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# Stint
# Copyright 2018 Status Research & Development GmbH
# Licensed under either of
#
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * 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
./private/datatypes,
./private/int_negabs,
./private/as_words,
./int_public, ./uint_public,
typetraits, algorithm
template static_check_size(T: typedesc[SomeInteger], bits: static[int]) =
# To avoid a costly runtime check, we refuse storing into StUint types smaller
# than the input type.
static: assert sizeof(T) * 8 <= bits, "Input type (" & $T &
") cannot be stored in a multi-precision " &
$bits & "-bit integer." &
"\nUse a smaller input type instead. This is a compile-time check" &
" to avoid a costly run-time bit_length check at each StUint initialization."
template assign_least_significant_words[T: SomeInteger](result: var (Stuint|Stint), n: T) =
template lsw_result: untyped = least_significant_word(result.data)
template slsw_result: untyped = second_least_significant_word(result.data)
const wordSize = lsw_result.getSize
when sizeof(T) * 8 <= wordSize:
lsw_result = (type lsw_result)(n)
else: # We try to store an int64 in 2 x uint32 or 4 x uint16
# For now we only support assignation from 64 to 2x32 bit
const
size = getSize(T)
halfSize = size div 2
halfMask = (1.T shl halfSize) - 1.T
lsw_result = (type lsw_result)(n and halfMask)
slsw_result = (type slsw_result)(n shr halfSize)
func stuint*[T: SomeInteger](n: T, bits: static[int]): StUint[bits] {.inline.}=
## Converts an integer to an arbitrary precision integer.
assert n >= 0.T
when result.data is UintImpl:
static_check_size(T, bits)
assign_least_significant_words(result, n)
else:
result.data = (type result.data)(n)
func stint*[T: SomeInteger](n: T, bits: static[int]): StInt[bits] {.inline.}=
## Converts an integer to an arbitrary precision signed integer.
when result.data is IntImpl:
static_check_size(T, bits)
when T is SomeSignedInt:
if n < 0:
assign_least_significant_words(result, -n)
result = -result
else:
assign_least_significant_words(result, n)
else:
assign_least_significant_words(result, n)
else:
result.data = (type result.data)(n)
func to*(x: SomeInteger, T: typedesc[Stint]): T =
stint(x, result.bits)
func to*(x: SomeUnsignedInt, T: typedesc[StUint]): T =
stuint(x, result.bits)
func toInt*(num: Stint or StUint): int {.inline.}=
# Returns as int. Result is modulo 2^(sizeof(int)
num.data.least_significant_word.int
func toUint*(num: Stint or StUint): uint {.inline.}=
# Returns as int. Result is modulo 2^(sizeof(int)
num.data.least_significant_word
func readHexChar(c: char): int8 {.inline.}=
## Converts an hex char to an int
case c
of '0'..'9': result = int8 ord(c) - ord('0')
of 'a'..'f': result = int8 ord(c) - ord('a') + 10
of 'A'..'F': result = int8 ord(c) - ord('A') + 10
else:
raise newException(ValueError, $c & "is not a hexadecimal character")
func skipPrefixes(current_idx: var int, str: string, base: range[2..16]) {.inline.} =
## Returns the index of the first meaningful char in `hexStr` by skipping
## "0x" prefix
if str.len < 2:
return
assert current_idx == 0, "skipPrefixes only works for prefixes (position 0 and 1 of the string)"
if str[0] == '0':
if str[1] in {'x', 'X'}:
assert base == 16, "Parsing mismatch, 0x prefix is only valid for a hexadecimal number (base 16)"
current_idx = 2
elif str[1] in {'o', 'O'}:
assert base == 8, "Parsing mismatch, 0o prefix is only valid for an octal number (base 8)"
current_idx = 2
elif str[1] in {'b', 'B'}:
assert base == 2, "Parsing mismatch, 0b prefix is only valid for a binary number (base 2)"
current_idx = 2
func nextNonBlank(current_idx: var int, s: string) {.inline.} =
## Move the current index, skipping white spaces and "_" characters.
const blanks = {' ', '_'}
inc current_idx
while current_idx < s.len and s[current_idx] in blanks:
inc current_idx
func readDecChar(c: range['0'..'9']): int {.inline.}=
## Converts a decimal char to an int
# specialization without branching for base <= 10.
ord(c) - ord('0')
func parse*[bits: static[int]](input: string, T: typedesc[Stuint[bits]], base: static[uint8]): T =
