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#
#
# Nim's Runtime Library
# (c) Copyright 2017 Nim Authors
# (c) Copyright 2019 Status Research
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module implements a series of low level methods for bit manipulation.
## By default, this module use compiler intrinsics to improve performance
## on supported compilers: ``GCC``, ``LLVM_GCC``, ``CLANG``, ``VCC``, ``ICC``.
##
## The module will fallback to pure nim procs incase the backend is not supported.
## You can also use the flag `noIntrinsicsBitOpts` to disable compiler intrinsics.
##
## This module is also compatible with other backends: ``Javascript``, ``Nimscript``
## as well as the ``compiletime VM``.
{.push raises: [].}
import
endians2
const
useBuiltins = not defined(noIntrinsicsBitOpts)
template bitsof*(T: typedesc[SomeInteger]): int = 8 * sizeof(T)
template bitsof*(x: SomeInteger): int = 8 * sizeof(x)
type BitIndexable = SomeUnsignedInt
# #### Pure Nim version ####
func nextPow2Nim(x: SomeUnsignedInt): SomeUnsignedInt =
var v = x - 1
# round down, make sure all bits are 1 below the threshold, then add 1
v = v or v shr 1
v = v or v shr 2
v = v or v shr 4
when bitsof(x) > 8:
v = v or v shr 8
when bitsof(x) > 16:
v = v or v shr 16
when bitsof(x) > 32:
v = v or v shr 32
v + 1
func firstOneNim(x: uint32): int =
## Returns the 1-based index of the least significant set bit of x, or if x is zero, returns zero.
# https://graphics.stanford.edu/%7Eseander/bithacks.html#ZerosOnRightMultLookup
const lookup = [0'u8, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15,
25, 17, 4, 8, 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9]
if x == 0:
0
else:
let k = not x + 1 # get two's complement
cast[int](1 + lookup[((x and k) * 0x077CB531'u32) shr 27])
func firstOneNim(x: uint8|uint16): int = firstOneNim(x.uint32)
func firstOneNim(x: uint64): int =
## Returns the 1-based index of the least significant set bit of x, or if x is zero, returns zero.
# https://graphics.stanford.edu/%7Eseander/bithacks.html#ZerosOnRightMultLookup
if (x and uint32.high) == 0:
cast[int](32 + uint(firstOneNim(uint32(x shr 32'u32))))
else:
firstOneNim(uint32(x))
func log2truncNim(x: uint8|uint16|uint32): int =
## Quickly find the log base 2 of a 32-bit or less integer.
# https://graphics.stanford.edu/%7Eseander/bithacks.html#IntegerLogDeBruijn
# https://stackoverflow.com/questions/11376288/fast-computing-of-log2-for-64-bit-integers
const lookup: array[32, uint8] = [0'u8, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18,
22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31]
var v = x.uint32
v = v or v shr 1 # first round down to one less than a power of 2
v = v or v shr 2
v = v or v shr 4
v = v or v shr 8
v = v or v shr 16
cast[int](lookup[uint32(v * 0x07C4ACDD'u32) shr 27])
func log2truncNim(x: uint64): int =
## Quickly find the log base 2 of a 64-bit integer.
# https://graphics.stanford.edu/%7Eseander/bithacks.html#IntegerLogDeBruijn
# https://stackoverflow.com/questions/11376288/fast-computing-of-log2-for-64-bit-integers
const lookup: array[64, uint8] = [0'u8, 58, 1, 59, 47, 53, 2, 60, 39, 48, 27, 54,
33, 42, 3, 61, 51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22, 4, 62,
57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21, 56, 45, 25, 31,
35, 16, 9, 12, 44, 24, 15, 8, 23, 7, 6, 5, 63]
var v = x
v = v or v shr 1 # first round down to one less than a power of 2
v = v or v shr 2
v = v or v shr 4
v = v or v shr 8
v = v or v shr 16
v = v or v shr 32
cast[int](lookup[(v * 0x03F6EAF2CD271461'u64) shr 58])
