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implemented strategy that doesn't use free blocks in zipmaps
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@pietern
pietern committed Mar 28, 2010
1 parent 570e43c commit 43078ff
Showing 1 changed file with 52 additions and 62 deletions.
114 changes: 52 additions & 62 deletions zipmap.c
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Expand Up @@ -149,43 +149,33 @@ static unsigned int zipmapEncodeLength(unsigned char *p, unsigned int len) {
* (freelen is an integer pointer used both to signal the required length
* and to get the reply from the function). If there is not a suitable
* free space block to hold the requested bytes, *freelen is set to 0. */
static unsigned char *zipmapLookupRaw(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned int *totlen, unsigned int *freeoff, unsigned int *freelen) {
unsigned char *p = zm+1;
static unsigned char *zipmapLookupRaw(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned int *totlen) {
unsigned char *p = zm+1, *k = NULL;
unsigned int l;
unsigned int reqfreelen = 0; /* initialized just to prevent warning */

if (freelen) {
reqfreelen = *freelen;
*freelen = 0;
assert(reqfreelen != 0);
}
while(*p != ZIPMAP_END) {
if (*p == ZIPMAP_EMPTY) {
l = zipmapDecodeLength(p+1);
/* if the user want a free space report, and this space is
* enough, and we did't already found a suitable space... */
if (freelen && l >= reqfreelen && *freelen == 0) {
*freelen = l;
*freeoff = p-zm;
unsigned char free;

/* Match or skip the key */
l = zipmapDecodeLength(p);
if (k == NULL && l == klen && !memcmp(p+1,key,l)) {
/* Only return when the user doesn't care
* for the total length of the zipmap. */
if (totlen != NULL) {
k = p;
} else {
return p;
}
p += l;
zm[0] |= ZIPMAP_STATUS_FRAGMENTED;
} else {
unsigned char free;

/* Match or skip the key */
l = zipmapDecodeLength(p);
if (l == klen && !memcmp(p+1,key,l)) return p;
p += zipmapEncodeLength(NULL,l) + l;
/* Skip the value as well */
l = zipmapDecodeLength(p);
p += zipmapEncodeLength(NULL,l);
free = p[0];
p += l+1+free; /* +1 to skip the free byte */
}
p += zipmapEncodeLength(NULL,l) + l;
/* Skip the value as well */
l = zipmapDecodeLength(p);
p += zipmapEncodeLength(NULL,l);
free = p[0];
p += l+1+free; /* +1 to skip the free byte */
}
if (totlen != NULL) *totlen = (unsigned int)(p-zm)+1;
return NULL;
return k;
}

static unsigned long zipmapRequiredLength(unsigned int klen, unsigned int vlen) {
Expand Down Expand Up @@ -224,28 +214,29 @@ static unsigned int zipmapRawEntryLength(unsigned char *p) {
return l + zipmapRawValueLength(p+l);
}

static inline unsigned char *zipmapResize(unsigned char *zm, unsigned int len) {
zm = zrealloc(zm, len);
zm[len-1] = ZIPMAP_END;
return zm;
}

/* Set key to value, creating the key if it does not already exist.
* If 'update' is not NULL, *update is set to 1 if the key was
* already preset, otherwise to 0. */
unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char *val, unsigned int vlen, int *update) {
unsigned int oldlen = 0, freeoff = 0, freelen;
unsigned int reqlen = zipmapRequiredLength(klen,vlen);
unsigned int zmlen;
unsigned int freelen, reqlen = zipmapRequiredLength(klen,vlen);
unsigned int empty, vempty;
unsigned char *p;

freelen = reqlen;
if (update) *update = 0;
p = zipmapLookupRaw(zm,key,klen,&oldlen,&freeoff,&freelen);
if (p == NULL && freelen == 0) {
/* Key not found, and not space for the new key. Enlarge */
zm = zrealloc(zm,oldlen+reqlen);
p = zm+oldlen-1;
zm[oldlen+reqlen-1] = ZIPMAP_END;
freelen = reqlen;
} else if (p == NULL) {
/* Key not found, but there is enough free space. */
p = zm+freeoff;
/* note: freelen is already set in this case */
p = zipmapLookupRaw(zm,key,klen,&zmlen);
if (p == NULL) {
/* Key not found: enlarge */
zm = zipmapResize(zm, zmlen+reqlen);
p = zm+zmlen-1;
zmlen = zmlen+reqlen;
} else {
unsigned char *b = p;

