1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use std::io::{IoError, IoResult, SeekStyle};
14 use std::iter::repeat;
16 static BUF_CAPACITY: uint = 128;
18 fn combine(seek: SeekStyle, cur: uint, end: uint, offset: i64) -> IoResult<u64> {
19 // compute offset as signed and clamp to prevent overflow
20 let pos = match seek {
28 kind: io::InvalidInput,
29 desc: "invalid seek to a negative offset",
33 Ok((offset + pos) as u64)
37 /// Writes to an owned, growable byte vector that supports seeking.
42 /// # #![allow(unused_must_use)]
43 /// use rbml::io::SeekableMemWriter;
45 /// let mut w = SeekableMemWriter::new();
46 /// w.write(&[0, 1, 2]);
48 /// assert_eq!(w.unwrap(), vec!(0, 1, 2));
50 pub struct SeekableMemWriter {
55 impl SeekableMemWriter {
56 /// Create a new `SeekableMemWriter`.
58 pub fn new() -> SeekableMemWriter {
59 SeekableMemWriter::with_capacity(BUF_CAPACITY)
61 /// Create a new `SeekableMemWriter`, allocating at least `n` bytes for
62 /// the internal buffer.
64 pub fn with_capacity(n: uint) -> SeekableMemWriter {
65 SeekableMemWriter { buf: Vec::with_capacity(n), pos: 0 }
68 /// Acquires an immutable reference to the underlying buffer of this
69 /// `SeekableMemWriter`.
71 /// No method is exposed for acquiring a mutable reference to the buffer
72 /// because it could corrupt the state of this `MemWriter`.
74 pub fn get_ref<'a>(&'a self) -> &'a [u8] { self.buf.as_slice() }
76 /// Unwraps this `SeekableMemWriter`, returning the underlying buffer
78 pub fn unwrap(self) -> Vec<u8> { self.buf }
81 impl Writer for SeekableMemWriter {
83 fn write(&mut self, buf: &[u8]) -> IoResult<()> {
84 if self.pos == self.buf.len() {
85 self.buf.push_all(buf)
87 // Make sure the internal buffer is as least as big as where we
89 let difference = self.pos as i64 - self.buf.len() as i64;
91 self.buf.extend(repeat(0).take(difference as uint));
94 // Figure out what bytes will be used to overwrite what's currently
95 // there (left), and what will be appended on the end (right)
96 let cap = self.buf.len() - self.pos;
97 let (left, right) = if cap <= buf.len() {
98 (buf[..cap], buf[cap..])
100 let result: (_, &[_]) = (buf, &[]);
104 // Do the necessary writes
106 slice::bytes::copy_memory(self.buf.slice_from_mut(self.pos), left);
109 self.buf.push_all(right);
114 self.pos += buf.len();
119 impl Seek for SeekableMemWriter {
121 fn tell(&self) -> IoResult<u64> { Ok(self.pos as u64) }
124 fn seek(&mut self, pos: i64, style: SeekStyle) -> IoResult<()> {
125 let new = try!(combine(style, self.pos, self.buf.len(), pos));
126 self.pos = new as uint;
134 use super::SeekableMemWriter;
139 fn test_seekable_mem_writer() {
140 let mut writer = SeekableMemWriter::new();
141 assert_eq!(writer.tell(), Ok(0));
142 writer.write(&[0]).unwrap();
143 assert_eq!(writer.tell(), Ok(1));
144 writer.write(&[1, 2, 3]).unwrap();
145 writer.write(&[4, 5, 6, 7]).unwrap();
146 assert_eq!(writer.tell(), Ok(8));
147 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
148 assert_eq!(writer.get_ref(), b);
150 writer.seek(0, io::SeekSet).unwrap();
151 assert_eq!(writer.tell(), Ok(0));
152 writer.write(&[3, 4]).unwrap();
153 let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
154 assert_eq!(writer.get_ref(), b);
156 writer.seek(1, io::SeekCur).unwrap();
157 writer.write(&[0, 1]).unwrap();
158 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
159 assert_eq!(writer.get_ref(), b);
161 writer.seek(-1, io::SeekEnd).unwrap();
162 writer.write(&[1, 2]).unwrap();
163 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
164 assert_eq!(writer.get_ref(), b);
166 writer.seek(1, io::SeekEnd).unwrap();
167 writer.write(&[1]).unwrap();
168 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
169 assert_eq!(writer.get_ref(), b);
174 let mut r = SeekableMemWriter::new();
175 r.seek(10, io::SeekSet).unwrap();
176 assert!(r.write(&[3]).is_ok());
181 let mut r = SeekableMemWriter::new();
182 assert!(r.seek(-1, io::SeekSet).is_err());
185 fn do_bench_seekable_mem_writer(b: &mut Bencher, times: uint, len: uint) {
186 let src: Vec<u8> = Vec::from_elem(len, 5);
188 b.bytes = (times * len) as u64;
190 let mut wr = SeekableMemWriter::new();
191 for _ in range(0, times) {
192 wr.write(src.as_slice()).unwrap();
196 assert_eq!(v.len(), times * len);
197 assert!(v.iter().all(|x| *x == 5));
202 fn bench_seekable_mem_writer_001_0000(b: &mut Bencher) {
203 do_bench_seekable_mem_writer(b, 1, 0)
207 fn bench_seekable_mem_writer_001_0010(b: &mut Bencher) {
208 do_bench_seekable_mem_writer(b, 1, 10)
212 fn bench_seekable_mem_writer_001_0100(b: &mut Bencher) {
213 do_bench_seekable_mem_writer(b, 1, 100)
217 fn bench_seekable_mem_writer_001_1000(b: &mut Bencher) {
218 do_bench_seekable_mem_writer(b, 1, 1000)
222 fn bench_seekable_mem_writer_100_0000(b: &mut Bencher) {
223 do_bench_seekable_mem_writer(b, 100, 0)
227 fn bench_seekable_mem_writer_100_0010(b: &mut Bencher) {
228 do_bench_seekable_mem_writer(b, 100, 10)
232 fn bench_seekable_mem_writer_100_0100(b: &mut Bencher) {
233 do_bench_seekable_mem_writer(b, 100, 100)
237 fn bench_seekable_mem_writer_100_1000(b: &mut Bencher) {
238 do_bench_seekable_mem_writer(b, 100, 1000)