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Rax: radix tree updated to latest version from antirez/rax.

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antirez 2018-10-13 14:17:32 +02:00
parent 3c140e7bcd
commit f54cde3a15
2 changed files with 234 additions and 69 deletions
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265
src/rax.c
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@ -1,6 +1,6 @@
/* Rax -- A radix tree implementation.
*
* Copyright (c) 2017, Salvatore Sanfilippo <antirez at gmail dot com>
* Copyright (c) 2017-2018, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@ -51,14 +51,18 @@ void *raxNotFound = (void*)"rax-not-found-pointer";
void raxDebugShowNode(const char *msg, raxNode *n);
/* Turn debugging messages on/off. */
#if 0
/* Turn debugging messages on/off by compiling with RAX_DEBUG_MSG macro on.
* When RAX_DEBUG_MSG is defined by default Rax operations will emit a lot
* of debugging info to the standard output, however you can still turn
* debugging on/off in order to enable it only when you suspect there is an
* operation causing a bug using the function raxSetDebugMsg(). */
#ifdef RAX_DEBUG_MSG
#define debugf(...) \
do { \
if (raxDebugMsg) { \
printf("%s:%s:%d:\t", __FILE__, __FUNCTION__, __LINE__); \
printf(__VA_ARGS__); \
fflush(stdout); \
} while (0);
}
#define debugnode(msg,n) raxDebugShowNode(msg,n)
#else
@ -66,6 +70,16 @@ void raxDebugShowNode(const char *msg, raxNode *n);
#define debugnode(msg,n)
#endif
/* By default log debug info if RAX_DEBUG_MSG is defined. */
static int raxDebugMsg = 1;
/* When debug messages are enabled, turn them on/off dynamically. By
* default they are enabled. Set the state to 0 to disable, and 1 to
* re-enable. */
void raxSetDebugMsg(int onoff) {
raxDebugMsg = onoff;
}
/* ------------------------- raxStack functions --------------------------
* The raxStack is a simple stack of pointers that is capable of switching
* from using a stack-allocated array to dynamic heap once a given number of
@ -134,12 +148,43 @@ static inline void raxStackFree(raxStack *ts) {
* Radix tree implementation
* --------------------------------------------------------------------------*/
/* Return the padding needed in the characters section of a node having size
* 'nodesize'. The padding is needed to store the child pointers to aligned
* addresses. Note that we add 4 to the node size because the node has a four
* bytes header. */
#define raxPadding(nodesize) ((sizeof(void*)-((nodesize+4) % sizeof(void*))) & (sizeof(void*)-1))
/* Return the pointer to the last child pointer in a node. For the compressed
* nodes this is the only child pointer. */
#define raxNodeLastChildPtr(n) ((raxNode**) ( \
((char*)(n)) + \
raxNodeCurrentLength(n) - \
sizeof(raxNode*) - \
(((n)->iskey && !(n)->isnull) ? sizeof(void*) : 0) \
))
/* Return the pointer to the first child pointer. */
#define raxNodeFirstChildPtr(n) ((raxNode**) ( \
(n)->data + \
(n)->size + \
raxPadding((n)->size)))
/* Return the current total size of the node. Note that the second line
* computes the padding after the string of characters, needed in order to
* save pointers to aligned addresses. */
#define raxNodeCurrentLength(n) ( \
sizeof(raxNode)+(n)->size+ \
raxPadding((n)->size)+ \
((n)->iscompr ? sizeof(raxNode*) : sizeof(raxNode*)*(n)->size)+ \
(((n)->iskey && !(n)->isnull)*sizeof(void*)) \
)
/* Allocate a new non compressed node with the specified number of children.
* If datafiled is true, the allocation is made large enough to hold the
* associated data pointer.
