Merge remote branch 'pietern/zfixes'

[redis.git] / ziplist.c

diff --git a/ziplist.c b/ziplist.c
index fe2bfaf6ccebafa8f0d218dc9e107562a5fc2701..4b9d0fadcd15f9a1277e66ffb615ec29dde321fb 100644 (file)
--- a/ziplist.c
+++ b/ziplist.c
@@ -17,19 +17,25 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

+#include <stdint.h>

 #include <assert.h>
 #include <limits.h>
 #include "zmalloc.h"
 #include <assert.h>
 #include <limits.h>
 #include "zmalloc.h"

-#include "sds.h"

 #include "ziplist.h"
 
 #include "ziplist.h"
 

+/* Important note: the ZIP_END value is used to depict the end of the
+ * ziplist structure. When a pointer contains an entry, the first couple
+ * of bytes contain the encoded length of the previous entry. This length
+ * is encoded as ZIP_ENC_RAW length, so the first two bits will contain 00
+ * and the byte will therefore never have a value of 255. */

 #define ZIP_END 255
 #define ZIP_END 255

+#define ZIP_BIGLEN 254

 
 /* Entry encoding */
 #define ZIP_ENC_RAW     0
 
 /* Entry encoding */
 #define ZIP_ENC_RAW     0

-#define ZIP_ENC_SHORT   1
-#define ZIP_ENC_INT     2
-#define ZIP_ENC_LLONG   3
+#define ZIP_ENC_INT16   1
+#define ZIP_ENC_INT32   2
+#define ZIP_ENC_INT64   3

 #define ZIP_ENCODING(p) ((p)[0] >> 6)
 
 /* Length encoding for raw entries */
 #define ZIP_ENCODING(p) ((p)[0] >> 6)
 
 /* Length encoding for raw entries */


@@ -38,20 +44,35 @@
 #define ZIP_LEN_UINT32  2
 
 /* Utility macros */
 #define ZIP_LEN_UINT32  2
 
 /* Utility macros */

-#define ZIPLIST_BYTES(zl) (*((unsigned int*)(zl)))
-#define ZIPLIST_LENGTH(zl) (*((zl)+sizeof(unsigned int)))
-#define ZIPLIST_HEADER_SIZE (sizeof(unsigned int)+1)
+#define ZIPLIST_BYTES(zl)       (*((uint32_t*)(zl)))
+#define ZIPLIST_TAIL_OFFSET(zl) (*((uint32_t*)((zl)+sizeof(uint32_t))))
+#define ZIPLIST_LENGTH(zl)      (*((uint16_t*)((zl)+sizeof(uint32_t)*2)))
+#define ZIPLIST_HEADER_SIZE     (sizeof(uint32_t)*2+sizeof(uint16_t))
+#define ZIPLIST_ENTRY_HEAD(zl)  ((zl)+ZIPLIST_HEADER_SIZE)
+#define ZIPLIST_ENTRY_TAIL(zl)  ((zl)+ZIPLIST_TAIL_OFFSET(zl))
+#define ZIPLIST_ENTRY_END(zl)   ((zl)+ZIPLIST_BYTES(zl)-1)
+
+/* We know a positive increment can only be 1 because entries can only be
+ * pushed one at a time. */

 #define ZIPLIST_INCR_LENGTH(zl,incr) { \
 #define ZIPLIST_INCR_LENGTH(zl,incr) { \

-    if (ZIPLIST_LENGTH(zl) < (ZIP_END-1)) ZIPLIST_LENGTH(zl)+=incr; }
+    if (ZIPLIST_LENGTH(zl) < UINT16_MAX) ZIPLIST_LENGTH(zl)+=incr; }
+
+typedef struct zlentry {
+    unsigned int prevrawlensize, prevrawlen;
+    unsigned int lensize, len;
+    unsigned int headersize;
+    unsigned char encoding;
+    unsigned char *p;
+} zlentry;

 
 /* Return bytes needed to store integer encoded by 'encoding' */
 
 /* Return bytes needed to store integer encoded by 'encoding' */

-static unsigned int zipEncodingSize(char encoding) {
-    if (encoding == ZIP_ENC_SHORT) {
-        return sizeof(short int);
-    } else if (encoding == ZIP_ENC_INT) {
-        return sizeof(int);
-    } else if (encoding == ZIP_ENC_LLONG) {
-        return sizeof(long long);
+static unsigned int zipEncodingSize(unsigned char encoding) {
+    if (encoding == ZIP_ENC_INT16) {
+        return sizeof(int16_t);
+    } else if (encoding == ZIP_ENC_INT32) {
+        return sizeof(int32_t);
+    } else if (encoding == ZIP_ENC_INT64) {
+        return sizeof(int64_t);

