393 lines
13 KiB
Nim
393 lines
13 KiB
Nim
## Nim-Libp2p
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## Copyright (c) 2018 Status Research & Development GmbH
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## Licensed under either of
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## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
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## * MIT license ([LICENSE-MIT](LICENSE-MIT))
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## at your option.
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## This file may not be copied, modified, or distributed except according to
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## those terms.
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## This module implements Variable Integer `VARINT`.
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## This module supports two variants of variable integer
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## - Google ProtoBuf varint, which is able to encode full uint64 number and
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## maximum size of encoded value is 10 octets (bytes).
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## https://developers.google.com/protocol-buffers/docs/encoding#varints
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## - LibP2P varint, which is able to encode only 63bits of uint64 number and
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## maximum size of encoded value is 9 octets (bytes).
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## https://github.com/multiformats/unsigned-varint
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import bitops, typetraits
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type
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VarintStatus* {.pure.} = enum
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Error,
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Success,
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Overflow,
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Incomplete,
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Overlong,
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Overrun
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PB* = object
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## Use this type to specify Google ProtoBuf's varint encoding
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LP* = object
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## Use this type to specify LibP2P varint encoding
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zint32* = distinct int32
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zint64* = distinct int64
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zint* = distinct int
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## Signed integer types which will be encoded using zigzag encoding.
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hint32* = distinct int32
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hint64* = distinct int64
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hint* = distinct int
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## Signed integer types which will be encoded using simple cast.
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PBSomeUVarint* = uint | uint64 | uint32
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PBSomeSVarint* = hint | hint64 | hint32
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PBZigVarint* = zint | zint64 | zint32
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PBSomeVarint* = PBSomeUVarint | PBSomeSVarint | PBZigVarint
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LPSomeUVarint* = uint | uint64 | uint32 | uint16 | uint8
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LPSomeVarint* = LPSomeUVarint
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SomeVarint* = PBSomeVarint | LPSomeVarint
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SomeUVarint* = PBSomeUVarint | LPSomeUVarint
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VarintError* = object of CatchableError
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proc vsizeof*(x: SomeUVarint): int {.inline.} =
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## Returns number of bytes required to encode integer ``x`` as varint.
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if x == type(x)(0):
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1
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else:
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(fastLog2(x) + 1 + 7 - 1) div 7
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proc vsizeof*(x: PBSomeSVarint): int {.inline.} =
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## Returns number of bytes required to encode signed integer ``x``.
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##
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## Note: This procedure interprets signed integer as ProtoBuffer's
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## ``int32`` and ``int64`` integers.
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when sizeof(x) == 8:
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if int64(x) == 0'i64:
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1
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else:
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(fastLog2(uint64(x)) + 1 + 7 - 1) div 7
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else:
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if int32(x) == 0'i32:
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1
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else:
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(fastLog2(uint32(x)) + 1 + 7 - 1) div 7
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proc vsizeof*(x: PBZigVarint): int {.inline.} =
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## Returns number of bytes required to encode signed integer ``x``.
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##
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## Note: This procedure interprets signed integer as ProtoBuffer's
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## ``sint32`` and ``sint64`` integer.
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when sizeof(x) == 8:
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if int64(x) == 0'i64:
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1
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else:
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if int64(x) < 0'i64:
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vsizeof(not(uint64(x) shl 1))
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else:
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vsizeof(uint64(x) shl 1)
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else:
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if int32(x) == 0'i32:
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1
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else:
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if int32(x) < 0'i32:
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vsizeof(not(uint32(x) shl 1))
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else:
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vsizeof(uint32(x) shl 1)
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proc getUVarint*[T: PB|LP](vtype: typedesc[T],
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pbytes: openarray[byte],
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outlen: var int,
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outval: var SomeUVarint): VarintStatus =
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## Decode `unsigned varint` from buffer ``pbytes`` and store it to ``outval``.
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## On success ``outlen`` will be set to number of bytes processed while
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## decoding `unsigned varint`.
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##
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## If array ``pbytes`` is empty, ``Incomplete`` error will be returned.
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##
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## If there not enough bytes available in array ``pbytes`` to decode `unsigned
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## varint`, ``Incomplete`` error will be returned.
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##
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## If encoded value can produce integer overflow, ``Overflow`` error will be
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## returned.
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##
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## Google ProtoBuf
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## When decoding 10th byte of Google Protobuf's 64bit integer only 1 bit from
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## byte will be decoded, all other bits will be ignored. When decoding 5th
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## byte of 32bit integer only 4 bits from byte will be decoded, all other bits
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## will be ignored.
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##
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## LibP2P
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## When decoding 5th byte of 32bit integer only 4 bits from byte will be
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## decoded, all other bits will be ignored.