func countOnesNim(x: uint8|uint16|uint32): int =
## Counts the set bits in integer. (also called Hamming weight.)
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
var v = x.uint32
v = v - ((v shr 1) and 0x55555555)
v = (v and 0x33333333) + ((v shr 2) and 0x33333333)
cast[int](((v + (v shr 4) and 0xF0F0F0F) * 0x1010101) shr 24)
func countOnesNim(x: uint64): int =
## Counts the set bits in integer. (also called Hamming weight.)
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
var v = x
v = v - ((v shr 1'u64) and 0x5555555555555555'u64)
v = (v and 0x3333333333333333'u64) + ((v shr 2'u64) and 0x3333333333333333'u64)
v = (v + (v shr 4'u64) and 0x0F0F0F0F0F0F0F0F'u64)
cast[int]((v * 0x0101010101010101'u64) shr 56'u64)
func parityNim(x: SomeUnsignedInt): int =
# formula id from: https://graphics.stanford.edu/%7Eseander/bithacks.html#ParityParallel
var v = x
when sizeof(v) == 8:
v = v xor (v shr 32)
when sizeof(v) >= 4:
v = v xor (v shr 16)
when sizeof(v) >= 2:
v = v xor (v shr 8)
v = v xor (v shr 4)
v = v and 0xf
cast[int]((0x6996'u shr v) and 1)
when (defined(gcc) or defined(llvm_gcc) or defined(clang)) and useBuiltins:
# Returns the number of set 1-bits in value.
func builtin_popcount(x: cuint): cint {.importc: "__builtin_popcount", nodecl.}
func builtin_popcountll(x: culonglong): cint {.importc: "__builtin_popcountll", nodecl.}
# Returns the bit parity in value
func builtin_parity(x: cuint): cint {.importc: "__builtin_parity", nodecl.}
func builtin_parityll(x: culonglong): cint {.importc: "__builtin_parityll", nodecl.}
# Returns one plus the index of the least significant 1-bit of x, or if x is zero, returns zero.
func builtin_ffs(x: cint): cint {.importc: "__builtin_ffs", nodecl.}
func builtin_ffsll(x: clonglong): cint {.importc: "__builtin_ffsll", nodecl.}
# Returns the number of leading 0-bits in x, starting at the most significant bit position. If x is 0, the result is undefined.
func builtin_clz(x: cuint): cint {.importc: "__builtin_clz", nodecl.}
func builtin_clzll(x: culonglong): cint {.importc: "__builtin_clzll", nodecl.}
func countOnesBuiltin(x: SomeUnsignedInt): int =
when bitsof(x) == bitsof(culonglong):
cast[int](builtin_popcountll(x.culonglong))
else:
cast[int](builtin_popcount(x.cuint))
func parityBuiltin(x: SomeUnsignedInt): int =
when bitsof(x) == bitsof(culonglong):
cast[int](builtin_parityll(x.culonglong))
else:
cast[int](builtin_parity(x.cuint))
func firstOneBuiltin(x: SomeUnsignedInt): int =
when bitsof(x) == bitsof(clonglong):
cast[int](builtin_ffsll(cast[clonglong](x)))
else:
cast[int](builtin_ffs(cast[cint](x.cuint)))
func log2truncBuiltin(v: uint8|uint16|uint32): int =
cast[int](31 - cast[cuint](builtin_clz(v.uint32)))
func log2truncBuiltin(v: uint64): int =
cast[int](63 - cast[cuint](builtin_clzll(v)))
elif defined(vcc) and useBuiltins:
