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#![cfg_attr(feature = "nightly", deny(missing_docs))]
#![cfg_attr(feature = "nightly", feature(external_doc))]
#![cfg_attr(feature = "nightly", doc(include = "../README.md"))]
#![cfg_attr(test, deny(warnings))]
#[macro_use]
extern crate failure;
extern crate random_access_storage;
use failure::Error;
use random_access_storage::RandomAccess;
use std::cmp;
use std::io;
#[derive(Debug)]
pub struct RandomAccessMemory {
page_size: usize,
buffers: Vec<Vec<u8>>,
length: usize,
}
impl RandomAccessMemory {
#[cfg_attr(feature = "cargo-clippy", allow(new_ret_no_self))]
pub fn new(page_size: usize) -> Self {
RandomAccessMemory {
buffers: Vec::new(),
page_size,
length: 0,
}
}
pub fn default() -> Self {
RandomAccessMemory {
buffers: Vec::new(),
page_size: 1024 * 1024,
length: 0,
}
}
pub fn with_buffers(page_size: usize, buffers: Vec<Vec<u8>>) -> Self {
RandomAccessMemory {
page_size,
buffers,
length: 0,
}
}
}
impl RandomAccess for RandomAccessMemory {
type Error = Error;
fn write(&mut self, offset: usize, data: &[u8]) -> Result<(), Self::Error> {
let new_len = offset + data.len();
if new_len > self.length {
self.length = new_len;
}
let mut page_num = offset / self.page_size;
let mut page_cursor = offset - (page_num * self.page_size);
let mut data_cursor = 0;
while data_cursor < data.len() {
let data_bound = data.len() - data_cursor;
let upper_bound = cmp::min(self.page_size, page_cursor + data_bound);
let range = page_cursor..upper_bound;
let range_len = range.len();
if self.buffers.get(page_num).is_none() {
let buf = vec![0; self.page_size];
if self.buffers.len() < page_num + 1 {
self.buffers.resize(page_num + 1, buf);
} else {
self.buffers[page_num] = buf;
}
}
let buffer = &mut self.buffers[page_num];
for (index, buf_index) in range.enumerate() {
buffer[buf_index] = data[data_cursor + index];
}
page_num += 1;
page_cursor = 0;
data_cursor += range_len;
}
Ok(())
}
fn read(
&mut self,
offset: usize,
length: usize,
) -> Result<Vec<u8>, Self::Error> {
ensure!(
(offset + length) <= self.length,
format!(
"Read bounds exceeded. {} < {}..{}",
self.length,
offset,
offset + length
)
);
let mut page_num = offset / self.page_size;
let mut page_cursor = offset - (page_num * self.page_size);
let mut res_buf = vec![0; length];
let mut res_cursor = 0;
let res_capacity = length;
while res_cursor < res_capacity {
let res_bound = res_capacity - res_cursor;
let page_bound = self.page_size - page_cursor;
let relative_bound = cmp::min(res_bound, page_bound);
let upper_bound = page_cursor + relative_bound;
let range = page_cursor..upper_bound;
match self.buffers.get(page_num) {
Some(buf) => {
for (index, buf_index) in range.enumerate() {
res_buf[res_cursor + index] = buf[buf_index];
}
}
None => {
for (index, _) in range.enumerate() {
res_buf[res_cursor + index] = 0;
}
}
}
res_cursor += relative_bound;
page_num += 1;
page_cursor = 0;
}
Ok(res_buf)
}
fn read_to_writer(
&mut self,
_offset: usize,
_length: usize,
_buf: &mut impl io::Write,
) -> Result<(), Self::Error> {
unimplemented!()
}
fn del(&mut self, offset: usize, length: usize) -> Result<(), Self::Error> {
let overflow = offset % self.page_size;
let inc = match overflow {
0 => 0,
_ => self.page_size - overflow,
};
if inc < length {
let mut offset = offset + inc;
let length = length - overflow;
let end = offset + length;
let mut i = offset - self.page_size;
while (offset + self.page_size <= end) && i < self.buffers.capacity() {
self.buffers.remove(i);
offset += self.page_size;
i += 1;
}
}
Ok(())
}
fn truncate(&mut self, _length: usize) -> Result<(), Self::Error> {
unimplemented!()
}
fn len(&mut self) -> Result<usize, Self::Error> {
Ok(self.length)
}
fn is_empty(&mut self) -> Result<bool, Self::Error> {
Ok(self.length == 0)
}
}