/* This function is used to iterate through all the zipmap elements.
*
* 这个函数用于遍历 zipmap 的所有元素。
*
* In the first call the first argument is the pointer to the zipmap + 1.
*
* 在第一次调用这个函数时， zm 参数的值为 zipmap + 1
* （也即是，指向 zipmap 的第一个节点）
*
* In the next calls what zipmapNext returns is used as first argument.
*
* 而在之后的调用中， zm 参数的值为之前调用 zipmapNext 时所返回的值。
*
* Example:
*
* 示例：
*
* unsigned char *i = zipmapRewind(my_zipmap);
* while((i = zipmapNext(i,&key,&klen,&value,&vlen)) != NULL) {
* printf("%d bytes key at $p\n", klen, key);
* printf("%d bytes value at $p\n", vlen, value);
* }
*
* T = O(1)
*/
unsigned char *zipmapNext(unsigned char *zm, unsigned char **key, unsigned int *klen, unsigned char **value, unsigned int *vlen) {
// 已到达列表末尾，停止迭代
if (zm[0] == ZIPMAP_END) return NULL;
// 取出键，并保存到 key 参数中
if (key) {
*key = zm;
*klen = zipmapDecodeLength(zm);
*key += ZIPMAP_LEN_BYTES(*klen);
}
// 越过键
zm += zipmapRawKeyLength(zm);
// 取出值，并保存到 value 参数中
if (value) {
*value = zm+1;
*vlen = zipmapDecodeLength(zm);
*value += ZIPMAP_LEN_BYTES(*vlen);
}
// 越过值
zm += zipmapRawValueLength(zm);
// 返回指向下一节点的指针
return zm;
}
/* This function is used to iterate through all the zipmap elements.
* In the first call the first argument is the pointer to the zipmap + 1.
* In the next calls what zipmapNext returns is used as first argument.
* Example:
*
* unsigned char *i = zipmapRewind(my_zipmap);
* while((i = zipmapNext(i,&key,&klen,&value,&vlen)) != NULL) {
* printf("%d bytes key at $p\n", klen, key);
* printf("%d bytes value at $p\n", vlen, value);
* }
*/
unsigned char *zipmapNext(unsigned char *zm, unsigned char **key, unsigned int *klen, unsigned char **value, unsigned int *vlen) {
if (zm[0] == ZIPMAP_END) return NULL;
if (key) {
*key = zm;
*klen = zipmapDecodeLength(zm);
*key += ZIPMAP_LEN_BYTES(*klen);
}
zm += zipmapRawKeyLength(zm);
if (value) {
*value = zm+1;
*vlen = zipmapDecodeLength(zm);
*value += ZIPMAP_LEN_BYTES(*vlen);
}
zm += zipmapRawValueLength(zm);
return zm;
}
/* zipmap的迭代器式遍历函数，典型用法如下：
*
* unsigned char *i = zipmapRewind(my_zipmap);
* while((i = zipmapNext(i,&key,&klen,&value,&vlen)) != NULL) {
* printf("%d bytes key at $p\n", klen, key);
* printf("%d bytes value at $p\n", vlen, value);
* }
*/
unsigned char *zipmapNext(unsigned char *zm, unsigned char **key, unsigned int *klen, unsigned char **value, unsigned int *vlen) {
// 如果达到尾部，直接返回NULL
if (zm[0] == ZIPMAP_END) return NULL;
// 获取key
if (key) {
*key = zm;
*klen = zipmapDecodeLength(zm);
*key += ZIPMAP_LEN_BYTES(*klen);
}
zm += zipmapRawKeyLength(zm);
// 获取value
if (value) {
// +1是为了跳过free字段，该字段占用一个字节
*value = zm+1;
*vlen = zipmapDecodeLength(zm);
*value += ZIPMAP_LEN_BYTES(*vlen);
}
// 此时zm指向下一个键值对的首地址
zm += zipmapRawValueLength(zm);
return zm;
}
/* If 'p' points to a key, this function returns the total amount of
* bytes used to store this entry (entry = key + associated value + trailing
* free space if any). */
static unsigned int zipmapRawEntryLength(unsigned char *p) {
unsigned int l = zipmapRawKeyLength(p);
return l + zipmapRawValueLength(p+l);
}
/* Set key to value, creating the key if it does not already exist. */
unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char *val, unsigned int vlen) {
unsigned int oldlen = 0, freeoff = 0, freelen;
unsigned int reqlen = zipmapRequiredLength(klen,vlen);
unsigned int empty, vempty;
unsigned char *p;
freelen = reqlen;
p = zipmapLookupRaw(zm,key,klen,&oldlen,&freeoff,&freelen);
if (p == NULL && freelen == 0) {
printf("HERE oldlen:%u required:%u\n",oldlen,reqlen);
/* 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;
printf("New total length is: %u\n", oldlen+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 */
} else {
unsigned char *b = p;
/* Key found. Is there enough space for the new value? */
/* Compute the total length: */
freelen = zipmapRawKeyLength(b);
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);
}
}
/* Ok we have a suitable block where to write the new key/value
* entry. */
empty = freelen-reqlen;
/* 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);
vempty = 0;
zm[0] |= ZIPMAP_STATUS_FRAGMENTED;
} else {
vempty = empty;
}
/* Just write the key + value and we are done. */
/* Key: */
p += zipmapEncodeLength(p,klen);
memcpy(p,key,klen);
p += klen;
/* Value: */
p += zipmapEncodeLength(p,vlen);
*p++ = vempty;
memcpy(p,val,vlen);
return zm;
}
/* If 'p' points to a key, this function returns the total amount of
* bytes used to store this entry (entry = key + associated value + trailing
* free space if any). */
static unsigned int zipmapXRawEntryLength(unsigned char *p) {
unsigned int l = zipmapRawKeyLength(p);
return l + sizeof(unsigned int) + zipmapRawValueLength(p+l+sizeof(unsigned int));
}
