Redis 5.0 RC2 (4.9.102) - Released Wed Jun 13 12:49:13 CEST 2018

 Upgrade urgency CRITICAL: This release fixes important security issues.
                     HIGH: This release fixes a SCAN commands family bug.
                 MODERATE: This release fixes a PSYNC2 edge case with expires.
                 MODERATE: Sentinel related fixes.
                      LOW: All the other issues

1 files changed, 164 insertions, 0 deletions

diff --git a/rax.h b/rax.h
new file mode 100644
index 0000000..5b4d451
--- /dev/null
+++ b/rax.h
@@ -0,0 +1,164 @@
+#ifndef RAX_H
+#define RAX_H
+
+#include <stdint.h>
+
+/* Representation of a radix tree as implemented in this file, that contains
+ * the strings "foo", "foobar" and "footer" after the insertion of each
+ * word. When the node represents a key inside the radix tree, we write it
+ * between [], otherwise it is written between ().
+ *
+ * This is the vanilla representation:
+ *
+ *              (f) ""
+ *                \
+ *                (o) "f"
+ *                  \
+ *                  (o) "fo"
+ *                    \
+ *                  [t   b] "foo"
+ *                  /     \
+ *         "foot" (e)     (a) "foob"
+ *                /         \
+ *      "foote" (r)         (r) "fooba"
+ *              /             \
+ *    "footer" []             [] "foobar"
+ *
+ * However, this implementation implements a very common optimization where
+ * successive nodes having a single child are "compressed" into the node
+ * itself as a string of characters, each representing a next-level child,
+ * and only the link to the node representing the last character node is
+ * provided inside the representation. So the above representation is turend
+ * into:
+ *
+ *                  ["foo"] ""
+ *                     |
+ *                  [t   b] "foo"
+ *                  /     \
+ *        "foot" ("er")    ("ar") "foob"
+ *                 /          \
+ *       "footer" []          [] "foobar"
+ *
+ * However this optimization makes the implementation a bit more complex.
+ * For instance if a key "first" is added in the above radix tree, a
+ * "node splitting" operation is needed, since the "foo" prefix is no longer
+ * composed of nodes having a single child one after the other. This is the
+ * above tree and the resulting node splitting after this event happens:
+ *
+ *
+ *                    (f) ""
+ *                    /
+ *                 (i o) "f"
+ *                 /   \
+ *    "firs"  ("rst")  (o) "fo"
+ *              /        \
+ *    "first" []       [t   b] "foo"
+ *                     /     \
+ *           "foot" ("er")    ("ar") "foob"
+ *                    /          \
+ *          "footer" []          [] "foobar"
+ *
+ * Similarly after deletion, if a new chain of nodes having a single child
+ * is created (the chain must also not include nodes that represent keys),
+ * it must be compressed back into a single node.
+ *
+ */
+
+#define RAX_NODE_MAX_SIZE ((1<<29)-1)
+typedef struct raxNode {
+    uint32_t iskey:1;     /* Does this node contain a key? */
+    uint32_t isnull:1;    /* Associated value is NULL (don't store it). */
+    uint32_t iscompr:1;   /* Node is compressed. */
+    uint32_t size:29;     /* Number of children, or compressed string len. */
+    /* Data layout is as follows:
+     *
+     * If node is not compressed we have 'size' bytes, one for each children
+     * character, and 'size' raxNode pointers, point to each child node.
+     * Note how the character is not stored in the children but in the
+     * edge of the parents:
+     *
+     * [header strlen=0][abc][a-ptr][b-ptr][c-ptr](value-ptr?)
+     *
+     * if node is compressed (strlen != 0) the node has 1 children.
+     * In that case the 'size' bytes of the string stored immediately at
+     * the start of the data section, represent a sequence of successive
+     * nodes linked one after the other, for which only the last one in
+     * the sequence is actually represented as a node, and pointed to by
+     * the current compressed node.
+     *
+     * [header strlen=3][xyz][z-ptr](value-ptr?)
+     *
+     * Both compressed and not compressed nodes can represent a key
+     * with associated data in the radix tree at any level (not just terminal
+     * nodes).
+     *
+     * If the node has an associated key (iskey=1) and is not NULL
+     * (isnull=0), then after the raxNode pointers poiting to the
+     * childen, an additional value pointer is present (as you can see
+     * in the representation above as "value-ptr" field).
+     */
+    unsigned char data[];
+} raxNode;
+
+typedef struct rax {
+    raxNode *head;
+    uint64_t numele;
+    uint64_t numnodes;
+} rax;
+
+/* Stack data structure used by raxLowWalk() in order to, optionally, return
+ * a list of parent nodes to the caller. The nodes do not have a "parent"
+ * field for space concerns, so we use the auxiliary stack when needed. */
+#define RAX_STACK_STATIC_ITEMS 32
+typedef struct raxStack {
+    void **stack; /* Points to static_items or an heap allocated array. */
+    size_t items, maxitems; /* Number of items contained and total space. */
+    /* Up to RAXSTACK_STACK_ITEMS items we avoid to allocate on the heap
+     * and use this static array of pointers instead. */
+    void *static_items[RAX_STACK_STATIC_ITEMS];
+    int oom; /* True if pushing into this stack failed for OOM at some point. */
+} raxStack;
+
+/* Radix tree iterator state is encapsulated into this data structure. */
+#define RAX_ITER_STATIC_LEN 128
+#define RAX_ITER_JUST_SEEKED (1<<0) /* Iterator was just seeked. Return current
+                                       element for the first iteration and
+                                       clear the flag. */
+#define RAX_ITER_EOF (1<<1)    /* End of iteration reached. */
+#define RAX_ITER_SAFE (1<<2)   /* Safe iterator, allows operations while
+                                  iterating. But it is slower. */
+typedef struct raxIterator {
+    int flags;
+    rax *rt;                /* Radix tree we are iterating. */
+    unsigned char *key;     /* The current string. */
+    void *data;             /* Data associated to this key. */
+    size_t key_len;         /* Current key length. */
+    size_t key_max;         /* Max key len the current key buffer can hold. */
+    unsigned char key_static_string[RAX_ITER_STATIC_LEN];
+    raxNode *node;          /* Current node. Only for unsafe iteration. */
+    raxStack stack;         /* Stack used for unsafe iteration. */
+} raxIterator;
+
+/* A special pointer returned for not found items. */
+extern void *raxNotFound;
+
+/* Exported API. */
+rax *raxNew(void);
+int raxInsert(rax *rax, unsigned char *s, size_t len, void *data, void **old);
+int raxTryInsert(rax *rax, unsigned char *s, size_t len, void *data, void **old);
+int raxRemove(rax *rax, unsigned char *s, size_t len, void **old);
+void *raxFind(rax *rax, unsigned char *s, size_t len);
+void raxFree(rax *rax);
+void raxFreeWithCallback(rax *rax, void (*free_callback)(void*));
+void raxStart(raxIterator *it, rax *rt);
+int raxSeek(raxIterator *it, const char *op, unsigned char *ele, size_t len);
+int raxNext(raxIterator *it);
+int raxPrev(raxIterator *it);
+int raxRandomWalk(raxIterator *it, size_t steps);
+int raxCompare(raxIterator *iter, const char *op, unsigned char *key, size_t key_len);
+void raxStop(raxIterator *it);
+int raxEOF(raxIterator *it);
+void raxShow(rax *rax);
+uint64_t raxSize(rax *rax);
+
+#endif