     }
     assert(NULL);
 }
     }
     assert(NULL);
 }


@@ -115,22 +136,59 @@ static unsigned int zipEncodeLength(unsigned char *p, char encoding, unsigned in
     return len;
 }
 
     return len;
 }
 

+/* Decode the length of the previous element stored at "p". */
+static unsigned int zipPrevDecodeLength(unsigned char *p, unsigned int *lensize) {
+    unsigned int len = *p;
+    if (len < ZIP_BIGLEN) {
+        if (lensize) *lensize = 1;
+    } else {
+        if (lensize) *lensize = 1+sizeof(len);
+        memcpy(&len,p+1,sizeof(len));
+    }
+    return len;
+}
+
+/* Encode the length of the previous entry and write it to "p". Return the
+ * number of bytes needed to encode this length if "p" is NULL. */
+static unsigned int zipPrevEncodeLength(unsigned char *p, unsigned int len) {
+    if (p == NULL) {
+        return (len < ZIP_BIGLEN) ? 1 : sizeof(len)+1;
+    } else {
+        if (len < ZIP_BIGLEN) {
+            p[0] = len;
+            return 1;
+        } else {
+            p[0] = ZIP_BIGLEN;
+            memcpy(p+1,&len,sizeof(len));
+            return 1+sizeof(len);
+        }
+    }
+}
+
+/* Return the difference in number of bytes needed to store the new length
+ * "len" on the entry pointed to by "p". */
+static int zipPrevLenByteDiff(unsigned char *p, unsigned int len) {
+    unsigned int prevlensize;
+    zipPrevDecodeLength(p,&prevlensize);
+    return zipPrevEncodeLength(NULL,len)-prevlensize;
+}
+

 /* Check if string pointed to by 'entry' can be encoded as an integer.
  * Stores the integer value in 'v' and its encoding in 'encoding'.
  * Warning: this function requires a NULL-terminated string! */
 /* Check if string pointed to by 'entry' can be encoded as an integer.
  * Stores the integer value in 'v' and its encoding in 'encoding'.
  * Warning: this function requires a NULL-terminated string! */

-static int zipTryEncoding(unsigned char *entry, long long *v, char *encoding) {
+static int zipTryEncoding(unsigned char *entry, long long *v, unsigned char *encoding) {

     long long value;
     char *eptr;
 
     if (entry[0] == '-' || (entry[0] >= '0' && entry[0] <= '9')) {
     long long value;
     char *eptr;
 
     if (entry[0] == '-' || (entry[0] >= '0' && entry[0] <= '9')) {

-        value = strtoll(entry,&eptr,10);
+        value = strtoll((char*)entry,&eptr,10);

         if (eptr[0] != '\0') return 0;
         if (eptr[0] != '\0') return 0;

-        if (value >= SHRT_MIN && value <= SHRT_MAX) {
-            *encoding = ZIP_ENC_SHORT;
-        } else if (value >= INT_MIN && value <= INT_MAX) {
-            *encoding = ZIP_ENC_INT;
+        if (value >= INT16_MIN && value <= INT16_MAX) {
+            *encoding = ZIP_ENC_INT16;
+        } else if (value >= INT32_MIN && value <= INT32_MAX) {
+            *encoding = ZIP_ENC_INT32;

         } else {
         } else {

-            *encoding = ZIP_ENC_LLONG;
+            *encoding = ZIP_ENC_INT64;

         }
         *v = value;
         return 1;
         }
         *v = value;
         return 1;


@@ -139,49 +197,59 @@ static int zipTryEncoding(unsigned char *entry, long long *v, char *encoding) {
 }
 
 /* Store integer 'value' at 'p', encoded as 'encoding' */
 }
 
 /* Store integer 'value' at 'p', encoded as 'encoding' */

-static void zipSaveInteger(unsigned char *p, long long value, char encoding) {
-    short int s;
-    int i;
-    long long l;
-    if (encoding == ZIP_ENC_SHORT) {
-        s = value;
-        memcpy(p,&s,sizeof(s));
-    } else if (encoding == ZIP_ENC_INT) {
-        i = value;
-        memcpy(p,&i,sizeof(i));
-    } else if (encoding == ZIP_ENC_LLONG) {
-        l = value;
-        memcpy(p,&l,sizeof(l));
+static void zipSaveInteger(unsigned char *p, int64_t value, unsigned char encoding) {
+    int16_t i16;
+    int32_t i32;
+    int64_t i64;
+    if (encoding == ZIP_ENC_INT16) {
+        i16 = value;
+        memcpy(p,&i16,sizeof(i16));
+    } else if (encoding == ZIP_ENC_INT32) {
+        i32 = value;
+        memcpy(p,&i32,sizeof(i32));
+    } else if (encoding == ZIP_ENC_INT64) {
+        i64 = value;
+        memcpy(p,&i64,sizeof(i64));

     } else {
         assert(NULL);
     }
 }
 
 /* Read integer encoded as 'encoding' from 'p' */
     } else {
         assert(NULL);
     }
 }
 
 /* Read integer encoded as 'encoding' from 'p' */

-static long long zipLoadInteger(unsigned char *p, char encoding) {
-    short int s;
-    int i;
-    long long l, ret;
-    if (encoding == ZIP_ENC_SHORT) {
-        memcpy(&s,p,sizeof(s));
-        ret = s;
-    } else if (encoding == ZIP_ENC_INT) {
-        memcpy(&i,p,sizeof(i));
-        ret = i;
-    } else if (encoding == ZIP_ENC_LLONG) {
-        memcpy(&l,p,sizeof(l));
-        ret = l;
+static int64_t zipLoadInteger(unsigned char *p, unsigned char encoding) {
+    int16_t i16;
+    int32_t i32;
+    int64_t i64, ret;
+    if (encoding == ZIP_ENC_INT16) {
+        memcpy(&i16,p,sizeof(i16));
+        ret = i16;
+    } else if (encoding == ZIP_ENC_INT32) {
+        memcpy(&i32,p,sizeof(i32));
+        ret = i32;
+    } else if (encoding == ZIP_ENC_INT64) {
+        memcpy(&i64,p,sizeof(i64));
+        ret = i64;