## Parse a string and store the result in a Stint[bits] or Stuint[bits].
static: assert (base >= 2) and base <= 16, "Only base from 2..16 are supported"
# TODO: use static[range[2 .. 16]], not supported at the moment (2018-04-26)
# TODO: we can special case hex result/input as an array of bytes
# and be much faster
const radix = base.uint8.stuint(bits)
var curr = 0 # Current index in the string
skipPrefixes(curr, input, base)
while curr < input.len:
# TODO: overflow detection
when base <= 10:
result = result * radix + input[curr].readDecChar.stuint(bits)
else:
result = result * radix + input[curr].readHexChar.stuint(bits)
nextNonBlank(curr, input)
func parse*[bits: static[int]](input: string, T: typedesc[Stint[bits]], base: static[int8]): T =
## Parse a string and store the result in a Stint[bits] or Stuint[bits].
static: assert (base >= 2) and base <= 16, "Only base from 2..16 are supported"
# TODO: use static[range[2 .. 16]], not supported at the moment (2018-04-26)
# TODO: we can special case hex result/input as an array of bytes
# and be much faster
# For conversion we require overflowing operations (for example for negative hex numbers)
const radix = base.int8.stuint(bits)
var
curr = 0 # Current index in the string
isNeg = false
no_overflow: Stuint[bits]
if input[curr] == '-':
assert base == 10, "Negative numbers are only supported with base 10 input."
isNeg = true
inc curr
else:
skipPrefixes(curr, input, base)
while curr < input.len:
# TODO: overflow detection
when base <= 10:
no_overflow = no_overflow * radix + input[curr].readDecChar.stuint(bits)
else:
no_overflow = no_overflow * radix + input[curr].readHexChar.stuint(bits)
nextNonBlank(curr, input)
# TODO: we can't create the lowest int this way
if isNeg:
result = -cast[Stint[bits]](no_overflow)
else:
result = cast[Stint[bits]](no_overflow)
func parse*[bits: static[int]](input: string, T: typedesc[Stint[bits]|Stuint[bits]]): T {.inline.}=
## Parse a string and store the result in a Stint[bits] or Stuint[bits].
## Input is considered a decimal string.
# TODO: Have a default static argument in the previous proc. Currently we get
# "Cannot evaluate at compile-time" in several places (2018-04-26).
parse(input, T, 10)
func fromHex*(T: type StUint, s: string): T {.inline.} =
## Convert an hex string to the corresponding unsigned integer
parse(s, type result, base = 16)
func hexToUint*[bits: static[int]](hexString: string): Stuint[bits] {.inline.} =
## Convert an hex string to the corresponding unsigned integer
parse(hexString, type result, base = 16)
func toString*[bits: static[int]](num: StUint[bits], base: static[uint8]): string =
## Convert a Stint or Stuint to string.
## In case of negative numbers:
## - they are prefixed with "-" for base 10.
## - if not base 10, they are returned raw in two-complement form.
static: assert (base >= 2) and base <= 16, "Only base from 2..16 are supported"
# TODO: use static[range[2 .. 16]], not supported at the moment (2018-04-26)
const hexChars = "0123456789abcdef"
const radix = base.uint8.stuint(bits)
result = ""
var (q, r) = divmod(num, radix)
while true:
result.add hexChars[r.toInt]
if q.isZero:
break
(q, r) = divmod(q, radix)
reverse(result)
func toString*[bits: static[int]](num: Stint[bits], base: static[int8]): string =
## Convert a Stint or Stuint to string.
## In case of negative numbers:
## - they are prefixed with "-" for base 10.
## - if not base 10, they are returned raw in two-complement form.
static: assert (base >= 2) and base <= 16, "Only base from 2..16 are supported"
# TODO: use static[range[2 .. 16]], not supported at the moment (2018-04-26)
const hexChars = "0123456789abcdef"
const radix = base.int8.stint(bits)
result = ""
let isNeg = num.isNegative
let num = if base == 10 and isNeg: -num
else: num
var (q, r) = divmod(num, radix)
while true:
result.add hexChars[r.toInt]
if q.isZero:
break
(q, r) = divmod(q, radix)
if isNeg:
result.add '-'
reverse(result)
func toString*[bits: static[int]](num: Stint[bits] or StUint[bits]): string {.inline.}=
## Convert to a string.
## Output is considered a decimal string.
#
# TODO: Have a default static argument in the previous proc. Currently we get
# "Error: type mismatch: got <int, type StInt[128]>, required type static[int]"
when num.data is SomeInteger:
$num.data
else:
toString(num, 10)
func `$`*(num: Stint or StUint): string {.inline.}=
when num.data is SomeInteger:
$num.data
else:
toString(num, 10)
func toHex*[bits: static[int]](num: Stint[bits] or StUint[bits]): string {.inline.}=
