nim-stew/stew/byteutils.nim

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# byteutils
# Copyright (c) 2018 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
########################################################################################################
#################################### Array utilities ###############################################
import algorithm
func initArrayWith*[N: static[int], T](value: T): array[N, T] {.noInit, inline.}=
result.fill(value)
func `&`*[N1, N2: static[int], T](
a: array[N1, T],
b: array[N2, T]
): array[N1 + N2, T] {.inline, noInit.}=
## Array concatenation
result[0 ..< N1] = a
result[N1 ..< result.len] = b
########################################################################################################
##################################### Hex utilities ################################################
proc readHexChar*(c: char): byte {.noSideEffect, inline.}=
## Converts an hex char to a byte
case c
of '0'..'9': result = byte(ord(c) - ord('0'))
of 'a'..'f': result = byte(ord(c) - ord('a') + 10)
of 'A'..'F': result = byte(ord(c) - ord('A') + 10)
else:
raise newException(ValueError, $c & "is not a hexademical character")
template skip0xPrefix(hexStr: string): int =
## Returns the index of the first meaningful char in `hexStr` by skipping
## "0x" prefix
if hexStr[0] == '0' and hexStr[1] in {'x', 'X'}: 2
else: 0
func hexToByteArray*(hexStr: string, output: var openArray[byte], fromIdx, toIdx: int) =
## Read a hex string and store it in a byte array `output`. No "endianness" reordering is done.
## Allows specifying the byte range to process into the array
var sIdx = skip0xPrefix(hexStr)
doAssert(fromIdx >= 0 and toIdx >= fromIdx and fromIdx < output.len and toIdx < output.len)
let sz = toIdx - fromIdx + 1
doAssert hexStr.len - sIdx >= 2*sz
sIdx += fromIdx * 2
for bIdx in fromIdx ..< sz + fromIdx:
output[bIdx] = hexStr[sIdx].readHexChar shl 4 or hexStr[sIdx + 1].readHexChar
inc(sIdx, 2)
func hexToByteArray*(hexStr: string, output: var openArray[byte]) {.inline.} =
## Read a hex string and store it in a byte array `output`. No "endianness" reordering is done.
hexToByteArray(hexStr, output, 0, output.high)
func hexToByteArray*[N: static[int]](hexStr: string): array[N, byte] {.noInit, inline.}=
## Read an hex string and store it in a byte array. No "endianness" reordering is done.
hexToByteArray(hexStr, result)
func hexToPaddedByteArray*[N: static[int]](hexStr: string): array[N, byte] =
## Read a hex string and store it in a byte array `output`.
## The string may be shorter than the byte array.
## No "endianness" reordering is done.
let
p = skip0xPrefix(hexStr)
sz = hexStr.len - p
maxStrSize = result.len * 2
var
bIdx: int
shift = 4
doAssert hexStr.len - p <= maxStrSize
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if sz < maxStrSize:
# include extra byte if odd length
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bIdx = result.len - (sz + 1) div 2
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# start with shl of 4 if length is even
shift = 4 - sz mod 2 * 4
for sIdx in p ..< hexStr.len:
let nibble = hexStr[sIdx].readHexChar shl shift
result[bIdx] = result[bIdx] or nibble
shift = shift + 4 and 4
bIdx += shift shr 2
func hexToSeqByte*(hexStr: string): seq[byte] =
## Read an hex string and store it in a sequence of bytes. No "endianness" reordering is done.
doAssert (hexStr.len and 1) == 0
let skip = skip0xPrefix(hexStr)
let N = (hexStr.len - skip) div 2
result = newSeq[byte](N)
for i in 0 ..< N:
result[i] = hexStr[2*i + skip].readHexChar shl 4 or hexStr[2*i + 1 + skip].readHexChar
func toHexAux(ba: openarray[byte]): string =
## Convert a byte-array to its hex representation
## Output is in lowercase
## No "endianness" reordering is done.
const hexChars = "0123456789abcdef"
let sz = ba.len
result = newString(2 * sz)
for i in 0 ..< sz:
result[2*i] = hexChars[int ba[i] shr 4 and 0xF]
result[2*i+1] = hexChars[int ba[i] and 0xF]
func toHex*(ba: openarray[byte]): string {.inline.} =
## Convert a byte-array to its hex representation
## Output is in lowercase
## No "endianness" reordering is done.
toHexAux(ba)
func toHex*[N: static[int]](ba: array[N, byte]): string {.inline.} =
## Convert a big endian byte-array to its hex representation
## Output is in lowercase
## No "endianness" reordering is done.
toHexAux(ba)
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func toBytes*(s: string): seq[byte] =
## Convert a string to the corresponding byte sequence - since strings in
## nim essentially are byte sequences without any particular encoding, this
## simply copies the bytes without a null terminator
@(s.toOpenArrayByte(0, s.high))
func fromBytes*(T: type string, v: openArray[byte]): string =
result = newString(v.len)
copyMem(addr result[0], unsafeAddr v[0], v.len)
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func `<`*(a, b: openArray[byte]): bool =
## Lexicographical compare of two byte arrays
let minlen = min(a.len, b.len)
for i in 0..<minlen:
if a[i] != b[i]: return a[i] < b[i]
a.len < b.len