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65 lines
1.4 KiB
65 lines
1.4 KiB
//! Mask applied to a data source or destination
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use crate::error::AsmError;
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/// Bit mask to apply to a value
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#[derive(Debug, Clone, Copy, Eq, PartialEq)]
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pub struct Mask {
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/// Length of the selected bit slice
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len: u8,
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/// Offset of the selected bit slice from bit zero
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offset: u8,
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}
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impl Default for Mask {
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fn default() -> Self {
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Mask {
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len: 64,
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offset: 0,
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}
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}
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}
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impl Mask {
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pub const BYTE: Mask = Mask {
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len: 8,
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offset: 0,
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};
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pub const HALF_WORD: Mask = Mask {
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len: 16,
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offset: 0,
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};
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pub const WORD: Mask = Mask {
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len: 32,
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offset: 0,
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};
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pub const DOUBLE_WORD: Mask = Mask {
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len: 64,
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offset: 0,
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};
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pub const FULL: Mask = Self::DOUBLE_WORD;
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pub fn new(len: u8, offset: u8) -> Result<Self, AsmError> {
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if len == 0 || offset >= 64 {
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// create the invalid mask to display it in the error
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return Err(AsmError::BadMask(Mask {
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len,
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offset,
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}));
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}
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Ok(Self {
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len: len.min(64 - offset),
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offset,
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})
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}
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/// Get a binary mask representing the span
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pub fn as_bitmask(self) -> u64 {
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((1 << self.len) - 1) << self.offset
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}
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pub fn is_default(self) -> bool {
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self == Self::default()
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}
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}
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