#include "sds.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_BIGLEN 254
/* 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_TAIL_OFFSET(zl) (*((zl)+sizeof(unsigned int)))
+#define ZIPLIST_LENGTH(zl) (*((zl)+2*sizeof(unsigned int)))
+#define ZIPLIST_HEADER_SIZE (2*sizeof(unsigned int)+1)
#define ZIPLIST_INCR_LENGTH(zl,incr) { \
if (ZIPLIST_LENGTH(zl) < ZIP_BIGLEN) ZIPLIST_LENGTH(zl)+=incr; }
+typedef struct zlentry {
+ unsigned int prevrawlensize, prevrawlen;
+ unsigned int lensize, len;
+ unsigned int headersize;
+ unsigned char encoding;
+} zlentry;
+
/* Return bytes needed to store integer encoded by 'encoding' */
static unsigned int zipEncodingSize(char encoding) {
if (encoding == ZIP_ENC_SHORT) {
return 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;
+ zipDecodeLength(p,&prevlensize);
+ return zipEncodeLength(NULL,ZIP_ENC_RAW,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! */
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 (value >= SHRT_MIN && value <= SHRT_MAX) {
*encoding = ZIP_ENC_SHORT;
return ret;
}
+/* Return a struct with all information about an entry. */
+static zlentry zipEntry(unsigned char *p) {
+ zlentry e;
+ e.prevrawlen = zipDecodeLength(p,&e.prevrawlensize);
+ e.len = zipDecodeLength(p+e.prevrawlensize,&e.lensize);
+ e.headersize = e.prevrawlensize+e.lensize;
+ e.encoding = ZIP_ENCODING(p+e.prevrawlensize);
+ return e;
+}
+
/* Return the total amount used by an entry (encoded length + payload). */
static unsigned int zipRawEntryLength(unsigned char *p) {
- unsigned int lensize, len;
- len = zipDecodeLength(p, &lensize);
- return lensize + len;
+ unsigned int prevlensize, lensize, len;
+ /* Byte-size of encoded length of previous entry */
+ zipDecodeLength(p,&prevlensize);
+ /* Encoded length of this entry's payload */
+ len = zipDecodeLength(p+prevlensize, &lensize);
+ return prevlensize+lensize+len;
}
/* Create a new empty ziplist. */
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;
}
unsigned char *ziplistPush(unsigned char *zl, unsigned char *entry, unsigned int elen, int where) {
- unsigned int curlen = ZIPLIST_BYTES(zl), reqlen;
- unsigned char *p;
+ unsigned int curlen = ZIPLIST_BYTES(zl), reqlen, prevlen;
+ unsigned char *p, *curtail;
char encoding = ZIP_ENC_RAW;
long long value;
+ /* We need to store the length of the current tail when the list
+ * is non-empty and we push at the tail. */
+ curtail = zl+ZIPLIST_TAIL_OFFSET(zl);
+ if (where == ZIPLIST_TAIL && curtail[0] != ZIP_END) {
+ prevlen = zipRawEntryLength(curtail);
+ } else {
+ prevlen = 0;
+ }
+
/* See if the entry can be encoded */
if (zipTryEncoding(entry,&value,&encoding)) {
reqlen = zipEncodingSize(encoding);
} else {
reqlen = elen;
}
+
+ /* We need space for both the length of the previous entry and
+ * the length of the payload. */
+ reqlen += zipEncodeLength(NULL,ZIP_ENC_RAW,prevlen);
reqlen += zipEncodeLength(NULL,encoding,elen);
/* Resize the ziplist and move if needed */
p = zl+curlen-1;
}
+ /* Update tail offset if this is not the first element */
+ if (curtail[0] != ZIP_END) {
+ if (where == ZIPLIST_HEAD) {
+ ZIPLIST_TAIL_OFFSET(zl) += reqlen;
+ } else {
+ ZIPLIST_TAIL_OFFSET(zl) += prevlen;
+ }
+ }
+
/* Write the entry */
+ p += zipEncodeLength(p,ZIP_ENC_RAW,prevlen);
p += zipEncodeLength(p,encoding,elen);
if (encoding != ZIP_ENC_RAW) {
zipSaveInteger(p,value,encoding);
unsigned char *ziplistPop(unsigned char *zl, sds *target, int where) {
unsigned int curlen = ZIPLIST_BYTES(zl), rawlen;
- unsigned int len, lensize;
+ zlentry entry;
+ int nextdiff = 0;
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);
+
+ entry = zipEntry(p);
+ rawlen = entry.headersize+entry.len;
if (target) {
- if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
- *target = sdsnewlen(p+lensize,len);
+ if (entry.encoding == ZIP_ENC_RAW) {
+ *target = sdsnewlen(p+entry.headersize,entry.len);
} else {
- value = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
+ value = zipLoadInteger(p+entry.headersize,entry.encoding);
*target = sdscatprintf(sdsempty(), "%lld", value);
}
}
- /* 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);
+ /* The next entry will now be the head of the list */
+ if (p[rawlen] != ZIP_END) {
+ /* Tricky: storing the length of the previous entry in the next
+ * entry (this previous length is always 0 when popping from the
+ * head), might reduce the number of bytes needed.
