com.allanbank.mongodb.bson.io

Class StringEncoder

java.lang.Object

com.allanbank.mongodb.bson.io.StringEncoder

public class StringEncoder
extends Object

StringEncoder provides a single location for the string encoding and sizing logic. This class if backed by a cache of strings to the encoded bytes.

The cache is controlled via two parameters:

Copyright ©:

2013, Allanbank Consulting, Inc., All Rights Reserved

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_CACHE_ENTRIES The default maximum number of strings to keep in the trie cache.
static int	DEFAULT_MAX_CACHE_LENGTH The default maximum length byte array to cache.
protected static Log	LOG The logger for the StringEncoder.
protected int	myMaxCachEntries The maximum number of strings to have in the cache.

Constructor Summary

Constructors

Constructor and Description
StringEncoder() Creates a new StringEncoder.

Method Summary

Methods

Modifier and Type	Method and Description
void	encode(String string, OutputStream out) Writes the string as a UTF-8 string.
int	encodeSize(String string) Computes the size of the encoded UTF8 String based on the table below.
protected byte[]	fastEncode(String string, OutputStream out) Writes the string as a UTF-8 string.
int	getMaxCacheEntries() Returns the maximum number of strings that can be cached.
int	getMaxCacheLength() Returns the maximum length for a string that the encoder is allowed to cache.
void	setMaxCacheEntries(int maxCacheEntries) Sets the value of maximum number of cached strings.
void	setMaxCacheLength(int maxlength) Sets the value of length for a string that the encoder is allowed to cache to the new value.
static int	utf8Size(String string) Computes the size of the encoded UTF8 String based on the table below.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_MAX_CACHE_ENTRIES

public static final int DEFAULT_MAX_CACHE_ENTRIES

The default maximum number of strings to keep in the trie cache.

See Also:

Constant Field Values

DEFAULT_MAX_CACHE_LENGTH

public static final int DEFAULT_MAX_CACHE_LENGTH

The default maximum length byte array to cache.

See Also:

Constant Field Values

LOG

protected static final Log LOG

The logger for the StringEncoder.

myMaxCachEntries

protected int myMaxCachEntries

The maximum number of strings to have in the cache.

Constructor Detail

StringEncoder

public StringEncoder()

Creates a new StringEncoder.

Method Detail

utf8Size

public static int utf8Size(String string)

Computes the size of the encoded UTF8 String based on the table below.

 #    Code Points      Bytes
 1    U+0000..U+007F   1
 
 2    U+0080..U+07FF   2
 
 3    U+0800..U+0FFF   3
      U+1000..U+FFFF
 
 4   U+10000..U+3FFFF  4
     U+40000..U+FFFFF  4
    U+100000..U10FFFF  4
 

Parameters:

string - The string to determine the length of.

Returns:

The length of the string encoded as UTF8.

encode

public void encode(String string,
          OutputStream out)
            throws IOException

Writes the string as a UTF-8 string. This method handles the "normal/easy" cases and delegates to the full character set if things get complicated.

Parameters:

string - The string to encode.

out - The stream to write to.

Throws:

IOException - On a failure to write the bytes.

encodeSize

public int encodeSize(String string)

Computes the size of the encoded UTF8 String based on the table below. This method may use a cached copy of the encoded string to determine the size.

 #    Code Points      Bytes
 1    U+0000..U+007F   1
 
 2    U+0080..U+07FF   2
 
 3    U+0800..U+0FFF   3
      U+1000..U+FFFF
 
 4   U+10000..U+3FFFF  4
     U+40000..U+FFFFF  4
    U+100000..U10FFFF  4
 

Parameters:

string - The string to determine the length of.

Returns:

The length of the string encoded as UTF8.

getMaxCacheEntries

public int getMaxCacheEntries()

Returns the maximum number of strings that can be cached.

Returns:

The maximum number of strings that can be cached.

getMaxCacheLength

public int getMaxCacheLength()

Returns the maximum length for a string that the encoder is allowed to cache.

Returns:

The maximum length for a string that the encoder is allowed to cache.

setMaxCacheEntries

public void setMaxCacheEntries(int maxCacheEntries)

Sets the value of maximum number of cached strings.

Parameters:

maxCacheEntries - The new value for the maximum number of cached strings.

setMaxCacheLength

public void setMaxCacheLength(int maxlength)

Sets the value of length for a string that the encoder is allowed to cache to the new value. This can be used to stop a single long string from pushing useful values out of the cache.

Parameters:

maxlength - The new value for the length for a string that the encoder is allowed to cache.

fastEncode

protected byte[] fastEncode(String string,
                OutputStream out)
                     throws IOException

Writes the string as a UTF-8 string. This method handles the "normal/easy" cases and delegates to the full character set if things get complicated.

Parameters:

string - The string to encode.

out - The stream to write to.

Returns:

The encoded bytes shorted that the internal buffer.

Throws:

IOException - On a failure to write the bytes.