if (lensize) *lensize = 1;
break;
case ZIP_STR_14B:
- len = ((p[0] & 0x3f) << 6) | p[1];
+ len = ((p[0] & 0x3f) << 8) | p[1];
if (lensize) *lensize = 2;
break;
case ZIP_STR_32B:
}
}
+/* Encode the length of the previous entry and write it to "p". This only
+ * uses the larger encoding (required in __ziplistCascadeUpdate). */
+static void zipPrevEncodeLengthForceLarge(unsigned char *p, unsigned int len) {
+ if (p == NULL) return;
+ p[0] = ZIP_BIGLEN;
+ memcpy(p+1,&len,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) {
return zl;
}
+/* When an entry is inserted, we need to set the prevlen field of the next
+ * entry to equal the length of the inserted entry. It can occur that this
+ * length cannot be encoded in 1 byte and the next entry needs to be grow
+ * a bit larger to hold the 5-byte encoded prevlen. This can be done for free,
+ * because this only happens when an entry is already being inserted (which
+ * causes a realloc and memmove). However, encoding the prevlen may require
+ * that this entry is grown as well. This effect may cascade throughout
+ * the ziplist when there are consecutive entries with a size close to
+ * ZIP_BIGLEN, so we need to check that the prevlen can be encoded in every
+ * consecutive entry.
+ *
+ * Note that this effect can also happen in reverse, where the bytes required
+ * to encode the prevlen field can shrink. This effect is deliberately ignored,
+ * because it can cause a "flapping" effect where a chain prevlen fields is
+ * first grown and then shrunk again after consecutive inserts. Rather, the
+ * field is allowed to stay larger than necessary, because a large prevlen
+ * field implies the ziplist is holding large entries anyway.
+ *
+ * The pointer "p" points to the first entry that does NOT need to be
+ * updated, i.e. consecutive fields MAY need an update. */
+static unsigned char *__ziplistCascadeUpdate(unsigned char *zl, unsigned char *p) {
+ unsigned int curlen = ZIPLIST_BYTES(zl), rawlen, rawlensize;
+ unsigned int offset, noffset, extra;
+ unsigned char *np;
+ zlentry cur, next;
+
+ while (p[0] != ZIP_END) {
+ cur = zipEntry(p);
+ rawlen = cur.headersize + cur.len;
+ rawlensize = zipPrevEncodeLength(NULL,rawlen);
+
+ /* Abort if there is no next entry. */
+ if (p[rawlen] == ZIP_END) break;
+ next = zipEntry(p+rawlen);
+
+ /* Abort when "prevlen" has not changed. */
+ if (next.prevrawlen == rawlen) break;
+
+ if (next.prevrawlensize < rawlensize) {
+ /* The "prevlen" field of "next" needs more bytes to hold
+ * the raw length of "cur". */
+ offset = p-zl;
+ extra = rawlensize-next.prevrawlensize;
+ zl = ziplistResize(zl,curlen+extra);
+ ZIPLIST_TAIL_OFFSET(zl) += extra;
+ p = zl+offset;
+
+ /* Move the tail to the back. */
+ np = p+rawlen;
+ noffset = np-zl;
+ memmove(np+rawlensize,
+ np+next.prevrawlensize,
+ curlen-noffset-next.prevrawlensize-1);
+ zipPrevEncodeLength(np,rawlen);
+
+ /* Advance the cursor */
+ p += rawlen;
+ curlen += extra;
+ } else {
+ if (next.prevrawlensize > rawlensize) {
+ /* This would result in shrinking, which we want to avoid.
