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#include
"Python.h"
#include
"structmember.h"
#include
"internal/pystate.h"
#include
"internal/hamt.h"
/* popcnt support in Visual Studio */
#ifdef
_MSC_VER
#include
<intrin.h>
#endif
/*
This file provides an implemention of an immutable mapping using the
Hash Array Mapped Trie (or HAMT) datastructure.
This design allows to have:
1. Efficient copy: immutable mappings can be copied by reference,
making it an O(1) operation.
2. Efficient mutations: due to structural sharing, only a portion of
the trie needs to be copied when the collection is mutated. The
cost of set/delete operations is O(log N).
3. Efficient lookups: O(log N).
(where N is number of key/value items in the immutable mapping.)
HAMT
====
The core idea of HAMT is that the shape of the trie is encoded into the
hashes of keys.
Say we want to store a K/V pair in our mapping. First, we calculate the
hash of K, let's say it's 19830128, or in binary:
0b1001011101001010101110000 = 19830128
Now let's partition this bit representation of the hash into blocks of
5 bits each:
0b00_00000_10010_11101_00101_01011_10000 = 19830128
(6) (5) (4) (3) (2) (1)
Each block of 5 bits represents a number betwen 0 and 31. So if we have
a tree that consists of nodes, each of which is an array of 32 pointers,
those 5-bit blocks will encode a position on a single tree level.
For example, storing the key K with hash 19830128, results in the following
tree structure:
(array of 32 pointers)
+---+ -- +----+----+----+ -- +----+
root node | 0 | .. | 15 | 16 | 17 | .. | 31 | 0b10000 = 16 (1)
(level 1) +---+ -- +----+----+----+ -- +----+
|
+---+ -- +----+----+----+ -- +----+
a 2nd level node | 0 | .. | 10 | 11 | 12 | .. | 31 | 0b01011 = 11 (2)
+---+ -- +----+----+----+ -- +----+
|
+---+ -- +----+----+----+ -- +----+
a 3rd level node | 0 | .. | 04 | 05 | 06 | .. | 31 | 0b01011 = 5 (3)
+---+ -- +----+----+----+ -- +----+
|
+---+ -- +----+----+----+----+
a 4th level node | 0 | .. | 04 | 29 | 30 | 31 | 0b11101 = 29 (4)
+---+ -- +----+----+----+----+
|
+---+ -- +----+----+----+ -- +----+
a 5th level node | 0 | .. | 17 | 18 | 19 | .. | 31 | 0b10010 = 18 (5)
+---+ -- +----+----+----+ -- +----+
|
+--------------+
|
+---+ -- +----+----+----+ -- +----+
a 6th level node | 0 | .. | 15 | 16 | 17 | .. | 31 | 0b00000 = 0 (6)
+---+ -- +----+----+----+ -- +----+
|
V -- our value (or collision)
To rehash: for a K/V pair, the hash of K encodes where in the tree V will
be stored.
To optimize memory footprint and handle hash collisions, our implementation
uses three different types of nodes:
* A Bitmap node;
* An Array node;
* A Collision node.
Because we implement an immutable dictionary, our nodes are also
immutable. Therefore, when we need to modify a node, we copy it, and
do that modification to the copy.
Array Nodes
-----------
These nodes are very simple. Essentially they are arrays of 32 pointers
we used to illustrate the high-level idea in the previous section.
We use Array nodes only when we need to store more than 16 pointers
in a single node.
Array nodes do not store key objects or value objects. They are used
only as an indirection level - their pointers point to other nodes in
the tree.
Bitmap Node
-----------
Allocating a new 32-pointers array for every node of our tree would be
very expensive. Unless we store millions of keys, most of tree nodes would
be very sparse.
When we have less than 16 elements in a node, we don't want to use the
Array node, that would mean that we waste a lot of memory. Instead,
we can use bitmap compression and can have just as many pointers
as we need!
Bitmap nodes consist of two fields:
1. An array of pointers. If a Bitmap node holds N elements, the
array will be of N pointers.
2. A 32bit integer -- a bitmap field. If an N-th bit is set in the
bitmap, it means that the node has an N-th element.