const arch64 = sizeof(int) == 8
# Counts the number of one bits (population count) in a 16-, 32-, or 64-byte unsigned integer.
func builtin_popcnt16(a2: uint16): uint16 {.importc: "__popcnt16" header: "<intrin.h>".}
func builtin_popcnt32(a2: uint32): uint32 {.importc: "__popcnt" header: "<intrin.h>".}
# Search the mask data from most significant bit (MSB) to least significant bit (LSB) for a set bit (1).
func bitScanReverse(index: ptr culong, mask: culong): cuchar {.importc: "_BitScanReverse", header: "<intrin.h>".}
# Search the mask data from least significant bit (LSB) to the most significant bit (MSB) for a set bit (1).
func bitScanForward(index: ptr culong, mask: culong): cuchar {.importc: "_BitScanForward", header: "<intrin.h>".}
when arch64:
func builtin_popcnt64(a2: uint64): uint64 {.importc: "__popcnt64" header: "<intrin.h>".}
func bitScanReverse64(index: ptr culong, mask: uint64): cuchar {.importc: "_BitScanReverse64", header: "<intrin.h>".}
func bitScanForward64(index: ptr culong, mask: uint64): cuchar {.importc: "_BitScanForward64", header: "<intrin.h>".}
func countOnesBuiltin(v: uint8|uint16): int =
cast[int](builtin_popcnt16(v.uint16))
func countOnesBuiltin(v: uint32): int =
cast[int](builtin_popcnt32(v))
func countOnesBuiltin(v: uint64): int =
when arch64:
cast[int](builtin_popcnt64(v))
else:
cast[int](
builtin_popcnt32((v and uint32.high).uint32) +
builtin_popcnt32((v shr 32'u64).uint32))
template checkedScan(fnc: untyped, x: typed, def: typed): int =
var index{.noinit.}: culong
if fnc(index.addr, v) == cuchar(0): def
else: cast[int](index)
func firstOneBuiltin(v: uint8|uint16|uint32): int =
1 + checkedScan(bitScanForward, v.culong, -1)
func firstOneBuiltin(v: uint64): int =
when arch64:
1 + checkedScan(bitScanForward64, v.culonglong, -1)
else:
firstOneNim(v)
template bitScan(fnc: untyped, x: typed): int =
var index{.noinit.}: culong
if fnc(index.addr, v) == cuchar(0): 0
else: cast[int](index)
func log2truncBuiltin(v: uint8|uint16|uint32): int =
bitScan(bitScanReverse, v.culong)
func log2truncBuiltin(v: uint64): int =
when arch64:
bitScan(bitScanReverse64, v.culong)
else:
log2truncNim(v)
elif defined(icc) and useBuiltins:
const arch64 = sizeof(int) == 8
# Intel compiler intrinsics: http://fulla.fnal.gov/intel/compiler_c/main_cls/intref_cls/common/intref_allia_misc.htm
# see also: https://software.intel.com/en-us/node/523362
# Count the number of bits set to 1 in an integer a, and return that count in dst.
func builtin_popcnt32(x: cint): cint {.importc: "_popcnt32" header: "<immintrin.h>".}
# Returns the number of trailing 0-bits in x, starting at the least significant bit position. If x is 0, the result is undefined.
func bitScanForward(p: ptr uint32, b: uint32): cuchar {.importc: "_BitScanForward", header: "<immintrin.h>".}
# Returns the number of leading 0-bits in x, starting at the most significant bit position. If x is 0, the result is undefined.