+ * So, set "rawlen" in the available bytes. */
+ zipPrevEncodeLengthForceLarge(p+rawlen,rawlen);
+ } else {
+ zipPrevEncodeLength(p+rawlen,rawlen);
+ }
+
+ /* Stop here, as the raw length of "next" has not changed. */
+ break;
+ }
+ }
+ return zl;
+}
+
/* 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);
+ int offset, nextdiff = 0;
+ zlentry first, tail;
+
+ first = zipEntry(p);
for (i = 0; p[0] != ZIP_END && i < num; i++) {
p += zipRawEntryLength(p);
deleted++;
zipPrevEncodeLength(p-nextdiff,first.prevrawlen);
/* Update offset for tail */
- ZIPLIST_TAIL_OFFSET(zl) -= totlen+nextdiff;
+ ZIPLIST_TAIL_OFFSET(zl) -= totlen;
+
+ /* When the tail contains more than one entry, we need to take
+ * "nextdiff" in account as well. Otherwise, a change in the
+ * size of prevlen doesn't have an effect on the *tail* offset. */
+ tail = zipEntry(p);
+ if (p[tail.headersize+tail.len] != ZIP_END)
+ ZIPLIST_TAIL_OFFSET(zl) += nextdiff;
/* Move tail to the front of the ziplist */
memmove(first.p,p-nextdiff,ZIPLIST_BYTES(zl)-(p-zl)-1+nextdiff);
}
/* Resize and update length */
+ offset = first.p-zl;
zl = ziplistResize(zl, ZIPLIST_BYTES(zl)-totlen+nextdiff);
ZIPLIST_INCR_LENGTH(zl,-deleted);
+ p = zl+offset;
+
+ /* When nextdiff != 0, the raw length of the next entry has changed, so
+ * we need to cascade the update throughout the ziplist */
+ if (nextdiff != 0)
+ zl = __ziplistCascadeUpdate(zl,p);
}
return zl;
}
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 = 0;
long long value;
- zlentry entry;
+ zlentry entry, tail;
/* 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);
+ unsigned char *ptail = ZIPLIST_ENTRY_TAIL(zl);
+ if (ptail[0] != ZIP_END) {
+ prevlen = zipRawEntryLength(ptail);
}
}
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;
+ ZIPLIST_TAIL_OFFSET(zl) += reqlen;
+
+ /* When the tail contains more than one entry, we need to take
+ * "nextdiff" in account as well. Otherwise, a change in the
+ * size of prevlen doesn't have an effect on the *tail* offset. */
+ tail = zipEntry(p+reqlen);
+ if (p[reqlen+tail.headersize+tail.len] != ZIP_END)
+ ZIPLIST_TAIL_OFFSET(zl) += nextdiff;
} else {
/* This element will be the new tail. */
ZIPLIST_TAIL_OFFSET(zl) = p-zl;
}
+ /* When nextdiff != 0, the raw length of the next entry has changed, so
+ * we need to cascade the update throughout the ziplist */
+ if (nextdiff != 0) {
+ offset = p-zl;
+ zl = __ziplistCascadeUpdate(zl,p+reqlen);
+ p = zl+offset;
+ }
+
/* Write the entry */
p += zipPrevEncodeLength(p,prevlen);
p += zipEncodeLength(p,encoding,slen);
return NULL;
} else {
entry = zipEntry(p);
+ assert(entry.prevrawlen > 0);
return p-entry.prevrawlen;
}
}
void ziplistRepr(unsigned char *zl) {
unsigned char *p;
+ int index = 0;
zlentry entry;
- printf("{total bytes %d} {length %u}\n",ZIPLIST_BYTES(zl), ZIPLIST_LENGTH(zl));
+ printf(
+ "{total bytes %d} "
+ "{length %u}\n"
+ "{tail offset %u}\n",
+ ZIPLIST_BYTES(zl),
+ ZIPLIST_LENGTH(zl),
+ ZIPLIST_TAIL_OFFSET(zl));
p = ZIPLIST_ENTRY_HEAD(zl);
while(*p != ZIP_END) {
entry = zipEntry(p);
- printf("{offset %ld, header %u, payload %u} ",p-zl,entry.headersize,entry.len);
+ printf(
+ "{"
+ "addr 0x%08lx, "
+ "index %2d, "
+ "offset %5ld, "
+ "rl: %5u, "
+ "hs %2u, "
+ "pl: %5u, "
+ "pls: %2u, "
+ "payload %5u"
+ "} ",
+ (long unsigned int)p,
+ index,
+ p-zl,
+ entry.headersize+entry.len,
+ entry.headersize,
+ entry.prevrawlen,
+ entry.prevrawlensize,
+ entry.len);
p += entry.headersize;
if (ZIP_IS_STR(entry.encoding)) {
- fwrite(p,entry.len,1,stdout);
+ if (entry.len > 40) {
+ fwrite(p,40,1,stdout);
+ printf("...");
+ } else {
+ fwrite(p,entry.len,1,stdout);
