BytesToNameCanonicalizer (Jackson JSON Processor)

java.lang.Object
- org.codehaus.jackson.sym.BytesToNameCanonicalizer

```
public final class BytesToNameCanonicalizer
extends Object
```
A caching symbol table implementation used for canonicalizing JSON field names (as Names which are constructed directly from a byte-based input source). Complications arise from trying to do efficient reuse and merging of symbol tables, to be able to make use of usually shared vocabulary of subsequent parsing runs.

作者:

Tatu Saloranta

字段概要

字段
限定符和类型	字段和说明
`protected int`	`_collCount` Total number of Names in collision buckets (included in `_count` along with primary entries)
`protected int`	`_collEnd` Index of the first unused collision bucket entry (== size of the used portion of collision list): less than or equal to 0xFF (255), since max number of entries is 255 (8-bit, minus 0 used as 'empty' marker)
`protected org.codehaus.jackson.sym.BytesToNameCanonicalizer.Bucket[]`	`_collList` Array of heads of collision bucket chains; size dynamically
`protected int`	`_count` Total number of Names in the symbol table; only used for child tables.
`protected boolean`	`_intern` Whether canonical symbol Strings are to be intern()ed before added to the table or not
`protected int`	`_longestCollisionList` We need to keep track of the longest collision list; this is needed both to indicate problems with attacks and to allow flushing for other cases.
`protected int[]`	`_mainHash` Array of 2^N size, which contains combination of 24-bits of hash (0 to indicate 'empty' slot), and 8-bit collision bucket index (0 to indicate empty collision bucket chain; otherwise subtract one from index)
`protected int`	`_mainHashMask` Mask used to truncate 32-bit hash value to current hash array size; essentially, hash array size - 1 (since hash array sizes are 2^N).
`protected Name[]`	`_mainNames` Array that contains `Name` instances matching entries in `_mainHash`.
`protected BytesToNameCanonicalizer`	`_parent` Reference to the root symbol table, for child tables, so that they can merge table information back as necessary.
`protected AtomicReference<org.codehaus.jackson.sym.BytesToNameCanonicalizer.TableInfo>`	`_tableInfo` Member that is only used by the root table instance: root passes immutable state into child instances, and children may return new state if they add entries to the table.
`protected static int`	`DEFAULT_TABLE_SIZE`
`protected static int`	`MAX_TABLE_SIZE` Let's not expand symbol tables past some maximum size; this should protected against OOMEs caused by large documents with unique (~= random) names.

方法概要

方法
限定符和类型	方法和说明
`Name`	`addName(String symbolStr, int[] quads, int qlen)`
`Name`	`addName(String symbolStr, int q1, int q2)`
`int`	`bucketCount()`
`int`	`calcHash(int firstQuad)`
`int`	`calcHash(int[] quads, int qlen)`
`int`	`calcHash(int firstQuad, int secondQuad)`
`protected static int[]`	`calcQuads(byte[] wordBytes)`
`int`	`collisionCount()` Method mostly needed by unit tests; calculates number of entries that are in collision list.
`static BytesToNameCanonicalizer`	`createRoot()` Factory method to call to create a symbol table instance with a randomized seed value.
`protected static BytesToNameCanonicalizer`	`createRoot(int hashSeed)` Factory method that should only be called from unit tests, where seed value should remain the same.
`Name`	`findName(int firstQuad)` Finds and returns name matching the specified symbol, if such name already exists in the table.
`Name`	`findName(int[] quads, int qlen)` Finds and returns name matching the specified symbol, if such name already exists in the table; or if not, creates name object, adds to the table, and returns it.
`Name`	`findName(int firstQuad, int secondQuad)` Finds and returns name matching the specified symbol, if such name already exists in the table.
`static Name`	`getEmptyName()`
`int`	`hashSeed()`
`BytesToNameCanonicalizer`	`makeChild(boolean canonicalize, boolean intern)` Factory method used to create actual symbol table instance to use for parsing.
`int`	`maxCollisionLength()` Method mostly needed by unit tests; calculates length of the longest collision chain.
`boolean`	`maybeDirty()` Method called to check to quickly see if a child symbol table may have gotten additional entries.
`void`	`release()` Method called by the using code to indicate it is done with this instance.
`protected void`	`reportTooManyCollisions(int maxLen)`
`int`	`size()`

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 字段详细资料
  - DEFAULT_TABLE_SIZE
```
protected static final int DEFAULT_TABLE_SIZE
```
    另请参阅:
    常量字段值
  - MAX_TABLE_SIZE
```
protected static final int MAX_TABLE_SIZE
```
    Let's not expand symbol tables past some maximum size; this should protected against OOMEs caused by large documents with unique (~= random) names.
    
    另请参阅:
    常量字段值
  - _parent
```
protected final BytesToNameCanonicalizer _parent
```
    Reference to the root symbol table, for child tables, so that they can merge table information back as necessary.
  - _tableInfo
```
protected final AtomicReference<org.codehaus.jackson.sym.BytesToNameCanonicalizer.TableInfo> _tableInfo
```
    Member that is only used by the root table instance: root passes immutable state into child instances, and children may return new state if they add entries to the table. Child tables do NOT use the reference.
  - _intern
```
protected final boolean _intern
```
    Whether canonical symbol Strings are to be intern()ed before added to the table or not
  - _count
```
protected int _count
```
    Total number of Names in the symbol table; only used for child tables.
  - _longestCollisionList
```
protected int _longestCollisionList
```
    We need to keep track of the longest collision list; this is needed both to indicate problems with attacks and to allow flushing for other cases.
    
