漫话Redis源码之三十五
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2024-03-18 08:15:10
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早年我写代码时候，也喜欢用#if 0来调试，现在不用了。如下代码主要是跟优化level相关：
#ifndef REDIS_STATIC
#define REDIS_STATIC static
#endif
/* Optimization levels for size-based filling.
* Note that the largest possible limit is 16k, so even if each record takes
* just one byte, it still won't overflow the 16 bit count field. */
static const size_t optimization_level[] = {4096, 8192, 16384, 32768, 65536};
/* Maximum size in bytes of any multi-element ziplist.
* Larger values will live in their own isolated ziplists.
* This is used only if we're limited by record count. when we're limited by
* size, the maximum limit is bigger, but still safe.
* 8k is a recommended / default size limit */
#define SIZE_SAFETY_LIMIT 8192
/* Minimum ziplist size in bytes for attempting compression. */
#define MIN_COMPRESS_BYTES 48
/* Minimum size reduction in bytes to store compressed quicklistNode data.
* This also prevents us from storing compression if the compression
* resulted in a larger size than the original data. */
#define MIN_COMPRESS_IMPROVE 8
/* If not verbose testing, remove all debug printing. */
#ifndef REDIS_TEST_VERBOSE
#define D(...)
#else
#define D(...) \
do { \
printf("%s:%s:%d:\t", __FILE__, __func__, __LINE__); \
printf(__VA_ARGS__); \
printf("\n"); \
} while (0)
#endif
/* Bookmarks forward declarations */
#define QL_MAX_BM ((1 << QL_BM_BITS)-1)
quicklistBookmark *_quicklistBookmarkFindByName(quicklist *ql, const char *name);
quicklistBookmark *_quicklistBookmarkFindByNode(quicklist *ql, quicklistNode *node);
void _quicklistBookmarkDelete(quicklist *ql, quicklistBookmark *bm);
/* Simple way to give quicklistEntry structs default values with one call. */
#define initEntry(e) \
do { \
(e)->zi = (e)->value = NULL; \
(e)->longval = -123456789; \
(e)->quicklist = NULL; \
(e)->node = NULL; \
(e)->offset = 123456789; \
(e)->sz = 0; \
} while (0)
/* Create a new quicklist.
* Free with quicklistRelease(). */
quicklist *quicklistCreate(void) {
struct quicklist *quicklist;
quicklist = zmalloc(sizeof(*quicklist));
quicklist->head = quicklist->tail = NULL;
quicklist->len = 0;
quicklist->count = 0;
quicklist->compress = 0;
quicklist->fill = -2;
quicklist->bookmark_count = 0;
return quicklist;
}
#define COMPRESS_MAX ((1 << QL_COMP_BITS)-1)
void quicklistSetCompressDepth(quicklist *quicklist, int compress) {
if (compress > COMPRESS_MAX) {
compress = COMPRESS_MAX;
} else if (compress < 0) {
compress = 0;
}
quicklist->compress = compress;
}
#define FILL_MAX ((1 << (QL_FILL_BITS-1))-1)
void quicklistSetFill(quicklist *quicklist, int fill) {
if (fill > FILL_MAX) {
fill = FILL_MAX;
} else if (fill < -5) {
fill = -5;
}
quicklist->fill = fill;
}
void quicklistSetOptions(quicklist *quicklist, int fill, int depth) {
quicklistSetFill(quicklist, fill);
quicklistSetCompressDepth(quicklist, depth);
}
/* Create a new quicklist with some default parameters. */
quicklist *quicklistNew(int fill, int compress) {
quicklist *quicklist = quicklistCreate();
quicklistSetOptions(quicklist, fill, compress);
return quicklist;
}
REDIS_STATIC quicklistNode *quicklistCreateNode(void) {
quicklistNode *node;
node = zmalloc(sizeof(*node));
node->zl = NULL;
node->count = 0;
node->sz = 0;
node->next = node->prev = NULL;
node->encoding = QUICKLIST_NODE_ENCODING_RAW;
node->container = QUICKLIST_NODE_CONTAINER_ZIPLIST;
node->recompress = 0;
return node;
}
/* Return cached quicklist count */
unsigned long quicklistCount(const quicklist *ql) { return ql->count; }
/* Free entire quicklist. */
void quicklistRelease(quicklist *quicklist) {
unsigned long len;
quicklistNode *current, *next;
current = quicklist->head;
len = quicklist->len;
while (len--) {
next = current->next;
zfree(current->zl);
quicklist->count -= current->count;
zfree(current);
quicklist->len--;
current = next;
}
quicklistBookmarksClear(quicklist);
zfree(quicklist);
}
/* Compress the ziplist in 'node' and update encoding details.
