use super::{InputNumType, NumberBytes, get_input_num_type, get_number_bytes};
use itertools::Itertools;
use nu_cmd_base::input_handler::{CmdArgument, operate};
use nu_engine::command_prelude::*;
use nu_protocol::shell_error::generic::GenericError;
use std::iter;
struct Arguments {
signed: bool,
bits: Spanned<usize>,
number_size: NumberBytes,
}
impl CmdArgument for Arguments {
fn take_cell_paths(&mut self) -> Option<Vec<CellPath>> {
None
}
}
#[derive(Clone)]
pub struct BitsShl;
impl Command for BitsShl {
fn name(&self) -> &str {
"bits shl"
}
fn signature(&self) -> Signature {
Signature::build("bits shl")
.input_output_types(vec![
(Type::Int, Type::Int),
(Type::Binary, Type::Binary),
(
Type::List(Box::new(Type::Int)),
Type::List(Box::new(Type::Int)),
),
(
Type::List(Box::new(Type::Binary)),
Type::List(Box::new(Type::Binary)),
),
])
.allow_variants_without_examples(true)
.required("bits", SyntaxShape::Int, "Number of bits to shift left.")
.switch(
"signed",
"Always treat input number as a signed number.",
Some('s'),
)
.named(
"number-bytes",
SyntaxShape::Int,
"The word size in number of bytes. Must be `1`, `2`, `4`, or `8` (defaults to the smallest of those that fits the input number).",
Some('n'),
)
.category(Category::Bits)
}
fn description(&self) -> &str {
"Bitwise shift left for ints or binary values."
}
fn search_terms(&self) -> Vec<&str> {
vec!["shift left"]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let head = call.head;
let bits: Spanned<usize> = call.req(engine_state, stack, 0)?;
let signed = call.has_flag(engine_state, stack, "signed")?;
let number_bytes: Option<Spanned<usize>> =
call.get_flag(engine_state, stack, "number-bytes")?;
let number_size = get_number_bytes(number_bytes, head)?;
if let PipelineData::Empty = input {
return Err(ShellError::PipelineEmpty { dst_span: head });
}
let args = Arguments {
signed,
number_size,
bits,
};
operate(action, args, input, head, engine_state.signals())
}
fn examples(&self) -> Vec<Example<'_>> {
vec![
Example {
description: "Shift left a number by 7 bits",
example: "2 | bits shl 7",
result: Some(Value::test_int(0)),
},
Example {
description: "Shift left a number with 2 byte by 7 bits",
example: "2 | bits shl 7 --number-bytes 2",
result: Some(Value::test_int(256)),
},
Example {
description: "Shift left a signed number by 1 bit",
example: "0x7F | bits shl 1 --signed",
result: Some(Value::test_int(-2)),
},
Example {
description: "Shift left a list of numbers",
example: "[5 3 2] | bits shl 2",
result: Some(Value::list(
vec![Value::test_int(20), Value::test_int(12), Value::test_int(8)],
Span::test_data(),
)),
},
Example {
description: "Shift left a binary value",
example: "0x[4f f4] | bits shl 4",
result: Some(Value::binary(vec![0xff, 0x40], Span::test_data())),
},
]
}
}
fn action(input: &Value, args: &Arguments, span: Span) -> Value {
let Arguments {
signed,
number_size,
bits,
} = *args;
let bits_span = bits.span;
let bits = bits.item;
match input {
Value::Int { val, .. } => {
use InputNumType::*;
let val = *val;
let bits = bits as u32;
let input_num_type = get_input_num_type(val, signed, number_size);
if !input_num_type.is_permitted_bit_shift(bits) {
return Value::error(
ShellError::IncorrectValue {
msg: format!(
"Trying to shift by more than the available bits (permitted < {})",
input_num_type.num_bits()
),
val_span: bits_span,
call_span: span,
},
span,
);
}
let int = match input_num_type {
One => ((val as u8) << bits) as i64,
Two => ((val as u16) << bits) as i64,
Four => ((val as u32) << bits) as i64,
Eight => {
let Ok(i) = i64::try_from((val as u64) << bits) else {
return Value::error(
ShellError::Generic(
GenericError::new(
"result out of range for int",
format!(
"shifting left by {bits} is out of range for the value {val}"
),
span,
)
.with_help("Ensure the result fits in a 64-bit signed integer."),
),
span,
);
};
i
}
SignedOne => ((val as i8) << bits) as i64,
SignedTwo => ((val as i16) << bits) as i64,
SignedFour => ((val as i32) << bits) as i64,
SignedEight => val << bits,
};
Value::int(int, span)
}
Value::Binary { val, .. } => {
let byte_shift = bits / 8;
let bit_shift = bits % 8;
if bits > val.len() * 8 {
return Value::error(
ShellError::IncorrectValue {
msg: format!(
"Trying to shift by more than the available bits ({})",
val.len() * 8
),
val_span: bits_span,
call_span: span,
},
span,
);
}
let bytes = if bit_shift == 0 {
shift_bytes_left(val, byte_shift)
} else {
shift_bytes_and_bits_left(val, byte_shift, bit_shift)
};
Value::binary(bytes, span)
}
Value::Error { .. } => input.clone(),
other => Value::error(
ShellError::OnlySupportsThisInputType {
exp_input_type: "int or binary".into(),
wrong_type: other.get_type().to_string(),
dst_span: span,
src_span: other.span(),
},
span,
),
}
}
fn shift_bytes_left(data: &[u8], byte_shift: usize) -> Vec<u8> {
let len = data.len();
let mut output = vec![0; len];
output[..len - byte_shift].copy_from_slice(&data[byte_shift..]);
output
}
fn shift_bytes_and_bits_left(data: &[u8], byte_shift: usize, bit_shift: usize) -> Vec<u8> {
use itertools::Position::*;
debug_assert!(
(1..8).contains(&bit_shift),
"Bit shifts of 0 can't be handled by this impl and everything else should be part of the byteshift"
);
data.iter()
.copied()
.skip(byte_shift)
.circular_tuple_windows::<(u8, u8)>()
.with_position()
.map(|(pos, (lhs, rhs))| match pos {
Last | Only => lhs << bit_shift,
_ => (lhs << bit_shift) | (rhs >> (8 - bit_shift)),
})
.chain(iter::repeat_n(0, byte_shift))
.collect::<Vec<u8>>()
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() -> nu_test_support::Result {
nu_test_support::test().examples(BitsShl)
}
}