* Returns the new node pointer. On out of memory NULL is returned. */
raxNode *raxNewNode(size_t children, int datafield) {
size_t nodesize = sizeof(raxNode)+children+
size_t nodesize = sizeof(raxNode)+children+raxPadding(children)+
sizeof(raxNode*)*children;
if (datafield) nodesize += sizeof(void*);
raxNode *node = rax_malloc(nodesize);
@ -167,13 +212,6 @@ rax *raxNew(void) {
}
}
/* Return the current total size of the node. */
#define raxNodeCurrentLength(n) ( \
sizeof(raxNode)+(n)->size+ \
((n)->iscompr ? sizeof(raxNode*) : sizeof(raxNode*)*(n)->size)+ \
(((n)->iskey && !(n)->isnull)*sizeof(void*)) \
)
/* realloc the node to make room for auxiliary data in order
* to store an item in that node. On out of memory NULL is returned. */
raxNode *raxReallocForData(raxNode *n, void *data) {
@ -216,18 +254,17 @@ void *raxGetData(raxNode *n) {
raxNode *raxAddChild(raxNode *n, unsigned char c, raxNode **childptr, raxNode ***parentlink) {
assert(n->iscompr == 0);
size_t curlen = sizeof(raxNode)+
n->size+
sizeof(raxNode*)*n->size;
size_t newlen;
size_t curlen = raxNodeCurrentLength(n);
n->size++;
size_t newlen = raxNodeCurrentLength(n);
n->size--; /* For now restore the orignal size. We'll update it only on
success at the end. */
/* Alloc the new child we will link to 'n'. */
raxNode *child = raxNewNode(0,0);
if (child == NULL) return NULL;
/* Make space in the original node. */
if (n->iskey) curlen += sizeof(void*);
newlen = curlen+sizeof(raxNode*)+1; /* Add 1 char and 1 pointer. */
raxNode *newn = rax_realloc(n,newlen);
if (newn == NULL) {
rax_free(child);
@ -235,14 +272,34 @@ raxNode *raxAddChild(raxNode *n, unsigned char c, raxNode **childptr, raxNode **
}
n = newn;
/* After the reallocation, we have 5/9 (depending on the system
* pointer size) bytes at the end, that is, the additional char
* in the 'data' section, plus one pointer to the new child:
/* After the reallocation, we have up to 8/16 (depending on the system
* pointer size, and the required node padding) bytes at the end, that is,
* the additional char in the 'data' section, plus one pointer to the new
* child, plus the padding needed in order to store addresses into aligned
* locations.
*
* [numc][abx][ap][bp][xp]|auxp|.....
* So if we start with the following node, having "abde" edges.
*
* Note:
* - We assume 4 bytes pointer for simplicity.
* - Each space below corresponds to one byte
*
* [HDR*][abde][Aptr][Bptr][Dptr][Eptr]|AUXP|
*
* After the reallocation we need: 1 byte for the new edge character
* plus 4 bytes for a new child pointer (assuming 32 bit machine).
* However after adding 1 byte to the edge char, the header + the edge
* characters are no longer aligned, so we also need 3 bytes of padding.
* In total the reallocation will add 1+4+3 bytes = 8 bytes:
*
* (Blank bytes are represented by ".")
*
* [HDR*][abde][Aptr][Bptr][Dptr][Eptr]|AUXP|[....][....]
*
* Let's find where to insert the new child in order to make sure
* it is inserted in-place lexicographically. */
* it is inserted in-place lexicographically. Assuming we are adding
* a child "c" in our case pos will be = 2 after the end of the following
* loop. */
int pos;
for (pos = 0; pos < n->size; pos++) {
if (n->data[pos] > c) break;
@ -252,55 +309,81 @@ raxNode *raxAddChild(raxNode *n, unsigned char c, raxNode **childptr, raxNode **
* so that we can mess with the other data without overwriting it.
* We will obtain something like that:
*
* [numc][abx][ap][bp][xp].....|auxp| */
unsigned char *src;
* [HDR*][abde][Aptr][Bptr][Dptr][Eptr][....][....]|AUXP|
*/
unsigned char *src, *dst;
if (n->iskey && !n->isnull) {
src = n->data+n->size+sizeof(raxNode*)*n->size;
memmove(src+1+sizeof(raxNode*),src,sizeof(void*));
src = ((unsigned char*)n+curlen-sizeof(void*));
dst = ((unsigned char*)n+newlen-sizeof(void*));
memmove(dst,src,sizeof(void*));
}
/* Now imagine we are adding a node with edge 'c'. The insertion
* point is between 'b' and 'x', so the 'pos' variable value is
* To start, move all the child pointers after the insertion point
* of 1+sizeof(pointer) bytes on the right, to obtain:
/* Compute the "shift", that is, how many bytes we need to move the
* pointers section forward because of the addition of the new child
* byte in the string section. Note that if we had no padding, that
* would be always "1", since we are adding a single byte in the string
* section of the node (where now there is "abde" basically).
