org.h2.util
Class Utils

java.lang.Object
  extended by org.h2.util.Utils

public class Utils
extends java.lang.Object

This utility class contains miscellaneous functions.


Field Summary
static byte[] EMPTY_BYTES
          An 0-size byte array.
static int[] EMPTY_INT_ARRAY
          An 0-size int array.
 
Method Summary
static java.lang.Object callMethod(java.lang.Object instance, java.lang.String methodName, java.lang.Object... params)
          Calls an instance method via reflection.
static java.lang.Object callStaticMethod(java.lang.String classAndMethod, java.lang.Object... params)
          Calls a static method via reflection.
static byte[] cloneByteArray(byte[] b)
          Create a new byte array and copy all the data.
static int compareNotNull(byte[] data1, byte[] data2)
          Compare the contents of two byte arrays.
static boolean compareSecure(byte[] test, byte[] good)
          Compare two byte arrays.
static byte[] copy(byte[] source, byte[] target)
          Copy the contents of the source array to the target array.
static java.lang.Object deserialize(byte[] data)
          De-serialize the byte array to an object.
static int getByteArrayHash(byte[] value)
          Calculate the hash code of the given byte array.
static java.lang.Object getField(java.lang.Object instance, java.lang.String fieldName)
          Returns a static field.
static int getMemoryFree()
          Get the free memory in KB.
static long getMemoryMax()
          Get the maximum memory in KB.
static int getMemoryUsed()
          Get the used memory in KB.
static java.lang.Class<?> getNonPrimitiveClass(java.lang.Class<?> clazz)
          Convert primitive class names to java.lang.* class names.
static byte[] getResource(java.lang.String name)
          Get a resource from the resource map.
static java.lang.Object getStaticField(java.lang.String classAndField)
          Returns a static field.
static int hashCode(java.lang.Object o)
          Calculate the hash code of the given object.
static int indexOf(byte[] bytes, byte[] pattern, int start)
          Calculate the index of the first occurrence of the pattern in the byte array, starting with the given index.
static boolean isClassPresent(java.lang.String fullyQualifiedClassName)
          Returns true if the class is present in the current class loader.
static java.lang.Class<?> loadUserClass(java.lang.String className)
          Load a class, but check if it is allowed to load this class first.
static byte[] newBytes(int len)
          Create an array of bytes with the given size.
static java.lang.Object newInstance(java.lang.String className, java.lang.Object... params)
          Creates a new instance.
static int[] newIntArray(int len)
          Create an int array with the given size.
static long[] newLongArray(int len)
          Create a long array with the given size.
static long readLong(byte[] buff, int pos)
          Read a long value from the byte array at the given position.
static byte[] serialize(java.lang.Object obj)
          Serialize the object to a byte array.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

EMPTY_BYTES

public static final byte[] EMPTY_BYTES
An 0-size byte array.


EMPTY_INT_ARRAY

public static final int[] EMPTY_INT_ARRAY
An 0-size int array.

Method Detail

readLong

public static long readLong(byte[] buff,
                            int pos)
Read a long value from the byte array at the given position. The most significant byte is read first.

Parameters:
buff - the byte array
pos - the position
Returns:
the value

indexOf

public static int indexOf(byte[] bytes,
                          byte[] pattern,
                          int start)
Calculate the index of the first occurrence of the pattern in the byte array, starting with the given index. This methods returns -1 if the pattern has not been found, and the start position if the pattern is empty.

Parameters:
bytes - the byte array
pattern - the pattern
start - the start index from where to search
Returns:
the index

getByteArrayHash

public static int getByteArrayHash(byte[] value)
Calculate the hash code of the given byte array.

Parameters:
value - the byte array
Returns:
the hash code

compareSecure

public static boolean compareSecure(byte[] test,
                                    byte[] good)
Compare two byte arrays. This method will always loop over all bytes and doesn't use conditional operations in the loop to make sure an attacker can not use a timing attack when trying out passwords.

Parameters:
test - the first array
good - the second array
Returns:
true if both byte arrays contain the same bytes

compareNotNull

public static int compareNotNull(byte[] data1,
                                 byte[] data2)
Compare the contents of two byte arrays. If the content or length of the first array is smaller than the second array, -1 is returned. If the content or length of the second array is smaller than the first array, 1 is returned. If the contents and lengths are the same, 0 is returned.

Parameters:
data1 - the first byte array (must not be null)
data2 - the second byte array (must not be null)
Returns:
the result of the comparison (-1, 1 or 0)

copy

public static byte[] copy(byte[] source,
                          byte[] target)
Copy the contents of the source array to the target array. If the size if the target array is too small, a larger array is created.

