{"id":201704,"date":"2025-05-10T08:10:24","date_gmt":"2025-05-10T00:10:24","guid":{"rendered":"https:\/\/server.hk\/cnblog\/201704\/"},"modified":"2025-05-10T08:10:24","modified_gmt":"2025-05-10T00:10:24","slug":"redis%e4%b8%adsds%e7%ae%80%e5%8d%95%e5%8a%a8%e6%80%81%e5%ad%97%e7%ac%a6%e4%b8%b2%e9%97%ae%e9%a2%98%e6%80%8e%e4%b9%88%e8%a7%a3%e5%86%b3","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/201704\/","title":{"rendered":"Redis\u4e2dSDS\u7b80\u5355\u52a8\u6001\u5b57\u7b26\u4e32\u95ee\u9898\u600e\u4e48\u89e3\u51b3"},"content":{"rendered":"

<\/b> <\/p>\n

Redis\u4e2dSDS\u7b80\u5355\u52a8\u6001\u5b57\u7b26\u4e32\u95ee\u9898\u600e\u4e48\u89e3\u51b3<\/h1>\n

<\/i>\u6536\u85cf<\/span> <\/p>\n

\u672c\u7bc7\u6587\u7ae0\u4e3b\u8981\u662f\u7ed3\u5408\u6211\u4e4b\u524d\u9762\u8bd5\u7684\u5404\u79cd\u7ecf\u5386\u548c\u5b9e\u6218\u5f00\u53d1\u4e2d\u9047\u5230\u7684\u95ee\u9898\u89e3\u51b3\u7ecf\u9a8c\u6574\u7406\u7684\uff0c\u5e0c\u671b\u8fd9\u7bc7\u300aRedis\u4e2dSDS\u7b80\u5355\u52a8\u6001\u5b57\u7b26\u4e32\u95ee\u9898\u600e\u4e48\u89e3\u51b3\u300b\u5bf9\u4f60\u6709\u5f88\u5927\u5e2e\u52a9\uff01\u6b22\u8fce\u6536\u85cf\uff0c\u5206\u4eab\u7ed9\u66f4\u591a\u7684\u9700\u8981\u7684\u670b\u53cb\u5b66\u4e60~<\/p>\n

\u4e00\u3001SDS\u7684\u7ed3\u6784 <\/h3>\n

c\u8bed\u8a00\u6ca1\u6709string\u7c7b\u578b\uff0c\u672c\u8d28\u662fchar[]\u6570\u7ec4\uff1b\u800c\u4e14c\u8bed\u8a00\u6570\u7ec4\u521b\u5efa\u65f6\u5fc5\u987b\u521d\u59cb\u5316\u5927\u5c0f\uff0c\u6307\u5b9a\u7c7b\u578b\u540e\u5c31\u4e0d\u80fd\u6539\u53d8\uff0c\u5e76\u4e14\u5b57\u7b26\u6570\u7ec4\u7684\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u603b\u662f\u7a7a\u5b57\u7b26 ‘\\0’ \u3002<\/p>\n

\u4ee5\u4e0b\u5c55\u793a\u4e86\u4e00\u4e2a\u503c\u4e3a “Redis” \u7684 C \u5b57\u7b26\u4e32\uff1a<\/p>\n

<\/p>\n

Redis\u6ca1\u6709\u76f4\u63a5\u4f7f\u7528C\u8bed\u8a00\u7684\u5b57\u7b26\u4e32\u65b9\u5f0f\uff0c\u800c\u662f\u6784\u5efa\u4e86\u4e00\u79cd\u7b80\u5355\u52a8\u6001\u5b57\u7b26\u4e32\uff08Simple dynamic string\uff0c SDS\uff09\u7684\u7c7b\u578b\uff0cRedis\u4e2d\u7684\u5b57\u7b26\u4e32\u5e95\u5c42\u90fd\u662f\u4f7f\u7528SDS\u7ed3\u6784\u8fdb\u884c\u5b58\u50a8\uff0c\u6bd4\u5982\u5305\u542b\u5b57\u7b26\u4e32\u7684\u952e\u503c\u5bf9\u5e95\u5c42\u90fd\u662f\u4f7f\u7528SDS\u7ed3\u6784\u5b9e\u73b0\u7684\u3002<\/p>\n