     } else {
         assert(NULL);
     }
     return ret;
 }
 
     } else {
         assert(NULL);
     }
     return ret;
 }
 

-/* Return the total amount used by an entry (encoded length + payload). */
+/* Return a struct with all information about an entry. */
+static zlentry zipEntry(unsigned char *p) {
+    zlentry e;
+    e.prevrawlen = zipPrevDecodeLength(p,&e.prevrawlensize);
+    e.len = zipDecodeLength(p+e.prevrawlensize,&e.lensize);
+    e.headersize = e.prevrawlensize+e.lensize;
+    e.encoding = ZIP_ENCODING(p+e.prevrawlensize);
+    e.p = p;
+    return e;
+}
+
+/* Return the total number of bytes used by the entry at "p". */

 static unsigned int zipRawEntryLength(unsigned char *p) {
 static unsigned int zipRawEntryLength(unsigned char *p) {

-    unsigned int lensize, len;
-    len = zipDecodeLength(p, &lensize);
-    return lensize + len;
+    zlentry e = zipEntry(p);
+    return e.headersize + e.len;

 }
 
 /* Create a new empty ziplist. */
 }
 
 /* Create a new empty ziplist. */


@@ -189,6 +257,7 @@ unsigned char *ziplistNew(void) {
     unsigned int bytes = ZIPLIST_HEADER_SIZE+1;
     unsigned char *zl = zmalloc(bytes);
     ZIPLIST_BYTES(zl) = bytes;
     unsigned int bytes = ZIPLIST_HEADER_SIZE+1;
     unsigned char *zl = zmalloc(bytes);
     ZIPLIST_BYTES(zl) = bytes;

+    ZIPLIST_TAIL_OFFSET(zl) = ZIPLIST_HEADER_SIZE;

     ZIPLIST_LENGTH(zl) = 0;
     zl[bytes-1] = ZIP_END;
     return zl;
     ZIPLIST_LENGTH(zl) = 0;
     zl[bytes-1] = ZIP_END;
     return zl;


@@ -202,193 +271,296 @@ static unsigned char *ziplistResize(unsigned char *zl, unsigned int len) {
     return zl;
 }
 
     return zl;
 }
 

-static unsigned char *ziplistHead(unsigned char *zl) {
-    return zl+ZIPLIST_HEADER_SIZE;
-}
-
-static unsigned char *ziplistTail(unsigned char *zl) {
-    unsigned char *p, *q;
-    p = q = ziplistHead(zl);
-    while (*p != ZIP_END) {
-        q = p;
+/* Delete "num" entries, starting at "p". Returns pointer to the ziplist. */
+static unsigned char *__ziplistDelete(unsigned char *zl, unsigned char *p, unsigned int num) {
+    unsigned int i, totlen, deleted = 0;
+    int nextdiff = 0;
+    zlentry first = zipEntry(p);
+    for (i = 0; p[0] != ZIP_END && i < num; i++) {

         p += zipRawEntryLength(p);
         p += zipRawEntryLength(p);

+        deleted++;

     }
     }

-    return q;
+
+    totlen = p-first.p;
+    if (totlen > 0) {
+        if (p[0] != ZIP_END) {
+            /* Tricky: storing the prevlen in this entry might reduce or
+             * increase the number of bytes needed, compared to the current
+             * prevlen. Note that we can always store this length because
+             * it was previously stored by an entry that is being deleted. */
+            nextdiff = zipPrevLenByteDiff(p,first.prevrawlen);
+            zipPrevEncodeLength(p-nextdiff,first.prevrawlen);
+
+            /* Update offset for tail */
+            ZIPLIST_TAIL_OFFSET(zl) -= totlen+nextdiff;
+
+            /* Move tail to the front of the ziplist */
+            memmove(first.p,p-nextdiff,ZIPLIST_BYTES(zl)-(p-zl)-1+nextdiff);
+        } else {
+            /* The entire tail was deleted. No need to move memory. */
+            ZIPLIST_TAIL_OFFSET(zl) = (first.p-zl)-first.prevrawlen;
+        }
+
+        /* Resize and update length */
+        zl = ziplistResize(zl, ZIPLIST_BYTES(zl)-totlen+nextdiff);
+        ZIPLIST_INCR_LENGTH(zl,-deleted);
+    }
+    return zl;

 }
 
 }
 

-unsigned char *ziplistPush(unsigned char *zl, unsigned char *entry, unsigned int elen, int where) {
-    unsigned int curlen = ZIPLIST_BYTES(zl), reqlen;
-    unsigned char *p;
-    char encoding = ZIP_ENC_RAW;
+/* Insert item at "p". */
+static unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsigned char *s, unsigned int slen) {
+    unsigned int curlen = ZIPLIST_BYTES(zl), reqlen, prevlen = 0;
+    unsigned int offset, nextdiff = 0;
+    unsigned char *tail;
+    unsigned char encoding = ZIP_ENC_RAW;

     long long value;
     long long value;

+    zlentry entry;
+
+    /* Find out prevlen for the entry that is inserted. */
+    if (p[0] != ZIP_END) {
+        entry = zipEntry(p);
+        prevlen = entry.prevrawlen;
+    } else {
+        tail = ZIPLIST_ENTRY_TAIL(zl);
+        if (tail[0] != ZIP_END) {
+            prevlen = zipRawEntryLength(tail);
+        }
+    }