func bitScanReverse(p: ptr uint32, b: uint32): cuchar {.importc: "_BitScanReverse", header: "<immintrin.h>".}
when arch64:
func builtin_popcnt64(x: uint64): cint {.importc: "_popcnt64" header: "<immintrin.h>".}
func bitScanForward64(p: ptr uint32, b: uint64): cuchar {.importc: "_BitScanForward64", header: "<immintrin.h>".}
func bitScanReverse64(p: ptr uint32, b: uint64): cuchar {.importc: "_BitScanReverse64", header: "<immintrin.h>".}
template checkedScan(fnc: untyped, x: typed, def: typed): int =
var index{.noinit.}: culong
if fnc(index.addr, v) == cuchar(0): def
else: cast[int](index)
template bitScan(fnc: untyped, x: typed): int =
var index{.noinit.}: culong
if fnc(index.addr, v) == cuchar(0): 0
else: cast[int](index)
func countOnesBuiltin(v: uint8|uint16|uint32): int =
cast[int](builtin_popcnt32(cast[cint](v)))
func countOnesBuiltin(v: uint64): int =
when arch64:
cast[int](builtin_popcnt64(v))
else:
cast[int](
builtin_popcnt32(cast[cint](v and 0xFFFFFFFF'u64)) +
builtin_popcnt32(cast[cint](v shr 32'u64)))
func firstOneBuiltin(v: uint8|uint16|uint32): int =
1 + checkedScan(bitScanForward, v.culong, -1)
func firstOneBuiltin(v: uint64): int =
when arch64:
1 + checkedScan(bitScanForward64, v.culong, -1)
else:
firstOneNim(v)
func log2truncBuiltin(v: uint8|uint16|uint32): int =
bitScan(bitScanReverse, v.culong)
func log2truncBuiltin(v: uint64): int =
when arch64:
bitScan(bitScanReverse64, v.culong)
else:
log2truncNim(v)
func countOnes*(x: SomeUnsignedInt): int {.inline.} =
## Counts the set bits in integer. (also called `Hamming weight`:idx:.)
##
## Example:
## doAssert countOnes(0b01000100'u8) == 2
when nimvm:
countOnesNim(x)
else:
when declared(countOnesBuiltin):
countOnesBuiltin(x)
else:
countOnesNim(x)
func countZeros*(x: SomeUnsignedInt): int {.inline.} =
bitsof(x) - countOnes(x)
func parity*(x: SomeUnsignedInt): int {.inline.} =
## Calculate the bit parity in integer. If number of 1-bit
## is odd parity is 1, otherwise 0.
##
## Example:
## doAssert parity(0b00000001'u8) == 1
# Can be used a base if creating ASM version.
# https://stackoverflow.com/questions/21617970/how-to-check-if-value-has-even-parity-of-bits-or-odd
when nimvm:
parityNim(x)
else:
when declared(parityBuiltin):
parityBuiltin(x)
else:
parityNim(x)
func firstOne*(x: SomeUnsignedInt): int {.inline.} =
## Returns the 1-based index of the least significant set bit of x.
## If `x` is zero result is 0
##
## firstOne(x) == trailingZeros(x) + 1
##
## Example:
## doAssert firstOneBit(0b00000010'u8) == 2
##
when nimvm:
firstOneNim(x)
else:
when declared(firstOneBuiltin):
firstOneBuiltin(x)
else:
firstOneNim(x)
func log2trunc*(x: SomeUnsignedInt): int {.inline.} =
## Return the truncated base 2 logarithm of `x` - this is the zero-based
## index of the last set bit.
##
## If `x` is zero result is -1
##
## log2trunc(x) == bitsof(x) - leadingZeros(x) - 1.
##
## Example:
## doAssert log2trunc(0b01001000'u8) == 6
if x == 0: -1
else:
when nimvm:
log2truncNim(x)
else:
when declared(log2truncBuiltin):
log2truncBuiltin(x)
else:
log2truncNim(x)
template bitWidth*(x: SomeUnsignedInt): int =
## Returns the number of bits needed to write down the
## number `x` in binary. If `x` is zero, the result is 0.
log2trunc(x) + 1
func leadingZeros*(x: SomeInteger): int {.inline.} =
## Returns the number of leading zero bits in integer.
## If `x` is zero, result is bitsof(x)
##
## Example:
## doAssert leadingZeros(0b00000000'u8) == 8
## doAssert leadingZeros(0b00100000'u8) == 2
##
# Performance note:
# On recent x86_64 cpu's, this translates to the LZCNT instruction
bitsof(x) - 1 - log2trunc(x)
