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88 lines
2.6 KiB
88 lines
2.6 KiB
// Copyright 2017-2018 DERO Project. All rights reserved.
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// Use of this source code in any form is governed by RESEARCH license.
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// license can be found in the LICENSE file.
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// GPG: 0F39 E425 8C65 3947 702A 8234 08B2 0360 A03A 9DE8
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//
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package p2p
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import "encoding/binary"
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// boost varint can encode upto 1 gb size
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func Decode_Boost_Varint(buf []byte) (uint64, int) {
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first_byte := buf[0]
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num_bytes := first_byte & 3 // lower 2 bits contain bytes count, which follow current byte
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// grab full 4 bytes
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value := binary.LittleEndian.Uint32(buf)
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switch num_bytes {
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case 0:
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value &= 0xff
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case 1:
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value &= 0xffff
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case 2:
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value &= 0xffffff
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case 3:
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value &= 0xffffffff
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}
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value = value >> 2 // discard lower 2 bits
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if num_bytes == 2 { // holy hell, let god have mercy on this boost parser
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num_bytes = 3
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}
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return uint64(value), int(num_bytes + 1)
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}
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// this function encodes Value to bu in boost varint style
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func Encode_Boost_Varint(buf []byte, Value uint64) int {
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bytes_required := byte(0)
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switch {
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case Value > 1073741823:
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panic("Exceeded boost varint capacity while encoding\n") // (2^30) -1
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case Value > 4194303:
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bytes_required = 4
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case Value > 16383:
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bytes_required = 3
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case Value > 63:
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bytes_required = 2
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default:
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bytes_required = 1
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}
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first_byte := (Value % 64) << 2
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Value = Value >> 6
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second_byte := Value % 256
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Value = Value >> 8
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third_byte := Value % 256
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Value = Value >> 8
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fourth_byte := Value % 256
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Value = Value >> 8
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// encode bytes length in lower 2 bits of first byte
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first_byte |= uint64(byte(bytes_required - 1))
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buf[0] = byte(first_byte)
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buf[1] = byte(second_byte)
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buf[2] = byte(third_byte)
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buf[3] = byte(fourth_byte)
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if bytes_required == 3 { // thank god we are soon going to migrate from boost hell, once and for all
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bytes_required = 4
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}
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return int(bytes_required)
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}
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