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when vtype is PB:
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const MaxBits = byte(sizeof(outval) * 8)
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else:
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when sizeof(outval) == 8:
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const MaxBits = 63'u8
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else:
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const MaxBits = byte(sizeof(outval) * 8)
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var shift = 0'u8
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result = VarintStatus.Incomplete
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outlen = 0
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outval = type(outval)(0)
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for i in 0..<len(pbytes):
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let b = pbytes[i]
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if shift >= MaxBits:
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result = VarintStatus.Overflow
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outlen = 0
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outval = type(outval)(0)
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break
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else:
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outval = outval or (type(outval)(b and 0x7F'u8) shl shift)
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shift += 7
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inc(outlen)
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if (b and 0x80'u8) == 0'u8:
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result = VarintStatus.Success
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break
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if result == VarintStatus.Incomplete:
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outlen = 0
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outval = type(outval)(0)
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when vtype is LP:
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if result == VarintStatus.Success:
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if outlen != vsizeof(outval):
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outval = type(outval)(0)
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outlen = 0
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result = VarintStatus.Overlong
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proc putUVarint*[T: PB|LP](vtype: typedesc[T],
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pbytes: var openarray[byte],
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outlen: var int,
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outval: SomeUVarint): VarintStatus =
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## Encode `unsigned varint` ``outval`` and store it to array ``pbytes``.
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##
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## On success ``outlen`` will hold number of bytes (octets) used to encode
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## unsigned integer ``v``.
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##
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## If there not enough bytes available in buffer ``pbytes``, ``Incomplete``
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## error will be returned and ``outlen`` will be set to number of bytes
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## required.
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##
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## Google ProtoBuf
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## Maximum encoded length of 64bit integer is 10 octets.
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## Maximum encoded length of 32bit integer is 5 octets.
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##
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## LibP2P
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## Maximum encoded length of 63bit integer is 9 octets.
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## Maximum encoded length of 32bit integer is 5 octets.
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var buffer: array[10, byte]
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var value = outval
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var k = 0
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when vtype is LP:
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if sizeof(outval) == 8:
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if (uint64(outval) and 0x8000_0000_0000_0000'u64) != 0'u64:
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result = Overflow
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return
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if value <= type(outval)(0x7F):
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buffer[0] = byte(outval and 0xFF)
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inc(k)
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else:
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while value != type(outval)(0):
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buffer[k] = byte((value and 0x7F) or 0x80)
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value = value shr 7
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inc(k)
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buffer[k - 1] = buffer[k - 1] and 0x7F'u8
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outlen = k
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if len(pbytes) >= k:
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copyMem(addr pbytes[0], addr buffer[0], k)
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result = VarintStatus.Success
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else:
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result = VarintStatus.Overrun
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proc getSVarint*(pbytes: openarray[byte], outsize: var int,
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outval: var PBSomeSVarint): VarintStatus {.inline.} =
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## Decode signed integer (``int32`` or ``int64``) from buffer ``pbytes``
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## and store it to ``outval``.
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##
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## On success ``outlen`` will be set to number of bytes processed while
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## decoding signed varint.
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##
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## If array ``pbytes`` is empty, ``Incomplete`` error will be returned.
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##
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## If there not enough bytes available in array ``pbytes`` to decode `signed
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## varint`, ``Incomplete`` error will be returned.
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##
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## If encoded value can produce integer overflow, ``Overflow`` error will be
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## returned.
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##
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## Note, when decoding 10th byte of 64bit integer only 1 bit from byte will be
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## decoded, all other bits will be ignored. When decoding 5th byte of 32bit
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## integer only 4 bits from byte will be decoded, all other bits will be
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## ignored.
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when sizeof(outval) == 8:
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var value: uint64
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else:
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var value: uint32
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result = PB.getUVarint(pbytes, outsize, value)
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if result == VarintStatus.Success:
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outval = cast[type(outval)](value)
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proc getSVarint*(pbytes: openarray[byte], outsize: var int,
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outval: var PBZigVarint): VarintStatus {.inline.} =
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## Decode Google ProtoBuf's zigzag encoded signed integer (``sint32`` or
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## ``sint64`` ) from buffer ``pbytes`` and store it to ``outval``.
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##
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## On success ``outlen`` will be set to number of bytes processed while
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## decoding signed varint.
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##
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## If array ``pbytes`` is empty, ``Incomplete`` error will be returned.
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##
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## If there not enough bytes available in array ``pbytes`` to decode `signed
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## varint`, ``Incomplete`` error will be returned.
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##
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## If encoded value can produce integer overflow, ``Overflow`` error will be
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## returned.
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##
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## Note, when decoding 10th byte of 64bit integer only 1 bit from byte will be
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## decoded, all other bits will be ignored. When decoding 5th byte of 32bit
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## integer only 4 bits from byte will be decoded, all other bits will be
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## ignored.
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when sizeof(outval) == 8:
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var value: uint64
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else:
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var value: uint32
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result = PB.getUVarint(pbytes, outsize, value)
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if result == VarintStatus.Success:
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if (value and type(value)(1)) != type(value)(0):
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outval = cast[type(outval)](not(value shr 1))
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else:
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outval = cast[type(outval)](value shr 1)
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proc putSVarint*(pbytes: var openarray[byte], outsize: var int,
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outval: PBZigVarint): VarintStatus {.inline.} =
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## Encode signed integer ``outval`` using ProtoBuffer's zigzag encoding
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## (``sint32`` or ``sint64``) and store it to array ``pbytes``.