func trailingZeros*(x: SomeUnsignedInt): int {.inline.} =
## Returns the number of trailing zeros in integer.
## If `x` is zero, result is sizeof(x) * 8
##
## Example:
## doAssert trailingZeros(0b00000010'u8) == 1
##
# Performance note:
# On recent x86_64 cpu's, this translates to the TZCNT instruction
if x == 0:
bitsof(x)
else:
firstOne(x) - 1
func nextPow2*(x: SomeUnsignedInt): SomeUnsignedInt {.inline.} =
## Calculate the next power-of-2 of x - wraps to 0
##
## Examples:
## doAssert nextPow2(3) == 4
## doAssert nextPow2(4) == 4
nextPow2Nim(x)
func rotateLeft*(v: SomeUnsignedInt, amount: SomeInteger):
SomeUnsignedInt {.inline.} =
## Left-rotate bits in an unsigned value
# using this form instead of the one below should handle any value
# out of range as well as negative values.
# taken from: https://en.wikipedia.org/wiki/Circular_shift#Implementing_circular_shifts
const mask = 8 * sizeof(v) - 1
let amount = int(amount and mask)
(v shl amount) or (v shr ( (-amount) and mask))
func rotateRight*(v: SomeUnsignedInt, amount: SomeInteger):
SomeUnsignedInt {.inline.} =
## Right-rotate bits in an unsigned value.
const mask = bitsof(v) - 1
let amount = int(amount and mask)
(v shr amount) or (v shl ( (-amount) and mask))
template mostSignificantBit(T: type): auto =
const res = 1 shl (sizeof(T) * 8 - 1)
T(res)
template getBit*(x: BitIndexable, bit: Natural): bool =
## reads a bit from `x`, assuming 0 to be the position of the
## least significant bit
type T = type(x)
((x shr bit) and T(1)) != 0
template getBitLE*(x: BitIndexable, bit: Natural): bool =
getBit(x, bit)
template getBitBE*(x: BitIndexable, bit: Natural): bool =
## Reads a bit from `x`, assuming 0 to be the position of
## the most significant bit.
##
## This indexing may be natural when you are considering the
## string representation of a bit field. For example, 72 can
## be written in binary as 0b01001000. The first bit here is
## zero, while the second bit is one.
##
## Since the string representation will depend on the size of
## the operand, using `getBitBE` with the same numeric value
## and a bit position may produce different results depending
## on the machine type used to store the value. For this reason,
## this indexing scheme is considered more error-prone and
## `getBitLE` is considering the default indexing scheme.
(x and mostSignificantBit(x.type) shr bit) != 0
func setBit*(x: var BitIndexable, bit: Natural) {.inline.} =
## sets bit in `x`, assuming 0 to be the position of the
## least significant bit
type T = type(x)
let mask = T(1) shl bit
x = x or mask
template setBitLE*(x: var BitIndexable, bit: Natural) =
setBit(x, bit)
func setBitBE*(x: var BitIndexable, bit: Natural) {.inline.} =
## sets a bit in `x`, assuming 0 to be the position of the
## most significant bit
let mask = mostSignificantBit(x.type) shr bit
x = x or mask
func changeBit*(x: var BitIndexable, bit: Natural, val: bool) {.inline.} =
## changes a bit in `x` to val, assuming 0 to be the position of the
## least significant bit
type T = type(x)
x = (x and not (T(1) shl bit)) or (T(val) shl bit)
template changeBitLE*(x: var BitIndexable, bit: Natural, val: bool) =
setBit(x, bit, val)
func changeBitBE*(x: var BitIndexable, bit: Natural, val: bool) {.inline.} =
