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redis/src/rax.c

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/* Rax -- A radix tree implementation.
*
* Copyright (c) 2017-Present, Redis Ltd.
* All rights reserved.
*
* Licensed under your choice of the Redis Source Available License 2.0
* (RSALv2) or the Server Side Public License v1 (SSPLv1).
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <math.h>
#include "rax.h"
#include "redisassert.h"
#ifndef RAX_MALLOC_INCLUDE
#define RAX_MALLOC_INCLUDE "rax_malloc.h"
#endif
#include RAX_MALLOC_INCLUDE
/* -------------------------------- Debugging ------------------------------ */
void raxDebugShowNode(const char *msg, raxNode *n);
/* 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(...) \
if (raxDebugMsg) { \
printf("%s:%s:%d:\t", __FILE__, __func__, __LINE__); \
printf(__VA_ARGS__); \
fflush(stdout); \
}
#define debugnode(msg,n) raxDebugShowNode(msg,n)
#else
#define debugf(...)
#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
* items are reached. It is used in order to retain the list of parent nodes
* while walking the radix tree in order to implement certain operations that
* need to navigate the tree upward.
* ------------------------------------------------------------------------- */
/* Initialize the stack. */
static inline void raxStackInit(raxStack *ts) {
ts->stack = ts->static_items;
ts->items = 0;
ts->maxitems = RAX_STACK_STATIC_ITEMS;
ts->oom = 0;
}
/* Push an item into the stack, returns 1 on success, 0 on out of memory. */
static inline int raxStackPush(raxStack *ts, void *ptr) {
if (ts->items == ts->maxitems) {
if (ts->stack == ts->static_items) {
ts->stack = rax_malloc(sizeof(void*)*ts->maxitems*2);
if (ts->stack == NULL) {
ts->stack = ts->static_items;
ts->oom = 1;
errno = ENOMEM;
return 0;
}
memcpy(ts->stack,ts->static_items,sizeof(void*)*ts->maxitems);
} else {
void **newalloc = rax_realloc(ts->stack,sizeof(void*)*ts->maxitems*2);
if (newalloc == NULL) {
ts->oom = 1;
errno = ENOMEM;
return 0;
}
ts->stack = newalloc;
}
ts->maxitems *= 2;
}
ts->stack[ts->items] = ptr;
ts->items++;
return 1;
}
/* Pop an item from the stack, the function returns NULL if there are no
* items to pop. */
static inline void *raxStackPop(raxStack *ts) {
if (ts->items == 0) return NULL;
ts->items--;
return ts->stack[ts->items];
}
/* Return the stack item at the top of the stack without actually consuming
* it. */
static inline void *raxStackPeek(raxStack *ts) {
if (ts->items == 0) return NULL;
return ts->stack[ts->items-1];
}
/* Free the stack in case we used heap allocation. */
static inline void raxStackFree(raxStack *ts) {
if (ts->stack != ts->static_items) rax_free(ts->stack);
}
/* ----------------------------------------------------------------------------
* 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 datafield 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+raxPadding(children)+
sizeof(raxNode*)*children;
if (datafield) nodesize += sizeof(void*);
raxNode *node = rax_malloc(nodesize);
if (node == NULL) return NULL;
node->iskey = 0;
node->isnull = 0;
node->iscompr = 0;
node->size = children;
return node;
}
/* Allocate a new rax and return its pointer. On out of memory the function
* returns NULL. */
rax *raxNew(void) {
rax *rax = rax_malloc(sizeof(*rax));
if (rax == NULL) return NULL;
rax->numele = 0;
rax->numnodes = 1;
rax->head = raxNewNode(0,0);
if (rax->head == NULL) {
rax_free(rax);
return NULL;
} else {
return rax;
}
}
/* 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) {
if (data == NULL) return n; /* No reallocation needed, setting isnull=1 */
size_t curlen = raxNodeCurrentLength(n);
return rax_realloc(n,curlen+sizeof(void*));
}
/* Set the node auxiliary data to the specified pointer. */
void raxSetData(raxNode *n, void *data) {
n->iskey = 1;
if (data != NULL) {
n->isnull = 0;
void **ndata = (void**)
((char*)n+raxNodeCurrentLength(n)-sizeof(void*));
memcpy(ndata,&data,sizeof(data));
} else {
n->isnull = 1;
}
}
/* Get the node auxiliary data. */
void *raxGetData(raxNode *n) {
if (n->isnull) return NULL;
void **ndata =(void**)((char*)n+raxNodeCurrentLength(n)-sizeof(void*));
void *data;
memcpy(&data,ndata,sizeof(data));
return data;
}
/* Add a new child to the node 'n' representing the character 'c' and return
* its new pointer, as well as the child pointer by reference. Additionally
* '***parentlink' is populated with the raxNode pointer-to-pointer of where
* the new child was stored, which is useful for the caller to replace the
* child pointer if it gets reallocated.
*
* On success the new parent node pointer is returned (it may change because
* of the realloc, so the caller should discard 'n' and use the new value).
* On out of memory NULL is returned, and the old node is still valid. */
raxNode *raxAddChild(raxNode *n, unsigned char c, raxNode **childptr, raxNode ***parentlink) {
assert(n->iscompr == 0);
size_t curlen = raxNodeCurrentLength(n);
n->size++;
size_t newlen = raxNodeCurrentLength(n);
n->size--; /* For now restore the original 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. */
raxNode *newn = rax_realloc(n,newlen);
if (newn == NULL) {
rax_free(child);
return NULL;
}
n = newn;
/* 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.
*
* 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. 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;
}
/* Now, if present, move auxiliary data pointer at the end
* so that we can mess with the other data without overwriting it.
* We will obtain something like that:
*
* [HDR*][abde][Aptr][Bptr][Dptr][Eptr][....][....]|AUXP|
*/
unsigned char *src, *dst;
if (n->iskey && !n->isnull) {
src = ((unsigned char*)n+curlen-sizeof(void*));
dst = ((unsigned char*)n+newlen-sizeof(void*));
memmove(dst,src,sizeof(void*));
}
/* 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).
*
* 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 three bytes of padding. After the next memmove() things will look
* like that:
*
* [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 to the right
* by shift bytes, in order to obtain the following:
*
* [HDR*][ab.d][e...][Aptr][Bptr][....][Dptr][Eptr]|AUXP|
*/
src = n->data+pos;
memmove(src+1,src,n->size-pos);
/* We can now set the character and its child node pointer to get:
*
* [HDR*][abcd][e...][Aptr][Bptr][....][Dptr][Eptr]|AUXP|
* [HDR*][abcd][e...][Aptr][Bptr][Cptr][Dptr][Eptr]|AUXP|
*/
n->data[pos] = c;
n->size++;
src = (unsigned char*) raxNodeFirstChildPtr(n);
raxNode **childfield = (raxNode**)(src+sizeof(raxNode*)*pos);
memcpy(childfield,&child,sizeof(child));
*childptr = child;
*parentlink = childfield;
return n;
}
/* 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
* property and the associated value if any will be preserved.