 
     /* See if the entry can be encoded */
 
     /* See if the entry can be encoded */

-    if (zipTryEncoding(entry,&value,&encoding)) {
+    if (zipTryEncoding(s,&value,&encoding)) {

         reqlen = zipEncodingSize(encoding);
     } else {
         reqlen = zipEncodingSize(encoding);
     } else {

-        reqlen = elen;
+        reqlen = slen;

     }
     }

-    reqlen += zipEncodeLength(NULL,encoding,elen);

 
 

-    /* Resize the ziplist and move if needed */
-    zl = ziplistResize(zl,curlen+reqlen);
-    if (where == ZIPLIST_HEAD) {
-        p = zl+ZIPLIST_HEADER_SIZE;
-        if (*p != ZIP_END) {
-            /* Subtract one because of the ZIP_END bytes */
-            memmove(p+reqlen,p,curlen-ZIPLIST_HEADER_SIZE-1);
-        }
+    /* We need space for both the length of the previous entry and
+     * the length of the payload. */
+    reqlen += zipPrevEncodeLength(NULL,prevlen);
+    reqlen += zipEncodeLength(NULL,encoding,slen);
+
+    /* When the insert position is not equal to the tail, we need to
+     * make sure that the next entry can hold this entry's length in
+     * its prevlen field. */
+    nextdiff = (p[0] != ZIP_END) ? zipPrevLenByteDiff(p,reqlen) : 0;
+
+    /* Store offset because a realloc may change the address of zl. */
+    offset = p-zl;
+    zl = ziplistResize(zl,curlen+reqlen+nextdiff);
+    p = zl+offset;
+
+    /* Apply memory move when necessary and update tail offset. */
+    if (p[0] != ZIP_END) {
+        /* Subtract one because of the ZIP_END bytes */
+        memmove(p+reqlen,p-nextdiff,curlen-offset-1+nextdiff);
+        /* Encode this entry's raw length in the next entry. */
+        zipPrevEncodeLength(p+reqlen,reqlen);
+        /* Update offset for tail */
+        ZIPLIST_TAIL_OFFSET(zl) += reqlen+nextdiff;

     } else {
     } else {

-        p = zl+curlen-1;
+        /* This element will be the new tail. */
+        ZIPLIST_TAIL_OFFSET(zl) = p-zl;

     }
 
     /* Write the entry */
     }
 
     /* Write the entry */

-    p += zipEncodeLength(p,encoding,elen);
+    p += zipPrevEncodeLength(p,prevlen);
+    p += zipEncodeLength(p,encoding,slen);

     if (encoding != ZIP_ENC_RAW) {
         zipSaveInteger(p,value,encoding);
     } else {
     if (encoding != ZIP_ENC_RAW) {
         zipSaveInteger(p,value,encoding);
     } else {

-        memcpy(p,entry,elen);
+        memcpy(p,s,slen);

     }
     ZIPLIST_INCR_LENGTH(zl,1);
     return zl;
 }
 
     }
     ZIPLIST_INCR_LENGTH(zl,1);
     return zl;
 }
 

-unsigned char *ziplistPop(unsigned char *zl, sds *target, int where) {
-    unsigned int curlen = ZIPLIST_BYTES(zl), rawlen;
-    unsigned int len, lensize;
+unsigned char *ziplistPush(unsigned char *zl, unsigned char *s, unsigned int slen, int where) {

     unsigned char *p;
     unsigned char *p;

-    long long value;
-    if (target) *target = NULL;
-
-    /* Get pointer to element to remove */
-    p = (where == ZIPLIST_HEAD) ? ziplistHead(zl) : ziplistTail(zl);
-    if (*p == ZIP_END) return zl;
-    len = zipDecodeLength(p,&lensize);
-    if (target) {
-        if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
-            *target = sdsnewlen(p+lensize,len);
-        } else {
-            value = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
-            *target = sdscatprintf(sdsempty(), "%lld", value);
-        }
-    }
+    p = (where == ZIPLIST_HEAD) ? ZIPLIST_ENTRY_HEAD(zl) : ZIPLIST_ENTRY_END(zl);
+    return __ziplistInsert(zl,p,s,slen);
+}

 
 

-    /* Move list to front when popping from the head */
-    rawlen = lensize+len;
-    if (where == ZIPLIST_HEAD) {
-        memmove(p,p+rawlen,curlen-ZIPLIST_HEADER_SIZE-len);
+/* Returns an offset to use for iterating with ziplistNext. When the given
+ * index is negative, the list is traversed back to front. When the list
+ * doesn't contain an element at the provided index, NULL is returned. */
+unsigned char *ziplistIndex(unsigned char *zl, int index) {
+    unsigned char *p;
+    zlentry entry;
+    if (index < 0) {
+        index = (-index)-1;
+        p = ZIPLIST_ENTRY_TAIL(zl);
+        if (p[0] != ZIP_END) {
+            entry = zipEntry(p);
+            while (entry.prevrawlen > 0 && index--) {
+                p -= entry.prevrawlen;
+                entry = zipEntry(p);
+            }
+        }
+    } else {
+        p = ZIPLIST_ENTRY_HEAD(zl);
+        while (p[0] != ZIP_END && index--) {
+            p += zipRawEntryLength(p);
+        }

     }
     }

-
-    /* Resize and update length */
-    zl = ziplistResize(zl,curlen-rawlen);
-    ZIPLIST_INCR_LENGTH(zl,-1);
-    return zl;
+    return (p[0] == ZIP_END || index > 0) ? NULL : p;