For example, say we need to store a 3 elements sparse array:
+---+ -- +---+ -- +----+ -- +----+
| 0 | .. | 4 | .. | 11 | .. | 17 |
+---+ -- +---+ -- +----+ -- +----+
| | |
o1 o2 o3
We allocate a three-pointer Bitmap node. Its bitmap field will be
then set to:
0b_00100_00010_00000_10000 == (1 << 17) | (1 << 11) | (1 << 4)
To check if our Bitmap node has an I-th element we can do:
bitmap & (1 << I)
And here's a formula to calculate a position in our pointer array
which would correspond to an I-th element:
popcount(bitmap & ((1 << I) - 1))
Let's break it down:
* `popcount` is a function that returns a number of bits set to 1;
* `((1 << I) - 1)` is a mask to filter the bitmask to contain bits
set to the *right* of our bit.
So for our 17, 11, and 4 indexes:
* bitmap & ((1 << 17) - 1) == 0b100000010000 => 2 bits are set => index is 2.
* bitmap & ((1 << 11) - 1) == 0b10000 => 1 bit is set => index is 1.
* bitmap & ((1 << 4) - 1) == 0b0 => 0 bits are set => index is 0.
To conclude: Bitmap nodes are just like Array nodes -- they can store
a number of pointers, but use bitmap compression to eliminate unused
pointers.
Bitmap nodes have two pointers for each item:
+----+----+----+----+ -- +----+----+
| k1 | v1 | k2 | v2 | .. | kN | vN |
+----+----+----+----+ -- +----+----+
When kI == NULL, vI points to another tree level.
When kI != NULL, the actual key object is stored in kI, and its
value is stored in vI.
Collision Nodes
---------------
Collision nodes are simple arrays of pointers -- two pointers per
key/value. When there's a hash collision, say for k1/v1 and k2/v2
we have `hash(k1)==hash(k2)`. Then our collision node will be:
+----+----+----+----+
| k1 | v1 | k2 | v2 |
+----+----+----+----+
Tree Structure
--------------
All nodes are PyObjects.
The `PyHamtObject` object has a pointer to the root node (h_root),
and has a length field (h_count).
High-level functions accept a PyHamtObject object and dispatch to
lower-level functions depending on what kind of node h_root points to.
Operations
==========
There are three fundamental operations on an immutable dictionary:
1. "o.assoc(k, v)" will return a new immutable dictionary, that will be
a copy of "o", but with the "k/v" item set.
Functions in this file:
hamt_node_assoc, hamt_node_bitmap_assoc,
hamt_node_array_assoc, hamt_node_collision_assoc
`hamt_node_assoc` function accepts a node object, and calls
other functions depending on its actual type.
2. "o.find(k)" will lookup key "k" in "o".
Functions:
hamt_node_find, hamt_node_bitmap_find,
hamt_node_array_find, hamt_node_collision_find
3. "o.without(k)" will return a new immutable dictionary, that will be
a copy of "o", buth without the "k" key.
Functions:
hamt_node_without, hamt_node_bitmap_without,
hamt_node_array_without, hamt_node_collision_without
Further Reading
===============
1. http://blog.higher-order.net/2009/09/08/understanding-clojures-persistenthashmap-deftwice.html
2. http://blog.higher-order.net/2010/08/16/assoc-and-clojures-persistenthashmap-part-ii.html
3. Clojure's PersistentHashMap implementation:
https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/PersistentHashMap.java
Debug
=====
The HAMT datatype is accessible for testing purposes under the
`_testcapi` module:
>>> from _testcapi import hamt
>>> h = hamt()
>>> h2 = h.set('a', 2)
>>> h3 = h2.set('b', 3)
>>> list(h3)
['a', 'b']
When CPython is built in debug mode, a '__dump__()' method is available
to introspect the tree:
>>> print(h3.__dump__())
HAMT(len=2):
BitmapNode(size=4 count=2 bitmap=0b110 id=0x10eb9d9e8):
'a': 2
'b': 3
*/
#define
IS_ARRAY_NODE
(
node
) (Py_TYPE(node) == &_PyHamt_ArrayNode_Type)
#define
IS_BITMAP_NODE
(
node
) (Py_TYPE(node) == &_PyHamt_BitmapNode_Type)
#define
IS_COLLISION_NODE
(
node
) (Py_TYPE(node) == &_PyHamt_CollisionNode_Type)
/* Return type for 'find' (lookup a key) functions.
