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add byteutils

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Jacek Sieka 2019-07-06 20:07:41 +02:00
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README.md
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# stew - status e-something w-something
[![Build Status (Travis)](https://img.shields.io/travis/status-im/nim-stew/master.svg?label=Linux%20/%20macOS "Linux/macOS build status (Travis)")](https://travis-ci.org/status-im/nim-stew)
[![Windows build status (Appveyor)](https://img.shields.io/appveyor/ci/nimbus/nim-stew/master.svg?label=Windows "Windows build status (Appveyor)")](https://ci.appveyor.com/project/nimbus/nim-stew)
[![License: Apache](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
![Stability: experimental](https://img.shields.io/badge/stability-experimental-orange.svg)
`stew` is collection of utilities, std library extensions and budding libraries
that are frequently used at Status, but are too small to deserve their own
git repository.
We use `stew` as a staging ground for code that has yet to be battle-tested.
We also use `stew` as a staging ground for code that has yet to be
battle-tested.
Some of these libraries may eventually be proposed for inclusion in Nim or
broken out into separate repositories.
@ -46,7 +53,8 @@ welcome patches.
Libraries are documented either in-module or on a separate README in their
respective folders
- `bitops2` - an updated version of `bitops.nim`, filling in gaps in original code\
- `bitops2` - an updated version of `bitops.nim`, filling in gaps in original code
- `byteutils` - utilities that make working with the Nim `byte` type convenient
- `shims` - backports of nim `devel` code to the stable version that Status is using
## Using stew in your project

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stew/byteutils.nim Normal file
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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
if sz < maxStrSize:
# include extra byte if odd length
bIdx = result.len - (sz + 1) div 2
# 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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tests/all_tests.nim
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
#
# at your option. This file may not be copied, modified, or distributed except according to those terms.
import
test_byteutils

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tests/test_byteutils.nim Normal file
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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.
import unittest,
../stew/byteutils
suite "Byte utils":
let simpleBArray = [0x12.byte, 0x34, 0x56, 0x78]
test "hexToByteArray: Inplace partial string":
let s = "0x1234567890"
var a: array[5, byte]
hexToByteArray(s, a, 1, 3)
check a == [0.byte, 0x34, 0x56, 0x78, 0]
test "hexToByteArray: Inplace full string":
let s = "0xffffffff"
var a: array[4, byte]
hexToByteArray(s, a)
check a == [255.byte, 255, 255, 255]
test "hexToByteArray: Return array":
let
s = "0x12345678"
a = hexToByteArray[4](s)
check a == simpleBArray
test "toHex":
check simpleBArray.toHex == "12345678"
test "Array concatenation":
check simpleBArray & simpleBArray ==
[0x12.byte, 0x34, 0x56, 0x78, 0x12, 0x34, 0x56, 0x78]
test "hexToPaddedByteArray":
block:
let a = hexToPaddedByteArray[4]("0x123")
check a.toHex == "00000123"
block:
let a = hexToPaddedByteArray[4]("0x1234")
check a.toHex == "00001234"
block:
let a = hexToPaddedByteArray[4]("0x1234567")
check a.toHex == "01234567"
block:
let a = hexToPaddedByteArray[4]("0x12345678")
check a.toHex == "12345678"
block:
let a = hexToPaddedByteArray[32]("0x68656c6c6f20776f726c64")
check a.toHex == "00000000000000000000000000000000000000000068656c6c6f20776f726c64"
block:
expect AssertionError:
let a = hexToPaddedByteArray[2]("0x12345")