT;
+    const size_t maxByteLength = (numBits - 1) / 7 + 1; // numBits / 7 rounding up.
+    if (length <= offset)
+        return false;
+    result = 0;
+    unsigned shift = 0;
+    size_t last = std::min(maxByteLength, length - offset) - 1;
+    for (unsigned i = 0; true; ++i) {
+        uint8_t byte = bytes[offset++];
+        result |= static_cast<T>(byte & 0x7f) << shift;
+        shift += 7;
+        if (!(byte & 0x80))
+            return true;
+        if (i == last)
+            return false;
+    }
+    RELEASE_ASSERT_NOT_REACHED();
+    return true;
+}
+
+template<typename T>
+inline bool WARN_UNUSED_RETURN decodeInt(const uint8_t* bytes, size_t length, size_t& offset, T& result)
+{
+    const size_t numBits = sizeof(T) * CHAR_BIT;
+    const size_t maxByteLength = (numBits - 1) / 7 + 1; // numBits / 7 rounding up.
+    if (length <= offset)
+        return false;
+    result = 0;
+    unsigned shift = 0;
+    size_t last = std::min(maxByteLength, length - offset) - 1;
+    uint8_t byte;
+    for (unsigned i = 0; true; ++i) {
+        byte = bytes[offset++];
+        result |= static_cast<T>(byte & 0x7f) << shift;
+        shift += 7;
+        if (!(byte & 0x80))
+            break;
+        if (i == last)
+            return false;
+    }
+
+    using UnsignedT = typename std::make_unsigned<T>::type;
+    if (shift < numBits && (byte & 0x40))
+        result = static_cast<T>(static_cast<UnsignedT>(result) | (static_cast<UnsignedT>(-1) << shift));
+    return true;
+}
+
+inline bool WARN_UNUSED_RETURN decodeUInt32(const uint8_t* bytes, size_t length, size_t& offset, uint32_t& result)
+{
+    return decodeUInt<uint32_t>(bytes, length, offset, result);
+}
+
+inline bool WARN_UNUSED_RETURN decodeUInt64(const uint8_t* bytes, size_t length, size_t& offset, uint64_t& result)
+{
+    return decodeUInt<uint64_t>(bytes, length, offset, result);
+}
+
+inline bool WARN_UNUSED_RETURN decodeInt32(const uint8_t* bytes, size_t length, size_t& offset, int32_t& result)
+{
+    return decodeInt<int32_t>(bytes, length, offset, result);
+}
+
+inline bool WARN_UNUSED_RETURN decodeInt64(const uint8_t* bytes, size_t length, size_t& offset, int64_t& result)
+{
+    return decodeInt<int64_t>(bytes, length, offset, result);
+}
+
+} } // WTF::LEBDecoder