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eb9610a102
closes #13 This prevents accidentally writing when reading is intended, and vice versa. It also allows specialising the APIs and constructors.
42 lines
1.7 KiB
PHP
42 lines
1.7 KiB
PHP
--TEST--
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writeUnsignedVar(Int|Long)() must terminate when given a negative number
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--DESCRIPTION--
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Due to the use of arithmetic right-shift for extracting bits from a number for varint encoding (PHP has no unsigned
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types, nor a logical right-shift operator), BinaryUtils in the early days of varints ran into a bug where encoding
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a negative varint as unsigned would never terminate, because -1 >> anything = -1.
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This should not be an issue in ext-encoding because of the exclusive use of unsigned integer types for the actual
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encoding (meaning that the compiler always generates logical right-shift instructions), but this needs to be tested
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anyway.
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In such cases, we expect that the type will be truncated to the appropriate size, and the remainder of the bits
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treated as unsigned. This means that -1 written as a varint32 will be interpreted as 4,294,967,295 and so on.
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In the varint64 case we would not truncate, but still interpret the number as its unsigned counterpart during writing.
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However, during decoding this would lead to the MSB being interpreted as a sign bit, which also happens for actual
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unsigned numbers. Due to the lack of unsigned types in PHP, there isn't much that can be done about this.
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--EXTENSIONS--
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encoding
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--FILE--
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<?php
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use pmmp\encoding\ByteBufferWriter;
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use pmmp\encoding\ByteBufferReader;
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use pmmp\encoding\VarInt;
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$buffer = new ByteBufferWriter("");
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VarInt::writeUnsignedInt($buffer, -1);
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$reader = new ByteBufferReader($buffer->getData());
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var_dump(VarInt::readUnsignedInt($reader));
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$buffer->setOffset(0);
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VarInt::writeUnsignedLong($buffer, -1);
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$reader = new ByteBufferReader($buffer->getData());
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var_dump(VarInt::readUnsignedLong($reader));
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?>
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--EXPECT--
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int(4294967295)
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int(-1)
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