de.schlichtherle.truezip.zip.LittleEndian Maven / Gradle / Ivy
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The file system driver family for ZIP and related archive file types.
Add the JAR artifact of this module to the run time class path to
make its file system drivers available for service location in the
client API modules.
/*
* Copyright (C) 2005-2013 Schlichtherle IT Services.
* All rights reserved. Use is subject to license terms.
*/
package de.schlichtherle.truezip.zip;
import javax.annotation.concurrent.ThreadSafe;
/**
* Provides static utility methods for reading and writing integer values in
* little endian format from or to byte arrays.
*
* @author Christian Schlichtherle
*/
@ThreadSafe
final class LittleEndian {
/** This class cannot get instantiated. */
private LittleEndian() {
}
/**
* Reads a signed byte integer value from the byte array
* {@code buf} at the offset {@code off}.
*
* @param buf The byte array to read the signed byte integer value from.
* @param off The zero based offset in the byte array where the signed
* byte integer value is read from.
* @return The signed byte integer value read from the byte array.
*/
static byte readByte(final byte[] buf, final int off) {
return buf[off];
}
/**
* Reads an unsigned byte integer value from the byte array
* {@code buf} at the offset {@code off}.
* Note that it is not necessary to check the return value with
* {@link UByte#check}.
*
* @param buf The byte array to read the unsigned byte integer value from.
* @param off The zero based offset in the byte array where the unsigned
* byte integer value is read from.
* @return The unsigned byte integer value read from the byte array.
* Java does not provide {@code unsigned short} as a primitive
* type, hence an {@code int} is returned which's three most
* significant bytes are zero.
*/
static int readUByte(final byte[] buf, final int off) {
return buf[off] & UByte.MAX_VALUE;
}
/**
* Reads a signed short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
*
* @param buf The byte array to read the signed short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed short integer value is read from.
* @return The signed short integer value read from the byte array.
*/
static int readShort(final byte[] buf, final int off) {
return (buf[off + 1] << 8) | (buf[off] & UByte.MAX_VALUE);
}
/**
* Reads an unsigned short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UShort#check}.
*
* @param buf The byte array to read the unsigned short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned short integer value is read from.
* @return The unsigned short integer value read from the byte array.
* Java does not provide {@code unsigned short} as a primitive
* type, hence an {@code int} is returned which's two most
* significant bytes are zero.
*/
static int readUShort(final byte[] buf, final int off) {
return ((buf[off + 1] & UByte.MAX_VALUE) << 8) | (buf[off] & UByte.MAX_VALUE);
}
/**
* Reads a signed integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
*
* @param buf The byte array to read the signed integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed integer value is read from.
* @return The signed integer value read from the byte array.
*/
static int readInt(final byte[] buf, int off) {
off += 3;
int i = buf[off--]; // expands sign
i <<= 8;
i |= buf[off--] & UByte.MAX_VALUE;
i <<= 8;
i |= buf[off--] & UByte.MAX_VALUE;
i <<= 8;
i |= buf[off] & UByte.MAX_VALUE;
return i;
}
/**
* Reads an unsigned integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UInt#check}.
*
* @param buf The byte array to read the unsigned integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned integer value is read from.
* @return The unsigned integer value read from the byte array.
* Java does not provide {@code unsigned int} as a primitive
* type, hence a {@code long} is returned which's four most
* significant bytes are zero.
*/
static long readUInt(final byte[] buf, int off) {
return readInt(buf, off) & UInt.MAX_VALUE;
}
/**
* Reads a (signed) long integer value from the byte array
* {@code buf} at the offset {@code off}
* as eight bytes, low byte first.
*
* @param buf The byte array to read the signed long integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the (signed) long integer value is read from.
* @return The (signed) long integer value read from the byte array.
*/
static long readLong(final byte[] buf, int off) {
off += 7;
long l = buf[off--]; // expands sign
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off--] & UByte.MAX_VALUE;
l <<= 8;
l |= buf[off] & UByte.MAX_VALUE;
return l;
}
/**
* Writes the integer value {@code b} to the byte array
* {@code buf} at the zero based offset {@code off}
* as one byte.
* The most significant three bytes of the integer value are ignored.
*
* @param b The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the byte
* of the integer value is written to.
*/
static void writeByte(int b, byte[] buf, int off) {
buf[off] = (byte) b;
}
/**
* Writes the integer value {@code s} to the byte array
* {@code buf} at the zero based offset {@code off}
* as two bytes, low byte first.
* The most significant two bytes of the integer value are ignored.
*
* @param s The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the integer value is written to.
*/
static void writeShort(int s, final byte[] buf, final int off) {
buf[off] = (byte) s;
s >>= 8;
buf[off + 1] = (byte) s;
}
/**
* Writes the integer value {@code i} to the byte array
* {@code buf} at the zero based offset {@code off}
* as four bytes, low byte first.
*
* @param i The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the integer value is written to.
*/
static void writeInt(int i, final byte[] buf, final int off) {
buf[off] = (byte) i;
i >>= 8;
buf[off + 1] = (byte) i;
i >>= 8;
buf[off + 2] = (byte) i;
i >>= 8;
buf[off + 3] = (byte) i;
}
/**
* Writes the long integer value {@code l} to the byte array
* {@code buf} at the zero based offset {@code off}
* as eight bytes, low byte first.
*
* @param l The long integer value to be written.
* @param buf The byte array to write the long integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the long integer value is written to.
*/
static void writeLong(long l, final byte[] buf, final int off) {
buf[off] = (byte) l;
l >>= 8;
buf[off + 1] = (byte) l;
l >>= 8;
buf[off + 2] = (byte) l;
l >>= 8;
buf[off + 3] = (byte) l;
l >>= 8;
buf[off + 4] = (byte) l;
l >>= 8;
buf[off + 5] = (byte) l;
l >>= 8;
buf[off + 6] = (byte) l;
l >>= 8;
buf[off + 7] = (byte) l;
}
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