+ }
} else {
printf("%lld", (long long) zipLoadInteger(p,entry.encoding));
}
printf("\n");
p += entry.len;
+ index++;
}
printf("{end}\n\n");
}
#ifdef ZIPLIST_TEST_MAIN
#include <sys/time.h>
+#include "adlist.h"
+#include "sds.h"
+
+#define debug(f, ...) { if (DEBUG) printf(f, __VA_ARGS__); }
unsigned char *createList() {
unsigned char *zl = ziplistNew();
}
}
+void randstring(char *target, unsigned int min, unsigned int max) {
+ int p, len = min+rand()%(max-min+1);
+ int minval, maxval;
+ switch(rand() % 3) {
+ case 0:
+ minval = 0;
+ maxval = 255;
+ break;
+ case 1:
+ minval = 48;
+ maxval = 122;
+ break;
+ case 2:
+ minval = 48;
+ maxval = 52;
+ break;
+ default:
+ assert(NULL);
+ }
+
+ while(p < len)
+ target[p++] = minval+rand()%(maxval-minval+1);
+ return;
+}
+
+
int main(int argc, char **argv) {
unsigned char *zl, *p;
unsigned char *entry;
unsigned int elen;
long long value;
+ /* If an argument is given, use it as the random seed. */
+ if (argc == 2)
+ srand(atoi(argv[1]));
+
zl = createIntList();
ziplistRepr(zl);
ziplistRepr(zl);
}
+ printf("Regression test for >255 byte strings:\n");
+ {
+ char v1[257],v2[257];
+ memset(v1,'x',256);
+ memset(v2,'y',256);
+ zl = ziplistNew();
+ zl = ziplistPush(zl,(unsigned char*)v1,strlen(v1),ZIPLIST_TAIL);
+ zl = ziplistPush(zl,(unsigned char*)v2,strlen(v2),ZIPLIST_TAIL);
+
+ /* Pop values again and compare their value. */
+ p = ziplistIndex(zl,0);
+ assert(ziplistGet(p,&entry,&elen,&value));
+ assert(strncmp(v1,(char*)entry,elen) == 0);
+ p = ziplistIndex(zl,1);
+ assert(ziplistGet(p,&entry,&elen,&value));
+ assert(strncmp(v2,(char*)entry,elen) == 0);
+ printf("SUCCESS\n\n");
+ }
+
printf("Create long list and check indices:\n");
{
zl = ziplistNew();
printf("ERROR: \"1025\"\n");
return 1;
}
- printf("SUCCESS\n");
+ printf("SUCCESS\n\n");
+ }
+
+ printf("Stress with random payloads of different encoding:\n");
+ {
+ int i,j,len,where;
+ unsigned char *p;
+ char buf[1024];
+ list *ref;
+ listNode *refnode;
+
+ /* Hold temp vars from ziplist */
+ unsigned char *sstr;
+ unsigned int slen;
+ long long sval;
+
+ /* In the regression for the cascade bug, it was triggered
+ * with a random seed of 2. */
+ srand(2);
+
+ for (i = 0; i < 20000; i++) {
+ zl = ziplistNew();
+ ref = listCreate();
+ listSetFreeMethod(ref,sdsfree);
+ len = rand() % 256;
+
+ /* Create lists */
+ for (j = 0; j < len; j++) {
+ where = (rand() & 1) ? ZIPLIST_HEAD : ZIPLIST_TAIL;
+ switch(rand() % 4) {
+ case 0:
+ sprintf(buf,"%lld",(0LL + rand()) >> 20);
+ break;
+ case 1:
+ sprintf(buf,"%lld",(0LL + rand()));
+ break;
+ case 2:
+ sprintf(buf,"%lld",(0LL + rand()) << 20);
+ break;
+ case 3:
+ randstring(buf,0,256);
+ break;
+ default:
+ assert(NULL);
+ }
+
+ /* Add to ziplist */
+ zl = ziplistPush(zl, (unsigned char*)buf, strlen(buf), where);
+
+ /* Add to reference list */
+ if (where == ZIPLIST_HEAD) {
+ listAddNodeHead(ref,sdsnew(buf));
+ } else if (where == ZIPLIST_TAIL) {
+ listAddNodeTail(ref,sdsnew(buf));
+ } else {
+ assert(NULL);
+ }
+ }
+
+ assert(listLength(ref) == ziplistLen(zl));
+ for (j = 0; j < len; j++) {
+ /* Naive way to get elements, but similar to the stresser
+ * executed from the Tcl test suite. */
+ p = ziplistIndex(zl,j);
+ refnode = listIndex(ref,j);
+
+ assert(ziplistGet(p,&sstr,&slen,&sval));
+ if (sstr == NULL) {
+ sprintf(buf,"%lld",sval);
+ } else {
+ memcpy(buf,sstr,slen);
+ buf[slen] = '\0';
+ }
+ assert(strcmp(buf,listNodeValue(refnode)) == 0);
+ }
+ zfree(zl);
+ listRelease(ref);
+ }
+ printf("SUCCESS\n\n");
}
printf("Stress with variable ziplist size:\n");
projects / redis.git / blobdiff