ByteQuadsCanonicalizer (jackson-core 2.16.0)

java.lang.Object
- com.fasterxml.jackson.core.sym.ByteQuadsCanonicalizer

```
public final class ByteQuadsCanonicalizer
extends Object
```
Replacement for BytesToNameCanonicalizer which aims at more localized memory access due to flattening of name quad data. Performance improvement modest for simple JSON document data binding (maybe 3%), but should help more for larger symbol tables, or for binary formats like Smile.
Hash area is divided into 4 sections:
1. Primary area (1/2 of total size), direct match from hash (LSB)
2. Secondary area (1/4 of total size), match from hash (LSB) >> 1
3. Tertiary area (1/8 of total size), match from hash (LSB) >> 2
4. Spill-over area (remaining 1/8) with linear scan, insertion order
and within every area, entries are 4 ints, where 1 - 3 ints contain 1 - 12 UTF-8 encoded bytes of name (null-padded), and last int is offset in _names that contains actual name Strings.
Since:

2.6

Field Summary

Fields
Modifier and Type	Field and Description
`protected int`	`_count` Total number of Strings in the symbol table; only used for child tables.
`protected boolean`	`_failOnDoS` Flag that indicates whether we should throw an exception if enough hash collisions are detected (true); or just worked around (false).
`protected int[]`	`_hashArea` Primary hash information area: consists of `2 * _hashSize` entries of 16 bytes (4 ints), arranged in a cascading lookup structure (details of which may be tweaked depending on expected rates of collisions).
`protected boolean`	`_hashShared` Flag that indicates whether underlying data structures for the main hash area are shared or not.
`protected int`	`_hashSize` Number of slots for primary entries within `_hashArea`; which is at most `1/8` of actual size of the underlying array (4-int slots, primary covers only half of the area; plus, additional area for longer symbols after hash area).
`protected InternCache`	`_interner` Entity that knows how to `intern` Strings, if needed, or `null` if no interning is wanted.
`protected int`	`_longNameOffset` Offset within `_hashArea` that follows main slots and contains quads for longer names (13 bytes or longer), and points to the first available int that may be used for appending quads of the next long name.
`protected String[]`	`_names` Array that contains `String` instances matching entries in `_hashArea`.
`protected ByteQuadsCanonicalizer`	`_parent` Reference to the root symbol table, for child tables, so that they can merge table information back as necessary.
`protected int`	`_secondaryStart` Offset within `_hashArea` where secondary entries start
`protected int`	`_seed` Seed value we use as the base to make hash codes non-static between different runs, but still stable for lifetime of a single symbol table instance.
`protected int`	`_spilloverEnd` Pointer to the offset within spill-over area where there is room for more spilled over entries (if any).
`protected AtomicReference<com.fasterxml.jackson.core.sym.ByteQuadsCanonicalizer.TableInfo>`	`_tableInfo` Member that is only used by the root table instance: root passes immutable state info child instances, and children may return new state if they add entries to the table.
`protected int`	`_tertiaryShift` Constant that determines size of buckets for tertiary entries: `1 << _tertiaryShift` is the size, and shift value is also used for translating from primary offset into tertiary bucket (shift right by `4 + _tertiaryShift`).
`protected int`	`_tertiaryStart` Offset within `_hashArea` where tertiary entries start
`protected static int`	`MAX_ENTRIES_FOR_REUSE` Let's only share reasonably sized symbol tables.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`_reportTooManyCollisions()`
`String`	`addName(String name, int q1)`
`String`	`addName(String name, int[] q, int qlen)`
`String`	`addName(String name, int q1, int q2)`
`String`	`addName(String name, int q1, int q2, int q3)`
`int`	`bucketCount()`
`int`	`calcHash(int q1)`
`int`	`calcHash(int[] q, int qlen)`
`int`	`calcHash(int q1, int q2)`
`int`	`calcHash(int q1, int q2, int q3)`
`static ByteQuadsCanonicalizer`	`createRoot()` Factory method to call to create a symbol table instance with a randomized seed value.
`protected static ByteQuadsCanonicalizer`	`createRoot(int seed)`
`String`	`findName(int q1)`
`String`	`findName(int[] q, int qlen)`
`String`	`findName(int q1, int q2)`
`String`	`findName(int q1, int q2, int q3)`
`int`	`hashSeed()`
`boolean`	`isCanonicalizing()`
`ByteQuadsCanonicalizer`	`makeChild(int flags)` Factory method used to create actual symbol table instance to use for parsing.
`ByteQuadsCanonicalizer`	`makeChildOrPlaceholder(int flags)` Method similar to `makeChild(int)` but one that only creates real instance of `JsonFactory.Feature.CANONICALIZE_FIELD_NAMES` is enabled: otherwise a "bogus" instance is created.
`boolean`	`maybeDirty()` Method called to check to quickly see if a child symbol table may have gotten additional entries.
`int`	`primaryCount()` Method mostly needed by unit tests; calculates number of entries that are in the primary slot set.
`void`	`release()` Method called by the using code to indicate it is done with this instance.
`int`	`secondaryCount()` Method mostly needed by unit tests; calculates number of entries in secondary buckets
`int`	`size()`
`int`	`spilloverCount()` Method mostly needed by unit tests; calculates number of entries in shared spill-over area
`int`	`tertiaryCount()` Method mostly needed by unit tests; calculates number of entries in tertiary buckets
`String`	`toString()`
`int`	`totalCount()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - MAX_ENTRIES_FOR_REUSE
```
protected static final int MAX_ENTRIES_FOR_REUSE
```
    Let's only share reasonably sized symbol tables. Max size set to 3/4 of 8k; this corresponds to 256k main hash index. This should allow for enough distinct names for almost any case, while preventing ballooning for cases where names are unique (or close thereof).
    
