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Refactor bitslice: distinguish usize for indexing vs word type being indexed.

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This commit is contained in:
Felix S. Klock II 2016-05-20 17:40:22 +02:00
parent 59008cbd71
commit f18bafdbe1
1 changed files with 13 additions and 11 deletions
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24
src/librustc_borrowck/bitslice.rs
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@ -10,7 +10,9 @@
use std::mem;
/// `BitSlice` provides helper methods for treating a `[usize]`
pub type Word = usize;
/// `BitSlice` provides helper methods for treating a `[Word]`
/// as a bitvector.
pub trait BitSlice {
fn clear_bit(&mut self, idx: usize) -> bool;
@ -18,12 +20,12 @@ pub trait BitSlice {
fn get_bit(&self, idx: usize) -> bool;
}
impl BitSlice for [usize] {
impl BitSlice for [Word] {
/// Clears bit at `idx` to 0; returns true iff this changed `self.`
fn clear_bit(&mut self, idx: usize) -> bool {
let words = self;
debug!("clear_bit: words={} idx={}",
bits_to_string(words, words.len() * mem::size_of::<usize>()), bit_str(idx));
bits_to_string(words, words.len() * mem::size_of::<Word>()), bit_str(idx));
let BitLookup { word, bit_in_word, bit_mask } = bit_lookup(idx);
debug!("word={} bit_in_word={} bit_mask={}", word, bit_in_word, bit_mask);
let oldv = words[word];
@ -36,7 +38,7 @@ impl BitSlice for [usize] {
fn set_bit(&mut self, idx: usize) -> bool {
let words = self;
debug!("set_bit: words={} idx={}",
bits_to_string(words, words.len() * mem::size_of::<usize>()), bit_str(idx));
bits_to_string(words, words.len() * mem::size_of::<Word>()), bit_str(idx));
let BitLookup { word, bit_in_word, bit_mask } = bit_lookup(idx);
debug!("word={} bit_in_word={} bit_mask={}", word, bit_in_word, bit_mask);
let oldv = words[word];
@ -54,31 +56,31 @@ impl BitSlice for [usize] {
}
struct BitLookup {
/// An index of the word holding the bit in original `[usize]` of query.
/// An index of the word holding the bit in original `[Word]` of query.
word: usize,
/// Index of the particular bit within the word holding the bit.
bit_in_word: usize,
/// Word with single 1-bit set corresponding to where the bit is located.
bit_mask: usize,
bit_mask: Word,
}
#[inline]
fn bit_lookup(bit: usize) -> BitLookup {
let usize_bits = mem::size_of::<usize>() * 8;
let word = bit / usize_bits;
let bit_in_word = bit % usize_bits;
let word_bits = mem::size_of::<Word>() * 8;
let word = bit / word_bits;
let bit_in_word = bit % word_bits;
let bit_mask = 1 << bit_in_word;
BitLookup { word: word, bit_in_word: bit_in_word, bit_mask: bit_mask }
}
fn bit_str(bit: usize) -> String {
fn bit_str(bit: Word) -> String {
let byte = bit >> 3;
let lobits = 1 << (bit & 0b111);
format!("[{}:{}-{:02x}]", bit, byte, lobits)
}
pub fn bits_to_string(words: &[usize], bits: usize) -> String {
pub fn bits_to_string(words: &[Word], bits: usize) -> String {
let mut result = String::new();
let mut sep = '[';