void zipmapRepr(unsigned char *p) {
unsigned int l;
printf("{status %u}",*p++);
while(1) {
if (p[0] == ZIPMAP_END) {
printf("{end}");
break;
} else {
unsigned char e;
l = zipmapDecodeLength(p);
printf("{key %u}",l);
p += zipmapEncodeLength(NULL,l);
if (l != 0 && fwrite(p,l,1,stdout) == 0) perror("fwrite");
p += l;
l = zipmapDecodeLength(p);
printf("{value %u}",l);
p += zipmapEncodeLength(NULL,l);
e = *p++;
if (l != 0 && fwrite(p,l,1,stdout) == 0) perror("fwrite");
p += l+e;
if (e) {
printf("[");
while(e--) printf(".");
printf("]");
}
}
}
printf("\n");
}
/* Search for a matching key, returning a pointer to the entry inside the
* zipmap. Returns NULL if the key is not found.
*
* If NULL is returned, and totlen is not NULL, it is set to the entire
* size of the zimap, so that the calling function will be able to
* reallocate the original zipmap to make room for more entries. */
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,llen;
// 遍历zipmap
while(*p != ZIPMAP_END) {
unsigned char free;
// 返回len表示的长度
/* Match or skip the key */
l = zipmapDecodeLength(p);
// 返回要编码l表示的长度需要的字节数,1还是5字节
llen = zipmapEncodeLength(NULL,l);
// 看看Key是不是相等
if (key != NULL && k == NULL && l == klen && !memcmp(p+llen,key,l)) {
// 如果外部不想知道总长度的时候,直接返回
/* Only return when the user doesn't care
* for the total length of the zipmap. */
if (totlen != NULL) {
k = p;
} else {
return p;
}
}
// p到达下一个元素的位置
p += llen+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 */
}
// 返回zm的总字节长度
if (totlen != NULL) *totlen = (unsigned int)(p-zm)+1;
return k;
}
/* 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;
}
/* Search for a matching key, returning a pointer to the entry inside the
* zipmap. Returns NULL if the key is not found.
*
* If NULL is returned, and totlen is not NULL, it is set to the entire
* size of the zimap, so that the calling function will be able to
* reallocate the original zipmap to make room for more entries. */
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,llen;
while(*p != ZIPMAP_END) {
unsigned char free;
/* Match or skip the key */
l = zipmapDecodeLength(p);
llen = zipmapEncodeLength(NULL,l);
if (key != NULL && k == NULL && l == klen && !memcmp(p+llen,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 += llen+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 k;
}
/* Search for a matching key, returning a pointer to the entry inside the
* zipmap. Returns NULL if the key is not found.
*
* 在 zipmap 中查找和给定 key 匹配的节点：
*
* 1)找到的话就返回节点的指针。
*
* 2)没找到则返回 NULL 。
*
* If NULL is returned, and totlen is not NULL, it is set to the entire
* size of the zimap, so that the calling function will be able to
* reallocate the original zipmap to make room for more entries.