    See Also:
    
    Constant Field Values
  - _parent
```
protected final ByteQuadsCanonicalizer _parent
```
    Reference to the root symbol table, for child tables, so that they can merge table information back as necessary.
  - _tableInfo
```
protected final AtomicReference<com.fasterxml.jackson.core.sym.ByteQuadsCanonicalizer.TableInfo> _tableInfo
```
    Member that is only used by the root table instance: root passes immutable state info child instances, and children may return new state if they add entries to the table. Child tables do NOT use the reference.
  - _seed
```
protected final int _seed
```
    Seed value we use as the base to make hash codes non-static between different runs, but still stable for lifetime of a single symbol table instance. This is done for security reasons, to avoid potential DoS attack via hash collisions.
  - _interner
```
protected final InternCache _interner
```
    Entity that knows how to intern Strings, if needed, or null if no interning is wanted.
    
    Since:
    
    2.16
  - _failOnDoS
```
protected final boolean _failOnDoS
```
    Flag that indicates whether we should throw an exception if enough hash collisions are detected (true); or just worked around (false).
    
    Since:
    
    2.4
  - _hashArea
```
protected int[] _hashArea
```
    Primary hash information area: consists of 2 * _hashSize entries of 16 bytes (4 ints), arranged in a cascading lookup structure (details of which may be tweaked depending on expected rates of collisions).
  - _hashSize
```
protected int _hashSize
```
    Number of slots for primary entries within _hashArea; which is at most 1/8 of actual size of the underlying array (4-int slots, primary covers only half of the area; plus, additional area for longer symbols after hash area).
  - _secondaryStart
```
protected int _secondaryStart
```
    Offset within _hashArea where secondary entries start
  - _tertiaryStart
```
protected int _tertiaryStart
```
    Offset within _hashArea where tertiary entries start
  - _tertiaryShift
```
protected int _tertiaryShift
```
    Constant that determines size of buckets for tertiary entries: 1 << _tertiaryShift is the size, and shift value is also used for translating from primary offset into tertiary bucket (shift right by 4 + _tertiaryShift).
    Default value is 2, for buckets of 4 slots; grows bigger with bigger table sizes.
  - _count
```
protected int _count
```
    Total number of Strings in the symbol table; only used for child tables.
  - _names
```
protected String[] _names
```
    Array that contains String instances matching entries in _hashArea. Contains nulls for unused entries. Note that this size is twice that of _hashArea
  - _spilloverEnd
```
protected int _spilloverEnd
```
    Pointer to the offset within spill-over area where there is room for more spilled over entries (if any). Spill over area is within fixed-size portion of _hashArea.
  - _longNameOffset
```
protected int _longNameOffset
```
    Offset within _hashArea that follows main slots and contains quads for longer names (13 bytes or longer), and points to the first available int that may be used for appending quads of the next long name. Note that long name area follows immediately after the fixed-size main hash area (_hashArea).
  - _hashShared
```
protected boolean _hashShared
```
    Flag that indicates whether underlying data structures for the main hash area are shared or not. If they are, then they need to be handled in copy-on-write way, i.e. if they need to be modified, a copy needs to be made first; at this point it will not be shared any more, and can be modified.
    This flag needs to be checked both when adding new main entries, and when adding new collision list queues (i.e. creating a new collision list head entry)
- Method Detail
  - createRoot
```
public static ByteQuadsCanonicalizer createRoot()
```
    Factory method to call to create a symbol table instance with a randomized seed value.
    
    Returns:
    
    Root instance to use for constructing new child instances
  - createRoot
```
protected static ByteQuadsCanonicalizer createRoot(int seed)
```
  - makeChild
```
public ByteQuadsCanonicalizer makeChild(int flags)
```
    Factory method used to create actual symbol table instance to use for parsing.
    
    Parameters:
    
    flags - Bit flags of active JsonFactory.Features enabled.
    
    Returns:
    
    Actual canonicalizer instance that can be used by a parser
  - makeChildOrPlaceholder
```
public ByteQuadsCanonicalizer makeChildOrPlaceholder(int flags)
```
    Method similar to makeChild(int) but one that only creates real instance of JsonFactory.Feature.CANONICALIZE_FIELD_NAMES is enabled: otherwise a "bogus" instance is created.
    