+ *
+ * In this special case (new length is 0), we know that the
+ * byte difference to store is always <= 0, which means that
+ * we always have space to store it. */
+ nextdiff = zipPrevLenByteDiff(p+rawlen,0);
+ zipEncodeLength(p+rawlen-nextdiff,ZIP_ENC_RAW,0);
+ }
+ /* Move list to the front */
+ memmove(p,p+rawlen-nextdiff,curlen-ZIPLIST_HEADER_SIZE-rawlen+nextdiff);
+
+ /* Subtract the gained space from the tail offset */
+ ZIPLIST_TAIL_OFFSET(zl) -= rawlen+nextdiff;
+ } else {
+ /* Subtract the length of the previous element from the tail offset. */
+ ZIPLIST_TAIL_OFFSET(zl) -= entry.prevrawlen;
}
/* Resize and update length */
- zl = ziplistResize(zl,curlen-rawlen);
+ zl = ziplistResize(zl,curlen-rawlen+nextdiff);
ZIPLIST_INCR_LENGTH(zl,-1);
return zl;
}
* 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;
+ zlentry entry;
if (*p == ZIP_END) return 0;
if (e) *e = NULL;
- len = zipDecodeLength(p,&lensize);
- if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
+
+ entry = zipEntry(p);
+ if (entry.encoding == ZIP_ENC_RAW) {
if (e) {
- *elen = len;
- *e = p+lensize;
+ *elen = entry.len;
+ *e = p+entry.headersize;
}
} else {
if (v) {
- *v = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
+ *v = zipLoadInteger(p+entry.headersize,entry.encoding);
}
}
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;
+ unsigned int i, totlen, deleted = 0;
for (p = first, i = 0; *p != ZIP_END && i < num; i++) {
p += zipRawEntryLength(p);
deleted++;
}
/* Compare entry pointer to by 'p' with 'entry'. Return 1 if equal. */
-unsigned int ziplistCompare(unsigned char *p, unsigned char *entry, unsigned int elen) {
- unsigned int zlen, lensize;
- char encoding;
- long long zval, eval;
+unsigned int ziplistCompare(unsigned char *p, unsigned char *s, unsigned int slen) {
+ zlentry entry;
+ unsigned char sencoding;
+ long long val, sval;
if (*p == ZIP_END) return 0;
- zlen = zipDecodeLength(p,&lensize);
- if (ZIP_ENCODING(p) == ZIP_ENC_RAW) {
+ entry = zipEntry(p);
+ if (entry.encoding == ZIP_ENC_RAW) {
/* Raw compare */
- if (zlen == elen) {
- return memcmp(p+lensize,entry,elen) == 0;
+ if (entry.len == slen) {
+ return memcmp(p+entry.headersize,s,slen) == 0;
} else {
return 0;
}
} else {
- if (zipTryEncoding(entry,&eval,&encoding)) {
- /* Do integer compare */
- zval = zipLoadInteger(p+lensize,ZIP_ENCODING(p));
- return zval == eval;
- } else {
- /* Ziplist entry is integer encoded, but given entry is not. */
+ /* Try to compare encoded values */
+ if (zipTryEncoding(s,&sval,&sencoding)) {
+ if (entry.encoding == sencoding) {
+ val = zipLoadInteger(p+entry.headersize,entry.encoding);
+ return val == sval;
+ }
}
}
return 0;
}
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));
p = ziplistHead(zl);
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 {
- printf("%lld", zipLoadInteger(p,encoding));
+ printf("%lld", zipLoadInteger(p,entry.encoding));
}
printf("\n");
- p += l;
+ p += entry.len;
}
printf("{end}\n\n");
}
printf("Pop head: %s (length %ld)\n", s, sdslen(s));
ziplistRepr(zl);
+ zl = ziplistPop(zl, &s, ZIPLIST_TAIL);
+ printf("Pop tail: %s (length %ld)\n", s, sdslen(s));
+ ziplistRepr(zl);
+
+ zl = ziplistPop(zl, &s, ZIPLIST_TAIL);
+ printf("Pop tail: %s (length %ld)\n", s, sdslen(s));
+ ziplistRepr(zl);
+
printf("Iterate list from 0 to end:\n");
{
zl = createList();
zl = createList();
p = ziplistIndex(zl, 0);
if (!ziplistCompare(p,"hello",5)) {
- printf("ERROR\n");
+ printf("ERROR: not \"hello\"\n");
return;
}
if (ziplistCompare(p,"hella",5)) {
- printf("ERROR\n");
+ printf("ERROR: \"hella\"\n");
return;
}
p = ziplistIndex(zl, 3);
if (!ziplistCompare(p,"1024",4)) {
- printf("ERROR\n");
+ printf("ERROR: not \"1024\"\n");
return;
}
if (ziplistCompare(p,"1025",4)) {
- printf("ERROR\n");
+ printf("ERROR: \"1025\"\n");
return;
}
printf("SUCCESS\n");
projects / redis.git / blobdiff