108 lines
4.1 KiB
Nim
108 lines
4.1 KiB
Nim
# nimbus-eth1
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# Copyright (c) 2023 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) or
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# http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
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# http://opensource.org/licenses/MIT)
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# at your option. This file may not be copied, modified, or distributed
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# except according to those terms.
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{.push raises: [].}
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import
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std/sequtils,
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eth/[common, trie/nibbles],
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results,
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./aristo_desc
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# Info snippet (just a reminder to keep somewhere)
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#
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# Extension of a compact encoded as prefixed sequence of nibbles (i.e.
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# half bytes with 4 bits.)
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#
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# pfx | bits | vertex type | layout
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# ----+ -----+-------------+----------------------------------------
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# 0 | 0000 | extension | @[<pfx, ignored>, nibble-pair, ..]
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# 1 | 0001 | extension | @[<pfx, first-nibble>, nibble-pair, ..]
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# 2 | 0010 | leaf | @[<pfx, ignored>, nibble-pair, ..]
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# 3 | 0011 | leaf | @[<pfx, first-nibble>, nibble-pair, ..]
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#
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# where the `ignored` part is typically expected a zero nibble.
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func pathPfxPad*(pfx: NibblesSeq; dblNibble: static[byte]): NibblesSeq
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# ------------------------------------------------------------------------------
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# Public functions
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# ------------------------------------------------------------------------------
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func pathAsBlob*(tag: PathID): Blob =
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## Convert the `tag` argument to a sequence of an even number of nibbles
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## represented by a `Blob`. If the argument `tag` represents an odd number
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## of nibbles, a zero nibble is appendend.
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##
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## This function is useful only if there is a tacit agreement that all paths
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## used to index database leaf values can be represented as `Blob`, i.e.
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## `PathID` type paths with an even number of nibbles.
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if 0 < tag.length:
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let key = @(tag.pfx.UInt256.toBytesBE)
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if 64 <= tag.length:
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return key
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else:
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return key[0 .. (tag.length + 1) div 2]
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func pathAsHEP*(tag: PathID; isLeaf = false): Blob =
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## Convert the `tag` argument to a hex encoded partial path as used in `eth`
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## or `snap` protocol where full paths of nibble length 64 are encoded as 32
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## byte `Blob` and non-leaf partial paths are *compact encoded* (i.e. per
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## the Ethereum wire protocol.)
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if 64 <= tag.length:
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@(tag.pfx.UInt256.toBytesBE)
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else:
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tag.to(NibblesSeq).hexPrefixEncode(isLeaf=true)
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func pathToTag*(partPath: NibblesSeq): Result[PathID,AristoError] =
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## Convert the argument `partPath` to a `PathID` type value.
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if partPath.len == 0:
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return ok PathID()
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if partPath.len <= 64:
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return ok PathID(
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pfx: UInt256.fromBytesBE partPath.pathPfxPad(0).getBytes(),
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length: partPath.len.uint8)
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err(PathAtMost64Nibbles)
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func pathToTag*(partPath: openArray[byte]): Result[PathID,AristoError] =
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## Variant of `pathToTag()`
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if partPath.len == 0:
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return ok PathID()
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if partPath.len <= 32:
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return ok PathID(
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pfx: UInt256.fromBytesBE @partPath & 0u8.repeat(32-partPath.len),
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length: 2 * partPath.len.uint8)
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err(PathAtMost64Nibbles)
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# --------------------
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func pathPfxPad*(pfx: NibblesSeq; dblNibble: static[byte]): NibblesSeq =
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## Extend (or cut) the argument nibbles sequence `pfx` for generating a
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## `NibblesSeq` with exactly 64 nibbles, the equivalent of a path key.
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##
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## This function must be handled with some care regarding a meaningful value
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## for the `dblNibble` argument. Currently, only static values `0` and `255`
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## are allowed for padding. This is checked at compile time.
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static:
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doAssert dblNibble == 0 or dblNibble == 255
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let padLen = 64 - pfx.len
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if 0 <= padLen:
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result = pfx & dblNibble.repeat(padlen div 2).mapIt(it.byte).initNibbleRange
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if (padLen and 1) == 1:
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result = result & @[dblNibble.byte].initNibbleRange.slice(1)
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else:
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let nope = seq[byte].default.initNibbleRange
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result = pfx.slice(0,64) & nope # nope forces re-alignment
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# ------------------------------------------------------------------------------
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# End
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# ------------------------------------------------------------------------------
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