    Parameters:
    
    flags - Bit flags of active JsonFactory.Features enabled.
    
    Returns:
    
    Actual canonicalizer instance that can be used by a parser if (and only if) canonicalization is enabled; otherwise a non-null "placeholder" instance.
    
    Since:
    
    2.13
  - 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()
```
    Returns:
    
    Number of symbol entries contained by this canonicalizer instance
  - bucketCount
```
public int bucketCount()
```
    Returns:
    
    number of primary slots table has currently
  - 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.
    
    Returns:
    
    Whether main hash area has been modified
  - hashSeed
```
public int hashSeed()
```
  - isCanonicalizing
```
public boolean isCanonicalizing()
```
    Returns:
    
    True for "real", canonicalizing child tables; false for root table as well as placeholder "child" tables.
    
    Since:
    
    2.13
  - primaryCount
```
public int primaryCount()
```
    Method mostly needed by unit tests; calculates number of entries that are in the primary slot set. These are "perfect" entries, accessible with a single lookup
    
    Returns:
    
    Number of entries in the primary hash area
  - secondaryCount
```
public int secondaryCount()
```
    Method mostly needed by unit tests; calculates number of entries in secondary buckets
    
    Returns:
    
    Number of entries in the secondary hash area
  - tertiaryCount
```
public int tertiaryCount()
```
    Method mostly needed by unit tests; calculates number of entries in tertiary buckets
    
    Returns:
    
    Number of entries in the tertiary hash area
  - spilloverCount
```
public int spilloverCount()
```
    Method mostly needed by unit tests; calculates number of entries in shared spill-over area
    
    Returns:
    
    Number of entries in the linear spill-over areay
  - totalCount
```
public int totalCount()
```
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - findName
```
public String findName(int q1)
```
  - findName
```
public String findName(int q1,
                       int q2)
```
  - findName
```
public String findName(int q1,
                       int q2,
                       int q3)
```
  - findName
```
public String findName(int[] q,
                       int qlen)
```
  - addName
```
public String addName(String name,
                      int q1)
               throws StreamConstraintsException
```
    Parameters:
    
    name - Name to add
    
    q1 - Quad representation of the name
    
    Returns:
    
    name (possibly interned)
    
    Throws:
    
    StreamConstraintsException - if the constraint exceptions
  - addName
```
public String addName(String name,
                      int q1,
                      int q2)
               throws StreamConstraintsException
```
    Parameters:
    
    name - Name to add
    
    q1 - First quad of name representation
    
    q2 - Second quad of name representation
    
    Returns:
    
    name (possibly interned)
    
    Throws:
    
    StreamConstraintsException - if the constraint exceptions
  - addName
```
public String addName(String name,
                      int q1,
                      int q2,
                      int q3)
               throws StreamConstraintsException
```
    Parameters:
    
    name - Name to add
    
    q1 - First quad of name representation
    
    q2 - Second quad of name representation
    
    q3 - Third quad of name representation
    
    Returns:
    
    name (possibly interned)
    
    Throws:
    
    StreamConstraintsException - if the constraint exceptions
  - addName
```
public String addName(String name,
                      int[] q,
                      int qlen)
               throws StreamConstraintsException
```
    Parameters:
    
    name - Name to add
    
    q - Quads of name representation
    
    qlen - Number of quads in q
    
    Returns:
    
    name (possibly interned)
    
    Throws:
    
    StreamConstraintsException - if the constraint exceptions
  - calcHash
```
public int calcHash(int q1)
```
  - calcHash
```
public int calcHash(int q1,
                    int q2)
```
  - calcHash
```
public int calcHash(int q1,
                    int q2,
                    int q3)
```
  - calcHash
```
public int calcHash(int[] q,
                    int qlen)
```
    Parameters:
    
    q - int array
    
    qlen - length
    
    Returns:
    
    hash
    
    Throws:
    
    IllegalArgumentException - if qlen is less than 4
  - _reportTooManyCollisions
```
protected void _reportTooManyCollisions()
                                 throws StreamConstraintsException
```
    Throws:
    
    StreamConstraintsException

Class ByteQuadsCanonicalizer

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MAX_ENTRIES_FOR_REUSE

_parent

_tableInfo

_seed

_interner

_failOnDoS

_hashArea

_hashSize

_secondaryStart

_tertiaryStart

_tertiaryShift

_count

_names

_spilloverEnd

_longNameOffset

_hashShared

Method Detail

createRoot

createRoot

makeChild

makeChildOrPlaceholder

release

size

bucketCount

maybeDirty

hashSeed

isCanonicalizing

primaryCount

secondaryCount

tertiaryCount

spilloverCount

totalCount

toString

findName

findName

findName

findName

addName

addName

addName

addName

calcHash

calcHash

calcHash

calcHash

_reportTooManyCollisions