*
* The function also returns a child node, since the last node of the
* compressed chain cannot be part of the chain: it has zero children while
* we can only compress inner nodes with exactly one child each. */
raxNode *raxCompressNode(raxNode *n, unsigned char *s, size_t len, raxNode **child) {
assert(n->size == 0 && n->iscompr == 0);
void *data = NULL; /* Initialized only to avoid warnings. */
size_t newsize;
debugf("Compress node: %.*s\n", (int)len,s);
/* Allocate the child to link to this node. */
*child = raxNewNode(0,0);
if (*child == NULL) return NULL;
/* Make space in the parent node. */
newsize = sizeof(raxNode)+len+raxPadding(len)+sizeof(raxNode*);
if (n->iskey) {
data = raxGetData(n); /* To restore it later. */
if (!n->isnull) newsize += sizeof(void*);
}
raxNode *newn = rax_realloc(n,newsize);
if (newn == NULL) {
rax_free(*child);
return NULL;
}
n = newn;
n->iscompr = 1;
n->size = len;
memcpy(n->data,s,len);
if (n->iskey) raxSetData(n,data);
raxNode **childfield = raxNodeLastChildPtr(n);
memcpy(childfield,child,sizeof(*child));
return n;
}
/* Low level function that walks the tree looking for the string
* 's' of 'len' bytes. The function returns the number of characters
* of the key that was possible to process: if the returned integer
* is the same as 'len', then it means that the node corresponding to the
* string was found (however it may not be a key in case the node->iskey is
* zero or if simply we stopped in the middle of a compressed node, so that
* 'splitpos' is non zero).
*
* Otherwise if the returned integer is not the same as 'len', there was an
* early stop during the tree walk because of a character mismatch.
*
* The node where the search ended (because the full string was processed
* or because there was an early stop) is returned by reference as
* '*stopnode' if the passed pointer is not NULL. This node link in the
* parent's node is returned as '*plink' if not NULL. Finally, if the
* search stopped in a compressed node, '*splitpos' returns the index
* inside the compressed node where the search ended. This is useful to
* know where to split the node for insertion.
*
* Note that when we stop in the middle of a compressed node with
* a perfect match, this function will return a length equal to the
* 'len' argument (all the key matched), and will return a *splitpos which is
* always positive (that will represent the index of the character immediately
* *after* the last match in the current compressed node).
*
* When instead we stop at a compressed node and *splitpos is zero, it
* means that the current node represents the key (that is, none of the
* compressed node characters are needed to represent the key, just all
* its parents nodes). */
static inline size_t raxLowWalk(rax *rax, unsigned char *s, size_t len, raxNode **stopnode, raxNode ***plink, int *splitpos, raxStack *ts) {
raxNode *h = rax->head;
raxNode **parentlink = &rax->head;
size_t i = 0; /* Position in the string. */
size_t j = 0; /* Position in the node children (or bytes if compressed).*/
while(h->size && i < len) {
debugnode("Lookup current node",h);
unsigned char *v = h->data;
if (h->iscompr) {
for (j = 0; j < h->size && i < len; j++, i++) {
if (v[j] != s[i]) break;
}
if (j != h->size) break;
} else {
/* Even when h->size is large, linear scan provides good
* performances compared to other approaches that are in theory
* more sounding, like performing a binary search. */
for (j = 0; j < h->size; j++) {
if (v[j] == s[i]) break;
}
if (j == h->size) break;
i++;
}
if (ts) raxStackPush(ts,h); /* Save stack of parent nodes. */
raxNode **children = raxNodeFirstChildPtr(h);
if (h->iscompr) j = 0; /* Compressed node only child is at index 0. */
memcpy(&h,children+j,sizeof(h));
parentlink = children+j;
j = 0; /* If the new node is non compressed and we do not
iterate again (since i == len) set the split
position to 0 to signal this node represents
the searched key. */
}
debugnode("Lookup stop node is",h);
if (stopnode) *stopnode = h;
if (plink) *plink = parentlink;
if (splitpos && h->iscompr) *splitpos = j;
return i;
}
/* Insert the element 's' of size 'len', setting as auxiliary data
* the pointer 'data'. If the element is already present, the associated
* data is updated (only if 'overwrite' is set to 1), and 0 is returned,
* otherwise the element is inserted and 1 is returned. On out of memory the
* function returns 0 as well but sets errno to ENOMEM, otherwise errno will
* be set to 0.
*/
int raxGenericInsert(rax *rax, unsigned char *s, size_t len, void *data, void **old, int overwrite) {
size_t i;
int j = 0; /* Split position. If raxLowWalk() stops in a compressed
node, the index 'j' represents the char we stopped within the
compressed node, that is, the position where to split the
node for insertion. */
raxNode *h, **parentlink;
debugf("### Insert %.*s with value %p\n", (int)len, s, data);
i = raxLowWalk(rax,s,len,&h,&parentlink,&j,NULL);
/* If i == len we walked following the whole string. If we are not
* in the middle of a compressed node, the string is either already
* inserted or this middle node is currently not a key, but can represent
* our key. We have just to reallocate the node and make space for the
* data pointer. */
if (i == len && (!h->iscompr || j == 0 /* not in the middle if j is 0 */)) {
debugf("### Insert: node representing key exists\n");
/* Make space for the value pointer if needed. */
if (!h->iskey || (h->isnull && overwrite)) {
h = raxReallocForData(h,data);
if (h) memcpy(parentlink,&h,sizeof(h));
}
if (h == NULL) {
errno = ENOMEM;
return 0;
}
/* Update the existing key if there is already one. */
if (h->iskey) {
if (old) *old = raxGetData(h);
if (overwrite) raxSetData(h,data);
errno = 0;
return 0; /* Element already exists. */
}
/* Otherwise set the node as a key. Note that raxSetData()
* will set h->iskey. */
raxSetData(h,data);
rax->numele++;
return 1; /* Element inserted. */
}
/* If the node we stopped at is a compressed node, we need to
* split it before to continue.
*
* Splitting a compressed node have a few possible cases.
* Imagine that the node 'h' we are currently at is a compressed
* node containing the string "ANNIBALE" (it means that it represents
* nodes A -> N -> N -> I -> B -> A -> L -> E with the only child
* pointer of this node pointing at the 'E' node, because remember that
* we have characters at the edges of the graph, not inside the nodes
* themselves.
*
* In order to show a real case imagine our node to also point to
* another compressed node, that finally points at the node without
* children, representing 'O':
*
* "ANNIBALE" -> "SCO" -> []
*
* When inserting we may face the following cases. Note that all the cases
* require the insertion of a non compressed node with exactly two
* children, except for the last case which just requires splitting a
* compressed node.
*
* 1) Inserting "ANNIENTARE"
*
* |B| -> "ALE" -> "SCO" -> []
* "ANNI" -> |-|
* |E| -> (... continue algo ...) "NTARE" -> []
*
* 2) Inserting "ANNIBALI"
*
* |E| -> "SCO" -> []
* "ANNIBAL" -> |-|
* |I| -> (... continue algo ...) []
*
* 3) Inserting "AGO" (Like case 1, but set iscompr = 0 into original node)
*
* |N| -> "NIBALE" -> "SCO" -> []
* |A| -> |-|
* |G| -> (... continue algo ...) |O| -> []
*
* 4) Inserting "CIAO"
*
* |A| -> "NNIBALE" -> "SCO" -> []
* |-|
* |C| -> (... continue algo ...) "IAO" -> []
*
* 5) Inserting "ANNI"
*
* "ANNI" -> "BALE" -> "SCO" -> []
*
* The final algorithm for insertion covering all the above cases is as
* follows.
