com.ionic.sdk.core.io.ByteBlock Maven / Gradle / Ivy
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package com.ionic.sdk.core.io;
/**
* Container for byte data. This object is intended to be used as an intermediate cache for data
* in support of Ionic file ciphers.
*
* This object is meant to be wrapped by {@link ByteQueue}, which manages multiple blocks and allows for
* caching of arbitrary amounts of data (subject to JVM memory constraints).
*
* In order to simplify its logic, this object handles manipulation of its state naively, and depends
* on its wrapping object to protect against boundary conditions.
*/
public final class ByteBlock {
/**
* The byte data to be cached.
*/
private final byte[] block;
/**
* The position in this block at which existing data should be read.
*/
private int head;
/**
* The position in this block at which new data should be written.
*/
private int tail;
/**
* Constructor.
*
* @param size the maximum amount of data (in bytes) which should be cached in this object
*/
public ByteBlock(final int size) {
this.block = new byte[size];
this.head = 0;
this.tail = 0;
}
/**
* Reset the internal state of this object, allowing for reuse.
*/
public void reset() {
head = 0;
tail = 0;
}
/**
* @return the position in this block at which existing data should be read
*/
public int getHead() {
return head;
}
/**
* @return the position in this block at which new data should be written
*/
public int getTail() {
return tail;
}
/**
* @return the amount of data available in this block to read
*/
public int available() {
return tail - head;
}
/**
* Write data into this object, to be cached for later use.
*
* @param bytes the source buffer from which the data should be read
* @param offset the offset in the source buffer at which to start reading
* @param length the number of bytes of source buffer data to write
* @return the number of bytes of data written
*/
public int add(final byte[] bytes, final int offset, final int length) {
final int added = Math.min((block.length - tail), length);
System.arraycopy(bytes, offset, block, tail, added);
tail += added;
return added;
}
/**
* Read cached data from this object.
*
* @param bytes the target buffer to which the data should be written
* @param offset the offset in the target buffer at which to start writing
* @param length the number of bytes of data to read
* @return the number of bytes of data read
*/
public int remove(final byte[] bytes, final int offset, final int length) {
final int count = Math.min((tail - head), length);
System.arraycopy(block, head, bytes, offset, count);
head += count;
return count;
}
/**
* Skips over and discards n bytes of data from this data.
*
* @param count the number of bytes to be skipped
* @return the actual number of bytes skipped.
*/
public int skip(final int count) {
head += count;
return count;
}
/**
* Returns a {@code String} object representing this object's value.
*
* @return a string representation of the value of this object
*/
@Override
public String toString() {
return String.format(PATTERN_TO_STRING, hashCode(), block.length, head, tail);
}
/**
* The pattern used to construct a string representation of this object, for diagnostic purposes.
*/
private static final String PATTERN_TO_STRING = "[ByteBlock: hashCode=%x size=%d, head=%d, tail=%d]";
}