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use std::cmp;
use std::io::{self, Read, Write};
use std::ptr;
const INIT_BUFFER_SIZE: usize = 4096;
pub const MAX_BUFFER_SIZE: usize = 8192 + 4096 * 100;
#[derive(Debug, Default, Clone)]
pub struct Buffer {
vec: Vec<u8>,
tail: usize,
head: usize,
}
impl Buffer {
pub fn new() -> Buffer {
Buffer::default()
}
pub fn reset(&mut self) {
*self = Buffer::new()
}
#[inline]
pub fn len(&self) -> usize {
self.tail - self.head
}
#[inline]
fn available(&self) -> usize {
self.vec.len() - self.tail
}
#[inline]
pub fn is_max_size(&self) -> bool {
self.len() >= MAX_BUFFER_SIZE
}
#[inline]
pub fn is_empty(&self) -> bool {
self.len() == 0
}
#[inline]
pub fn bytes(&self) -> &[u8] {
&self.vec[self.head..self.tail]
}
#[inline]
pub fn consume(&mut self, pos: usize) {
debug_assert!(self.tail >= self.head + pos);
self.head += pos;
if self.head == self.tail {
self.head = 0;
self.tail = 0;
}
}
pub fn consume_leading_lines(&mut self) {
while !self.is_empty() {
match self.vec[self.head] {
b'\r' | b'\n' => {
self.consume(1);
},
_ => return
}
}
}
pub fn read_from<R: Read>(&mut self, r: &mut R) -> io::Result<usize> {
self.maybe_reserve(1);
let n = try!(r.read(&mut self.vec[self.tail..]));
self.tail += n;
self.maybe_reset();
Ok(n)
}
pub fn write_into<W: Write>(&mut self, w: &mut W) -> io::Result<usize> {
if self.is_empty() {
Ok(0)
} else {
let n = try!(w.write(&mut self.vec[self.head..self.tail]));
self.head += n;
self.maybe_reset();
Ok(n)
}
}
pub fn write(&mut self, data: &[u8]) -> usize {
self.maybe_reserve(data.len());
let len = cmp::min(self.available(), data.len());
assert!(self.available() >= len);
unsafe {
ptr::copy(
data.as_ptr(),
self.vec.as_mut_ptr().offset(self.tail as isize),
len
);
}
self.tail += len;
len
}
#[inline]
fn maybe_reserve(&mut self, needed: usize) {
let cap = self.vec.len();
if cap == 0 {
let init = cmp::max(INIT_BUFFER_SIZE, needed);
self.vec = vec![0; init];
} else if self.head > 0 && self.tail == cap && self.head >= needed {
let count = self.tail - self.head;
unsafe {
ptr::copy(
self.vec.as_ptr().offset(self.head as isize),
self.vec.as_mut_ptr(),
count
);
}
self.tail -= count;
self.head = 0;
} else if self.tail == cap && cap < MAX_BUFFER_SIZE {
self.vec.reserve(cmp::min(cap * 4, MAX_BUFFER_SIZE) - cap);
let new = self.vec.capacity() - cap;
unsafe { grow_zerofill(&mut self.vec, new) }
}
}
#[inline]
fn maybe_reset(&mut self) {
if self.tail != 0 && self.tail == self.head {
self.tail = 0;
self.head = 0;
}
}
}
#[inline]
unsafe fn grow_zerofill(buf: &mut Vec<u8>, additional: usize) {
let len = buf.len();
buf.set_len(len + additional);
ptr::write_bytes(buf.as_mut_ptr(), 0, buf.len());
}