    从以下版本开始:
    
    1.9.9
  - _mainHashMask
```
protected int _mainHashMask
```
    Mask used to truncate 32-bit hash value to current hash array size; essentially, hash array size - 1 (since hash array sizes are 2^N).
  - _mainHash
```
protected int[] _mainHash
```
    Array of 2^N size, which contains combination of 24-bits of hash (0 to indicate 'empty' slot), and 8-bit collision bucket index (0 to indicate empty collision bucket chain; otherwise subtract one from index)
  - _mainNames
```
protected Name[] _mainNames
```
    Array that contains Name instances matching entries in _mainHash. Contains nulls for unused entries.
  - _collList
```
protected org.codehaus.jackson.sym.BytesToNameCanonicalizer.Bucket[] _collList
```
    Array of heads of collision bucket chains; size dynamically
  - _collCount
```
protected int _collCount
```
    Total number of Names in collision buckets (included in _count along with primary entries)
  - _collEnd
```
protected int _collEnd
```
    Index of the first unused collision bucket entry (== size of the used portion of collision list): less than or equal to 0xFF (255), since max number of entries is 255 (8-bit, minus 0 used as 'empty' marker)
- 方法详细资料
  - createRoot
```
public static BytesToNameCanonicalizer createRoot()
```
    Factory method to call to create a symbol table instance with a randomized seed value.
  - createRoot
```
protected static BytesToNameCanonicalizer createRoot(int hashSeed)
```
    Factory method that should only be called from unit tests, where seed value should remain the same.
  - makeChild
```
public BytesToNameCanonicalizer makeChild(boolean canonicalize,
                                 boolean intern)
```
    Factory method used to create actual symbol table instance to use for parsing.
    
    参数:
    intern - Whether canonical symbol Strings should be interned or not
  - release
```
public void release()
```
    Method called by the using code to indicate it is done with this instance. This lets instance merge accumulated changes into parent (if need be), safely and efficiently, and without calling code having to know about parent information
  - size
```
public int size()
```
  - bucketCount
```
public int bucketCount()
```
    从以下版本开始:
    
    1.9.9
  - maybeDirty
```
public boolean maybeDirty()
```
    Method called to check to quickly see if a child symbol table may have gotten additional entries. Used for checking to see if a child table should be merged into shared table.
  - hashSeed
```
public int hashSeed()
```
    从以下版本开始:
    
    1.9.9
  - collisionCount
```
public int collisionCount()
```
    Method mostly needed by unit tests; calculates number of entries that are in collision list. Value can be at most (size() - 1), but should usually be much lower, ideally 0.
    
    从以下版本开始:
    
    1.9.9
  - maxCollisionLength
```
public int maxCollisionLength()
```
    Method mostly needed by unit tests; calculates length of the longest collision chain. This should typically be a low number, but may be up to size() - 1 in the pathological case
    
    从以下版本开始:
    
    1.9.9
  - getEmptyName
```
public static Name getEmptyName()
```
  - findName
```
public Name findName(int firstQuad)
```
    Finds and returns name matching the specified symbol, if such name already exists in the table. If not, will return null.
    Note: separate methods to optimize common case of short element/attribute names (4 or less ascii characters)
    
    参数:
    firstQuad - int32 containing first 4 bytes of the name; if the whole name less than 4 bytes, padded with zero bytes in front (zero MSBs, ie. right aligned)
    
    返回:
    Name matching the symbol passed (or constructed for it)
  - findName
```
public Name findName(int firstQuad,
            int secondQuad)
```
    Finds and returns name matching the specified symbol, if such name already exists in the table. If not, will return null.
    Note: separate methods to optimize common case of relatively short element/attribute names (8 or less ascii characters)
    
    参数:
    firstQuad - int32 containing first 4 bytes of the name.
    secondQuad - int32 containing bytes 5 through 8 of the name; if less than 8 bytes, padded with up to 3 zero bytes in front (zero MSBs, ie. right aligned)
    
    返回:
    Name matching the symbol passed (or constructed for it)
  - findName
```
public Name findName(int[] quads,
            int qlen)
```
    Finds and returns name matching the specified symbol, if such name already exists in the table; or if not, creates name object, adds to the table, and returns it.
    Note: this is the general purpose method that can be called for names of any length. However, if name is less than 9 bytes long, it is preferable to call the version optimized for short names.
    
    参数:
    quads - Array of int32s, each of which contain 4 bytes of encoded name
    qlen - Number of int32s, starting from index 0, in quads parameter
    
    返回:
    Name matching the symbol passed (or constructed for it)
  - addName
```
public Name addName(String symbolStr,
           int q1,
           int q2)
```
  - addName
```
public Name addName(String symbolStr,
           int[] quads,
           int qlen)
```
  - calcHash
```
public final int calcHash(int firstQuad)
```
  - calcHash
```
public final int calcHash(int firstQuad,
           int secondQuad)
```
  - calcHash
```
public final int calcHash(int[] quads,
           int qlen)
```
  - calcQuads
```
protected static int[] calcQuads(byte[] wordBytes)
```
  - reportTooManyCollisions
```
protected void reportTooManyCollisions(int maxLen)
```
    从以下版本开始:
    
    1.9.9

类 BytesToNameCanonicalizer

字段概要

方法概要

从类继承的方法 java.lang.Object

字段详细资料

DEFAULT_TABLE_SIZE

MAX_TABLE_SIZE

_parent

_tableInfo

_intern

_count

_longestCollisionList

_mainHashMask

_mainHash

_mainNames

_collList

_collCount

_collEnd

方法详细资料

createRoot

createRoot

makeChild

release

size

bucketCount

maybeDirty

hashSeed

collisionCount

maxCollisionLength

getEmptyName

findName

findName

findName

addName

addName

calcHash

calcHash

calcHash

calcQuads

reportTooManyCollisions