de.unkrig.commons.io.pipe.AbstractRingBuffer Maven / Gradle / Ivy
/*
* de.unkrig.commons - A general-purpose Java class library
*
* Copyright (c) 2014, Arno Unkrig
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
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*
* 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
* following disclaimer.
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* following disclaimer in the documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
* products derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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*/
package de.unkrig.commons.io.pipe;
import java.io.IOException;
/**
* Abstract implementation of a {@link Pipe} by a "backing store" of bytes with fixed size (the "capacity").
*
* Implementation must implement methods {@link #get(long, byte[], int, int)} and {@link #put(byte[], int, int, long)}
* to provide access to the backing store.
*
*/
public abstract
class AbstractRingBuffer extends AbstractPipe {
/**
* @param capacity The size of the backing store
*/
public
AbstractRingBuffer(long capacity) { this.capacity = capacity; }
/**
* Transfers len bytes from the backing store to buf{@code [off]...}.
*
* @param pos 0...capacity
* @param off 0...buf{@code .length}
* @param len 0...{@code min(capacity - pos, buf.length - off}
* @see #AbstractRingBuffer(long)
*/
protected abstract void
get(long pos, byte[] buf, int off, int len) throws IOException;
/**
* Transfers len bytes from {@code buf[off]...} to the backing store.
*
* @param off 0...{@code buf.length}
* @param len 0...{@code min(capacity - pos, buf.length - off}
* @param pos 0...capacity
* @see #AbstractRingBuffer(long)
*/
protected abstract void
put(byte[] buf, int off, int len, long pos) throws IOException;
// ------------ END PUBLIC API --------------
/**
* Size of the backing store; greater than zero.
*/
private final long capacity;
/**
* Index of the next byte to {@link #read(byte[], int, int)} from the backing store; {@code 0 ... capacity-1};
* {@code -1} means this ring buffer is empty.
*/
private long head = -1;
/**
* Index in the backing store where the next byte written will be stored; {@code 0 ... capacity-1}; undefined
* iff this ring buffer is empty.
*/
private long tail;
@Override public final int
read(byte[] buf, int off, int len) throws IOException {
if (len == 0) return 0;
if (this.head == -1) return 0; // This ring buffer is empty.
if (this.head == this.tail) {
// This ring buffer is full.
// Buffer structure: [ >= 0 allocated] [(tail = head) >= 1 allocated ] (capacity)
long av = this.capacity - this.head;
if (len < av) {
this.get(this.head, buf, off, len);
this.head += len;
} else
if (len >= this.capacity) {
this.get(this.head, buf, off, (int) av);
this.get(0, buf, off + (int) av, (int) (this.capacity - av));
this.head = -1;
len = (int) this.capacity;
} else
{
this.get(this.head, buf, off, (int) av);
this.get(0, buf, off + (int) av, len - (int) av);
this.head = len - av;
}
return len;
}
if (this.tail > this.head) {
// Buffer structure: [ >= 0 free] [(head) >= 1 allocated ] [(tail) >= 1 free ] (capacity)
long av = this.tail - this.head;
if (len < av) {
this.get(this.head, buf, off, len);
this.head += len;
return len;
} else {
this.get(this.head, buf, off, (int) av);
this.head = -1;
return (int) av;
}
} else {
// Buffer structure: [ >= 0 allocated] [(tail) >= 0 free ] [(head) >= 1 allocated ] (capacity)
long av = this.capacity - this.head;
if (len < av) {
this.get(this.head, buf, off, len);
this.head += len;
return len;
} else
if (len < av + this.tail) {
this.get(this.head, buf, off, (int) av);
this.get(0, buf, off + (int) av, len - (int) av);
this.head = len - av;
return len;
} else
{
this.get(this.head, buf, off, (int) av);
this.get(0, buf, off + (int) av, (int) this.tail);
this.head = -1;
return (int) (av + this.tail);
}
}
}
@Override public final int
write(byte[] buf, int off, int len) throws IOException {
if (len == 0) return 0;
if (this.head == -1) {
// This ring buffer is empty.
if (len > this.capacity) len = (int) this.capacity;
this.put(buf, off, len, 0);
this.head = 0;
this.tail = len;
return len;
}
if (this.tail > this.head) {
// Buffer structure: [ >= 0 free] [(head) >= 1 allocated ] [(tail) >= 1 free ] (capacity)
long av = this.capacity - this.tail;
if (len < av) {
this.put(buf, off, len, this.tail);
this.tail += len;
return len;
} else
if (len == av) {
this.put(buf, off, len, this.tail);
this.tail = 0;
return len;
} else
if (len > av + this.head) {
this.put(buf, off, (int) av, this.tail);
this.put(buf, off + (int) av, (int) this.head, 0);
this.tail = this.head;
return (int) (av + this.head);
} else
{
this.put(buf, off, (int) av, this.tail);
this.put(buf, off + (int) av, (int) (len - av), 0);
this.tail = len - av;
return len;
}
} else {
// Buffer structure: [ >= 0 allocated] [(tail) >= 0 free ] [(head) >= 1 allocated ] (capacity)
long av = this.head - this.tail;
if (len > av) len = (int) av;
this.put(buf, off, len, this.tail);
this.tail += len;
return len;
}
}
@Override public final boolean
isEmpty() { return this.head == -1; }
@Override public final boolean
isFull() { return this.head == this.tail; }
}
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