第 22 章： 二进制位数组 ============================= 位数组的表示 ----------------- .. graphviz:: digraph { label = "\n 图 22-1 SDS 表示的位数组"; rankdir = LR; // node [shape = record]; redisObject [label = " redisObject | ... | type \n REDIS_STRING | ... | ptr "]; sds [label = " sdshdr | free \n 0 | len \n 1 | buf "]; buf [label = " { buf[0] | buf[1] （空字符） } "]; // redisObject:ptr -> sds:head; sds:buf -> buf; } .. graphviz:: digraph { label = "\n 图 22-2 一字节长的位数组的 SDS 表示"; rankdir = LR; // node [shape = record]; redisObject [label = " redisObject | ... | type \n REDIS_STRING | ... | ptr "]; sds [label = " sdshdr | free \n 0 | len \n 1 | buf "]; buf [label = " { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] （空字符） } "]; // redisObject:ptr -> sds:head; sds:buf -> buf; } .. graphviz:: digraph { label = "\n 图 22-3 三字节长的位数组的 SDS 表示"; rankdir = LR; // node [shape = record]; redisObject [label = " redisObject | ... | type \n REDIS_STRING | ... | ptr "]; sds [label = " sdshdr | free \n 0 | len \n 3 | buf "]; buf [label = " { buf[0] | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 1 } | { buf[1] | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 } | { buf[2] | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 } | { buf[3] （空字符） } "]; // redisObject:ptr -> sds:head; sds:buf -> buf; } GETBIT 命令的实现 --------------------- .. graphviz:: digraph { label = "\n 图 22-4 查找并返回 offset 为 3 的二进制位的过程"; // rankdir = LR; point_to_buf0 [label = "1) 定位到 buf[0] 字节", shape = plaintext]; point_to_idx3 [label = "2) 返回第 4 个二进制位的值", shape = plaintext]; buf [label = " { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] （空字符） } ", shape = record]; // edge [style = dashed]; point_to_buf0 -> buf:buf0; point_to_idx3 -> buf:idx3; } .. graphviz:: digraph { label = "\n 图 22-5 查找并返回 offset 为 10 的二进制位的过程"; rankdir = LR; // node [shape = record]; buf [label = " { buf[0] | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 1 } | { buf[1] | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 } | { buf[2] | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 } | { buf[3] | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 } "]; node [shape = plaintext]; point_to_buf [label = "1） 定位到 buf[1] 字节"]; point_to_bit [label = "2） 返回第 3 个二进制位的值"]; // edge [style = dashed]; point_to_buf -> buf:buf1; point_to_bit -> buf:bit; } SETBIT 命令的实现 ---------------------- 无须扩展的 ``SETBIT`` 命令。 .. graphviz:: digraph { label = "\n 图 22-6 SETBIT 命令的执行过程"; // node [shape = plaintext]; point_to_byte [label = "1） 定位到 buf[0] 字节"]; point_to_bit [label = "2）定位到 buf[0] 字节的第 2 个二进制位 \n 将位现在的值 0 保存到 oldvalue 变量 \n 然后将位的值设置为 1 "]; buf [label = " { { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] （空字符） } } ", shape = record]; // edge [style = dashed]; point_to_byte -> buf:byte; point_to_bit -> buf:bit; } 需要进行扩展的 ``SETBIT`` 命令。 .. graphviz:: digraph { label = "\n 图 22-8 扩展空间之后的位数组"; rankdir = LR; // node [shape = record]; redisObject [label = " redisObject | ... | type \n REDIS_STRING | ... | ptr "]; sds [label = " sdshdr | free \n 2 | len \n 2 | buf "]; buf [label = " { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 } | { buf[2] （空字符） } | { buf[3] （未使用） } | { buf[4] （未使用） } "]; // redisObject:ptr -> sds:head; sds:buf -> buf; } .. graphviz:: digraph { label = "\n 图 22-9 SETBIT 命令的执行过程"; // node [shape = plaintext]; point_to_byte [label = "1）定位到 buf[1] 字节"]; point_yo_bit [label = "2）定位到 buf[1] 字节的第 5 个二进制位 \n 首先将位现在的值 0 保存到 oldvalue 变量 \n 然后将位的值设置为 1 "]; node [shape = record]; buf [label = " { { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 } | { buf[2] （空字符） } | { buf[3] （未使用） } | { buf[4] （未使用） } } "]; // edge [style = dashed]; point_to_byte -> buf:byte; point_yo_bit -> buf:bit; } .. graphviz:: digraph { label = "\n 图 22-10 执行 SETBIT 命令之后的位数组"; // node [shape = record]; buf [label = " { { buf[0] | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 } | { buf[1] | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 } | { buf[2] （空字符） } | { buf[3] （未使用） } | { buf[4] （未使用） } } "]; }