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//! Universal low-level interface to let Tokay read input from different sources.
use std::io::prelude::*;
/// Position inside a reader, with row and column counting.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct Offset {
// todo: Hold source filename information as well in the future?
pub offset: usize,
pub row: u32,
pub col: u32,
}
pub type Range = std::ops::Range<usize>;
// Abstraction of a buffered Reader with internal buffering, offset counting and clean-up.
pub struct Reader {
reader: Box<dyn BufRead>, // Reader object to read from
buffer: String, // Internal buffer
offset: Offset, // Current offset
eof: bool, // EOF marker
}
impl Reader {
/// Creates a new reader on buffer read.
pub fn new(reader: Box<dyn BufRead>) -> Self {
Self {
reader,
buffer: String::with_capacity(1024), //fixme: Modifyable capacity?
offset: Offset {
offset: 0,
row: 1,
col: 1,
},
eof: false,
}
}
/// Internal function for reading a line.
fn read_line(&mut self) -> Option<usize> {
if let Ok(n) = self.reader.read_line(&mut self.buffer) {
if n == 0 {
self.eof = true;
return None;
}
Some(n)
} else {
self.eof = true;
None
}
}
pub fn next(&mut self) -> Option<char> {
loop {
if let Some(ch) = self.buffer[self.offset.offset..].chars().next() {
self.offset.offset += ch.len_utf8();
if ch == '\n' {
self.offset.row += 1;
self.offset.col = 1;
} else {
self.offset.col += 1;
}
return Some(ch);
}
if self.eof {
return None;
}
self.read_line();
}
}
pub fn peek(&mut self) -> Option<char> {
loop {
if let Some(ch) = self.buffer[self.offset.offset..].chars().next() {
return Some(ch);
}
if self.eof {
return None;
}
self.read_line();
}
}
pub fn tell(&self) -> Offset {
self.offset
}
pub fn eof(&mut self) -> bool {
if self.buffer[self.offset.offset..].chars().next().is_some() {
false
} else {
if !self.eof {
self.peek();
}
self.eof
}
}
pub fn reset(&mut self, offset: Offset) {
self.offset = offset;
}
/// Capture last length characters.
pub fn capture_last(&self, mut length: usize) -> Range {
if length > self.offset.offset {
length = self.offset.offset;
}
self.offset.offset - length..self.offset.offset
}
// Capture all characters from start to current offset.
pub fn capture_from(&self, start: &Offset) -> Range {
let mut start = start.offset;
if start > self.offset.offset {
start = self.offset.offset;
}
start..self.offset.offset
}
pub fn print(&self, start: usize) {
println!("{:?}", &self.buffer[start..self.offset.offset])
}
/// Get slice from range
pub fn get(&self, range: &Range) -> &str {
&self.buffer[range.start..range.end]
}
/// Commits current input buffer and removes cached content
pub fn commit(&mut self) {
self.buffer.drain(0..self.offset.offset);
self.offset.offset = 0;
}
/// Take one character accepted by callback
pub fn take<F>(&mut self, accept: F) -> Option<char>
where
F: Fn(char) -> bool,
{
if let Some(ch) = self.peek() {
if accept(ch) {
return Some(self.next().unwrap());
}
}
None
}
/// Read while conditional callback accepts characters
pub fn span<F>(&mut self, accept: F) -> Option<&str>
where
F: Fn(char) -> bool + Copy,
{
let start = self.offset.offset;
while self.take(accept).is_some() {}
if start < self.offset.offset {
Some(&self.buffer[start..self.offset.offset])
} else {
None
}
}
}