SDS\u7ed3\u6784\u5b9a\u4e49\u5728sds.h\u4e2d<\/p>\n

struct sdshdr{\n\n\n    int len;\/\/SDS\u4fdd\u5b58\u7684\u5b57\u7b26\u4e32\u957f\u5ea6\n\n\n    int free;\/\/buf\u6570\u7ec4\u4e2d\u672a\u4f7f\u7528\u5b57\u8282\u6570\u91cf\n\n\n    char buf[];\/\/\u5b57\u7b26\u6570\u7ec4\uff0c\u4fdd\u5b58\u5b57\u7b26\u4e32\n\n\n}<\/pre>\n
<\/p>\n
\u6700\u540e\u4e00\u4e2a\u5b57\u8282\u4fdd\u5b58\u4e86\u7a7a\u5b57\u7b26’\\0’\uff0c\u4fdd\u7559\u4e86C\u5b57\u7b26\u4e32\u7684\u89c4\u8303\uff0c\u4f7f\u5f97SDS\u7ed3\u6784\u7684\u5b57\u7b26\u4e32\uff0c\u53ef\u4ee5\u91cd\u7528\u4e00\u90e8\u5206C\u51fd\u6570\u5e93\u7684\u51fd\u6570\u3002<\/p>\n
\u4e8c\u3001\u4e3a\u4ec0\u4e48\u4e0d\u4f7f\u7528C\u5b57\u7b26\u4e32<\/h3>\n
\u4e3b\u8981\u662f\u56e0\u4e3aC\u5b57\u7b26\u4e32\u6709\u4ee5\u4e0b\u7f3a\u70b9\uff1a<\/p>\n
\u83b7\u53d6\u5b57\u7b26\u4e32\u957f\u5ea6\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(N)\uff1aC\u5b57\u7b26\u4e32\u83b7\u53d6\u957f\u5ea6\u9700\u904d\u5386\u6574\u4e2a\u5b57\u7b26\u4e32\uff0c\u9047\u5230’\\0’\u7a7a\u5b57\u7b26\u4e3a\u6b62\u3002\u5982\u679c\u672a\u5206\u914d\u8db3\u591f\u7684\u5185\u5b58\uff0c\u5728\u8fdb\u884c\u5b57\u7b26\u4e32\u8ffd\u52a0\u64cd\u4f5c\u65f6\u53ef\u80fd\u4f1a\u5bfc\u81f4\u7f13\u51b2\u533a\u6ea2\u51fa\u3002 \u5185\u5b58\u91cd\u5206\u914d\uff1a\u6bcf\u6b21\u589e\u957f\u6216\u8005\u622a\u77ed\u5b57\u7b26\u4e32\uff0c\u7a0b\u5e8f\u90fd\u8981\u5bf9\u4fdd\u5b58C\u5b57\u7b26\u4e32\u7684\u6570\u7ec4\u8fdb\u884c\u5185\u5b58\u91cd\u5206\u914d\u64cd\u4f5c\uff0c\u800c\u5185\u5b58\u91cd\u5206\u914d\u6d89\u53ca\u590d\u6742\u7684\u7b97\u6cd5\uff0c\u5e76\u53ef\u80fd\u9700\u8981\u6267\u884c\u7cfb\u7edf\u8c03\u7528\uff0c\u6240\u4ee5\u5b83\u901a\u5e38\u6bd4\u8f83\u8017\u65f6\u3002\u5982\u679cC\u5b57\u7b26\u4e32\u4e2d\u95f4\u4fdd\u5b58\u6709\u7a7a\u683c\uff0c\u7a0b\u5e8f\u5728\u904d\u5386\u65f6\u4f1a\u9519\u8bef\u5730\u5c06\u5176\u8ba4\u4e3a\u662f\u5b57\u7b26\u4e32\u7684\u7ed3\u5c3e\u3002C\u5b57\u7b26\u4e32\u7531\u4e8e\u8fd9\u4e00\u9650\u5236\uff0c\u53ea\u80fd\u7528\u4e8e\u5b58\u50a8\u6587\u672c\u6570\u636e\uff0c\u800c\u4e0d\u80fd\u5b58\u50a8\u4e8c\u8fdb\u5236\u6570\u636e\uff0c\u4f8b\u5982\u56fe\u7247\u3001\u97f3\u89c6\u9891\u3001\u538b\u7f29\u6587\u4ef6\u7b49\u3002<\/p>\n