*
* ============================= ALGO 1 =============================
*
* For the above cases 1 to 4, that is, all cases where we stopped in
* the middle of a compressed node for a character mismatch, do:
*
* Let $SPLITPOS be the zero-based index at which, in the
* compressed node array of characters, we found the mismatching
* character. For example if the node contains "ANNIBALE" and we add
* "ANNIENTARE" the $SPLITPOS is 4, that is, the index at which the
* mismatching character is found.
*
* 1. Save the current compressed node $NEXT pointer (the pointer to the
* child element, that is always present in compressed nodes).
*
* 2. Create "split node" having as child the non common letter
* at the compressed node. The other non common letter (at the key)
* will be added later as we continue the normal insertion algorithm
* at step "6".
*
* 3a. IF $SPLITPOS == 0:
* Replace the old node with the split node, by copying the auxiliary
* data if any. Fix parent's reference. Free old node eventually
* (we still need its data for the next steps of the algorithm).
*
* 3b. IF $SPLITPOS != 0:
* Trim the compressed node (reallocating it as well) in order to
* contain $splitpos characters. Change child pointer in order to link
* to the split node. If new compressed node len is just 1, set
* iscompr to 0 (layout is the same). Fix parent's reference.
*
* 4a. IF the postfix len (the length of the remaining string of the
* original compressed node after the split character) is non zero,
* create a "postfix node". If the postfix node has just one character
* set iscompr to 0, otherwise iscompr to 1. Set the postfix node
* child pointer to $NEXT.
*
* 4b. IF the postfix len is zero, just use $NEXT as postfix pointer.
*
* 5. Set child[0] of split node to postfix node.
*
* 6. Set the split node as the current node, set current index at child[1]
* and continue insertion algorithm as usually.
*
* ============================= ALGO 2 =============================
*
* For case 5, that is, if we stopped in the middle of a compressed
* node but no mismatch was found, do:
*
* Let $SPLITPOS be the zero-based index at which, in the
* compressed node array of characters, we stopped iterating because
* there were no more keys character to match. So in the example of
* the node "ANNIBALE", adding the string "ANNI", the $SPLITPOS is 4.
*
* 1. Save the current compressed node $NEXT pointer (the pointer to the
* child element, that is always present in compressed nodes).
*
* 2. Create a "postfix node" containing all the characters from $SPLITPOS
* to the end. Use $NEXT as the postfix node child pointer.
* If the postfix node length is 1, set iscompr to 0.
* Set the node as a key with the associated value of the new
* inserted key.
*
* 3. Trim the current node to contain the first $SPLITPOS characters.
* As usually if the new node length is just 1, set iscompr to 0.
* Take the iskey / associated value as it was in the original node.
* Fix the parent's reference.
*
* 4. Set the postfix node as the only child pointer of the trimmed
* node created at step 1.
*/
/* ------------------------- ALGORITHM 1 --------------------------- */
if (h->iscompr && i != len) {
debugf("ALGO 1: Stopped at compressed node %.*s (%p)\n",
h->size, h->data, (void*)h);
debugf("Still to insert: %.*s\n", (int)(len-i), s+i);
debugf("Splitting at %d: '%c'\n", j, ((char*)h->data)[j]);
debugf("Other (key) letter is '%c'\n", s[i]);
/* 1: Save next pointer. */
raxNode **childfield = raxNodeLastChildPtr(h);
raxNode *next;
memcpy(&next,childfield,sizeof(next));
debugf("Next is %p\n", (void*)next);
debugf("iskey %d\n", h->iskey);
if (h->iskey) {
debugf("key value is %p\n", raxGetData(h));
}
/* Set the length of the additional nodes we will need. */
size_t trimmedlen = j;
size_t postfixlen = h->size - j - 1;
int split_node_is_key = !trimmedlen && h->iskey && !h->isnull;
size_t nodesize;
/* 2: Create the split node. Also allocate the other nodes we'll need
* ASAP, so that it will be simpler to handle OOM. */
raxNode *splitnode = raxNewNode(1, split_node_is_key);
raxNode *trimmed = NULL;
raxNode *postfix = NULL;
if (trimmedlen) {
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+raxPadding(postfixlen)+
sizeof(raxNode*);
postfix = rax_malloc(nodesize);
}
/* OOM? Abort now that the tree is untouched. */
if (splitnode == NULL ||
(trimmedlen && trimmed == NULL) ||
(postfixlen && postfix == NULL))
{
rax_free(splitnode);
rax_free(trimmed);
rax_free(postfix);
errno = ENOMEM;
return 0;
}
splitnode->data[0] = h->data[j];
if (j == 0) {
/* 3a: Replace the old node with the split node. */
if (h->iskey) {
void *ndata = raxGetData(h);
raxSetData(splitnode,ndata);
}
memcpy(parentlink,&splitnode,sizeof(splitnode));
} else {
/* 3b: Trim the compressed node. */
trimmed->size = j;
memcpy(trimmed->data,h->data,j);
trimmed->iscompr = j > 1 ? 1 : 0;
trimmed->iskey = h->iskey;
trimmed->isnull = h->isnull;
if (h->iskey && !h->isnull) {
void *ndata = raxGetData(h);
raxSetData(trimmed,ndata);
}
raxNode **cp = raxNodeLastChildPtr(trimmed);
memcpy(cp,&splitnode,sizeof(splitnode));
memcpy(parentlink,&trimmed,sizeof(trimmed));
parentlink = cp; /* Set parentlink to splitnode parent. */
rax->numnodes++;
}
/* 4: Create the postfix node: what remains of the original
* compressed node after the split. */
if (postfixlen) {
/* 4a: create a postfix node. */
postfix->iskey = 0;
postfix->isnull = 0;
postfix->size = postfixlen;
postfix->iscompr = postfixlen > 1;
memcpy(postfix->data,h->data+j+1,postfixlen);
raxNode **cp = raxNodeLastChildPtr(postfix);
memcpy(cp,&next,sizeof(next));
rax->numnodes++;
} else {
/* 4b: just use next as postfix node. */
postfix = next;
}
/* 5: Set splitnode first child as the postfix node. */
raxNode **splitchild = raxNodeLastChildPtr(splitnode);
memcpy(splitchild,&postfix,sizeof(postfix));
/* 6. Continue insertion: this will cause the splitnode to