Parameters:
source - the source array
target - the target array
Returns:
the target array or a new one if the target array was too small

cloneByteArray

public static byte[] cloneByteArray(byte[] b)
Create a new byte array and copy all the data. If the size of the byte array is zero, the same array is returned.

Parameters:
b - the byte array (may not be null)
Returns:
a new byte array

serialize

public static byte[] serialize(java.lang.Object obj)
Serialize the object to a byte array.

Parameters:
obj - the object to serialize
Returns:
the byte array

deserialize

public static java.lang.Object deserialize(byte[] data)
De-serialize the byte array to an object.

Parameters:
data - the byte array
Returns:
the object
Throws:
SQLException

hashCode

public static int hashCode(java.lang.Object o)
Calculate the hash code of the given object. The object may be null.

Parameters:
o - the object
Returns:
the hash code, or 0 if the object is null

getMemoryUsed

public static int getMemoryUsed()
Get the used memory in KB. This method possibly calls System.gc().

Returns:
the used memory

getMemoryFree

public static int getMemoryFree()
Get the free memory in KB. This method possibly calls System.gc().

Returns:
the free memory

getMemoryMax

public static long getMemoryMax()
Get the maximum memory in KB.

Returns:
the maximum memory

newBytes

public static byte[] newBytes(int len)
Create an array of bytes with the given size. If this is not possible because not enough memory is available, an OutOfMemoryError with the requested size in the message is thrown.

Parameters:
len - the number of bytes requested
Returns:
the byte array
Throws:
java.lang.OutOfMemoryError

newIntArray

public static int[] newIntArray(int len)
Create an int array with the given size.

Parameters:
len - the number of bytes requested
Returns:
the int array

newLongArray

public static long[] newLongArray(int len)
Create a long array with the given size.

Parameters:
len - the number of bytes requested
Returns:
the int array

loadUserClass

public static java.lang.Class<?> loadUserClass(java.lang.String className)
Load a class, but check if it is allowed to load this class first. To perform access rights checking, the system property h2.allowedClasses needs to be set to a list of class file name prefixes.

Parameters:
className - the name of the class
Returns:
the class object

getResource

public static byte[] getResource(java.lang.String name)
                          throws java.io.IOException
Get a resource from the resource map.

Parameters:
name - the name of the resource
Returns:
the resource data
Throws:
java.io.IOException

callStaticMethod

public static java.lang.Object callStaticMethod(java.lang.String classAndMethod,
                                                java.lang.Object... params)
                                         throws java.lang.Exception
Calls a static method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters:
classAndMethod - a string with the entire class and method name, eg. "java.lang.System.gc"
params - the method parameters
Returns:
the return value from this call
Throws:
java.lang.Exception

callMethod

public static java.lang.Object callMethod(java.lang.Object instance,
                                          java.lang.String methodName,
                                          java.lang.Object... params)
                                   throws java.lang.Exception
Calls an instance method via reflection. This will try to use the method where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters:
instance - the instance on which the call is done
methodName - a string with the method name
params - the method parameters
Returns:
the return value from this call
Throws:
java.lang.Exception

newInstance

public static java.lang.Object newInstance(java.lang.String className,
                                           java.lang.Object... params)
                                    throws java.lang.Exception
Creates a new instance. This will try to use the constructor where the most parameter classes match exactly (this algorithm is simpler than the one in the Java specification, but works well for most cases).

Parameters:
className - a string with the entire class, eg. "java.lang.Integer"
params - the constructor parameters
Returns:
the newly created object
Throws:
java.lang.Exception

getStaticField

public static java.lang.Object getStaticField(java.lang.String classAndField)
                                       throws java.lang.Exception
Returns a static field.

Parameters:
classAndField - a string with the entire class and field name
Returns:
the field value
Throws:
java.lang.Exception

getField

public static java.lang.Object getField(java.lang.Object instance,
                                        java.lang.String fieldName)
                                 throws java.lang.Exception
Returns a static field.

Parameters:
instance - the instance on which the call is done
fieldName - the field name
Returns:
the field value
Throws:
java.lang.Exception

isClassPresent

public static boolean isClassPresent(java.lang.String fullyQualifiedClassName)
Returns true if the class is present in the current class loader.

Parameters:
fullyQualifiedClassName - a string with the entire class name, eg. "java.lang.System"
Returns:
true if the class is present

getNonPrimitiveClass

public static java.lang.Class<?> getNonPrimitiveClass(java.lang.Class<?> clazz)
Convert primitive class names to java.lang.* class names.

Parameters:
clazz - the class (for example: int)
Returns:
the non-primitive class (for example: java.lang.Integer)