* F_ERROR - an error occurred;
* F_NOT_FOUND - the key was not found;
* F_FOUND - the key was found.
*/
typedef
enum
{
F_ERROR
,
F_NOT_FOUND
,
F_FOUND
}
hamt_find_t
;
/* Return type for 'without' (delete a key) functions.
* W_ERROR - an error occurred;
* W_NOT_FOUND - the key was not found: there's nothing to delete;
* W_EMPTY - the key was found: the node/tree would be empty
if the key is deleted;
* W_NEWNODE - the key was found: a new node/tree is returned
without that key.
*/
typedef
enum
{
W_ERROR
,
W_NOT_FOUND
,
W_EMPTY
,
W_NEWNODE
}
hamt_without_t
;
/* Low-level iterator protocol type.
* I_ITEM - a new item has been yielded;
* I_END - the whole tree was visited (similar to StopIteration).
*/
typedef
enum
{
I_ITEM
,
I_END
}
hamt_iter_t
;
#define
HAMT_ARRAY_NODE_SIZE
32
typedef
struct
{
PyObject_HEAD
PyHamtNode
*
a_array
[
HAMT_ARRAY_NODE_SIZE
];
Py_ssize_t
a_count
;
}
PyHamtNode_Array
;
typedef
struct
{
PyObject_VAR_HEAD
uint32_t
b_bitmap
;
PyObject
*
b_array
[
1
];
}
PyHamtNode_Bitmap
;
typedef
struct
{
PyObject_VAR_HEAD
int32_t
c_hash
;
PyObject
*
c_array
[
1
];
}
PyHamtNode_Collision
;
static
PyHamtNode_Bitmap
*
_empty_bitmap_node
;
static
PyHamtObject
*
_empty_hamt
;
static
PyHamtObject
*
hamt_alloc
(
void
);
static
PyHamtNode
*
hamt_node_assoc
(
PyHamtNode
*
node
,
uint32_t
shift
,
int32_t
hash
,
PyObject
*
key
,
PyObject
*
val
,
int
*
added_leaf
);
static
hamt_without_t
hamt_node_without
(
PyHamtNode
*
node
,
uint32_t
shift
,
int32_t
hash
,
PyObject
*
key
,
PyHamtNode
*
*
new_node
);
static
hamt_find_t
hamt_node_find
(
PyHamtNode
*
node
,
uint32_t
shift
,
int32_t
hash
,
PyObject
*
key
,
PyObject
*
*
val
);
#ifdef
Py_DEBUG
static
int
hamt_node_dump
(
PyHamtNode
*
node
,
_PyUnicodeWriter
*
writer
,
int
level
);
#endif
static
PyHamtNode
*
hamt_node_array_new
(
Py_ssize_t
);
static
PyHamtNode
*
hamt_node_collision_new
(
int32_t
hash
,
Py_ssize_t
size
);
static
inline
Py_ssize_t
hamt_node_collision_count
(
PyHamtNode_Collision
*
node
);
#ifdef
Py_DEBUG
static
void
_hamt_node_array_validate
(
void
*
o
)
{
assert
(
IS_ARRAY_NODE
(
o
));
PyHamtNode_Array
*
node
=
(
PyHamtNode_Array
*
)(
o
);
Py_ssize_t
i
=
0
,
count
=
0
;
for
(;
i
<
HAMT_ARRAY_NODE_SIZE
;
i
++
) {
if
(
node
->
a_array
[
i
]
!=
NULL
) {
count
++
;
}
}
assert
(
count
==
node
->
a_count
);
}
#define
VALIDATE_ARRAY_NODE
(
NODE
) \
do { _hamt_node_array_validate(NODE); } while (0);
#else
#define
VALIDATE_ARRAY_NODE
(
NODE
)
#endif
/* Returns -1 on error */
static
inline
int32_t
hamt_hash
(
PyObject
*
o
)
{
Py_hash_t
hash
=
PyObject_Hash
(
o
);
#if
SIZEOF_PY_HASH_T
<=
4
return
hash
;
#else
if
(
hash
==
-1
) {
/* exception */
return
-1
;
}
/* While it's suboptimal to reduce Python's 64 bit hash to
32 bits via XOR, it seems that the resulting hash function
is good enough (this is also how Long type is hashed in Java.)