* get a new child (the non common character at the currently
* inserted key). */
rax_free(h);
h = splitnode;
} else if (h->iscompr && i == len) {
/* ------------------------- ALGORITHM 2 --------------------------- */
debugf("ALGO 2: Stopped at compressed node %.*s (%p) j = %d\n",
h->size, h->data, (void*)h, j);
/* Allocate postfix & trimmed nodes ASAP to fail for OOM gracefully. */
size_t postfixlen = h->size - j;
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+raxPadding(j)+sizeof(raxNode*);
if (h->iskey && !h->isnull) nodesize += sizeof(void*);
raxNode *trimmed = rax_malloc(nodesize);
if (postfix == NULL || trimmed == NULL) {
rax_free(postfix);
rax_free(trimmed);
errno = ENOMEM;
return 0;
}
/* 1: Save next pointer. */
raxNode **childfield = raxNodeLastChildPtr(h);
raxNode *next;
memcpy(&next,childfield,sizeof(next));
/* 2: Create the postfix node. */
postfix->size = postfixlen;
postfix->iscompr = postfixlen > 1;
postfix->iskey = 1;
postfix->isnull = 0;
memcpy(postfix->data,h->data+j,postfixlen);
raxSetData(postfix,data);
raxNode **cp = raxNodeLastChildPtr(postfix);
memcpy(cp,&next,sizeof(next));
rax->numnodes++;
/* 3: Trim the compressed node. */
trimmed->size = j;
trimmed->iscompr = j > 1;
trimmed->iskey = 0;
trimmed->isnull = 0;
memcpy(trimmed->data,h->data,j);
memcpy(parentlink,&trimmed,sizeof(trimmed));
if (h->iskey) {
void *aux = raxGetData(h);
raxSetData(trimmed,aux);
}
/* Fix the trimmed node child pointer to point to
* the postfix node. */
cp = raxNodeLastChildPtr(trimmed);
memcpy(cp,&postfix,sizeof(postfix));
/* Finish! We don't need to continue with the insertion
* algorithm for ALGO 2. The key is already inserted. */
rax->numele++;
rax_free(h);
return 1; /* Key inserted. */
}
/* We walked the radix tree as far as we could, but still there are left
* chars in our string. We need to insert the missing nodes. */
while(i < len) {
raxNode *child;
/* If this node is going to have a single child, and there
* are other characters, so that that would result in a chain
* of single-childed nodes, turn it into a compressed node. */
if (h->size == 0 && len-i > 1) {
debugf("Inserting compressed node\n");
size_t comprsize = len-i;
if (comprsize > RAX_NODE_MAX_SIZE)
comprsize = RAX_NODE_MAX_SIZE;
raxNode *newh = raxCompressNode(h,s+i,comprsize,&child);
if (newh == NULL) goto oom;
h = newh;
memcpy(parentlink,&h,sizeof(h));
parentlink = raxNodeLastChildPtr(h);
i += comprsize;
} else {
debugf("Inserting normal node\n");
raxNode **new_parentlink;
raxNode *newh = raxAddChild(h,s[i],&child,&new_parentlink);
if (newh == NULL) goto oom;
h = newh;
memcpy(parentlink,&h,sizeof(h));
parentlink = new_parentlink;
i++;
}
rax->numnodes++;
h = child;
}
raxNode *newh = raxReallocForData(h,data);
if (newh == NULL) goto oom;
h = newh;
if (!h->iskey) rax->numele++;
raxSetData(h,data);
memcpy(parentlink,&h,sizeof(h));
return 1; /* Element inserted. */
oom:
/* This code path handles out of memory after part of the sub-tree was
* already modified. Set the node as a key, and then remove it. However we
* do that only if the node is a terminal node, otherwise if the OOM
* happened reallocating a node in the middle, we don't need to free
* anything. */
if (h->size == 0) {
h->isnull = 1;
h->iskey = 1;
rax->numele++; /* Compensate the next remove. */
assert(raxRemove(rax,s,i,NULL) != 0);
}
errno = ENOMEM;
return 0;
}
/* Overwriting insert. Just a wrapper for raxGenericInsert() that will
* update the element if there is already one for the same key. */
int raxInsert(rax *rax, unsigned char *s, size_t len, void *data, void **old) {
return raxGenericInsert(rax,s,len,data,old,1);
}
/* Non overwriting insert function: if an element with the same key
* exists, the value is not updated and the function returns 0.
* This is just a wrapper for raxGenericInsert(). */
int raxTryInsert(rax *rax, unsigned char *s, size_t len, void *data, void **old) {
return raxGenericInsert(rax,s,len,data,old,0);
}
/* Find a key in the rax: return 1 if the item is found, 0 otherwise.
* If there is an item and 'value' is passed in a non-NULL pointer,
* the value associated with the item is set at that address. */
int raxFind(rax *rax, unsigned char *s, size_t len, void **value) {
raxNode *h;
debugf("### Lookup: %.*s\n", (int)len, s);
int splitpos = 0;
size_t i = raxLowWalk(rax,s,len,&h,NULL,&splitpos,NULL);
if (i != len || (h->iscompr && splitpos != 0) || !h->iskey)
return 0;
if (value != NULL) *value = raxGetData(h);
return 1;
}
/* Return the memory address where the 'parent' node stores the specified
* 'child' pointer, so that the caller can update the pointer with another
* one if needed. The function assumes it will find a match, otherwise the
* operation is an undefined behavior (it will continue scanning the
* memory without any bound checking). */
raxNode **raxFindParentLink(raxNode *parent, raxNode *child) {
raxNode **cp = raxNodeFirstChildPtr(parent);
raxNode *c;
while(1) {
memcpy(&c,cp,sizeof(c));
if (c == child) break;
cp++;
}
return cp;
}
/* Low level child removal from node. The new node pointer (after the child
* removal) is returned. Note that this function does not fix the pointer
* of the parent node in its parent, so this task is up to the caller.
* The function never fails for out of memory. */
raxNode *raxRemoveChild(raxNode *parent, raxNode *child) {
debugnode("raxRemoveChild before", parent);
/* If parent is a compressed node (having a single child, as for definition
* of the data structure), the removal of the child consists into turning
* it into a normal node without children. */
if (parent->iscompr) {
void *data = NULL;
if (parent->iskey) data = raxGetData(parent);
parent->isnull = 0;
parent->iscompr = 0;
parent->size = 0;
if (parent->iskey) raxSetData(parent,data);
debugnode("raxRemoveChild after", parent);
return parent;
}
/* Otherwise we need to scan for the child pointer and memmove()
* accordingly.
