implemented strategy that doesn't use free blocks in zipmaps

diff --git a/zipmap.c b/zipmap.c
index f45ef0dd64c7d795638178d732934bb9755b6a36..f168d0a75fc98527999e1e8c4ac1be122afe5639 100644 (file)
--- 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 */