* Returns 1 if ziplist compressed successfully.
* Returns 0 if compression failed or if ziplist too small to compress. */
REDIS_STATIC int __quicklistCompressNode(quicklistNode *node) {
#ifdef REDIS_TEST
node->attempted_compress = 1;
#endif
/* Don't bother compressing small values */
if (node->sz < MIN_COMPRESS_BYTES)
return 0;
quicklistLZF *lzf = zmalloc(sizeof(*lzf) + node->sz);
/* Cancel if compression fails or doesn't compress small enough */
if (((lzf->sz = lzf_compress(node->zl, node->sz, lzf->compressed,
node->sz)) == 0) ||
lzf->sz + MIN_COMPRESS_IMPROVE >= node->sz) {
/* lzf_compress aborts/rejects compression if value not compressable. */
zfree(lzf);
return 0;
}
lzf = zrealloc(lzf, sizeof(*lzf) + lzf->sz);
zfree(node->zl);
node->zl = (unsigned char *)lzf;
node->encoding = QUICKLIST_NODE_ENCODING_LZF;
node->recompress = 0;
return 1;
}
/* Compress only uncompressed nodes. */
#define quicklistCompressNode(_node) \
do { \
if ((_node) && (_node)->encoding == QUICKLIST_NODE_ENCODING_RAW) { \
__quicklistCompressNode((_node)); \
} \
} while (0)
/* Uncompress the ziplist in 'node' and update encoding details.
* Returns 1 on successful decode, 0 on failure to decode. */
REDIS_STATIC int __quicklistDecompressNode(quicklistNode *node) {
#ifdef REDIS_TEST
node->attempted_compress = 0;
#endif
void *decompressed = zmalloc(node->sz);
quicklistLZF *lzf = (quicklistLZF *)node->zl;
if (lzf_decompress(lzf->compressed, lzf->sz, decompressed, node->sz) == 0) {
/* Someone requested decompress, but we can't decompress. Not good. */
zfree(decompressed);
return 0;
}
zfree(lzf);
node->zl = decompressed;
node->encoding = QUICKLIST_NODE_ENCODING_RAW;
return 1;
}
/* Decompress only compressed nodes. */
#define quicklistDecompressNode(_node) \
do { \
if ((_node) && (_node)->encoding == QUICKLIST_NODE_ENCODING_LZF) { \
__quicklistDecompressNode((_node)); \
} \
} while (0)
/* Force node to not be immediately re-compresable */
#define quicklistDecompressNodeForUse(_node) \
do { \
if ((_node) && (_node)->encoding == QUICKLIST_NODE_ENCODING_LZF) { \
__quicklistDecompressNode((_node)); \
(_node)->recompress = 1; \
} \
} while (0)
/* Extract the raw LZF data from this quicklistNode.
* Pointer to LZF data is assigned to '*data'.
* Return value is the length of compressed LZF data. */
size_t quicklistGetLzf(const quicklistNode *node, void **data) {
quicklistLZF *lzf = (quicklistLZF *)node->zl;
*data = lzf->compressed;
return lzf->sz;
}
#define quicklistAllowsCompression(_ql) ((_ql)->compress != 0)
/* Force 'quicklist' to meet compression guidelines set by compress depth.
