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Commits (2)
package org.briarproject.bramble.util;
import org.briarproject.bramble.api.FormatException;
public class ByteUtils {
/**
......@@ -12,15 +14,26 @@ public class ByteUtils {
*/
public static final long MAX_32_BIT_UNSIGNED = 4294967295L; // 2^32 - 1
/** The number of bytes needed to encode a 16-bit integer. */
/**
* The number of bytes needed to encode a 16-bit integer.
*/
public static final int INT_16_BYTES = 2;
/** The number of bytes needed to encode a 32-bit integer. */
/**
* The number of bytes needed to encode a 32-bit integer.
*/
public static final int INT_32_BYTES = 4;
/** The number of bytes needed to encode a 64-bit integer. */
/**
* The number of bytes needed to encode a 64-bit integer.
*/
public static final int INT_64_BYTES = 8;
/**
* The maximum number of bytes needed to encode a variable-length integer.
*/
public static final int MAX_VARINT_BYTES = 9;
public static void writeUint16(int src, byte[] dest, int offset) {
if (src < 0) throw new IllegalArgumentException();
if (src > MAX_16_BIT_UNSIGNED) throw new IllegalArgumentException();
......@@ -55,6 +68,42 @@ public class ByteUtils {
dest[offset + 7] = (byte) (src & 0xFF);
}
/**
* Returns the number of bytes needed to represent 'src' as a
* variable-length integer.
* <p>
* 'src' must not be negative.
*/
public static int getVarIntBytes(long src) {
if (src < 0) throw new IllegalArgumentException();
int len = 1;
while ((src >>= 7) > 0) len++;
return len;
}
/**
* Writes 'src' to 'dest' as a variable-length integer, starting at
* 'offset', and returns the number of bytes written.
* <p>
* `src` must not be negative.
*/
public static int writeVarInt(long src, byte[] dest, int offset) {
if (src < 0) throw new IllegalArgumentException();
int len = getVarIntBytes(src);
if (dest.length < offset + len) throw new IllegalArgumentException();
// Work backwards from the end
int end = offset + len - 1;
for (int i = end; i >= offset; i--) {
// Encode 7 bits
dest[i] = (byte) (src & 0x7F);
// Raise the continuation flag, except for the last byte
if (i < end) dest[i] |= (byte) 0x80;
// Shift out the bits that were encoded
src >>= 7;
}
return len;
}
public static int readUint16(byte[] src, int offset) {
if (src.length < offset + INT_16_BYTES)
throw new IllegalArgumentException();
......@@ -83,14 +132,46 @@ public class ByteUtils {
| (src[offset + 7] & 0xFFL);
}
public static int readUint(byte[] src, int bits) {
if (src.length << 3 < bits) throw new IllegalArgumentException();
int dest = 0;
for (int i = 0; i < bits; i++) {
if ((src[i >> 3] & 128 >> (i & 7)) != 0) dest |= 1 << bits - i - 1;
/**
* Returns the length in bytes of a variable-length integer encoded in
* 'src' starting at 'offset'.
*
* @throws FormatException if there is not a valid variable-length integer
* at the specified position.
*/
public static int getVarIntBytes(byte[] src, int offset)
throws FormatException {
if (src.length < offset) throw new IllegalArgumentException();
for (int i = 0; i < MAX_VARINT_BYTES && offset + i < src.length; i++) {
// If the continuation flag is lowered, this is the last byte
if ((src[offset + i] & 0x80) == 0) return i + 1;
}
// We've read 9 bytes or reached the end of the input without finding
// the last byte
throw new FormatException();
}
/**
* Reads a variable-length integer from 'src' starting at 'offset' and
* returns it.
*
* @throws FormatException if there is not a valid variable-length integer
* at the specified position.
*/
public static long readVarInt(byte[] src, int offset)
throws FormatException {
if (src.length < offset) throw new IllegalArgumentException();
long dest = 0;
for (int i = 0; i < MAX_VARINT_BYTES && offset + i < src.length; i++) {
// Decode 7 bits
dest |= src[offset + i] & 0x7F;
// If the continuation flag is lowered, this is the last byte
if ((src[offset + i] & 0x80) == 0) return dest;
// Make room for the next 7 bits
dest <<= 7;
}
if (dest < 0) throw new AssertionError();
if (dest >= 1 << bits) throw new AssertionError();
return dest;
// We've read 9 bytes or reached the end of the input without finding
// the last byte
throw new FormatException();
}
}