*
* [numc][abx][ap][bp].....[xp]|auxp| */
src = n->data+n->size+sizeof(raxNode*)*pos;
memmove(src+1+sizeof(raxNode*),src,sizeof(raxNode*)*(n->size-pos));
* However we have padding, so it could be zero, or up to 8.
*
* Another way to think at the shift is, how many bytes we need to
* move child pointers forward *other than* the obvious sizeof(void*)
* needed for the additional pointer itself. */
size_t shift = newlen - curlen - sizeof(void*);
/* We said we are adding a node with edge 'c'. The insertion
* point is between 'b' and 'd', so the 'pos' variable value is
* the index of the first child pointer that we need to move forward
* to make space for our new pointer.
*
* To start, move all the child pointers after the insertion point
* of shift+sizeof(pointer) bytes on the right, to obtain:
*
* [HDR*][abde][Aptr][Bptr][....][....][Dptr][Eptr]|AUXP|
*/
src = n->data+n->size+
raxPadding(n->size)+
sizeof(raxNode*)*pos;
memmove(src+shift+sizeof(raxNode*),src,sizeof(raxNode*)*(n->size-pos));
/* Move the pointers to the left of the insertion position as well. Often
* we don't need to do anything if there was already some padding to use. In
* that case the final destination of the pointers will be the same, however
* in our example there was no pre-existing padding, so we added one byte
* plus thre bytes of padding. After the next memmove() things will look
* like thata:
*
* [HDR*][abde][....][Aptr][Bptr][....][Dptr][Eptr]|AUXP|
*/
if (shift) {
src = (unsigned char*) raxNodeFirstChildPtr(n);
memmove(src+shift,src,sizeof(raxNode*)*pos);
}
/* Now make the space for the additional char in the data section,
* but also move the pointers before the insertion point in the right
* by 1 byte, in order to obtain the following:
* but also move the pointers before the insertion point to the right
* by shift bytes, in order to obtain the following:
*
* [numc][ab.x][ap][bp]....[xp]|auxp| */
* [HDR*][ab.d][e...][Aptr][Bptr][....][Dptr][Eptr]|AUXP|
*/
src = n->data+pos;
memmove(src+1,src,n->size-pos+sizeof(raxNode*)*pos);
memmove(src+1,src,n->size-pos);
/* We can now set the character and its child node pointer to get:
*
* [numc][abcx][ap][bp][cp]....|auxp|
* [numc][abcx][ap][bp][cp][xp]|auxp| */
* [HDR*][abcd][e...][Aptr][Bptr][....][Dptr][Eptr]|AUXP|
* [HDR*][abcd][e...][Aptr][Bptr][Cptr][Dptr][Eptr]|AUXP|
*/
n->data[pos] = c;
n->size++;
raxNode **childfield = (raxNode**)(n->data+n->size+sizeof(raxNode*)*pos);
src = (unsigned char*) raxNodeFirstChildPtr(n);
raxNode **childfield = (raxNode**)(src+sizeof(raxNode*)*pos);
memcpy(childfield,&child,sizeof(child));
*childptr = child;
*parentlink = childfield;
return n;
}
/* Return the pointer to the last child pointer in a node. For the compressed
* nodes this is the only child pointer. */
#define raxNodeLastChildPtr(n) ((raxNode**) ( \
((char*)(n)) + \