 }
 
 }
 

-/* Returns an offset to use for iterating with ziplistNext. */
-unsigned char *ziplistIndex(unsigned char *zl, unsigned int index) {
-    unsigned char *p = zl+ZIPLIST_HEADER_SIZE;
-    unsigned int i = 0;
-    for (; i < index; i++) {
-        if (*p == ZIP_END) break;
-        p += zipRawEntryLength(p);
+/* Return pointer to next entry in ziplist. */
+unsigned char *ziplistNext(unsigned char *zl, unsigned char *p) {
+    ((void) zl);
+
+    /* "p" could be equal to ZIP_END, caused by ziplistDelete,
+     * and we should return NULL. Otherwise, we should return NULL
+     * when the *next* element is ZIP_END (there is no next entry). */
+    if (p[0] == ZIP_END) {
+        return NULL;
+    } else {
+        p = p+zipRawEntryLength(p);
+        return (p[0] == ZIP_END) ? NULL : p;

     }
     }

-    return p;

 }
 
 }
 

-/* Return pointer to next entry in ziplist. */
-unsigned char *ziplistNext(unsigned char *p) {
-    return *p == ZIP_END ? p : p+zipRawEntryLength(p);
+/* Return pointer to previous entry in ziplist. */
+unsigned char *ziplistPrev(unsigned char *zl, unsigned char *p) {
+    zlentry entry;
+
+    /* Iterating backwards from ZIP_END should return the tail. When "p" is
+     * equal to the first element of the list, we're already at the head,
+     * and should return NULL. */
+    if (p[0] == ZIP_END) {
+        p = ZIPLIST_ENTRY_TAIL(zl);
+        return (p[0] == ZIP_END) ? NULL : p;
+    } else if (p == ZIPLIST_ENTRY_HEAD(zl)) {
+        return NULL;
+    } else {
+        entry = zipEntry(p);
+        return p-entry.prevrawlen;
+    }

 }
 
 /* Get entry pointer to by 'p' and store in either 'e' or 'v' depending
  * on the encoding of the entry. 'e' is always set to NULL to be able
  * to find out whether the string pointer or the integer value was set.
  * Return 0 if 'p' points to the end of the zipmap, 1 otherwise. */
 }
 
 /* Get entry pointer to by 'p' and store in either 'e' or 'v' depending
  * on the encoding of the entry. 'e' is always set to NULL to be able
  * to find out whether the string pointer or the integer value was set.
  * Return 0 if 'p' points to the end of the zipmap, 1 otherwise. */

-unsigned int ziplistGet(unsigned char *p, unsigned char **e, unsigned int *elen, long long *v) {
-    unsigned int len, lensize;
-    if (*p == ZIP_END) return 0;
-    if (e) *e = NULL;
-    len = zipDecodeLength(p,&lensize);
-    if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
-        if (e) {
-            *elen = len;
-            *e = p+lensize;
+unsigned int ziplistGet(unsigned char *p, unsigned char **sstr, unsigned int *slen, long long *sval) {
+    zlentry entry;
+    if (p == NULL || p[0] == ZIP_END) return 0;
+    if (sstr) *sstr = NULL;
+
+    entry = zipEntry(p);
+    if (entry.encoding == ZIP_ENC_RAW) {
+        if (sstr) {
+            *slen = entry.len;
+            *sstr = p+entry.headersize;

         }
     } else {
         }
     } else {

-        if (v) {
-            *v = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
+        if (sval) {
+            *sval = zipLoadInteger(p+entry.headersize,entry.encoding);

         }
     }
     return 1;
 }
 
         }
     }
     return 1;
 }
 

-/* Delete a range of entries from the ziplist. */
-unsigned char *ziplistDeleteRange(unsigned char *zl, unsigned int index, unsigned int num) {
-    unsigned char *p, *first = ziplistIndex(zl, index);
-    unsigned int i, deleted = 0, totlen, newlen;
-    for (p = first, i = 0; *p != ZIP_END && i < num; i++) {
-        p += zipRawEntryLength(p);
-        deleted++;
-    }
-
-    totlen = p-first;
-    if (totlen > 0) {
-        /* Move current tail to the new tail when there *is* a tail */
-        if (*p != ZIP_END) memmove(first,p,ZIPLIST_BYTES(zl)-(p-zl)-1);
-
-        /* Resize and update length */
-        zl = ziplistResize(zl, ZIPLIST_BYTES(zl)-totlen);
-        ZIPLIST_INCR_LENGTH(zl,-deleted);
-    }
-    return zl;
+/* Insert an entry at "p". */
+unsigned char *ziplistInsert(unsigned char *zl, unsigned char *p, unsigned char *s, unsigned int slen) {
+    return __ziplistInsert(zl,p,s,slen);

 }
 
 /* Delete a single entry from the ziplist, pointed to by *p.
  * Also update *p in place, to be able to iterate over the
  * ziplist, while deleting entries. */
 unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {
 }
 
 /* Delete a single entry from the ziplist, pointed to by *p.
  * Also update *p in place, to be able to iterate over the
  * ziplist, while deleting entries. */
 unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {