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##
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## On success ``outlen`` will hold number of bytes (octets) used to encode
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## unsigned integer ``v``.
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##
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## If there not enough bytes available in buffer ``pbytes``, ``Incomplete``
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## error will be returned and ``outlen`` will be set to number of bytes
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## required.
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##
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## Maximum encoded length of 64bit integer is 10 octets.
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## Maximum encoded length of 32bit integer is 5 octets.
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when sizeof(outval) == 8:
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var value: uint64 =
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if int64(outval) < 0'i64:
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not(uint64(outval) shl 1)
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else:
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uint64(outval) shl 1
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else:
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var value: uint32 =
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if int32(outval) < 0'i32:
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not(uint32(outval) shl 1)
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else:
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uint32(outval) shl 1
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result = PB.putUVarint(pbytes, outsize, value)
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proc putSVarint*(pbytes: var openarray[byte], outsize: var int,
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outval: PBSomeSVarint): VarintStatus {.inline.} =
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## Encode signed integer ``outval`` (``int32`` or ``int64``) and store it to
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## array ``pbytes``.
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##
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## On success ``outlen`` will hold number of bytes (octets) used to encode
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## unsigned integer ``v``.
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##
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## If there not enough bytes available in buffer ``pbytes``, ``Incomplete``
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## error will be returned and ``outlen`` will be set to number of bytes
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## required.
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##
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## Maximum encoded length of 64bit integer is 10 octets.
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## Maximum encoded length of 32bit integer is 5 octets.
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when sizeof(outval) == 8:
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result = PB.putUVarint(pbytes, outsize, uint64(outval))
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else:
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result = PB.putUVarint(pbytes, outsize, uint32(outval))
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template varintFatal(msg) =
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const m = msg
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{.fatal: m.}
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proc putVarint*[T: PB|LP](vtype: typedesc[T], pbytes: var openarray[byte],
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nbytes: var int, value: SomeVarint): VarintStatus {.inline.} =
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when vtype is PB:
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when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
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result = putSVarint(pbytes, nbytes, value)
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elif (type(value) is PBSomeUVarint):
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result = PB.putUVarint(pbytes, nbytes, value)
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else:
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varintFatal("Protobuf's varint do not support type [" &
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typetraits.name(type(value)) & "]")
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elif vtype is LP:
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when (type(value) is LPSomeVarint):
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result = LP.putUVarint(pbytes, nbytes, value)
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else:
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varintFatal("LibP2P's varint do not support type [" &
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typetraits.name(type(value)) & "]")
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proc getVarint*[T: PB|LP](vtype: typedesc[T], pbytes: openarray[byte],
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nbytes: var int,
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value: var SomeVarint): VarintStatus {.inline.} =
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when vtype is PB:
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when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
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result = getSVarint(pbytes, nbytes, value)
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elif (type(value) is PBSomeUVarint):
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result = PB.getUVarint(pbytes, nbytes, value)
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else:
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varintFatal("Protobuf's varint do not support type [" &
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typetraits.name(type(value)) & "]")
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elif vtype is LP:
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when (type(value) is LPSomeVarint):
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result = LP.getUVarint(pbytes, nbytes, value)
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else:
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varintFatal("LibP2P's varint do not support type [" &
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typetraits.name(type(value)) & "]")
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proc encodeVarint*(vtype: typedesc[PB],
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value: PBSomeVarint): seq[byte] {.inline.} =
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## Encode integer to Google ProtoBuf's `signed/unsigned varint` and returns
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## sequence of bytes as result.
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var outsize = 0
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result = newSeqOfCap[byte](10)
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when sizeof(value) == 4:
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result.setLen(5)
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else:
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result.setLen(10)
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when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
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let res = putSVarint(result, outsize, value)
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else:
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let res = PB.putUVarint(result, outsize, value)
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if res == VarintStatus.Success:
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result.setLen(outsize)
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else:
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raise newException(VarintError, "Error '" & $res & "'")
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proc encodeVarint*(vtype: typedesc[LP],
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value: LPSomeVarint): seq[byte] {.inline.} =
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## Encode integer to LibP2P `unsigned varint` and returns sequence of bytes
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## as result.
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var outsize = 0
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result = newSeqOfCap[byte](9)
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when sizeof(value) == 1:
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result.setLen(2)
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elif sizeof(value) == 2:
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result.setLen(3)
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elif sizeof(value) == 4:
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result.setLen(5)
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else:
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result.setLen(9)
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let res = LP.putUVarint(result, outsize, value)
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if res == VarintStatus.Success:
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result.setLen(outsize)
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else:
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raise newException(VarintError, "Error '" & $res & "'")
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