## changes a bit in `x` to val, assuming 0 to be the position of the
## most significant bit
changeBit(x, bitsof(x) - 1 - bit, val)
func clearBit*(x: var BitIndexable, bit: Natural) {.inline.} =
## clears bit in a byte, assuming 0 to be the position of the
## least significant bit
type T = type(x)
let mask = T(1) shl bit
x = x and not mask
template clearBitLE*(x: var BitIndexable, bit: Natural) =
clearBit(x, bit)
func clearBitBE*(x: var BitIndexable, bit: Natural) {.inline.} =
## clears a bit in `x`, assuming 0 to be the position of the
## most significant bit
let mask = mostSignificantBit(x.type) shr bit
x = x and not mask
func toggleBit*(x: var BitIndexable, bit: Natural) {.inline.} =
## toggles (inverts) bit in `x`, assuming 0 to be the position of the
## least significant bit
type T = type(x)
let mask = T(1) shl bit
x = x xor mask
template toggleBitLE*(x: var BitIndexable, bit: Natural) =
toggleBit(x, bit)
func toggleBitBE*(x: var BitIndexable, bit: Natural) {.inline.} =
## toggles (inverts) a bit in `x`, assuming 0 to be the position of the
## most significant bit
let mask = mostSignificantBit(x.type) shr bit
x = x xor mask
template byteIndex(pos: Natural): int =
pos shr 3 # same as pos div 8
template bitIndex(pos: Natural): int =
pos and 0b111 # same as pos mod 8
func getBit*(bytes: openArray[byte], pos: Natural): bool {.inline.} =
getBit(bytes[byteIndex pos], bitIndex pos)
template getBitLE*(bytes: openArray[byte], pos: Natural): bool =
getBit(bytes, pos)
func getBitBE*(bytes: openArray[byte], pos: Natural): bool {.inline.} =
getBitBE(bytes[byteIndex pos], bitIndex pos)
func changeBit*(bytes: var openArray[byte], pos: Natural, value: bool) {.inline.} =
changeBit(bytes[byteIndex pos], bitIndex pos, value)
template changeBitLE*(bytes: var openArray[byte], pos: Natural, value: bool) =
changeBit(bytes, pos, value)
func changeBitBE*(bytes: var openArray[byte], pos: Natural, value: bool) {.inline.} =
changeBitBE(bytes[byteIndex pos], bitIndex pos, value)
func setBit*(bytes: var openArray[byte], pos: Natural) {.inline.} =
setBit(bytes[byteIndex pos], bitIndex pos)
template setBitLE*(bytes: var openArray[byte], pos: Natural) =
setBit(bytes, pos)
func setBitBE*(bytes: var openArray[byte], pos: Natural) {.inline.} =
setBitBE(bytes[byteIndex pos], bitIndex pos)
func clearBit*(bytes: var openArray[byte], pos: Natural) {.inline.} =
clearBit(bytes[byteIndex pos], bitIndex pos)
template clearBitLE*(bytes: var openArray[byte], pos: Natural) =
clearBit(bytes, pos)
func clearBitBE*(bytes: var openArray[byte], pos: Natural) {.inline.} =
clearBitBE(bytes[byteIndex pos], bitIndex pos)
func toggleBit*(bytes: var openArray[byte], pos: Natural) {.inline.} =
toggleBit(bytes[byteIndex pos], bitIndex pos)
template toggleBitLE*(bytes: var openArray[byte], pos: Natural) =
toggleBit(bytes, pos)
func toggleBitBE*(bytes: var openArray[byte], pos: Natural) {.inline.} =
toggleBitBE(bytes[byteIndex pos], bitIndex pos)
template setBit*(x: var BitIndexable, bit: Natural, val: bool) {.deprecated: "changeBit".} =
changeBit(x, bit, val)
template setBitLE*(x: var BitIndexable, bit: Natural, val: bool) {.deprecated: "changeBitLE".} =
changeBitLE(x, bit, val)