-    unsigned int offset = *p-zl, tail, len;
-    len = zipRawEntryLength(*p);
-    tail = ZIPLIST_BYTES(zl)-offset-len-1;
-
-    /* Move current tail to the new tail when there *is* a tail */
-    if (tail > 0) memmove(*p,*p+len,tail);
-
-    /* Resize and update length */
-    zl = ziplistResize(zl, ZIPLIST_BYTES(zl)-len);
-    ZIPLIST_INCR_LENGTH(zl,-1);
+    unsigned int offset = *p-zl;
+    zl = __ziplistDelete(zl,*p,1);

 
 

-    /* Store new pointer to current element in p.
-     * This needs to be done because zl can change on realloc. */
+    /* Store pointer to current element in p, because ziplistDelete will
+     * do a realloc which might result in a different "zl"-pointer.
+     * When the delete direction is back to front, we might delete the last
+     * entry and end up with "p" pointing to ZIP_END, so check this. */

     *p = zl+offset;
     return zl;
 }
 
     *p = zl+offset;
     return zl;
 }
 

+/* Delete a range of entries from the ziplist. */
+unsigned char *ziplistDeleteRange(unsigned char *zl, unsigned int index, unsigned int num) {
+    unsigned char *p = ziplistIndex(zl,index);
+    return (p == NULL) ? zl : __ziplistDelete(zl,p,num);
+}
+
+/* Compare entry pointer to by 'p' with 'entry'. Return 1 if equal. */
+unsigned int ziplistCompare(unsigned char *p, unsigned char *sstr, unsigned int slen) {
+    zlentry entry;
+    unsigned char sencoding;
+    long long zval, sval;
+    if (p[0] == ZIP_END) return 0;
+
+    entry = zipEntry(p);
+    if (entry.encoding == ZIP_ENC_RAW) {
+        /* Raw compare */
+        if (entry.len == slen) {
+            return memcmp(p+entry.headersize,sstr,slen) == 0;
+        } else {
+            return 0;
+        }
+    } else {
+        /* Try to compare encoded values */
+        if (zipTryEncoding(sstr,&sval,&sencoding)) {
+            if (entry.encoding == sencoding) {
+                zval = zipLoadInteger(p+entry.headersize,entry.encoding);
+                return zval == sval;
+            }
+        }
+    }
+    return 0;
+}
+
+/* Return length of ziplist. */
+unsigned int ziplistLen(unsigned char *zl) {
+    unsigned int len = 0;
+    if (ZIPLIST_LENGTH(zl) < UINT16_MAX) {
+        len = ZIPLIST_LENGTH(zl);
+    } else {
+        unsigned char *p = zl+ZIPLIST_HEADER_SIZE;
+        while (*p != ZIP_END) {
+            p += zipRawEntryLength(p);
+            len++;
+        }
+
+        /* Re-store length if small enough */
+        if (len < UINT16_MAX) ZIPLIST_LENGTH(zl) = len;
+    }
+    return len;
+}
+
+/* Return size in bytes of ziplist. */
+unsigned int ziplistSize(unsigned char *zl) {
+    return ZIPLIST_BYTES(zl);
+}
+

 void ziplistRepr(unsigned char *zl) {
 void ziplistRepr(unsigned char *zl) {

-    unsigned char *p, encoding;
-    unsigned int l, lsize;
-    long long value;
+    unsigned char *p;
+    zlentry entry;

 
     printf("{total bytes %d} {length %u}\n",ZIPLIST_BYTES(zl), ZIPLIST_LENGTH(zl));
 
     printf("{total bytes %d} {length %u}\n",ZIPLIST_BYTES(zl), ZIPLIST_LENGTH(zl));

-    p = ziplistHead(zl);
+    p = ZIPLIST_ENTRY_HEAD(zl);

     while(*p != ZIP_END) {
     while(*p != ZIP_END) {

-        l = zipDecodeLength(p,&lsize);
-        printf("{header %u, payload %u} ",lsize,l);
-        encoding = ZIP_ENCODING(p);
-        p += lsize;
-        if (encoding == ZIP_ENC_RAW) {
-            fwrite(p,l,1,stdout);
+        entry = zipEntry(p);
+        printf("{offset %ld, header %u, payload %u} ",p-zl,entry.headersize,entry.len);
+        p += entry.headersize;
+        if (entry.encoding == ZIP_ENC_RAW) {
+            fwrite(p,entry.len,1,stdout);

         } else {
         } else {

-            printf("%lld", zipLoadInteger(p,encoding));
+            printf("%lld", zipLoadInteger(p,entry.encoding));

         }
         printf("\n");
         }
         printf("\n");

-        p += l;
+        p += entry.len;

     }
     printf("{end}\n\n");
 }
 
 #ifdef ZIPLIST_TEST_MAIN
     }
     printf("{end}\n\n");
 }
 
 #ifdef ZIPLIST_TEST_MAIN

+#include <sys/time.h>

 
 unsigned char *createList() {
     unsigned char *zl = ziplistNew();
 
 unsigned char *createList() {
     unsigned char *zl = ziplistNew();


@@ -404,25 +576,79 @@ unsigned char *createIntList() {
     char buf[32];
 
     sprintf(buf, "100");
     char buf[32];
 
     sprintf(buf, "100");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);

     sprintf(buf, "128000");
     sprintf(buf, "128000");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);

     sprintf(buf, "-100");
     sprintf(buf, "-100");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_HEAD);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_HEAD);

     sprintf(buf, "4294967296");
     sprintf(buf, "4294967296");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_HEAD);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_HEAD);

     sprintf(buf, "non integer");
     sprintf(buf, "non integer");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);

     sprintf(buf, "much much longer non integer");
     sprintf(buf, "much much longer non integer");

