From 43078ff844b14bb864e118d35795ddc3b3d18f00 Mon Sep 17 00:00:00 2001 From: Pieter Noordhuis Date: Sun, 28 Mar 2010 22:59:15 +0200 Subject: [PATCH] implemented strategy that doesn't use free blocks in zipmaps --- zipmap.c | 114 +++++++++++++++++++++++++------------------------------ 1 file changed, 52 insertions(+), 62 deletions(-) diff --git a/zipmap.c b/zipmap.c index f45ef0dd..f168d0a7 100644 --- a/zipmap.c +++ b/zipmap.c @@ -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) { @@ -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; @@ -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; } } @@ -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; } @@ -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; @@ -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; @@ -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 */ -- 2.47.2