*
* 1. To start we seek the first element in both the children
* pointers and edge bytes in the node. */
raxNode **cp = raxNodeFirstChildPtr(parent);
raxNode **c = cp;
unsigned char *e = parent->data;
/* 2. Search the child pointer to remove inside the array of children
* pointers. */
while(1) {
raxNode *aux;
memcpy(&aux,c,sizeof(aux));
if (aux == child) break;
c++;
e++;
}
/* 3. Remove the edge and the pointer by memmoving the remaining children
* pointer and edge bytes one position before. */
int taillen = parent->size - (e - parent->data) - 1;
debugf("raxRemoveChild tail len: %d\n", taillen);
memmove(e,e+1,taillen);
/* 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 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)-shift,c+1,taillen*sizeof(raxNode**)+valuelen);
/* 4. Update size. */
parent->size--;
/* realloc the node according to the theoretical memory usage, to free
* data if we are over-allocating right now. */
raxNode *newnode = rax_realloc(parent,raxNodeCurrentLength(parent));
if (newnode) {
debugnode("raxRemoveChild after", newnode);
}
/* Note: if rax_realloc() fails we just return the old address, which
* is valid. */
return newnode ? newnode : parent;
}
/* Remove the specified item. Returns 1 if the item was found and
* deleted, 0 otherwise. */
int raxRemove(rax *rax, unsigned char *s, size_t len, void **old) {
raxNode *h;
raxStack ts;
debugf("### Delete: %.*s\n", (int)len, s);
raxStackInit(&ts);
int splitpos = 0;
size_t i = raxLowWalk(rax,s,len,&h,NULL,&splitpos,&ts);
if (i != len || (h->iscompr && splitpos != 0) || !h->iskey) {
raxStackFree(&ts);
return 0;
}
if (old) *old = raxGetData(h);
h->iskey = 0;
rax->numele--;
/* If this node has no children, the deletion needs to reclaim the
* no longer used nodes. This is an iterative process that needs to
* walk the three upward, deleting all the nodes with just one child
* that are not keys, until the head of the rax is reached or the first
* node with more than one child is found. */
int trycompress = 0; /* Will be set to 1 if we should try to optimize the
tree resulting from the deletion. */
if (h->size == 0) {
debugf("Key deleted in node without children. Cleanup needed.\n");
raxNode *child = NULL;
while(h != rax->head) {
child = h;
debugf("Freeing child %p [%.*s] key:%d\n", (void*)child,
(int)child->size, (char*)child->data, child->iskey);
rax_free(child);
rax->numnodes--;
h = raxStackPop(&ts);
/* If this node has more then one child, or actually holds
* a key, stop here. */
if (h->iskey || (!h->iscompr && h->size != 1)) break;
}
if (child) {
debugf("Unlinking child %p from parent %p\n",
(void*)child, (void*)h);
raxNode *new = raxRemoveChild(h,child);
if (new != h) {
raxNode *parent = raxStackPeek(&ts);
raxNode **parentlink;
if (parent == NULL) {
parentlink = &rax->head;
} else {
parentlink = raxFindParentLink(parent,h);
}
memcpy(parentlink,&new,sizeof(new));
}
/* If after the removal the node has just a single child
* and is not a key, we need to try to compress it. */
if (new->size == 1 && new->iskey == 0) {
trycompress = 1;
h = new;
}
}
} else if (h->size == 1) {
/* If the node had just one child, after the removal of the key
* further compression with adjacent nodes is potentially possible. */
trycompress = 1;
}
/* Don't try node compression if our nodes pointers stack is not
* complete because of OOM while executing raxLowWalk() */
if (trycompress && ts.oom) trycompress = 0;
/* Recompression: if trycompress is true, 'h' points to a radix tree node
* that changed in a way that could allow to compress nodes in this
* sub-branch. Compressed nodes represent chains of nodes that are not
* keys and have a single child, so there are two deletion events that
* may alter the tree so that further compression is needed:
*
* 1) A node with a single child was a key and now no longer is a key.
* 2) A node with two children now has just one child.
*
* We try to navigate upward till there are other nodes that can be
* compressed, when we reach the upper node which is not a key and has
* a single child, we scan the chain of children to collect the
* compressible part of the tree, and replace the current node with the
* new one, fixing the child pointer to reference the first non
* compressible node.
*
* Example of case "1". A tree stores the keys "FOO" = 1 and
* "FOOBAR" = 2:
*
*
* "FOO" -> "BAR" -> [] (2)
* (1)
*
* After the removal of "FOO" the tree can be compressed as:
*
* "FOOBAR" -> [] (2)
*
*
* Example of case "2". A tree stores the keys "FOOBAR" = 1 and
* "FOOTER" = 2:
*
* |B| -> "AR" -> [] (1)
* "FOO" -> |-|
* |T| -> "ER" -> [] (2)
*
* After the removal of "FOOTER" the resulting tree is:
*
* "FOO" -> |B| -> "AR" -> [] (1)
*
* That can be compressed into:
*
* "FOOBAR" -> [] (1)
*/
if (trycompress) {
debugf("After removing %.*s:\n", (int)len, s);
debugnode("Compression may be needed",h);
debugf("Seek start node\n");
/* Try to reach the upper node that is compressible.
* At the end of the loop 'h' will point to the first node we
* can try to compress and 'parent' to its parent. */
raxNode *parent;
while(1) {
parent = raxStackPop(&ts);
if (!parent || parent->iskey ||
(!parent->iscompr && parent->size != 1)) break;
h = parent;
debugnode("Going up to",h);
}
raxNode *start = h; /* Compression starting node. */
/* Scan chain of nodes we can compress. */
size_t comprsize = h->size;
int nodes = 1;
while(h->size != 0) {
raxNode **cp = raxNodeLastChildPtr(h);
memcpy(&h,cp,sizeof(h));
if (h->iskey || (!h->iscompr && h->size != 1)) break;
/* Stop here if going to the next node would result into
* a compressed node larger than h->size can hold. */
if (comprsize + h->size > RAX_NODE_MAX_SIZE) break;
nodes++;
comprsize += h->size;
}
if (nodes > 1) {
/* If we can compress, create the new node and populate it. */
size_t nodesize =
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. */
if (new == NULL) {
raxStackFree(&ts);
return 1;
}
new->iskey = 0;
new->isnull = 0;
new->iscompr = 1;
new->size = comprsize;
rax->numnodes++;
/* Scan again, this time to populate the new node content and
* to fix the new node child pointer. At the same time we free
* all the nodes that we'll no longer use. */
comprsize = 0;
h = start;
while(h->size != 0) {
memcpy(new->data+comprsize,h->data,h->size);
comprsize += h->size;
raxNode **cp = raxNodeLastChildPtr(h);
raxNode *tofree = h;
memcpy(&h,cp,sizeof(h));
rax_free(tofree); rax->numnodes--;
if (h->iskey || (!h->iscompr && h->size != 1)) break;
}
debugnode("New node",new);
/* Now 'h' points to the first node that we still need to use,
* so our new node child pointer will point to it. */
raxNode **cp = raxNodeLastChildPtr(new);
memcpy(cp,&h,sizeof(h));
/* Fix parent link. */
if (parent) {
raxNode **parentlink = raxFindParentLink(parent,start);
memcpy(parentlink,&new,sizeof(new));
} else {
rax->head = new;
}
debugf("Compressed %d nodes, %d total bytes\n",
nodes, (int)comprsize);
}
}
raxStackFree(&ts);
return 1;
}
/* This is the core of raxFree(): performs a depth-first scan of the
* tree and releases all the nodes found. */
void raxRecursiveFree(rax *rax, raxNode *n, void (*free_callback)(void*)) {
debugnode("free traversing",n);
int numchildren = n->iscompr ? 1 : n->size;
raxNode **cp = raxNodeLastChildPtr(n);
while(numchildren--) {
raxNode *child;
memcpy(&child,cp,sizeof(child));
raxRecursiveFree(rax,child,free_callback);
cp--;
}
debugnode("free depth-first",n);
if (free_callback && n->iskey && !n->isnull)
free_callback(raxGetData(n));
rax_free(n);
rax->numnodes--;
}
/* Free a whole radix tree, calling the specified callback in order to
* free the auxiliary data. */
void raxFreeWithCallback(rax *rax, void (*free_callback)(void*)) {
raxRecursiveFree(rax,rax->head,free_callback);
assert(rax->numnodes == 0);
rax_free(rax);
}
/* Free a whole radix tree. */
void raxFree(rax *rax) {
raxFreeWithCallback(rax,NULL);
}
/* ------------------------------- Iterator --------------------------------- */
/* Initialize a Rax iterator. This call should be performed a single time
* to initialize the iterator, and must be followed by a raxSeek() call,
* otherwise the raxPrev()/raxNext() functions will just return EOF. */
void raxStart(raxIterator *it, rax *rt) {
it->flags = RAX_ITER_EOF; /* No crash if the iterator is not seeked. */
it->rt = rt;
it->key_len = 0;
it->key = it->key_static_string;
it->key_max = RAX_ITER_STATIC_LEN;
it->data = NULL;
it->node_cb = NULL;
raxStackInit(&it->stack);
}
/* Append characters at the current key string of the iterator 'it'. This
* is a low level function used to implement the iterator, not callable by
* the user. Returns 0 on out of memory, otherwise 1 is returned. */
int raxIteratorAddChars(raxIterator *it, unsigned char *s, size_t len) {
if (len == 0) return 1;
if (it->key_max < it->key_len+len) {
unsigned char *old = (it->key == it->key_static_string) ? NULL :
it->key;
size_t new_max = (it->key_len+len)*2;
it->key = rax_realloc(old,new_max);
if (it->key == NULL) {
it->key = (!old) ? it->key_static_string : old;
errno = ENOMEM;
return 0;
}
if (old == NULL) memcpy(it->key,it->key_static_string,it->key_len);
it->key_max = new_max;
}
/* Use memmove since there could be an overlap between 's' and
* it->key when we use the current key in order to re-seek. */
memmove(it->key+it->key_len,s,len);
it->key_len += len;
return 1;
}
/* Remove the specified number of chars from the right of the current
* iterator key. */
void raxIteratorDelChars(raxIterator *it, size_t count) {
it->key_len -= count;
}
/* Do an iteration step towards the next element. At the end of the step the
* iterator key will represent the (new) current key. If it is not possible
* to step in the specified direction since there are no longer elements, the
* iterator is flagged with RAX_ITER_EOF.