Storing 10, 100, 1000 Python strings results in a relatively
shallow and uniform tree structure.
Please don't change this hashing algorithm, as there are many
tests that test some exact tree shape to cover all code paths.
*/
int32_t
xored
=
(
int32_t
)(
hash
&
0xffffffffl
) ^ (
int32_t
)(
hash
>>
32
);
return
xored
==
-1
?
-2
:
xored
;
#endif
}
static
inline
uint32_t
hamt_mask
(
int32_t
hash
,
uint32_t
shift
)
{
return
(((
uint32_t
)
hash
>>
shift
)
&
0x01f
);
}
static
inline
uint32_t
hamt_bitpos
(
int32_t
hash
,
uint32_t
shift
)
{
return
(
uint32_t
)
1
<<
hamt_mask
(
hash
,
shift
);
}
static
inline
uint32_t
hamt_bitcount
(
uint32_t
i
)
{
#if
defined(
__GNUC__
)
&&
(
__GNUC__
>
4
)
return
(
uint32_t
)
__builtin_popcountl
(
i
);
#elif
defined(
__clang__
)
&&
(
__clang_major__
>
3
)
return
(
uint32_t
)
__builtin_popcountl
(
i
);
#elif
defined(
_MSC_VER
)
return
(
uint32_t
)
__popcnt
(
i
);
#else
/* https://graphics.stanford.edu/~seander/bithacks.html */
i
=
i
-
((
i
>>
1
)
&
0x55555555
);
i
=
(
i
&
0x33333333
)
+
((
i
>>
2
)
&
0x33333333
);
return
((
i
+
(
i
>>
4
)
&
0xF0F0F0F
)
*
0x1010101
) >>
24
;
#endif
}
static
inline
uint32_t
hamt_bitindex
(
uint32_t
bitmap
,
uint32_t
bit
)
{
return
hamt_bitcount
(
bitmap
&
(
bit
-
1
));
}
/////////////////////////////////// Dump Helpers
#ifdef
Py_DEBUG
static
int
_hamt_dump_ident
(
_PyUnicodeWriter
*
writer
,
int
level
)
{
/* Write `' ' * level` to the `writer` */
PyObject
*
str
=
NULL
;
PyObject
*
num
=
NULL
;
PyObject
*
res
=
NULL
;
int
ret
=
-1
;
str
=
PyUnicode_FromString
(
" "
);
if
(
str
==
NULL
) {
goto
error
;
}
num
=
PyLong_FromLong
((
long
)
level
);
if
(
num
==
NULL
) {
goto
error
;
}
res
=
PyNumber_Multiply
(
str
,
num
);
if
(
res
==
NULL
) {
goto
error
;
}
ret
=
_PyUnicodeWriter_WriteStr
(
writer
,
res
);
error
:
Py_XDECREF
(
res
);
Py_XDECREF
(
str
);
Py_XDECREF
(
num
);
return
ret
;
}
static
int
_hamt_dump_format
(
_PyUnicodeWriter
*
writer
,
const
char
*
format
, ...)
{
/* A convenient helper combining _PyUnicodeWriter_WriteStr and
PyUnicode_FromFormatV.
