caleb-brown/redict
1
0
Fork 0
mirror of https://codeberg.org/redict/redict.git synced 2025-01-23 00:28:26 -05:00
Code Issues Actions Packages Projects Releases Wiki Activity

use simpler encoding for the length of the previous entry

Browse Source
This commit is contained in:
Pieter Noordhuis 2010-05-29 19:26:35 +02:00
parent 1ce81fa59b
commit 7b1f85c0a2
1 changed files with 36 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
ziplist.c
View File

@ -133,12 +133,41 @@ static unsigned int zipEncodeLength(unsigned char *p, char encoding, unsigned in
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;
zipDecodeLength(p,&prevlensize);
return zipEncodeLength(NULL,ZIP_ENC_RAW,len)-prevlensize;
zipPrevDecodeLength(p,&prevlensize);
return zipPrevEncodeLength(NULL,len)-prevlensize;
}
/* Check if string pointed to by 'entry' can be encoded as an integer.
@ -206,7 +235,7 @@ static long long zipLoadInteger(unsigned char *p, char encoding) {
/* Return a struct with all information about an entry. */
static zlentry zipEntry(unsigned char *p) {
zlentry e;
e.prevrawlen = zipDecodeLength(p,&e.prevrawlensize);
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);
@ -257,7 +286,7 @@ static unsigned char *__ziplistDelete(unsigned char *zl, unsigned char *p, int n
* 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);
zipEncodeLength(p-nextdiff,ZIP_ENC_RAW,first.prevrawlen);
zipPrevEncodeLength(p-nextdiff,first.prevrawlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) -= totlen+nextdiff;
@ -305,7 +334,7 @@ static unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsig
/* 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 += zipPrevEncodeLength(NULL,prevlen);
reqlen += zipEncodeLength(NULL,encoding,slen);
/* When the insert position is not equal to the tail, we need to
@ -323,7 +352,7 @@ static unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsig
/* 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. */
zipEncodeLength(p+reqlen,ZIP_ENC_RAW,reqlen);
zipPrevEncodeLength(p+reqlen,reqlen);
/* Update offset for tail */
ZIPLIST_TAIL_OFFSET(zl) += reqlen+nextdiff;
} else {
@ -332,7 +361,7 @@ static unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, unsig
}
/* Write the entry */
p += zipEncodeLength(p,ZIP_ENC_RAW,prevlen);
p += zipPrevEncodeLength(p,prevlen);
p += zipEncodeLength(p,encoding,slen);
if (encoding != ZIP_ENC_RAW) {
zipSaveInteger(p,value,encoding);