*
* If 'noup' is true the function starts directly scanning for the next
* lexicographically smaller children, and the current node is already assumed
* to be the parent of the last key node, so the first operation to go back to
* the parent will be skipped. This option is used by raxSeek() when
* implementing seeking a non existing element with the ">" or "<" options:
* the starting node is not a key in that particular case, so we start the scan
* from a node that does not represent the key set.
*
* The function returns 1 on success or 0 on out of memory. */
int raxIteratorNextStep(raxIterator *it, int noup) {
if (it->flags & RAX_ITER_EOF) {
return 1;
} else if (it->flags & RAX_ITER_JUST_SEEKED) {
it->flags &= ~RAX_ITER_JUST_SEEKED;
return 1;
}
/* Save key len, stack items and the node where we are currently
* so that on iterator EOF we can restore the current key and state. */
size_t orig_key_len = it->key_len;
size_t orig_stack_items = it->stack.items;
raxNode *orig_node = it->node;
while(1) {
int children = it->node->iscompr ? 1 : it->node->size;
if (!noup && children) {
debugf("GO DEEPER\n");
/* Seek the lexicographically smaller key in this subtree, which
* is the first one found always going towards the first child
* of every successive node. */
if (!raxStackPush(&it->stack,it->node)) return 0;
raxNode **cp = raxNodeFirstChildPtr(it->node);
if (!raxIteratorAddChars(it,it->node->data,
it->node->iscompr ? it->node->size : 1)) return 0;
memcpy(&it->node,cp,sizeof(it->node));
/* Call the node callback if any, and replace the node pointer
* if the callback returns true. */
if (it->node_cb && it->node_cb(&it->node))
memcpy(cp,&it->node,sizeof(it->node));
/* For "next" step, stop every time we find a key along the
* way, since the key is lexicographically smaller compared to
* what follows in the sub-children. */
if (it->node->iskey) {
it->data = raxGetData(it->node);
return 1;
}
} else {
/* If we finished exploring the previous sub-tree, switch to the
* new one: go upper until a node is found where there are
* children representing keys lexicographically greater than the
* current key. */
while(1) {
int old_noup = noup;
/* Already on head? Can't go up, iteration finished. */
if (!noup && it->node == it->rt->head) {
it->flags |= RAX_ITER_EOF;
it->stack.items = orig_stack_items;
it->key_len = orig_key_len;
it->node = orig_node;
return 1;
}
/* If there are no children at the current node, try parent's
* next child. */
unsigned char prevchild = it->key[it->key_len-1];
if (!noup) {
it->node = raxStackPop(&it->stack);
} else {
noup = 0;
}
/* Adjust the current key to represent the node we are
* at. */
int todel = it->node->iscompr ? it->node->size : 1;
raxIteratorDelChars(it,todel);
/* Try visiting the next child if there was at least one
* additional child. */
if (!it->node->iscompr && it->node->size > (old_noup ? 0 : 1)) {
raxNode **cp = raxNodeFirstChildPtr(it->node);
int i = 0;
while (i < it->node->size) {
debugf("SCAN NEXT %c\n", it->node->data[i]);
if (it->node->data[i] > prevchild) break;
i++;
cp++;
}
if (i != it->node->size) {
debugf("SCAN found a new node\n");
raxIteratorAddChars(it,it->node->data+i,1);
if (!raxStackPush(&it->stack,it->node)) return 0;
memcpy(&it->node,cp,sizeof(it->node));
/* Call the node callback if any, and replace the node
* pointer if the callback returns true. */
if (it->node_cb && it->node_cb(&it->node))
memcpy(cp,&it->node,sizeof(it->node));
if (it->node->iskey) {
it->data = raxGetData(it->node);
return 1;
}
break;
}
}
}
}
}
}
/* Seek the greatest key in the subtree at the current node. Return 0 on
* out of memory, otherwise 1. This is a helper function for different
* iteration functions below. */
int raxSeekGreatest(raxIterator *it) {
while(it->node->size) {
if (it->node->iscompr) {
if (!raxIteratorAddChars(it,it->node->data,
it->node->size)) return 0;
} else {
if (!raxIteratorAddChars(it,it->node->data+it->node->size-1,1))
return 0;
}
raxNode **cp = raxNodeLastChildPtr(it->node);
if (!raxStackPush(&it->stack,it->node)) return 0;
memcpy(&it->node,cp,sizeof(it->node));
}
return 1;
}
/* Like raxIteratorNextStep() but implements an iteration step moving
* to the lexicographically previous element. The 'noup' option has a similar
* effect to the one of raxIteratorNextStep(). */
int raxIteratorPrevStep(raxIterator *it, int noup) {
if (it->flags & RAX_ITER_EOF) {
return 1;
} else if (it->flags & RAX_ITER_JUST_SEEKED) {
it->flags &= ~RAX_ITER_JUST_SEEKED;
return 1;
}
/* Save key len, stack items and the node where we are currently
* so that on iterator EOF we can restore the current key and state. */
size_t orig_key_len = it->key_len;
size_t orig_stack_items = it->stack.items;
raxNode *orig_node = it->node;
while(1) {
int old_noup = noup;
/* Already on head? Can't go up, iteration finished. */
if (!noup && it->node == it->rt->head) {
it->flags |= RAX_ITER_EOF;
it->stack.items = orig_stack_items;
it->key_len = orig_key_len;
it->node = orig_node;
return 1;
}
unsigned char prevchild = it->key[it->key_len-1];
if (!noup) {
it->node = raxStackPop(&it->stack);
} else {
noup = 0;
}
/* Adjust the current key to represent the node we are
* at. */
int todel = it->node->iscompr ? it->node->size : 1;
raxIteratorDelChars(it,todel);
/* Try visiting the prev child if there is at least one
* child. */
if (!it->node->iscompr && it->node->size > (old_noup ? 0 : 1)) {
raxNode **cp = raxNodeLastChildPtr(it->node);
int i = it->node->size-1;
while (i >= 0) {
debugf("SCAN PREV %c\n", it->node->data[i]);
if (it->node->data[i] < prevchild) break;
i--;
cp--;
}
/* If we found a new subtree to explore in this node,
* go deeper following all the last children in order to
* find the key lexicographically greater. */
if (i != -1) {
debugf("SCAN found a new node\n");
/* Enter the node we just found. */
if (!raxIteratorAddChars(it,it->node->data+i,1)) return 0;
if (!raxStackPush(&it->stack,it->node)) return 0;
memcpy(&it->node,cp,sizeof(it->node));
/* Seek sub-tree max. */
if (!raxSeekGreatest(it)) return 0;
}
}
/* Return the key: this could be the key we found scanning a new
* subtree, or if we did not find a new subtree to explore here,
* before giving up with this node, check if it's a key itself. */
if (it->node->iskey) {
it->data = raxGetData(it->node);
return 1;
}
}
}
/* Seek an iterator at the specified element.