*/
PyObject
*
msg
;
int
ret
;
va_list
vargs
;
#ifdef
HAVE_STDARG_PROTOTYPES
va_start
(
vargs
,
format
);
#else
va_start
(
vargs
);
#endif
msg
=
PyUnicode_FromFormatV
(
format
,
vargs
);
va_end
(
vargs
);
if
(
msg
==
NULL
) {
return
-1
;
}
ret
=
_PyUnicodeWriter_WriteStr
(
writer
,
msg
);
Py_DECREF
(
msg
);
return
ret
;
}
#endif
/* Py_DEBUG */
/////////////////////////////////// Bitmap Node
static
PyHamtNode
*
hamt_node_bitmap_new
(
Py_ssize_t
size
)
{
/* Create a new bitmap node of size 'size' */
PyHamtNode_Bitmap
*
node
;
Py_ssize_t
i
;
assert
(
size
>=
0
);
assert
(
size
%
2
==
0
);
if
(
size
==
0
&&
_empty_bitmap_node
!=
NULL
) {
Py_INCREF
(
_empty_bitmap_node
);
return
(
PyHamtNode
*
)
_empty_bitmap_node
;
}
/* No freelist; allocate a new bitmap node */
node
=
PyObject_GC_NewVar
(
PyHamtNode_Bitmap
,
&
_PyHamt_BitmapNode_Type
,
size
);
if
(
node
==
NULL
) {
return
NULL
;
}
Py_SIZE
(
node
)
=
size
;
for
(
i
=
0
;
i
<
size
;
i
++
) {
node
->
b_array
[
i
]
=
NULL
;
}
node
->
b_bitmap
=
0
;
_PyObject_GC_TRACK
(
node
);
if
(
size
==
0
&&
_empty_bitmap_node
==
NULL
) {
/* Since bitmap nodes are immutable, we can cache the instance
for size=0 and reuse it whenever we need an empty bitmap node.
*/
_empty_bitmap_node
=
node
;
Py_INCREF
(
_empty_bitmap_node
);
}
return
(
PyHamtNode
*
)
node
;
}
static
inline
Py_ssize_t
hamt_node_bitmap_count
(
PyHamtNode_Bitmap
*
node
)
{
return
Py_SIZE
(
node
) /
2
;
}
static
PyHamtNode_Bitmap
*
hamt_node_bitmap_clone
(
PyHamtNode_Bitmap
*
node
)
{
/* Clone a bitmap node; return a new one with the same child notes. */
PyHamtNode_Bitmap
*
clone
;
Py_ssize_t
i
;
clone
=
(
PyHamtNode_Bitmap
*
)
hamt_node_bitmap_new
(
Py_SIZE
(
node
));
if
(
clone
==
NULL
) {
return
NULL
;
}
for
(
i
=
0
;
i
<
Py_SIZE
(
node
);
i
++
) {
Py_XINCREF
(
node
->
b_array
[
i
]);
clone
->
b_array
[
i
]
=
node
->
b_array
[
i
];
}
clone
->
b_bitmap
=
node
->
b_bitmap
;
return
clone
;
}
static
PyHamtNode_Bitmap
*
hamt_node_bitmap_clone_without
(
PyHamtNode_Bitmap
*
o
,
uint32_t
bit
)
{
assert
(
bit
&
o
->
b_bitmap
);
assert
(
hamt_node_bitmap_count
(
o
)
>
1
);
PyHamtNode_Bitmap
*
new
=
(
PyHamtNode_Bitmap
*
)
hamt_node_bitmap_new
(
Py_SIZE
(
o
)
-
2
);
if
(
new
==
NULL
) {
return
NULL
;
}
uint32_t
idx
=
hamt_bitindex
(
o
->
b_bitmap
,
bit
);
uint32_t
key_idx
=
2
*
idx
;
uint32_t
val_idx
=
key_idx
+
1
;
uint32_t
i
;
for
(
i
=
0
;
i
<
key_idx
;
i
++
) {
Py_XINCREF
(
o
->
b_array
[
i
]);
new
->
b_array
[
i
]
=
o
->
b_array
[
i
];
}
for
(
i
=
val_idx
+
1
;
i
<
Py_SIZE
(
o
);
i
++
) {
Py_XINCREF
(
o
->
b_array
[
i
]);
new
->
b_array
[
i
-
2
]
=
o
->
b_array
[
i
];
}
new
->
b_bitmap
=
o
->
b_bitmap
&
~
bit
;
return
new
;
}
static
PyHamtNode
*
hamt_node_new_bitmap_or_collision
(
uint32_t
shift
,
PyObject
*
key1
,
PyObject
*
val1
,
int32_t
key2_hash
,
PyObject
*
key2
,
PyObject
*
val2
)
{
/* Helper method. Creates a new node for key1/val and key2/val2
pairs.
If key1 hash is equal to the hash of key2, a Collision node
will be created. If they are not equal, a Bitmap node is
created.
