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Conversion of little endian hex strings to bigints (#292)

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markspanbroek 2023-10-26 15:20:30 +02:00 committed by GitHub
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commit 5f7ba18f2e
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2 changed files with 18 additions and 11 deletions
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15
constantine/math/io/io_bigints.nim
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@ -131,14 +131,12 @@ func marshal*(
#
# ############################################################
func fromHex*(a: var BigInt, s: string) =
func fromHex*(a: var BigInt, s: string, order: static Endianness = bigEndian) =
## Convert a hex string to BigInt that can hold
## the specified number of bits
##
## For example `fromHex(BigInt[256], "0x123456")`
##
## Hex string is assumed big-endian
##
## Procedure is constant-time except for the presence (or absence) of the 0x prefix.
##
## This procedure is intended for configuration, prototyping, research and debugging purposes.
@ -152,23 +150,24 @@ func fromHex*(a: var BigInt, s: string) =
bytes.paddedFromHex(s, bigEndian)
# 2. Convert canonical uint to Big Int
a.unmarshal(bytes, bigEndian)
a.unmarshal(bytes, order)
func fromHex*(T: type BigInt, s: string): T {.noInit.} =
func fromHex*(
T: type BigInt,
s: string,
order: static Endianness = bigEndian): T {.noInit.} =
## Convert a hex string to BigInt that can hold
## the specified number of bits
##
## For example `fromHex(BigInt[256], "0x123456")`
##
## Hex string is assumed big-endian
##
## Procedure is constant-time except for the presence (or absence) of the 0x prefix.
##
## This procedure is intended for configuration, prototyping, research and debugging purposes.
## You MUST NOT use it for production.
##
## Can work at compile-time to declare curve moduli from their hex strings
result.fromHex(s)
result.fromHex(s, order)
func appendHex*(dst: var string, big: BigInt, order: static Endianness = bigEndian) =
## Append the BigInt hex into an accumulator

14
tests/math_bigints/t_io_bigints.nim
View File

@ -93,10 +93,18 @@ proc main() =
test "Round trip on 3072-bit integer":
const n = "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"
let x = BigInt[3072].fromHex(n)
let h = x.toHex(bigEndian)
check: n == h
block: # Big-Endian
let x = BigInt[3072].fromHex(n)
let h = x.toHex(bigEndian)
check: n == h
block: # Little-Endian
let x = BigInt[3072].fromHex(n, littleEndian)
let h = x.toHex(littleEndian)
check: n == h
suite "IO Decimal - BigInt" & " [" & $WordBitWidth & "-bit words]":
test "Checks elliptic curve constants":