nim-libp2p-experimental/libp2p/varint.nim

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## Nim-Libp2p
## Copyright (c) 2018 Status Research & Development GmbH
## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
## This module implements Variable Integer `VARINT`.
## This module supports two variants of variable integer
## - Google ProtoBuf varint, which is able to encode full uint64 number and
## maximum size of encoded value is 10 octets (bytes).
## https://developers.google.com/protocol-buffers/docs/encoding#varints
## - LibP2P varint, which is able to encode only 63bits of uint64 number and
## maximum size of encoded value is 9 octets (bytes).
## https://github.com/multiformats/unsigned-varint
{.push raises: [Defect].}
import stew/[byteutils, leb128, results]
export leb128, results
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type
VarintError* {.pure.} = enum
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Error,
Overflow,
Incomplete,
Overlong,
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Overrun
VarintResult*[T] = Result[T, VarintError]
PB* = object
## Use this type to specify Google ProtoBuf's varint encoding
LP* = object
## Use this type to specify LibP2P varint encoding
zint32* = distinct int32
zint64* = distinct int64
zint* = distinct int
## Signed integer types which will be encoded using zigzag encoding.
hint32* = distinct int32
hint64* = distinct int64
hint* = distinct int
## Signed integer types which will be encoded using simple cast.
PBSomeUVarint* = uint | uint64 | uint32
PBSomeSVarint* = hint | hint64 | hint32
PBZigVarint* = zint | zint64 | zint32
PBSomeVarint* = PBSomeUVarint | PBSomeSVarint | PBZigVarint
LPSomeUVarint* = uint | uint64 | uint32 | uint16 | uint8
LPSomeVarint* = LPSomeUVarint
SomeVarint* = PBSomeVarint | LPSomeVarint
SomeUVarint* = PBSomeUVarint | LPSomeUVarint
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template toUleb(x: uint64): uint64 = x
template toUleb(x: uint32): uint32 = x
template toUleb(x: uint16): uint16 = x
template toUleb(x: uint8): uint8 = x
func toUleb(x: zint64): uint64 =
let v = cast[uint64](x)
(v shl 1) xor (0 - (v shr 63))
func toUleb(x: zint32): uint32 =
let v = cast[uint32](x)
(v shl 1) xor (0 - (v shr 31))
template toUleb(x: hint64): uint64 = cast[uint64](x)
template toUleb(x: hint32): uint32 = cast[uint32](x)
template toUleb(x: zint): uint64 =
when sizeof(x) == sizeof(zint64):
uint(toUleb(zint64(x)))
else:
uint(toUleb(zint32(x)))
template toUleb(x: hint): uint =
when sizeof(x) == sizeof(hint64):
uint(toUleb(hint64(x)))
else:
uint(toUleb(hint32(x)))
template fromUleb(x: uint64, T: type uint64): T = x
template fromUleb(x: uint32, T: type uint32): T = x
template fromUleb(x: uint64, T: type zint64): T =
cast[T]((x shr 1) xor (0 - (x and 1)))
template fromUleb(x: uint32, T: type zint32): T =
cast[T]((x shr 1) xor (0 - (x and 1)))
template fromUleb(x: uint64, T: type hint64): T =
cast[T](x)
template fromUleb(x: uint32, T: type hint32): T =
cast[T](x)
proc vsizeof*(x: SomeVarint): int {.inline.} =
## Returns number of bytes required to encode integer ``x`` as varint.
Leb128.len(toUleb(x))
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proc getUVarint*[T: PB|LP](vtype: typedesc[T],
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pbytes: openArray[byte],
outlen: var int,
outval: var SomeUVarint): VarintResult[void] =
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## Decode `unsigned varint` from buffer ``pbytes`` and store it to ``outval``.
## On success ``outlen`` will be set to number of bytes processed while
## decoding `unsigned varint`.
##
## If array ``pbytes`` is empty, ``Incomplete`` error will be returned.
##
## If there not enough bytes available in array ``pbytes`` to decode `unsigned
## varint`, ``Incomplete`` error will be returned.
##
## If encoded value can produce integer overflow, ``Overflow`` error will be
## returned.
##
## Google ProtoBuf
## When decoding 10th byte of Google Protobuf's 64bit integer only 1 bit from
## byte will be decoded, all other bits will be ignored. When decoding 5th
## byte of 32bit integer only 4 bits from byte will be decoded, all other bits
## will be ignored.
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##
## LibP2P
## When decoding 5th byte of 32bit integer only 4 bits from byte will be
## decoded, all other bits will be ignored.
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outlen = 0
outval = type(outval)(0)
let parsed = type(outval).fromBytes(pbytes, Leb128)
if parsed.len == 0:
return err(VarintError.Incomplete)
if parsed.len < 0:
return err(VarintError.Overflow)
when vtype is LP and sizeof(outval) == 8:
if parsed.val >= 0x8000_0000_0000_0000'u64:
return err(VarintError.Overflow)
if vsizeof(parsed.val) != parsed.len:
return err(VarintError.Overlong)
(outval, outlen) = parsed
ok()
proc putUVarint*[T: PB|LP](vtype: typedesc[T],
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pbytes: var openArray[byte],
outlen: var int,
outval: SomeUVarint): VarintResult[void] =
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## Encode `unsigned varint` ``outval`` and store it to array ``pbytes``.
##
## On success ``outlen`` will hold number of bytes (octets) used to encode
## unsigned integer ``v``.
##
## If there not enough bytes available in buffer ``pbytes``, ``Incomplete``
## error will be returned and ``outlen`` will be set to number of bytes
## required.
##
## Google ProtoBuf
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## Maximum encoded length of 64bit integer is 10 octets.
