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code to iterate over a ziplist

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This commit is contained in:
Pieter Noordhuis 2010-05-21 13:16:08 +02:00
parent 11ac6ff613
commit 08253bf42b
1 changed files with 76 additions and 7 deletions
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83
ziplist.c
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@ -107,6 +107,30 @@ unsigned char *ziplistPop(unsigned char *zl, sds *value, int where) {
return zl; return zl;
} }
/* 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 p;
}
/* Store entry at current position in sds *value and return pointer
* to the next entry. */
unsigned char *ziplistNext(unsigned char *p, sds *value) {
if (*p == ZIP_END) return NULL;
if (value) {
unsigned int len;
len = zipDecodeLength(p);
*value = sdsnewlen(p+zipEncodeLength(NULL,len),len);
}
p += zipRawEntryLength(p);
return p;
}
void ziplistRepr(unsigned char *zl) { void ziplistRepr(unsigned char *zl) {
unsigned char *p; unsigned char *p;
unsigned int l; unsigned int l;
@ -125,16 +149,20 @@ void ziplistRepr(unsigned char *zl) {
} }
#ifdef ZIPLIST_TEST_MAIN #ifdef ZIPLIST_TEST_MAIN
unsigned char *createList() {
unsigned char *zl = ziplistNew();
zl = ziplistPush(zl, (unsigned char*)"foo", 3, ZIPLIST_TAIL);
zl = ziplistPush(zl, (unsigned char*)"quux", 4, ZIPLIST_TAIL);
zl = ziplistPush(zl, (unsigned char*)"hello", 5, ZIPLIST_HEAD);
return zl;
}
int main(int argc, char **argv) { int main(int argc, char **argv) {
unsigned char *zl; unsigned char *zl, *p;
sds s; sds s;
zl = ziplistNew(); zl = createList();
zl = ziplistPush(zl, (unsigned char*)"foo", 3, ZIPLIST_TAIL);
ziplistRepr(zl);
zl = ziplistPush(zl, (unsigned char*)"quux", 4, ZIPLIST_TAIL);
ziplistRepr(zl);
zl = ziplistPush(zl, (unsigned char*)"hello", 5, ZIPLIST_HEAD);
ziplistRepr(zl); ziplistRepr(zl);
zl = ziplistPop(zl, &s, ZIPLIST_TAIL); zl = ziplistPop(zl, &s, ZIPLIST_TAIL);
@ -145,6 +173,47 @@ int main(int argc, char **argv) {
printf("Pop head: %s (length %ld)\n", s, sdslen(s)); printf("Pop head: %s (length %ld)\n", s, sdslen(s));
ziplistRepr(zl); ziplistRepr(zl);
printf("Iterate list from 0 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 0);
while ((p = ziplistNext(p, &s)) != NULL) {
printf("Entry: %s (length %ld)\n", s, sdslen(s));
}
printf("\n");
}
printf("Iterate list from 1 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 1);
while ((p = ziplistNext(p, &s)) != NULL) {
printf("Entry: %s (length %ld)\n", s, sdslen(s));
}
printf("\n");
}
printf("Iterate list from 2 to end:\n");
{
zl = createList();
p = ziplistIndex(zl, 2);
while ((p = ziplistNext(p, &s)) != NULL) {
printf("Entry: %s (length %ld)\n", s, sdslen(s));
}
printf("\n");
}
printf("Iterate starting out of range:\n");
{
zl = createList();
p = ziplistIndex(zl, 3);
if (ziplistNext(p, &s) == NULL) {
printf("No entry\n");
} else {
printf("ERROR\n");
}
}
return 0; return 0;
} }
#endif #endif