*/
int32_t
key1_hash
=
hamt_hash
(
key1
);
if
(
key1_hash
==
-1
) {
return
NULL
;
}
if
(
key1_hash
==
key2_hash
) {
PyHamtNode_Collision
*
n
;
n
=
(
PyHamtNode_Collision
*
)
hamt_node_collision_new
(
key1_hash
,
4
);
if
(
n
==
NULL
) {
return
NULL
;
}
Py_INCREF
(
key1
);
n
->
c_array
[
0
]
=
key1
;
Py_INCREF
(
val1
);
n
->
c_array
[
1
]
=
val1
;
Py_INCREF
(
key2
);
n
->
c_array
[
2
]
=
key2
;
Py_INCREF
(
val2
);
n
->
c_array
[
3
]
=
val2
;
return
(
PyHamtNode
*
)
n
;
}
else
{
int
added_leaf
=
0
;
PyHamtNode
*
n
=
hamt_node_bitmap_new
(
0
);
if
(
n
==
NULL
) {
return
NULL
;
}
PyHamtNode
*
n2
=
hamt_node_assoc
(
n
,
shift
,
key1_hash
,
key1
,
val1
,
&
added_leaf
);
Py_DECREF
(
n
);
if
(
n2
==
NULL
) {
return
NULL
;
}
n
=
hamt_node_assoc
(
n2
,
shift
,
key2_hash
,
key2
,
val2
,
&
added_leaf
);
Py_DECREF
(
n2
);
if
(
n
==
NULL
) {
return
NULL
;
}
return
n
;
}
}
static
PyHamtNode
*
hamt_node_bitmap_assoc
(
PyHamtNode_Bitmap
*
self
,
uint32_t
shift
,
int32_t
hash
,
PyObject
*
key
,
PyObject
*
val
,
int
*
added_leaf
)
{
/* assoc operation for bitmap nodes.
Return: a new node, or self if key/val already is in the
collection.
'added_leaf' is later used in '_PyHamt_Assoc' to determine if
`hamt.set(key, val)` increased the size of the collection.
*/
uint32_t
bit
=
hamt_bitpos
(
hash
,
shift
);
uint32_t
idx
=
hamt_bitindex
(
self
->
b_bitmap
,
bit
);
/* Bitmap node layout:
+------+------+------+------+ --- +------+------+
| key1 | val1 | key2 | val2 | ... | keyN | valN |
+------+------+------+------+ --- +------+------+
where `N < Py_SIZE(node)`.
The `node->b_bitmap` field is a bitmap. For a given
`(shift, hash)` pair we can determine:
- If this node has the corresponding key/val slots.
- The index of key/val slots.
*/
if
(
self
->
b_bitmap
&
bit
) {
/* The key is set in this node */
uint32_t
key_idx
=
2
*
idx
;
uint32_t
val_idx
=
key_idx
+
1
;
assert
(
val_idx
<
Py_SIZE
(
self
));
PyObject
*
key_or_null
=
self
->
b_array
[
key_idx
];
PyObject
*
val_or_node
=
self
->
b_array
[
val_idx
];
if
(
key_or_null
==
NULL
) {
/* key is NULL. This means that we have a few keys
that have the same (hash, shift) pair. */
assert
(
val_or_node
!=
NULL
);
PyHamtNode
*
sub_node
=
hamt_node_assoc
(
(
PyHamtNode
*
)
val_or_node
,
shift
+
5
,
hash
,
key
,
val
,
added_leaf
);
if
(
sub_node
==
NULL
) {
return
NULL
;
}
if
(
val_or_node
==
(
PyObject
*
)
sub_node
) {
Py_DECREF
(
sub_node
);
Py_INCREF
(
self
);
return
(
PyHamtNode
*
)
self
;
}
PyHamtNode_Bitmap
*
ret
=
hamt_node_bitmap_clone
(
self
);
if
(
ret
==
NULL
) {
return
NULL
;
}
Py_SETREF
(
ret
->
b_array
[
val_idx
], (
PyObject
*
)
sub_node
);
return
(
PyHamtNode
*
)
ret
;
}
assert
(
key
!=
NULL
);
/* key is not NULL. This means that we have only one other
key in this collection that matches our hash for this shift. */
int
comp_err
=
PyObject_RichCompareBool
(
key
,
key_or_null
,
Py_EQ
);
if
(
comp_err
<
0
) {
/* exception in __eq__ */
return
NULL
;
}
if
(
comp_err
==
1
) {
/* key == key_or_null */
if
(
val
==
val_or_node
) {
/* we already have the same key/val pair; return self. */
Py_INCREF
(
self
);
return
(
PyHamtNode
*
)
self
;
}
/* We're setting a new value for the key we had before.