-    zl = ziplistPush(zl, buf, strlen(buf), ZIPLIST_TAIL);
+    zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), ZIPLIST_TAIL);

     return zl;
 }
 
     return zl;
 }
 

+long long usec(void) {
+    struct timeval tv;
+    gettimeofday(&tv,NULL);
+    return (((long long)tv.tv_sec)*1000000)+tv.tv_usec;
+}
+
+void stress(int pos, int num, int maxsize, int dnum) {
+    int i,j,k;
+    unsigned char *zl;
+    char posstr[2][5] = { "HEAD", "TAIL" };
+    long long start;
+    for (i = 0; i < maxsize; i+=dnum) {
+        zl = ziplistNew();
+        for (j = 0; j < i; j++) {
+            zl = ziplistPush(zl,(unsigned char*)"quux",4,ZIPLIST_TAIL);
+        }
+
+        /* Do num times a push+pop from pos */
+        start = usec();
+        for (k = 0; k < num; k++) {
+            zl = ziplistPush(zl,(unsigned char*)"quux",4,pos);
+            zl = ziplistDeleteRange(zl,0,1);
+        }
+        printf("List size: %8d, bytes: %8d, %dx push+pop (%s): %6lld usec\n",
+            i,ZIPLIST_BYTES(zl),num,posstr[pos],usec()-start);
+        zfree(zl);
+    }
+}
+
+void pop(unsigned char *zl, int where) {
+    unsigned char *p, *vstr;
+    unsigned int vlen;
+    long long vlong;
+
+    p = ziplistIndex(zl,where == ZIPLIST_HEAD ? 0 : -1);
+    if (ziplistGet(p,&vstr,&vlen,&vlong)) {
+        if (where == ZIPLIST_HEAD)
+            printf("Pop head: ");
+        else
+            printf("Pop tail: ");
+
+        if (vstr)
+            fwrite(vstr,vlen,1,stdout);
+        else
+            printf("%lld", vlong);
+
+        printf("\n");
+        ziplistDeleteRange(zl,-1,1);
+    } else {
+        printf("ERROR: Could not pop\n");
+        exit(1);
+    }
+}
+

 int main(int argc, char **argv) {
 int main(int argc, char **argv) {

-    unsigned char *zl, *p, *q, *entry;
+    unsigned char *zl, *p;
+    unsigned char *entry;

     unsigned int elen;
     long long value;
     unsigned int elen;
     long long value;

-    sds s;

 
     zl = createIntList();
     ziplistRepr(zl);
 
     zl = createIntList();
     ziplistRepr(zl);


@@ -430,14 +656,95 @@ int main(int argc, char **argv) {
     zl = createList();
     ziplistRepr(zl);
 
     zl = createList();
     ziplistRepr(zl);
 

-    zl = ziplistPop(zl, &s, ZIPLIST_TAIL);
-    printf("Pop tail: %s (length %ld)\n", s, sdslen(s));
+    pop(zl,ZIPLIST_TAIL);
+    ziplistRepr(zl);
+
+    pop(zl,ZIPLIST_HEAD);

     ziplistRepr(zl);
 
     ziplistRepr(zl);
 

-    zl = ziplistPop(zl, &s, ZIPLIST_HEAD);
-    printf("Pop head: %s (length %ld)\n", s, sdslen(s));
+    pop(zl,ZIPLIST_TAIL);

     ziplistRepr(zl);
 
     ziplistRepr(zl);
 

+    pop(zl,ZIPLIST_TAIL);
+    ziplistRepr(zl);
+
+    printf("Get element at index 3:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, 3);
+        if (!ziplistGet(p, &entry, &elen, &value)) {
+            printf("ERROR: Could not access index 3\n");
+            return 1;
+        }
+        if (entry) {
+            fwrite(entry,elen,1,stdout);
+            printf("\n");
+        } else {
+            printf("%lld\n", value);
+        }
+        printf("\n");
+    }
+
+    printf("Get element at index 4 (out of range):\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, 4);
+        if (p == NULL) {
+            printf("No entry\n");
+        } else {
+            printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
+            return 1;
+        }
+        printf("\n");
+    }
+
+    printf("Get element at index -1 (last element):\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -1);
+        if (!ziplistGet(p, &entry, &elen, &value)) {
+            printf("ERROR: Could not access index -1\n");
+            return 1;
+        }
+        if (entry) {
+            fwrite(entry,elen,1,stdout);
+            printf("\n");
+        } else {
+            printf("%lld\n", value);
+        }
+        printf("\n");
+    }
+
+    printf("Get element at index -4 (first element):\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -4);
+        if (!ziplistGet(p, &entry, &elen, &value)) {
+            printf("ERROR: Could not access index -4\n");
+            return 1;
+        }
+        if (entry) {
+            fwrite(entry,elen,1,stdout);
+            printf("\n");
+        } else {
+            printf("%lld\n", value);
+        }
+        printf("\n");
+    }
+
+    printf("Get element at index -5 (reverse out of range):\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -5);
+        if (p == NULL) {
+            printf("No entry\n");
+        } else {
+            printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
+            return 1;
+        }
+        printf("\n");
+    }
+

     printf("Iterate list from 0 to end:\n");
     {
         zl = createList();
     printf("Iterate list from 0 to end:\n");
     {
         zl = createList();


