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/*
* Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/crypto.h>
#include <openssl/bn.h>
#include "internal/sparse_array.h"
/*
* How many bits are used to index each level in the tree structre?
* This setting determines the number of pointers stored in each node of the
* tree used to represent the sparse array. Having more pointers reduces the
* depth of the tree but potentially wastes more memory. That is, this is a
* direct space versus time tradeoff.
*
* The large memory model uses twelve bits which means that the are 4096
* pointers in each tree node. This is more than sufficient to hold the
* largest defined NID (as of Feb 2019). This means that using a NID to
* index a sparse array becomes a constant time single array look up.
*
* The small memory model uses four bits which means the tree nodes contain
* sixteen pointers. This reduces the amount of unused space significantly
* at a cost in time.
*
* The library builder is also permitted to define other sizes in the closed
* interval [2, sizeof(ossl_uintmax_t) * 8].
*/
#ifndef OPENSSL_SA_BLOCK_BITS
# ifdef OPENSSL_SMALL_FOOTPRINT
# define OPENSSL_SA_BLOCK_BITS 4
# else
# define OPENSSL_SA_BLOCK_BITS 12
# endif
#elif OPENSSL_SA_BLOCK_BITS < 2 || OPENSSL_SA_BLOCK_BITS > (BN_BITS2 - 1)
# error OPENSSL_SA_BLOCK_BITS is out of range
#endif
/*
* From the number of bits, work out:
* the number of pointers in a tree node;
* a bit mask to quickly extract an index and
* the maximum depth of the tree structure.
*/
#define SA_BLOCK_MAX (1 << OPENSSL_SA_BLOCK_BITS)
#define SA_BLOCK_MASK (SA_BLOCK_MAX - 1)
#define SA_BLOCK_MAX_LEVELS (((int)sizeof(ossl_uintmax_t) * 8 \
+ OPENSSL_SA_BLOCK_BITS - 1) \
/ OPENSSL_SA_BLOCK_BITS)
struct sparse_array_st {
int levels;
ossl_uintmax_t top;
size_t nelem;
void **nodes;
};
OPENSSL_SA *OPENSSL_SA_new(void)
{
OPENSSL_SA *res = OPENSSL_zalloc(sizeof(*res));
return res;
}
static void sa_doall(const OPENSSL_SA *sa, void (*node)(void **),
void (*leaf)(ossl_uintmax_t, void *, void *), void *arg)
{
int i[SA_BLOCK_MAX_LEVELS];
void *nodes[SA_BLOCK_MAX_LEVELS];
ossl_uintmax_t idx = 0;
int l = 0;
i[0] = 0;
nodes[0] = sa->nodes;
while (l >= 0) {
const int n = i[l];
void ** const p = nodes[l];
if (n >= SA_BLOCK_MAX) {
if (p != NULL && node != NULL)
(*node)(p);
l--;
idx >>= OPENSSL_SA_BLOCK_BITS;
} else {
i[l] = n + 1;
if (p != NULL && p[n] != NULL) {
idx = (idx & ~SA_BLOCK_MASK) | n;
if (l < sa->levels - 1) {
i[++l] = 0;
nodes[l] = p[n];
idx <<= OPENSSL_SA_BLOCK_BITS;
} else if (leaf != NULL) {
(*leaf)(idx, p[n], arg);
}
}
}
}
}
static void sa_free_node(void **p)
{
OPENSSL_free(p);
}
static void sa_free_leaf(ossl_uintmax_t n, void *p, void *arg)
{
OPENSSL_free(p);
}
void OPENSSL_SA_free(OPENSSL_SA *sa)
{
sa_doall(sa, &sa_free_node, NULL, NULL);
OPENSSL_free(sa);
}
void OPENSSL_SA_free_leaves(OPENSSL_SA *sa)
{
sa_doall(sa, &sa_free_node, &sa_free_leaf, NULL);
OPENSSL_free(sa);
}
/* Wrap this in a structure to avoid compiler warnings */
struct trampoline_st {
void (*func)(ossl_uintmax_t, void *);
};
static void trampoline(ossl_uintmax_t n, void *l, void *arg)
{
((const struct trampoline_st *)arg)->func(n, l);
}
void OPENSSL_SA_doall(const OPENSSL_SA *sa, void (*leaf)(ossl_uintmax_t,
void *))
{
struct trampoline_st tramp;
tramp.func = leaf;
if (sa != NULL)
sa_doall(sa, NULL, &trampoline, &tramp);
}
void OPENSSL_SA_doall_arg(const OPENSSL_SA *sa,
void (*leaf)(ossl_uintmax_t, void *, void *),
void *arg)
{
if (sa != NULL)
sa_doall(sa, NULL, leaf, arg);
}
size_t OPENSSL_SA_num(const OPENSSL_SA *sa)
{
return sa == NULL ? 0 : sa->nelem;
}
void *OPENSSL_SA_get(const OPENSSL_SA *sa, ossl_uintmax_t n)
{
int level;
void **p, *r = NULL;
if (sa == NULL)
return NULL;
if (n <= sa->top) {
p = sa->nodes;
for (level = sa->levels - 1; p != NULL && level > 0; level--)
p = (void **)p[(n >> (OPENSSL_SA_BLOCK_BITS * level))
& SA_BLOCK_MASK];
r = p == NULL ? NULL : p[n & SA_BLOCK_MASK];
}
return r;
}
static ossl_inline void **alloc_node(void)
{
return OPENSSL_zalloc(SA_BLOCK_MAX * sizeof(void *));
}
int OPENSSL_SA_set(OPENSSL_SA *sa, ossl_uintmax_t posn, void *val)
{
int i, level = 1;
ossl_uintmax_t n = posn;
void **p;
if (sa == NULL)
return 0;
for (level = 1; level < SA_BLOCK_MAX_LEVELS; level++)
if ((n >>= OPENSSL_SA_BLOCK_BITS) == 0)
break;
for (;sa->levels < level; sa->levels++) {
p = alloc_node();
if (p == NULL)
return 0;
p[0] = sa->nodes;
sa->nodes = p;
}
if (sa->top < posn)
sa->top = posn;
p = sa->nodes;
for (level = sa->levels - 1; level > 0; level--) {
i = (posn >> (OPENSSL_SA_BLOCK_BITS * level)) & SA_BLOCK_MASK;
if (p[i] == NULL && (p[i] = alloc_node()) == NULL)
return 0;
p = p[i];
}
p += posn & SA_BLOCK_MASK;
if (val == NULL && *p != NULL)
sa->nelem--;
else if (val != NULL && *p == NULL)
sa->nelem++;
*p = val;
return 1;
}
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