## Convert to a hex string.
## Output is considered a big-endian base 16 string.
## Leading zeros are stripped. Use dumpHex instead if you need the in-memory representation
toString(num, 16)
func dumpHex*(x: Stint or StUint, order: static[Endianness]): string =
## Stringify an int to hex.
## Note. Leading zeros are not removed. Use toString(n, base = 16)/toHex instead.
##
## You can specify bigEndian or littleEndian order.
## i.e. in bigEndian:
## - 1.uint64 will be 00000001
## - (2.uint128)^64 + 1 will be 0000000100000001
##
## in littleEndian:
## - 1.uint64 will be 01000000
## - (2.uint128)^64 + 1 will be 0100000001000000
const
hexChars = "0123456789abcdef"
size = getSize(x.data) div 8
{.pragma: restrict, codegenDecl: "$# __restrict $#".}
let bytes {.restrict.}= cast[ptr array[size, byte]](x.unsafeaddr)
result = newString(2*size)
for i in 0 ..< size:
when order == system.cpuEndian:
result[2*i] = hexChars[int bytes[i] shr 4 and 0xF]
result[2*i+1] = hexChars[int bytes[i] and 0xF]
else:
result[2*i] = hexChars[int bytes[bytes[].high - i] shr 4 and 0xF]
result[2*i+1] = hexChars[int bytes[bytes[].high - i] and 0xF]
func dumpHex*(x: Stint or StUint): string {.inline.}=
## Stringify an int to hex.
## By default, dump is done in bigEndian order.
dumpHex(x, bigEndian)
# TODO: Have a default static argument in the previous proc. Currently we get
# "Cannot evaluate at compile-time".
proc initFromBytesBE*[bits: static[int]](val: var Stuint[bits], ba: openarray[byte], allowPadding: static[bool] = true) =
## Initializes a UInt[bits] value from a byte buffer storing a big-endian
## representation of a number.
##
## If `allowPadding` is set to false, the input array must be exactly
## (bits div 8) bytes long. Otherwise, it may be shorter and the remaining
## bytes will be assumed to be zero.
const N = bits div 8
when not allowPadding:
assert(ba.len == N)
else:
assert ba.len <= N
{.pragma: restrict, codegenDecl: "$# __restrict $#".}
let r_ptr {.restrict.} = cast[ptr array[N, byte]](val.addr)
when system.cpuEndian == bigEndian:
# TODO: due to https://github.com/status-im/nim-stint/issues/38
# We can't cast a stack byte array to stuint with a convenient proc signature.
when allowPadding:
let baseIdx = N - val.len
for i, b in ba: r_ptr[baseIdx + i] = b
else:
for i, b in ba: r_ptr[i] = b
else:
when allowPadding:
let baseIdx = ba.len - 1
for i, b in ba: r_ptr[baseIdx - i] = b
else:
for i, b in ba: r_ptr[N-1 - i] = b
func significantBytesBE*(val: openarray[byte]): int =
## Returns the number of significant trailing bytes in a big endian
## representation of a number.
for i in 0 ..< val.len:
if val[i] != 0:
return val.len - i
return 1
func fromBytesBE*(T: type Stuint, ba: openarray[byte],
allowPadding: static[bool] = true): T =
## This function provides a convenience wrapper around `initFromBytesBE`.
result.initFromBytesBE(ba, allowPadding)
func readUintBE*[bits: static[int]](ba: openarray[byte]): Stuint[bits] =
## Convert a big-endian array of (bits div 8) Bytes to an UInt[bits] (in native host endianness)
## Input:
## - a big-endian openarray of size (bits div 8) at least
## Returns:
## - A unsigned integer of the same size with `bits` bits
##
## ⚠ If the openarray length is bigger than bits div 8, part converted is undefined behaviour.
result.initFromBytesBE(ba, false)
func toByteArrayBE*[bits: static[int]](n: StUint[bits]): array[bits div 8, byte] =
## Convert a uint[bits] to to a big-endian array of bits div 8 bytes
## Input:
## - an unsigned integer
## Returns:
## - a big-endian array of the same size
const N = bits div 8
when system.cpuEndian == bigEndian:
result = cast[type result](n)
else:
{.pragma: restrict, codegenDecl: "$# __restrict $#".}
let n_ptr {.restrict.} = cast[ptr array[N, byte]](n.unsafeAddr)
for i in 0 ..< N:
result[N-1 - i] = n_ptr[i]
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