@@ -449,7 +756,7 @@ int main(int argc, char **argv) {
             } else {
                 printf("%lld", value);
             }
             } else {
                 printf("%lld", value);
             }

-            p = ziplistNext(p);
+            p = ziplistNext(zl,p);

             printf("\n");
         }
         printf("\n");
             printf("\n");
         }
         printf("\n");


@@ -466,7 +773,7 @@ int main(int argc, char **argv) {
             } else {
                 printf("%lld", value);
             }
             } else {
                 printf("%lld", value);
             }

-            p = ziplistNext(p);
+            p = ziplistNext(zl,p);

             printf("\n");
         }
         printf("\n");
             printf("\n");
         }
         printf("\n");


@@ -483,7 +790,7 @@ int main(int argc, char **argv) {
             } else {
                 printf("%lld", value);
             }
             } else {
                 printf("%lld", value);
             }

-            p = ziplistNext(p);
+            p = ziplistNext(zl,p);

             printf("\n");
         }
         printf("\n");
             printf("\n");
         }
         printf("\n");


@@ -501,6 +808,41 @@ int main(int argc, char **argv) {
         printf("\n");
     }
 
         printf("\n");
     }
 

+    printf("Iterate from back to front:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -1);
+        while (ziplistGet(p, &entry, &elen, &value)) {
+            printf("Entry: ");
+            if (entry) {
+                fwrite(entry,elen,1,stdout);
+            } else {
+                printf("%lld", value);
+            }
+            p = ziplistPrev(zl,p);
+            printf("\n");
+        }
+        printf("\n");
+    }
+
+    printf("Iterate from back to front, deleting all items:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -1);
+        while (ziplistGet(p, &entry, &elen, &value)) {
+            printf("Entry: ");
+            if (entry) {
+                fwrite(entry,elen,1,stdout);
+            } else {
+                printf("%lld", value);
+            }
+            zl = ziplistDelete(zl,&p);
+            p = ziplistPrev(zl,p);
+            printf("\n");
+        }
+        printf("\n");
+    }
+

     printf("Delete inclusive range 0,0:\n");
     {
         zl = createList();
     printf("Delete inclusive range 0,0:\n");
     {
         zl = createList();


@@ -539,27 +881,79 @@ int main(int argc, char **argv) {
     printf("Delete foo while iterating:\n");
     {
         zl = createList();
     printf("Delete foo while iterating:\n");
     {
         zl = createList();

-        p = ziplistIndex(zl, 0);
-        while (ziplistGet(p, &entry, &elen, &value)) {
-            if (entry && strncmp("foo", entry, elen) == 0) {
+        p = ziplistIndex(zl,0);
+        while (ziplistGet(p,&entry,&elen,&value)) {
+            if (entry && strncmp("foo",(char*)entry,elen) == 0) {

                 printf("Delete foo\n");
                 printf("Delete foo\n");

-                zl = ziplistDelete(zl, &p);
+                zl = ziplistDelete(zl,&p);

             } else {
                 printf("Entry: ");
                 if (entry) {
                     fwrite(entry,elen,1,stdout);
                 } else {
             } else {
                 printf("Entry: ");
                 if (entry) {
                     fwrite(entry,elen,1,stdout);
                 } else {

-                    printf("%lld", value);
+                    printf("%lld",value);

                 }
                 }

-                p = ziplistNext(p);
+                p = ziplistNext(zl,p);

                 printf("\n");
             }
         }
         printf("\n");
         ziplistRepr(zl);
                 printf("\n");
             }
         }
         printf("\n");
         ziplistRepr(zl);

-        printf("\n");
+    }
+
+    printf("Create long list and check indices:\n");
+    {
+        zl = ziplistNew();
+        char buf[32];
+        int i,len;
+        for (i = 0; i < 1000; i++) {
+            len = sprintf(buf,"%d",i);
+            zl = ziplistPush(zl,(unsigned char*)buf,len,ZIPLIST_TAIL);
+        }
+        for (i = 0; i < 1000; i++) {
+            p = ziplistIndex(zl,i);
+            assert(ziplistGet(p,NULL,NULL,&value));
+            assert(i == value);
+
+            p = ziplistIndex(zl,-i-1);
+            assert(ziplistGet(p,NULL,NULL,&value));
+            assert(999-i == value);
+        }
+        printf("SUCCESS\n\n");
+    }
+
+    printf("Compare strings with ziplist entries:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl,0);
+        if (!ziplistCompare(p,(unsigned char*)"hello",5)) {
+            printf("ERROR: not \"hello\"\n");
+            return 1;
+        }
+        if (ziplistCompare(p,(unsigned char*)"hella",5)) {
+            printf("ERROR: \"hella\"\n");
+            return 1;
+        }
+
+        p = ziplistIndex(zl,3);
+        if (!ziplistCompare(p,(unsigned char*)"1024",4)) {
+            printf("ERROR: not \"1024\"\n");
+            return 1;
+        }
+        if (ziplistCompare(p,(unsigned char*)"1025",4)) {
+            printf("ERROR: \"1025\"\n");
+            return 1;
+        }
+        printf("SUCCESS\n");
+    }
+
+    printf("Stress with variable ziplist size:\n");
+    {
+        stress(ZIPLIST_HEAD,100000,16384,256);
+        stress(ZIPLIST_TAIL,100000,16384,256);

     }
 
     return 0;
 }
     }
 
     return 0;
 }

+

 #endif
 #endif