Expand All @@ -256,11 +247,14 @@ unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int kle
b += freelen;
freelen += zipmapRawValueLength(b);
if (freelen < reqlen) {
/* Mark this entry as free and recurse */
p[0] = ZIPMAP_EMPTY;
zipmapEncodeLength(p+1,freelen);
zm[0] |= ZIPMAP_STATUS_FRAGMENTED;
return zipmapSet(zm,key,klen,val,vlen,NULL);
/* Move remaining entries to the current position, so this
* pair can be appended. Note: the +1 in memmove is caused
* by the end-of-zipmap byte. */
memmove(p, p+freelen, zmlen-((p-zm)+freelen+1));
zm = zipmapResize(zm, zmlen-freelen+reqlen);
p = zm+zmlen-1-freelen;
zmlen = zmlen-1-freelen+reqlen;
freelen = reqlen;
}
}

Expand All @@ -270,14 +264,11 @@ unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int kle
/* If there is too much free space mark it as a free block instead
* of adding it as trailing empty space for the value, as we want
* zipmaps to be very space efficient. */
if (empty > ZIPMAP_VALUE_MAX_FREE) {
unsigned char *e;

e = p+reqlen;
e[0] = ZIPMAP_EMPTY;
zipmapEncodeLength(e+1,empty);
if (empty >= ZIPMAP_VALUE_MAX_FREE) {
memmove(p+reqlen, p+freelen, zmlen-((p-zm)+freelen+1));
zmlen -= empty;
zm = zipmapResize(zm, zmlen);
vempty = 0;
zm[0] |= ZIPMAP_STATUS_FRAGMENTED;
} else {
vempty = empty;
}
Expand All @@ -297,13 +288,12 @@ unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int kle
/* Remove the specified key. If 'deleted' is not NULL the pointed integer is
* set to 0 if the key was not found, to 1 if it was found and deleted. */
unsigned char *zipmapDel(unsigned char *zm, unsigned char *key, unsigned int klen, int *deleted) {
unsigned char *p = zipmapLookupRaw(zm,key,klen,NULL,NULL,NULL);
unsigned int zmlen;
unsigned char *p = zipmapLookupRaw(zm,key,klen,&zmlen);
if (p) {
unsigned int freelen = zipmapRawEntryLength(p);

p[0] = ZIPMAP_EMPTY;
zipmapEncodeLength(p+1,freelen);
zm[0] |= ZIPMAP_STATUS_FRAGMENTED;
memmove(p, p+freelen, zmlen-((p-zm)+freelen+1));
zm = zipmapResize(zm, zmlen-freelen);
if (deleted) *deleted = 1;
} else {
if (deleted) *deleted = 0;
Expand Down Expand Up @@ -351,7 +341,7 @@ unsigned char *zipmapNext(unsigned char *zm, unsigned char **key, unsigned int *
int zipmapGet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char **value, unsigned int *vlen) {
unsigned char *p;

if ((p = zipmapLookupRaw(zm,key,klen,NULL,NULL,NULL)) == NULL) return 0;
if ((p = zipmapLookupRaw(zm,key,klen,NULL)) == NULL) return 0;
p += zipmapRawKeyLength(p);
*vlen = zipmapDecodeLength(p);
*value = p + ZIPMAP_LEN_BYTES(*vlen) + 1;
Expand All @@ -360,7 +350,7 @@ int zipmapGet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned

/* Return 1 if the key exists, otherwise 0 is returned. */
int zipmapExists(unsigned char *zm, unsigned char *key, unsigned int klen) {
return zipmapLookupRaw(zm,key,klen,NULL,NULL,NULL) != NULL;
return zipmapLookupRaw(zm,key,klen,NULL) != NULL;
}

/* Return the number of entries inside a zipmap */
Expand Down

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