*
* 如果没有找到相应的节点（函数返回 NULL），并且 totlen 不为 NULL ，
* 那么 *totlen 的值将被设为整个 zipmap 的大小，
* 这样调用者就可以根据 *totlen 的值，对 zipmap 进行内存重分配，
* 从而让 zipmap 容纳更多节点。
*
* T = O(N^2)
*/
static unsigned char *zipmapLookupRaw(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned int *totlen) {
// zm+1 略过 <zmlen> 属性，将 p 指向 zipmap 的首个节点
unsigned char *p = zm+1, *k = NULL;
unsigned int l,llen;
// 遍历整个 zipmap 来寻找
// T = O(N^2)
while(*p != ZIPMAP_END) {
unsigned char free;
/* Match or skip the key */
// 计算键的长度
l = zipmapDecodeLength(p);
// 计算编码键的长度所需的字节数
llen = zipmapEncodeLength(NULL,l);
// 对比 key
// T = O(N)
if (key != NULL && k == NULL && l == klen && !memcmp(p+llen,key,l)) {
/* Only return when the user doesn't care
* for the total length of the zipmap. */
if (totlen != NULL) {
// 如果调用者需要知道整个 zipmap 的长度，那么记录找到的指针到变量 k
// 之后遍历时，程序只计算 zipmap 剩余节点的长度，不再用 memcmp 进行对比
// 因为 k 已经不为 NULL 了
k = p;
} else {
// 如果调用者不需要知道整个 zipmap 的长度，那么直接返回 p
return p;
}
}
// 越过键节点，指向值节点
p += llen+l;
/* Skip the value as well */
// 计算值的长度
l = zipmapDecodeLength(p);
// 计算编码值的长度所需的字节数，
// 并移动指针 p ，越过该 <len> 属性，指向 <free> 属性
p += zipmapEncodeLength(NULL,l);
// 取出 <free> 属性的值
free = p[0];
// 略过值节点，指向下一节点
p += l+1+free; /* +1 to skip the free byte */
}
// 计算并记录 zipmap 的空间长度
// + 1 是将 ZIPMAP_END 也计算在内
if (totlen != NULL) *totlen = (unsigned int)(p-zm)+1;
// 返回找到 key 的指针
return k;
}
/* 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;
}
/* Return the total amount used by a value
* (encoded length + single byte free count + payload) */
static unsigned int zipmapRawValueLength(unsigned char *p) {
unsigned int l = zipmapDecodeLength(p);
unsigned int used;
used = zipmapEncodeLength(NULL,l);
used += p[used] + 1 + l;
return used;
}
/* Search a key and retrieve the pointer and len of the associated value.
* If the key is found the function returns 1, otherwise 0. */
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) return 0;
p += zipmapRawKeyLength(p);
*vlen = zipmapDecodeLength(p);
*value = p + ZIPMAP_LEN_BYTES(*vlen) + 1;
return 1;
}
/* 获取value节点占用的字节数，即len字段 + 1个字节free字段 + value字符串长度 + 空闲空间大小 */
static unsigned int zipmapRawValueLength(unsigned char *p) {
// 获取value字符串的长度
unsigned int l = zipmapDecodeLength(p);
unsigned int used;
// 获取保存value字符串长度所需要的字节数
used = zipmapEncodeLength(NULL,l);
// p[used]里面存储着空闲空间的大小
used += p[used] + 1 + l;
return used;
}
/* 按关键字key查找zipmap，如果totlen不为NULL，函数返回后存放zipmap占用的字节数 */
static unsigned char *zipmapLookupRaw(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned int *totlen) {
// zipmap中第1个字节是zmlen字段，zm+1跳过第1个字节
unsigned char *p = zm+1, *k = NULL;
unsigned int l,llen;
// 从前往后查找
while(*p != ZIPMAP_END) {
unsigned char free;
/* Match or skip the key */
// 确定key字符串的长度
l = zipmapDecodeLength(p);
// 确定保存key字符串长度所需要的字节数，也就是len字段所需要的字节数
llen = zipmapEncodeLength(NULL,l);
// 比较当前key与给定key是否匹配
if (key != NULL && k == NULL && l == klen && !memcmp(p+llen,key,l)) {
/* Only return when the user doesn't care
* for the total length of the zipmap. */
// 如果totlen为NULL，表示函数调用者不关心zipmap占用的字节数，此时直接返回p，否则先记录下p指针然后继续遍历
if (totlen != NULL) {
k = p;
} else {
return p;
}
}
// p加上llen和l，到了value节点处
p += llen+l;
/* Skip the value as well */
// 确定value字符串的长度
l = zipmapDecodeLength(p);
// 确定保存value字符串长度所需要的字节数，也就是len字段所需要的字节数
p += zipmapEncodeLength(NULL,l);
// 读出free字段的值（前面我们讲过：free只占用一个字节）
free = p[0];
// 跳到下一个key节点的
p += l+1+free; /* +1 to skip the free byte */
}
// 到这里遍历完整个zipmap，得到其占用的字节数
if (totlen != NULL) *totlen = (unsigned int)(p-zm)+1;
return k;
}
/* 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;
}
/* Return the total amount used by a value
* (encoded length + single byte free count + payload)
*
* 返回值所占用的字节总数
*
* 包括编码长度值所需的字节数，单个字节的 <free> 属性，以及值的长度本身
*
* T = O(1)
*/
static unsigned int zipmapRawValueLength(unsigned char *p) {
// 取出值的长度
unsigned int l = zipmapDecodeLength(p);
unsigned int used;
// 编码长度所需的字节数
used = zipmapEncodeLength(NULL,l);
// 计算总和
used += p[used] + 1 + l;
return used;
}
/* Search for a matching key, returning a pointer to the entry inside the
* zipmap. Returns NULL if the key is not found.