## Maximum encoded length of 32bit integer is 5 octets.
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##
## LibP2P
## Maximum encoded length of 63bit integer is 9 octets.
## Maximum encoded length of 32bit integer is 5 octets.
when vtype is LP and sizeof(outval) == 8:
if (uint64(outval) and 0x8000_0000_0000_0000'u64) != 0'u64:
return err(VarintError.Overflow)
let bytes = toBytes(outval, Leb128)
outlen = len(bytes)
if len(pbytes) >= outlen:
pbytes[0..<outlen] = bytes.toOpenArray()
ok()
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else:
err(VarintError.Overrun)
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proc getSVarint*(pbytes: openArray[byte], outsize: var int,
outval: var (PBZigVarint | PBSomeSVarint)): VarintResult[void] {.inline.} =
## Decode signed integer (``int32`` or ``int64``) from buffer ``pbytes``
## and store it to ``outval``.
##
## On success ``outlen`` will be set to number of bytes processed while
## decoding signed varint.
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##
## If array ``pbytes`` is empty, ``Incomplete`` error will be returned.
##
## If there not enough bytes available in array ``pbytes`` to decode `signed
## varint`, ``Incomplete`` error will be returned.
##
## If encoded value can produce integer overflow, ``Overflow`` error will be
## returned.
##
## Note, when decoding 10th byte of 64bit integer only 1 bit from byte will be
## decoded, all other bits will be ignored. When decoding 5th byte of 32bit
## integer only 4 bits from byte will be decoded, all other bits will be
## ignored.
when sizeof(outval) == 8:
var value: uint64
else:
var value: uint32
let res = PB.getUVarint(pbytes, outsize, value)
if res.isOk():
outval = fromUleb(value, type(outval))
res
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proc putSVarint*(pbytes: var openArray[byte], outsize: var int,
outval: (PBZigVarint | PBSomeSVarint)): VarintResult[void] {.inline.} =
## Encode signed integer ``outval`` using ProtoBuffer's zigzag encoding
## (``sint32`` or ``sint64``) and store it to array ``pbytes``.
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##
## On success ``outlen`` will hold number of bytes (octets) used to encode
## unsigned integer ``v``.
##
## If there not enough bytes available in buffer ``pbytes``, ``Incomplete``
## error will be returned and ``outlen`` will be set to number of bytes
## required.
##
## Maximum encoded length of 64bit integer is 10 octets.
## Maximum encoded length of 32bit integer is 5 octets.
PB.putUVarint(pbytes, outsize, toUleb(outval))
template varintFatal(msg) =
const m = msg
{.fatal: m.}
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proc putVarint*[T: PB|LP](vtype: typedesc[T], pbytes: var openArray[byte],
nbytes: var int, value: SomeVarint): VarintResult[void] {.inline.} =
when vtype is PB:
when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
putSVarint(pbytes, nbytes, value)
elif (type(value) is PBSomeUVarint):
PB.putUVarint(pbytes, nbytes, value)
else:
varintFatal("Protobuf's varint do not support type [" &
typetraits.name(type(value)) & "]")
elif vtype is LP:
when (type(value) is LPSomeVarint):
LP.putUVarint(pbytes, nbytes, value)
else:
varintFatal("LibP2P's varint do not support type [" &
typetraits.name(type(value)) & "]")
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proc getVarint*[T: PB|LP](vtype: typedesc[T], pbytes: openArray[byte],
nbytes: var int,
value: var SomeVarint): VarintResult[void] {.inline.} =
when vtype is PB:
when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
getSVarint(pbytes, nbytes, value)
elif (type(value) is PBSomeUVarint):
PB.getUVarint(pbytes, nbytes, value)
else:
varintFatal("Protobuf's varint do not support type [" &
typetraits.name(type(value)) & "]")
elif vtype is LP:
when (type(value) is LPSomeVarint):
LP.getUVarint(pbytes, nbytes, value)
else:
varintFatal("LibP2P's varint do not support type [" &
typetraits.name(type(value)) & "]")
template toBytes*(vtype: typedesc[PB], value: PBSomeVarint): auto =
toBytes(toUleb(value), Leb128)
proc encodeVarint*(vtype: typedesc[PB],
value: PBSomeVarint): VarintResult[seq[byte]] {.inline.} =
## Encode integer to Google ProtoBuf's `signed/unsigned varint` and returns
## sequence of bytes as buffer.
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var outsize = 0
var buffer = newSeqOfCap[byte](10)
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when sizeof(value) == 4:
buffer.setLen(5)
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else:
buffer.setLen(10)
when (type(value) is PBSomeSVarint) or (type(value) is PBZigVarint):
let res = putSVarint(buffer, outsize, value)
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else:
let res = PB.putUVarint(buffer, outsize, value)
if res.isOk():
buffer.setLen(outsize)
ok(buffer)
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else:
err(res.error())
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proc encodeVarint*(vtype: typedesc[LP],
value: LPSomeVarint): VarintResult[seq[byte]] {.inline.} =
## Encode integer to LibP2P `unsigned varint` and returns sequence of bytes
## as buffer.
var outsize = 0
var buffer = newSeqOfCap[byte](9)
when sizeof(value) == 1:
buffer.setLen(2)
elif sizeof(value) == 2:
buffer.setLen(3)
elif sizeof(value) == 4:
buffer.setLen(5)
else:
buffer.setLen(9)
let res = LP.putUVarint(buffer, outsize, value)
if res.isOk():
buffer.setLen(outsize)
ok(buffer)
else:
err(res.error)