mirror of https://github.com/bsnes-emu/bsnes.git
94 lines
3.8 KiB
Objective-C
94 lines
3.8 KiB
Objective-C
#import "HFGlyphTrie.h"
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#import <objc/objc-auto.h>
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/* If branchingDepth is 1, then this is a leaf and there's nothing to free (a parent frees its children). If branchingDepth is 2, then this is a branch whose children are leaves, so we have to free the leaves but we do not recurse. If branchingDepth is greater than 2, we do have to recurse. */
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static void freeTrie(struct HFGlyphTrieBranch_t *branch, uint8_t branchingDepth) {
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HFASSERT(branchingDepth >= 1);
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NSUInteger i;
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if (branchingDepth > 2) {
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/* Recurse */
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for (i=0; i < kHFGlyphTrieBranchCount; i++) {
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if (branch->children[i]) {
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freeTrie(branch->children[i], branchingDepth - 1);
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}
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}
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}
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if (branchingDepth > 1) {
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/* Free our children */
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for (i=0; i < kHFGlyphTrieBranchCount; i++) {
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free(branch->children[i]);
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}
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}
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}
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static void insertTrie(void *node, uint8_t branchingDepth, NSUInteger key, struct HFGlyph_t value) {
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HFASSERT(node != NULL);
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HFASSERT(branchingDepth >= 1);
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if (branchingDepth == 1) {
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/* Leaf */
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HFASSERT(key < kHFGlyphTrieBranchCount);
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((struct HFGlyphTrieLeaf_t *)node)->glyphs[key] = value;
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} else {
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/* Branch */
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struct HFGlyphTrieBranch_t *branch = node;
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NSUInteger keySlice = key & ((1 << kHFGlyphTrieBranchFactor) - 1), keyRemainder = key >> kHFGlyphTrieBranchFactor;
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__strong void *child = branch->children[keySlice];
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if (child == NULL) {
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if (branchingDepth == 2) {
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child = calloc(1, sizeof(struct HFGlyphTrieLeaf_t));
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} else {
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child = calloc(1, sizeof(struct HFGlyphTrieBranch_t));
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}
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/* We just zeroed out a block of memory and we are about to write its address somewhere where another thread could read it, so we need a memory barrier. */
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OSMemoryBarrier();
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branch->children[keySlice] = child;
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}
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insertTrie(child, branchingDepth - 1, keyRemainder, value);
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}
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}
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static struct HFGlyph_t getTrie(const void *node, uint8_t branchingDepth, NSUInteger key) {
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HFASSERT(node != NULL);
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HFASSERT(branchingDepth >= 1);
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if (branchingDepth == 1) {
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/* Leaf */
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HFASSERT(key < kHFGlyphTrieBranchCount);
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return ((const struct HFGlyphTrieLeaf_t *)node)->glyphs[key];
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} else {
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/* Branch */
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const struct HFGlyphTrieBranch_t *branch = node;
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NSUInteger keySlice = key & ((1 << kHFGlyphTrieBranchFactor) - 1), keyRemainder = key >> kHFGlyphTrieBranchFactor;
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if (branch->children[keySlice] == NULL) {
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/* Not found */
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return (struct HFGlyph_t){0, 0};
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} else {
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/* This dereference requires a data dependency barrier */
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return getTrie(branch->children[keySlice], branchingDepth - 1, keyRemainder);
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}
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}
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}
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void HFGlyphTrieInsert(struct HFGlyphTrie_t *trie, NSUInteger key, struct HFGlyph_t value) {
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insertTrie(&trie->root, trie->branchingDepth, key, value);
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}
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struct HFGlyph_t HFGlyphTrieGet(const struct HFGlyphTrie_t *trie, NSUInteger key) {
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struct HFGlyph_t result = getTrie(&trie->root, trie->branchingDepth, key);
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return result;
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}
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void HFGlyphTrieInitialize(struct HFGlyphTrie_t *trie, uint8_t keySize) {
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/* If the branch factor is 4 (bits) and the key size is 2 bytes = 16 bits, initialize branching depth to 16/4 = 4 */
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uint8_t keyBits = keySize * CHAR_BIT;
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HFASSERT(keyBits % kHFGlyphTrieBranchFactor == 0);
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trie->branchingDepth = keyBits / kHFGlyphTrieBranchFactor;
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memset(&trie->root, 0, sizeof(trie->root));
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}
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void HFGlyphTreeFree(struct HFGlyphTrie_t * trie) {
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/* Don't try to free under GC. And don't free if it's never been initialized. */
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if (trie->branchingDepth > 0) {
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freeTrie(&trie->root, trie->branchingDepth);
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}
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}
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