raxNodeCurrentLength(n) - \
sizeof(raxNode*) - \
(((n)->iskey && !(n)->isnull) ? sizeof(void*) : 0) \
))
/* Return the pointer to the first child pointer. */
#define raxNodeFirstChildPtr(n) ((raxNode**)((n)->data+(n)->size))
/* Turn the node 'n', that must be a node without any children, into a
* compressed node representing a set of nodes linked one after the other
* and having exactly one child each. The node can be a key or not: this
@ -321,7 +404,7 @@ raxNode *raxCompressNode(raxNode *n, unsigned char *s, size_t len, raxNode **chi
if (*child == NULL) return NULL;
/* Make space in the parent node. */
newsize = sizeof(raxNode)+len+sizeof(raxNode*);
newsize = sizeof(raxNode)+len+raxPadding(len)+sizeof(raxNode*);
if (n->iskey) {
data = raxGetData(n); /* To restore it later. */
if (!n->isnull) newsize += sizeof(void*);
@ -619,13 +702,14 @@ int raxGenericInsert(rax *rax, unsigned char *s, size_t len, void *data, void **
raxNode *postfix = NULL;
if (trimmedlen) {
nodesize = sizeof(raxNode)+trimmedlen+sizeof(raxNode*);
nodesize = sizeof(raxNode)+trimmedlen+raxPadding(trimmedlen)+
sizeof(raxNode*);
if (h->iskey && !h->isnull) nodesize += sizeof(void*);
trimmed = rax_malloc(nodesize);
}
if (postfixlen) {
nodesize = sizeof(raxNode)+postfixlen+
nodesize = sizeof(raxNode)+postfixlen+raxPadding(postfixlen)+
sizeof(raxNode*);
postfix = rax_malloc(nodesize);
}
@ -701,11 +785,12 @@ int raxGenericInsert(rax *rax, unsigned char *s, size_t len, void *data, void **
/* Allocate postfix & trimmed nodes ASAP to fail for OOM gracefully. */
size_t postfixlen = h->size - j;
size_t nodesize = sizeof(raxNode)+postfixlen+sizeof(raxNode*);
size_t nodesize = sizeof(raxNode)+postfixlen+raxPadding(postfixlen)+
sizeof(raxNode*);
if (data != NULL) nodesize += sizeof(void*);
raxNode *postfix = rax_malloc(nodesize);
nodesize = sizeof(raxNode)+j+sizeof(raxNode*);
nodesize = sizeof(raxNode)+j+raxPadding(j)+sizeof(raxNode*);
if (h->iskey && !h->isnull) nodesize += sizeof(void*);
raxNode *trimmed = rax_malloc(nodesize);
@ -875,7 +960,7 @@ raxNode *raxRemoveChild(raxNode *parent, raxNode *child) {
return parent;
}
/* Otherwise we need to scan for the children pointer and memmove()
/* Otherwise we need to scan for the child pointer and memmove()
* accordingly.
*
* 1. To start we seek the first element in both the children
@ -900,13 +985,21 @@ raxNode *raxRemoveChild(raxNode *parent, raxNode *child) {
debugf("raxRemoveChild tail len: %d\n", taillen);
memmove(e,e+1,taillen);
/* Since we have one data byte less, also child pointers start one byte
* before now. */
memmove(((char*)cp)-1,cp,(parent->size-taillen-1)*sizeof(raxNode**));
/* Compute the shift, that is the amount of bytes we should move our
* child pointers to the left, since the removal of one edge character
* and the corresponding padding change, may change the layout.