Make a new bitmap node with a replaced value, and return it. */
PyHamtNode_Bitmap
*
ret
=
hamt_node_bitmap_clone
(
self
);
if
(
ret
==
NULL
) {
return
NULL
;
}
Py_INCREF
(
val
);
Py_SETREF
(
ret
->
b_array
[
val_idx
],
val
);
return
(
PyHamtNode
*
)
ret
;
}
/* It's a new key, and it has the same index as *one* another key.
We have a collision. We need to create a new node which will
combine the existing key and the key we're adding.
`hamt_node_new_bitmap_or_collision` will either create a new
Collision node if the keys have identical hashes, or
a new Bitmap node.
*/
PyHamtNode
*
sub_node
=
hamt_node_new_bitmap_or_collision
(
shift
+
5
,
key_or_null
,
val_or_node
,
/* existing key/val */
hash
,
key
,
val
/* new key/val */
);
if
(
sub_node
==
NULL
) {
return
NULL
;
}
PyHamtNode_Bitmap
*
ret
=
hamt_node_bitmap_clone
(
self
);
if
(
ret
==
NULL
) {
Py_DECREF
(
sub_node
);
return
NULL
;
}
Py_SETREF
(
ret
->
b_array
[
key_idx
],
NULL
);
Py_SETREF
(
ret
->
b_array
[
val_idx
], (
PyObject
*
)
sub_node
);
*
added_leaf
=
1
;
return
(
PyHamtNode
*
)
ret
;
}
else
{
/* There was no key before with the same (shift,hash). */
uint32_t
n
=
hamt_bitcount
(
self
->
b_bitmap
);
if
(
n
>=
16
) {
/* When we have a situation where we want to store more
than 16 nodes at one level of the tree, we no longer
want to use the Bitmap node with bitmap encoding.
Instead we start using an Array node, which has
simpler (faster) implementation at the expense of
having prealocated 32 pointers for its keys/values
pairs.
Small hamt objects (<30 keys) usually don't have any
Array nodes at all. Betwen ~30 and ~400 keys hamt
objects usually have one Array node, and usually it's
a root node.
*/
uint32_t
jdx
=
hamt_mask
(
hash
,
shift
);
/* 'jdx' is the index of where the new key should be added
in the new Array node we're about to create. */
PyHamtNode
*
empty
=
NULL
;
PyHamtNode_Array
*
new_node
=
NULL
;
PyHamtNode
*
res
=
NULL
;
/* Create a new Array node. */
new_node
=
(
PyHamtNode_Array
*
)
hamt_node_array_new
(
n
+
1
);
if
(
new_node
==
NULL
) {
goto
fin
;
}
/* Create an empty bitmap node for the next
hamt_node_assoc call. */
empty
=
hamt_node_bitmap_new
(
0
);
if
(
empty
==
NULL
) {
goto
fin
;
}
/* Make a new bitmap node for the key/val we're adding.
Set that bitmap node to new-array-node[jdx]. */
new_node
->
a_array
[
jdx
]
=
hamt_node_assoc
(
empty
,
shift
+
5
,
hash
,
key
,
val
,
added_leaf
);
if
(
new_node
->
a_array
[
jdx
]
==
NULL
) {
goto
fin
;
}
/* Copy existing key/value pairs from the current Bitmap
node to the new Array node we've just created. */
Py_ssize_t
i
,
j
;
for
(
i
=
0
,
j
=
0
;
i
<
HAMT_ARRAY_NODE_SIZE
;
i
++
) {
if
(((
self
->
b_bitmap
>>
i
)
&
1
)
!=
0
) {
/* Ensure we don't accidentally override `jdx` element
we set few lines above.