* Return 0 if the seek failed for syntax error or out of memory. Otherwise
* 1 is returned. When 0 is returned for out of memory, errno is set to
* the ENOMEM value. */
int raxSeek(raxIterator *it, const char *op, unsigned char *ele, size_t len) {
int eq = 0, lt = 0, gt = 0, first = 0, last = 0;
it->stack.items = 0; /* Just resetting. Initialized by raxStart(). */
it->flags |= RAX_ITER_JUST_SEEKED;
it->flags &= ~RAX_ITER_EOF;
it->key_len = 0;
it->node = NULL;
/* Set flags according to the operator used to perform the seek. */
if (op[0] == '>') {
gt = 1;
if (op[1] == '=') eq = 1;
} else if (op[0] == '<') {
lt = 1;
if (op[1] == '=') eq = 1;
} else if (op[0] == '=') {
eq = 1;
} else if (op[0] == '^') {
first = 1;
} else if (op[0] == '$') {
last = 1;
} else {
errno = 0;
return 0; /* Error. */
}
/* If there are no elements, set the EOF condition immediately and
* return. */
if (it->rt->numele == 0) {
it->flags |= RAX_ITER_EOF;
return 1;
}
if (first) {
/* Seeking the first key greater or equal to the empty string
* is equivalent to seeking the smaller key available. */
return raxSeek(it,">=",NULL,0);
}
if (last) {
/* Find the greatest key taking always the last child till a
* final node is found. */
it->node = it->rt->head;
if (!raxSeekGreatest(it)) return 0;
assert(it->node->iskey);
it->data = raxGetData(it->node);
return 1;
}
/* We need to seek the specified key. What we do here is to actually
* perform a lookup, and later invoke the prev/next key code that
* we already use for iteration. */
int splitpos = 0;
size_t i = raxLowWalk(it->rt,ele,len,&it->node,NULL,&splitpos,&it->stack);
/* Return OOM on incomplete stack info. */
if (it->stack.oom) return 0;
if (eq && i == len && (!it->node->iscompr || splitpos == 0) &&
it->node->iskey)
{
/* We found our node, since the key matches and we have an
* "equal" condition. */
if (!raxIteratorAddChars(it,ele,len)) return 0; /* OOM. */
it->data = raxGetData(it->node);
} else if (lt || gt) {
/* Exact key not found or eq flag not set. We have to set as current
* key the one represented by the node we stopped at, and perform
* a next/prev operation to seek. */
raxIteratorAddChars(it, ele, i-splitpos);
/* We need to set the iterator in the correct state to call next/prev
* step in order to seek the desired element. */
debugf("After initial seek: i=%d len=%d key=%.*s\n",
(int)i, (int)len, (int)it->key_len, it->key);
if (i != len && !it->node->iscompr) {
/* If we stopped in the middle of a normal node because of a
* mismatch, add the mismatching character to the current key
* and call the iterator with the 'noup' flag so that it will try
* to seek the next/prev child in the current node directly based
* on the mismatching character. */
if (!raxIteratorAddChars(it,ele+i,1)) return 0;
debugf("Seek normal node on mismatch: %.*s\n",
(int)it->key_len, (char*)it->key);
it->flags &= ~RAX_ITER_JUST_SEEKED;
if (lt && !raxIteratorPrevStep(it,1)) return 0;
if (gt && !raxIteratorNextStep(it,1)) return 0;
it->flags |= RAX_ITER_JUST_SEEKED; /* Ignore next call. */
} else if (i != len && it->node->iscompr) {
debugf("Compressed mismatch: %.*s\n",
(int)it->key_len, (char*)it->key);
/* In case of a mismatch within a compressed node. */
int nodechar = it->node->data[splitpos];
int keychar = ele[i];
it->flags &= ~RAX_ITER_JUST_SEEKED;
if (gt) {
/* If the key the compressed node represents is greater
* than our seek element, continue forward, otherwise set the
* state in order to go back to the next sub-tree. */
if (nodechar > keychar) {
if (!raxIteratorNextStep(it,0)) return 0;
} else {
if (!raxIteratorAddChars(it,it->node->data,it->node->size))
return 0;
if (!raxIteratorNextStep(it,1)) return 0;
}
}
if (lt) {
/* If the key the compressed node represents is smaller
* than our seek element, seek the greater key in this
* subtree, otherwise set the state in order to go back to
* the previous sub-tree. */
if (nodechar < keychar) {
if (!raxSeekGreatest(it)) return 0;
it->data = raxGetData(it->node);
} else {
if (!raxIteratorAddChars(it,it->node->data,it->node->size))
return 0;
if (!raxIteratorPrevStep(it,1)) return 0;
}
}
it->flags |= RAX_ITER_JUST_SEEKED; /* Ignore next call. */
} else {
debugf("No mismatch: %.*s\n",
(int)it->key_len, (char*)it->key);
/* If there was no mismatch we are into a node representing the
* key, (but which is not a key or the seek operator does not
* include 'eq'), or we stopped in the middle of a compressed node
* after processing all the key. Continue iterating as this was
* a legitimate key we stopped at. */
it->flags &= ~RAX_ITER_JUST_SEEKED;
if (it->node->iscompr && it->node->iskey && splitpos && lt) {
/* If we stopped in the middle of a compressed node with
* perfect match, and the condition is to seek a key "<" than
* the specified one, then if this node is a key it already
* represents our match. For instance we may have nodes:
*
* "f" -> "oobar" = 1 -> "" = 2
*
* Representing keys "f" = 1, "foobar" = 2. A seek for
* the key < "foo" will stop in the middle of the "oobar"
* node, but will be our match, representing the key "f".