* The only way to guarantee interior nodes get compressed is to iterate
* to our "interior" compress depth then compress the next node we find.
* If compress depth is larger than the entire list, we return immediately. */
REDIS_STATIC void __quicklistCompress(const quicklist *quicklist,
quicklistNode *node) {
/* If length is less than our compress depth (from both sides),
* we can't compress anything. */
if (!quicklistAllowsCompression(quicklist) ||
quicklist->len < (unsigned int)(quicklist->compress * 2))
return;
#if 0
/* Optimized cases for small depth counts */
if (quicklist->compress == 1) {
quicklistNode *h = quicklist->head, *t = quicklist->tail;
quicklistDecompressNode(h);
quicklistDecompressNode(t);
if (h != node && t != node)
quicklistCompressNode(node);
return;
} else if (quicklist->compress == 2) {
quicklistNode *h = quicklist->head, *hn = h->next, *hnn = hn->next;
quicklistNode *t = quicklist->tail, *tp = t->prev, *tpp = tp->prev;
quicklistDecompressNode(h);
quicklistDecompressNode(hn);
quicklistDecompressNode(t);
quicklistDecompressNode(tp);
if (h != node && hn != node && t != node && tp != node) {
quicklistCompressNode(node);
}
if (hnn != t) {
quicklistCompressNode(hnn);
}
if (tpp != h) {
quicklistCompressNode(tpp);
}
return;
}
#endif
/* Iterate until we reach compress depth for both sides of the list.a
* Note: because we do length checks at the *top* of this function,
* we can skip explicit null checks below. Everything exists. */
quicklistNode *forward = quicklist->head;
quicklistNode *reverse = quicklist->tail;
int depth = 0;
int in_depth = 0;
while (depth++ < quicklist->compress) {
quicklistDecompressNode(forward);
quicklistDecompressNode(reverse);
if (forward == node || reverse == node)
in_depth = 1;
/* We passed into compress depth of opposite side of the quicklist
* so there's no need to compress anything and we can exit. */
if (forward == reverse || forward->next == reverse)
return;
forward = forward->next;
reverse = reverse->prev;
}
if (!in_depth)
quicklistCompressNode(node);
/* At this point, forward and reverse are one node beyond depth */
quicklistCompressNode(forward);
quicklistCompressNode(reverse);
}
#define quicklistCompress(_ql, _node) \
do { \
if ((_node)->recompress) \
quicklistCompressNode((_node)); \
else \
__quicklistCompress((_ql), (_node)); \
} while (0)
/* If we previously used quicklistDecompressNodeForUse(), just recompress. */
#define quicklistRecompressOnly(_ql, _node) \
do { \
if ((_node)->recompress) \
quicklistCompressNode((_node)); \
} while (0)
/* Insert 'new_node' after 'old_node' if 'after' is 1.
* Insert 'new_node' before 'old_node' if 'after' is 0.
* Note: 'new_node' is *always* uncompressed, so if we assign it to
* head or tail, we do not need to uncompress it. */
REDIS_STATIC void __quicklistInsertNode(quicklist *quicklist,
quicklistNode *old_node,
quicklistNode *new_node, int after) {
if (after) {
new_node->prev = old_node;
if (old_node) {
new_node->next = old_node->next;
if (old_node->next)
old_node->next->prev = new_node;
old_node->next = new_node;
}
if (quicklist->tail == old_node)
quicklist->tail = new_node;
} else {
new_node->next = old_node;
if (old_node) {
new_node->prev = old_node->prev;
if (old_node->prev)
old_node->prev->next = new_node;
old_node->prev = new_node;
}
if (quicklist->head == old_node)
quicklist->head = new_node;
}
/* If this insert creates the only element so far, initialize head/tail. */
if (quicklist->len == 0) {
quicklist->head = quicklist->tail = new_node;
}
/* Update len first, so in __quicklistCompress we know exactly len */
quicklist->len++;
if (old_node)
quicklistCompress(quicklist, old_node);
}