*/
assert
(
new_node
->
a_array
[
i
]
==
NULL
);
if
(
self
->
b_array
[
j
]
==
NULL
) {
new_node
->
a_array
[
i
]
=
(
PyHamtNode
*
)
self
->
b_array
[
j
+
1
];
Py_INCREF
(
new_node
->
a_array
[
i
]);
}
else
{
int32_t
rehash
=
hamt_hash
(
self
->
b_array
[
j
]);
if
(
rehash
==
-1
) {
goto
fin
;
}
new_node
->
a_array
[
i
]
=
hamt_node_assoc
(
empty
,
shift
+
5
,
rehash
,
self
->
b_array
[
j
],
self
->
b_array
[
j
+
1
],
added_leaf
);
if
(
new_node
->
a_array
[
i
]
==
NULL
) {
goto
fin
;
}
}
j
+=
2
;
}
}
VALIDATE_ARRAY_NODE
(
new_node
)
/* That's it! */
res
=
(
PyHamtNode
*
)
new_node
;
fin
:
Py_XDECREF
(
empty
);
if
(
res
==
NULL
) {
Py_XDECREF
(
new_node
);
}
return
res
;
}
else
{
/* We have less than 16 keys at this level; let's just
create a new bitmap node out of this node with the
new key/val pair added. */
uint32_t
key_idx
=
2
*
idx
;
uint32_t
val_idx
=
key_idx
+
1
;
Py_ssize_t
i
;
*
added_leaf
=
1
;
/* Allocate new Bitmap node which can have one more key/val
pair in addition to what we have already. */
PyHamtNode_Bitmap
*
new_node
=
(
PyHamtNode_Bitmap
*
)
hamt_node_bitmap_new
(
2
*
(
n
+
1
));
if
(
new_node
==
NULL
) {
return
NULL
;
}
/* Copy all keys/values that will be before the new key/value
we are adding. */
for
(
i
=
0
;
i
<
key_idx
;
i
++
) {
Py_XINCREF
(
self
->
b_array
[
i
]);
new_node
->
b_array
[
i
]
=
self
->
b_array
[
i
];
}
/* Set the new key/value to the new Bitmap node. */
Py_INCREF
(
key
);
new_node
->
b_array
[
key_idx
]
=
key
;
Py_INCREF
(
val
);
new_node
->
b_array
[
val_idx
]
=
val
;
/* Copy all keys/values that will be after the new key/value
we are adding. */
for
(
i
=
key_idx
;
i
<
Py_SIZE
(
self
);
i
++
) {
Py_XINCREF
(
self
->
b_array
[
i
]);
new_node
->
b_array
[
i
+
2
]
=
self
->
b_array
[
i
];
}
new_node
->
b_bitmap
=
self
->
b_bitmap
|
bit
;
return
(
PyHamtNode
*
)
new_node
;
}
}
}
static
hamt_without_t
hamt_node_bitmap_without
(
PyHamtNode_Bitmap
*
self
,
uint32_t
shift
,
int32_t
hash
,
PyObject
*
key
,
PyHamtNode
*
*
new_node
)
{
uint32_t
bit
=
hamt_bitpos
(
hash
,
shift
);
if
((
self
->
b_bitmap
&
bit
)
==
0
) {
return
W_NOT_FOUND
;
}
uint32_t
idx
=
hamt_bitindex
(
self
->
b_bitmap
,
bit
);
uint32_t
key_idx
=
2
*
idx
;
uint32_t
val_idx
=
key_idx
+
1
;
PyObject
*
key_or_null
=
self
->
b_array
[
key_idx
];
PyObject
*
val_or_node
=
self
->
b_array
[
val_idx
];
if
(
key_or_null
==
NULL
) {
/* key == NULL means that 'value' is another tree node. */
PyHamtNode
*
sub_node
=
NULL
;
hamt_without_t
res
=
hamt_node_without
(
(
PyHamtNode
*
)
val_or_node
,
shift
+
5
,
hash
,
key
,
&
sub_node
);
switch
(
res
) {
case
W_EMPTY
:
/* It's impossible for us to receive a W_EMPTY here:
- Array nodes are converted to Bitmap nodes when
we delete 16th item from them;
- Collision nodes are converted to Bitmap when
there is one item in them;
View remainder of file in raw view
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