*
* If NULL is returned, and totlen is not NULL, it is set to the entire
* size of the zimap, so that the calling function will be able to
* reallocate the original zipmap to make room for more entries.
*
* If NULL is returned, and freeoff and freelen are not NULL, they are set
* to the offset of the first empty space that can hold '*freelen' bytes
* (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;
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;
}
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 */
}
}
if (totlen != NULL) *totlen = (unsigned int)(p-zm)+1;
return NULL;
}
void zipmapRepr(unsigned char *p) {
unsigned int l;
printf("{status %u}",*p++);
while(1) {
if (p[0] == ZIPMAP_END) {
printf("{end}");
break;
} else if (p[0] == ZIPMAP_EMPTY) {
l = zipmapDecodeLength(p+1);
printf("{%u empty block}", l);
p += l;
} else {
unsigned char e;
l = zipmapDecodeLength(p);
printf("{key %u}",l);
p += zipmapEncodeLength(NULL,l);
fwrite(p,l,1,stdout);
p += l;
l = zipmapDecodeLength(p);
printf("{value %u}",l);
p += zipmapEncodeLength(NULL,l);
e = *p++;
fwrite(p,l,1,stdout);
p += l+e;
if (e) {
printf("[");
while(e--) printf(".");
printf("]");
}
}
}
printf("\n");
}
/* Search a key and retrieve the pointer and len of the associated value.
* If the key is found the function returns 1, otherwise 0. */
int zipmapXGet(unsigned char **zm, unsigned char *key, unsigned int klen,
unsigned char **value, unsigned int *vlen, unsigned int timestamp) {
unsigned char *p;
if ((p = zipmapXLookupRaw(*zm,key,klen,NULL,NULL)) == NULL) return 0;
p += zipmapRawKeyLength(p);
unsigned int ts = *(unsigned int*)p;
p += sizeof(unsigned int);
*vlen = zipmapDecodeLength(p);
*value = p + ZIPMAP_LEN_BYTES(*vlen) + 1;
if (ts < timestamp) {
*vlen = 0;
*value = NULL;
return 0;
}
return 1;
}
/* Search a key and retrieve the pointer and len of the associated value.
* If the key is found the function returns 1, otherwise 0.
*
* 在 zipmap 中按 key 进行查找，
* 将值的指针保存到 *value 中，并将值的长度保存到 *vlen 中。
*
* 成功找到值时函数返回 1 ，没找到则返回 0 。
*
* T = O(N^2)
*/
int zipmapGet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char **value, unsigned int *vlen) {
unsigned char *p;
// 在 zipmap 中按 key 查找
// 没找到直接返回 0
// T = O(N^2)
if ((p = zipmapLookupRaw(zm,key,klen,NULL)) == NULL) return 0;
// 越过键，指向值
p += zipmapRawKeyLength(p);
// 取出值的长度
*vlen = zipmapDecodeLength(p);
// 将 *value 指向值， +1 为越过 <free> 属性
*value = p + ZIPMAP_LEN_BYTES(*vlen) + 1;
// 找到，返回 1
return 1;
}
/* 获取key节点占用的字节数，即len字段 + key字符串长度 */
static unsigned int zipmapRawKeyLength(unsigned char *p) {
// 获取key字符串的长度
unsigned int l = zipmapDecodeLength(p);
// 加上保存key字符串长度所需要的字节数
return zipmapEncodeLength(NULL,l) + l;
}
/* Return the total amount used by a key (encoded length + payload) */
static unsigned int zipmapRawKeyLength(unsigned char *p) {
unsigned int l = zipmapDecodeLength(p);
return zipmapEncodeLength(NULL,l) + l;
}