*
* So in that case, we don't seek backward. */
it->data = raxGetData(it->node);
} else {
if (gt && !raxIteratorNextStep(it,0)) return 0;
if (lt && !raxIteratorPrevStep(it,0)) return 0;
}
it->flags |= RAX_ITER_JUST_SEEKED; /* Ignore next call. */
}
} else {
/* If we are here just eq was set but no match was found. */
it->flags |= RAX_ITER_EOF;
return 1;
}
return 1;
}
/* Go to the next element in the scope of the iterator 'it'.
* If EOF (or out of memory) is reached, 0 is returned, otherwise 1 is
* returned. In case 0 is returned because of OOM, errno is set to ENOMEM. */
int raxNext(raxIterator *it) {
if (!raxIteratorNextStep(it,0)) {
errno = ENOMEM;
return 0;
}
if (it->flags & RAX_ITER_EOF) {
errno = 0;
return 0;
}
return 1;
}
/* Go to the previous element in the scope of the iterator 'it'.
* If EOF (or out of memory) is reached, 0 is returned, otherwise 1 is
* returned. In case 0 is returned because of OOM, errno is set to ENOMEM. */
int raxPrev(raxIterator *it) {
if (!raxIteratorPrevStep(it,0)) {
errno = ENOMEM;
return 0;
}
if (it->flags & RAX_ITER_EOF) {
errno = 0;
return 0;
}
return 1;
}
/* Perform a random walk starting in the current position of the iterator.
* Return 0 if the tree is empty or on out of memory. Otherwise 1 is returned
* and the iterator is set to the node reached after doing a random walk
* of 'steps' steps. If the 'steps' argument is 0, the random walk is performed
* using a random number of steps between 1 and two times the logarithm of
* the number of elements.
*
* NOTE: if you use this function to generate random elements from the radix
* tree, expect a disappointing distribution. A random walk produces good
* random elements if the tree is not sparse, however in the case of a radix
* tree certain keys will be reported much more often than others. At least
* this function should be able to explore every possible element eventually. */
int raxRandomWalk(raxIterator *it, size_t steps) {
if (it->rt->numele == 0) {
it->flags |= RAX_ITER_EOF;
return 0;
}
if (steps == 0) {
size_t fle = 1+floor(log(it->rt->numele));
fle *= 2;
steps = 1 + rand() % fle;
}
raxNode *n = it->node;
while(steps > 0 || !n->iskey) {
int numchildren = n->iscompr ? 1 : n->size;
int r = rand() % (numchildren+(n != it->rt->head));
if (r == numchildren) {
/* Go up to parent. */
n = raxStackPop(&it->stack);
int todel = n->iscompr ? n->size : 1;
raxIteratorDelChars(it,todel);
} else {
/* Select a random child. */
if (n->iscompr) {
if (!raxIteratorAddChars(it,n->data,n->size)) return 0;
} else {
if (!raxIteratorAddChars(it,n->data+r,1)) return 0;
}
raxNode **cp = raxNodeFirstChildPtr(n)+r;
if (!raxStackPush(&it->stack,n)) return 0;
memcpy(&n,cp,sizeof(n));
}
if (n->iskey) steps--;
}
it->node = n;
it->data = raxGetData(it->node);
return 1;
}
/* Compare the key currently pointed by the iterator to the specified
* key according to the specified operator. Returns 1 if the comparison is
* true, otherwise 0 is returned. */
int raxCompare(raxIterator *iter, const char *op, unsigned char *key, size_t key_len) {
int eq = 0, lt = 0, gt = 0;
if (op[0] == '=' || op[1] == '=') eq = 1;
if (op[0] == '>') gt = 1;
else if (op[0] == '<') lt = 1;
else if (op[1] != '=') return 0; /* Syntax error. */
size_t minlen = key_len < iter->key_len ? key_len : iter->key_len;
int cmp = memcmp(iter->key,key,minlen);
/* Handle == */
if (lt == 0 && gt == 0) return cmp == 0 && key_len == iter->key_len;
/* Handle >, >=, <, <= */
if (cmp == 0) {
/* Same prefix: longer wins. */
if (eq && key_len == iter->key_len) return 1;
else if (lt) return iter->key_len < key_len;
else if (gt) return iter->key_len > key_len;
else return 0; /* Avoid warning, just 'eq' is handled before. */
} else if (cmp > 0) {
return gt ? 1 : 0;
} else /* (cmp < 0) */ {
return lt ? 1 : 0;
}
}
/* Free the iterator. */
void raxStop(raxIterator *it) {
if (it->key != it->key_static_string) rax_free(it->key);
raxStackFree(&it->stack);
}
/* Return if the iterator is in an EOF state. This happens when raxSeek()
* failed to seek an appropriate element, so that raxNext() or raxPrev()
* will return zero, or when an EOF condition was reached while iterating
* with raxNext() and raxPrev(). */
int raxEOF(raxIterator *it) {
return it->flags & RAX_ITER_EOF;
}
/* Return the number of elements inside the radix tree. */
uint64_t raxSize(rax *rax) {
return rax->numele;
}
/* ----------------------------- Introspection ------------------------------ */
/* This function is mostly used for debugging and learning purposes.
* It shows an ASCII representation of a tree on standard output, outline
* all the nodes and the contained keys.
*
* The representation is as follow:
*
* "foobar" (compressed node)
* [abc] (normal node with three children)
* [abc]=0x12345678 (node is a key, pointing to value 0x12345678)
* [] (a normal empty node)
*
* Children are represented in new indented lines, each children prefixed by
* the "`-(x)" string, where "x" is the edge byte.
*
* [abc]
* `-(a) "ladin"
* `-(b) [kj]
* `-(c) []
*
* However when a node has a single child the following representation
* is used instead:
*
* [abc] -> "ladin" -> []
*/
/* The actual implementation of raxShow(). */
void raxRecursiveShow(int level, int lpad, raxNode *n) {
char s = n->iscompr ? '"' : '[';
char e = n->iscompr ? '"' : ']';
int numchars = printf("%c%.*s%c", s, n->size, n->data, e);
if (n->iskey) {
numchars += printf("=%p",raxGetData(n));
}
int numchildren = n->iscompr ? 1 : n->size;
/* Note that 7 and 4 magic constants are the string length
* of " `-(x) " and " -> " respectively. */
if (level) {
lpad += (numchildren > 1) ? 7 : 4;
if (numchildren == 1) lpad += numchars;
}
raxNode **cp = raxNodeFirstChildPtr(n);
for (int i = 0; i < numchildren; i++) {
char *branch = " `-(%c) ";
if (numchildren > 1) {
printf("\n");
for (int j = 0; j < lpad; j++) putchar(' ');
printf(branch,n->data[i]);
} else {
printf(" -> ");
}
raxNode *child;
memcpy(&child,cp,sizeof(child));
raxRecursiveShow(level+1,lpad,child);
cp++;
}
}
/* Show a tree, as outlined in the comment above. */
void raxShow(rax *rax) {
raxRecursiveShow(0,0,rax->head);
putchar('\n');
}
/* 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:%u size:%u children:",
msg, (void*)n, (int)n->size, (char*)n->data, n->iskey, n->size);
int numcld = n->iscompr ? 1 : n->size;
raxNode **cldptr = raxNodeLastChildPtr(n) - (numcld-1);
while(numcld--) {
raxNode *child;
memcpy(&child,cldptr,sizeof(child));
cldptr++;
printf("%p ", (void*)child);
}
printf("\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;
}
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