template setBitBE*(x: var BitIndexable, bit: Natural, val: bool) {.deprecated: "changeBitBE".} =
changeBitBE(x, bit, val)
template raiseBit*(x: var BitIndexable, bit: Natural) {.deprecated: "setBit".} =
setBit(x, bit)
template raiseBitLE*(x: var BitIndexable, bit: Natural) {.deprecated: "setBitLE".} =
setBitLE(x, bit)
template raiseBitBE*(x: var BitIndexable, bit: Natural) {.deprecated: "setBitBE".} =
setBitBE(x, bit)
func lowerBit*(x: var BitIndexable, bit: Natural) {.inline, deprecated: "clearBit".} =
clearBit(x, bit)
template lowerBitLE*(x: var BitIndexable, bit: Natural) {.deprecated: "clearBitLE".} =
clearBit(x, bit)
template lowerBitBE*(x: var BitIndexable, bit: Natural) {.deprecated: "clearBitBE".} =
clearBitBE(x, bit)
template setBit*(bytes: var openArray[byte], pos: Natural, val: bool) {.deprecated: "changeBit".} =
changeBit(bytes, pos, val)
template setBitLE*(bytes: var openArray[byte], pos: Natural, val: bool) {.deprecated: "changeBitLE".} =
changeBitLE(bytes, pos, val)
template setBitBE*(bytes: var openArray[byte], pos: Natural, val: bool) {.deprecated: "changeBitBE".} =
changeBitBE(bytes, pos, val)
template raiseBit*(bytes: var openArray[byte], pos: Natural) {.deprecated: "setBit".} =
setBit(bytes, pos)
template raiseBitLE*(bytes: var openArray[byte], pos: Natural) {.deprecated: "setBitLE".} =
setBitLE(bytes, pos)
template raiseBitBE*(bytes: var openArray[byte], pos: Natural) {.deprecated: "setBitBE".} =
setBitBE(bytes, pos)
template lowerBit*(bytes: var openArray[byte], pos: Natural) {.deprecated: "clearBit".} =
clearBit(bytes, pos)
template lowerBitLE*(bytes: var openArray[byte], pos: Natural) {.deprecated: "clearBitLE".} =
clearBitLE(bytes, pos)
template lowerBitBE*(bytes: var openArray[byte], pos: Natural) {.deprecated: "clearBitBE".} =
clearBitBE(bytes, pos)
func getBitsBE*(data: openArray[byte], slice: HSlice, T: type[SomeUnsignedInt]): T =
## Treats `data` as an unsigned big endian integer and returns a slice of bits
## extracted from it, assuming 0 to be the possition of the most significant bit.
let totalBits = data.len * 8
template normalizeIdx(idx): int =
when idx is BackwardsIndex: totalBits - int(idx)
else: int(idx)
let
a = normalizeIdx(slice.a)
b = normalizeIdx(slice.b) + 1
sliceLen = b - a
const resultBits = sizeof(result) * 8
doAssert a < b and sliceLen <= resultBits and b <= totalBits
let limbs = cast[ptr UncheckedArray[T]](unsafeAddr data[0])
template readLimb(idx: int): auto =
when cpuEndian == bigEndian or sizeof(result) == 1:
limbs[][idx]
else:
swapBytes(limbs[][idx])
let
firstLimbIdx = a div resultBits
firstLimbUnusedBits = (a mod resultBits)
firstLimbUsedBits = resultBits - firstLimbUnusedBits
firstLimb = readLimb firstLimbIdx
if sliceLen > firstLimbUsedBits:
let
bitsFromSecondLimb = sliceLen - firstLimbUsedBits
secondLimb = readLimb(firstLimbIdx + 1)
((firstLimb shl firstLimbUnusedBits) shr (firstLimbUnusedBits - bitsFromSecondLimb)) or
(secondLimb shr (resultBits - bitsFromSecondLimb))
else:
(firstLimb shl firstLimbUnusedBits) shr (resultBits - sliceLen)
template getBitsBE*(data: openArray[byte], slice: HSlice): BiggestUInt =
getBitsBE(data, slice, BiggestUInt)
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