* We just check if in the old version of the node there was at the
* end just a single byte and all padding: in that case removing one char
* will remove a whole sizeof(void*) word. */
size_t shift = ((parent->size+4) % sizeof(void*)) == 1 ? sizeof(void*) : 0;
/* Move the remaining "tail" pointer at the right position as well. */
/* Move the children pointers before the deletion point. */
if (shift)
memmove(((char*)cp)-shift,cp,(parent->size-taillen-1)*sizeof(raxNode**));
/* Move the remaining "tail" pointers at the right position as well. */
size_t valuelen = (parent->iskey && !parent->isnull) ? sizeof(void*) : 0;
memmove(((char*)c)-1,c+1,taillen*sizeof(raxNode**)+valuelen);
memmove(((char*)c)-shift,c+1,taillen*sizeof(raxNode**)+valuelen);
/* 4. Update size. */
parent->size--;
@ -1072,7 +1165,7 @@ int raxRemove(rax *rax, unsigned char *s, size_t len, void **old) {
if (nodes > 1) {
/* If we can compress, create the new node and populate it. */
size_t nodesize =
sizeof(raxNode)+comprsize+sizeof(raxNode*);
sizeof(raxNode)+comprsize+raxPadding(comprsize)+sizeof(raxNode*);
raxNode *new = rax_malloc(nodesize);
/* An out of memory here just means we cannot optimize this
* node, but the tree is left in a consistent state. */
@ -1793,6 +1886,7 @@ void raxShow(rax *rax) {
/* Used by debugnode() macro to show info about a given node. */
void raxDebugShowNode(const char *msg, raxNode *n) {
if (raxDebugMsg == 0) return;
printf("%s: %p [%.*s] key:%d size:%d children:",
msg, (void*)n, (int)n->size, (char*)n->data, n->iskey, n->size);
int numcld = n->iscompr ? 1 : n->size;
@ -1807,4 +1901,43 @@ void raxDebugShowNode(const char *msg, raxNode *n) {
fflush(stdout);
}
/* Touch all the nodes of a tree returning a check sum. This is useful
* in order to make Valgrind detect if there is something wrong while
* reading the data structure.
*
* This function was used in order to identify Rax bugs after a big refactoring
* using this technique:
*
* 1. The rax-test is executed using Valgrind, adding a printf() so that for
* the fuzz tester we see what iteration in the loop we are in.
* 2. After every modification of the radix tree made by the fuzz tester
* in rax-test.c, we add a call to raxTouch().
* 3. Now as soon as an operation will corrupt the tree, raxTouch() will
* detect it (via Valgrind) immediately. We can add more calls to narrow
* the state.
* 4. At this point a good idea is to enable Rax debugging messages immediately
* before the moment the tree is corrupted, to see what happens.
*/
unsigned long raxTouch(raxNode *n) {
debugf("Touching %p\n", (void*)n);
unsigned long sum = 0;
if (n->iskey) {
sum += (unsigned long)raxGetData(n);
}
int numchildren = n->iscompr ? 1 : n->size;
raxNode **cp = raxNodeFirstChildPtr(n);
int count = 0;
for (int i = 0; i < numchildren; i++) {
if (numchildren > 1) {
sum += (long)n->data[i];
}
raxNode *child;
memcpy(&child,cp,sizeof(child));
if (child == (void*)0x65d1760) count++;
if (count > 1) exit(1);
sum += raxTouch(child);
cp++;
}
return sum;
}

38
src/rax.h
View File

@ -1,3 +1,33 @@
/* Rax -- A radix tree implementation.
*
* Copyright (c) 2017-2018, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef RAX_H
#define RAX_H
@ -77,16 +107,16 @@ typedef struct raxNode {
* Note how the character is not stored in the children but in the
* edge of the parents:
*
* [header strlen=0][abc][a-ptr][b-ptr][c-ptr](value-ptr?)
* [header iscompr=0][abc][a-ptr][b-ptr][c-ptr](value-ptr?)
*
* if node is compressed (strlen != 0) the node has 1 children.
* if node is compressed (iscompr bit is 1) the node has 1 children.
* In that case the 'size' bytes of the string stored immediately at
* the start of the data section, represent a sequence of successive
* nodes linked one after the other, for which only the last one in
* the sequence is actually represented as a node, and pointed to by
* the current compressed node.
*
* [header strlen=3][xyz][z-ptr](value-ptr?)
* [header iscompr=1][xyz][z-ptr](value-ptr?)
*
* Both compressed and not compressed nodes can represent a key
* with associated data in the radix tree at any level (not just terminal
@ -176,6 +206,8 @@ void raxStop(raxIterator *it);
int raxEOF(raxIterator *it);
void raxShow(rax *rax);
uint64_t raxSize(rax *rax);
unsigned long raxTouch(raxNode *n);
void raxSetDebugMsg(int onoff);
/* Internal API. May be used by the node callback in order to access rax nodes
* in a low level way, so this function is exported as well. */