漫话Redis源码之三十五

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);
}