\u4e09\u3001\u600e\u6837\u89e3\u51b3C\u5b57\u7b26\u4e32\u95ee\u9898 <\/h3>\n
 <\/p>\n
1\u3001SDS\u901a\u8fc7len\u5c5e\u6027\u8bb0\u5f55\u4e86SDS\u957f\u5ea6\uff0c\u6240\u4ee5\u83b7\u53d6\u957f\u5ea6\u7684\u65f6\u95f4\u590d\u6742\u5ea6\u4e3aO(1)\uff0c\u5373strlen\u547d\u4ee4\u7684\u65f6\u95f4\u590d\u6742\u5ea6\u662fO(1)\u3002<\/p>\n
2\u3001SDS\u7a7a\u95f4\u5206\u914d\u7b56\u7565\u907f\u514d\u4e86\u7f13\u51b2\u533a\u6ea2\u51fa\uff1a\u5f53\u5bf9SDS\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u4f1a\u5148\u68c0\u67e5SDS\u7a7a\u95f4\u662f\u5426\u6ee1\u8db3\u4fee\u6539\uff0c\u4e0d\u6ee1\u8db3\u4f1a\u81ea\u52a8\u6269\u5c55\u5230\u6240\u9700\u5927\u5c0f\uff0c\u7136\u540e\u624d\u6267\u884c\u4fee\u6539\u3002<\/p>\n
3\u3001\u8f83\u5c11\u4fee\u6539\u5b57\u7b26\u4e32\u65f6\u5185\u5b58\u91cd\u5206\u914d\u6b21\u6570\uff1aSDS\u4e2d\u7684free\u8bb0\u5f55buf\u5b57\u8282\u6570\u7ec4\u4e2d\u672a\u4f7f\u7528\u7684\u5b57\u8282\u3002<\/p>\n
redis\u901a\u8fc7free\u5c5e\u6027\u5b9e\u73b0\u7a7a\u95f4\u9884\u5206\u914d\u3001\u60f0\u6027\u7a7a\u95f4\u91ca\u653e\u4e24\u79cd\u4f18\u5316\u7b56\u7565\u3002<\/p>\n
\u7a7a\u95f4\u9884\u5206\u914d\uff1a\u5f53\u5bf9SDS\u8fdb\u884c\u589e\u957f\u64cd\u4f5c\u65f6\uff0c\u7a0b\u5e8f\u4e0d\u4ec5\u4f1a\u5206\u914d\u4fee\u6539\u6240\u5fc5\u987b\u5f97\u7a7a\u95f4\uff0c\u8fd8\u4f1a\u4e3aSDS\u5206\u914d\u989d\u5916\u7684\u672a\u4f7f\u7528\u7a7a\u95f4\u3002\u5185\u5b58\u91cd\u5206\u914d\u6b21\u6570\u5f97\u4ee5\u51cf\u5c11\uff0c\u56e0\u4e3a\u4f7f\u7528\u4e86\u9884\u5206\u914d\u7b56\u7565\u6765\u907f\u514d\u8fde\u7eed\u6267\u884c\u5b57\u7b26\u4e32\u589e\u957f\u64cd\u4f5c\u3002 \u60f0\u6027\u7a7a\u95f4\u91ca\u653e\uff1a\u5f53\u5bf9SDS\u8fdb\u884c\u622a\u77ed\u64cd\u4f5c\u65f6\uff0c\u7a0b\u5e8f\u5e76\u4e0d\u4f1a\u7acb\u5373\u56de\u6536\u7f29\u77ed\u540e\u591a\u51fa\u6765\u7684\u5b57\u8282\u6240\u5360\u7528\u7684\u5185\u5b58\uff0c\u800c\u662f\u4f7f\u7528free\u5c5e\u6027\u8bb0\u5f55\u591a\u51fa\u6765\u7684\u5b57\u8282\u6570\uff0c\u4ee5\u4f9b\u5c06\u6765\u4f7f\u7528\u3002\u5c06\u6765\u82e5\u9700\u8981\u6269\u5c55\u8fd9\u4e2aSDS\uff0c\u672a\u4f7f\u7528\u7684\u7a7a\u95f4\u53ef\u80fd\u4f1a\u88ab\u5229\u7528\uff0c\u5e76\u4e14\u6269\u5c55\u64cd\u4f5c\u5e76\u4e0d\u4fdd\u8bc1\u4f1a\u8fdb\u884c\u5185\u5b58\u91cd\u5206\u914d\u3002<\/p>\n
SDS\u7ed3\u6784\u4e2d\u7684buf\u5b57\u8282\u6570\u7ec4\uff0c\u662f\u4e8c\u8fdb\u5236\u5b89\u5168\u7684\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u4fdd\u5b58\u5b57\u7b26\uff0c\u4e5f\u53ef\u4ee5\u4fdd\u5b58\u4e8c\u8fdb\u5236\u6570\u636e\u3002<\/p>\n
SDS\u4fdd\u7559\u4e86C\u5b57\u7b26\u4e32\u7684\u60ef\u4f8b\uff0c\u5c06\u6570\u636e\u7684\u672b\u5c3e\u8bbe\u7f6e\u4e3a\u7a7a\u5b57\u7b26’\\0’\uff0cSDS\u4e2d\u4e4b\u6240\u4ee5\u4fdd\u7559\u8fd9\u4e00\u89c4\u8303\u662f\u53ef\u4ee5\u91cd\u7528C\u5b57\u7b26\u4e32\u51fd\u6570\u5e93\u7684\u4e00\u90e8\u5206\u51fd\u6570\uff0c\u4f8b\u5982\u8ffd\u52a0\u5b57\u7b26\u4e32\u3002<\/p>\n
\u56db\u3001\u5bf9\u5b57\u7b26\u4e32\u7684\u8fdb\u4e00\u6b65\u4f18\u5316<\/h3>\n
Redis string\u7684\u4e09\u79cd\u7f16\u7801\uff1a<\/p>\n
int \u5b58\u50a88\u4e2a\u5b57\u8282\u7684\u957f\u6574\u578b(long\uff0c2^63-1 ) embstr, embstr\u683c\u5f0f\u7684SDS (Simple Dynamic String) raw, raw\u683c\u5f0f\u7684SDS\uff0c\u5b58\u50a8\u5927\u4e8e44\u4e2a\u5b57\u8282\u7684\u957f\u5b57\u7b26\u4e32<\/p>\n
int\u7c7b\u578b\u5c31\u662f\u6307\u7684\u662f\u6570\u5b57\uff0c\u90a3\u4e48raw\u3001embstr\u90fd\u4ee3\u8868\u7684\u662f\u5b57\u7b26\u4e32\u6709\u4ec0\u4e48\u5f02\u540c\u5417\uff0c\u4e0b\u9762\u6211\u4eec\u5206\u6790\u4e0b\u3002<\/p>\n
<\/p>\n
\u56fe\u4e2d\u5c55\u793a\u4e86\u4e24\u8005\u7684\u533a\u522b\uff0c\u53ef\u4ee5\u770b\u5230embstr\u5c06redisObject\u548cSDS\u4fdd\u5b58\u5728\u8fde\u7eed\u768464\u5b57\u8282\u7a7a\u95f4\u5185\uff0c\u8fd9\u6837\u53ef\u4ee5\u53ea\u9700\u8981\u4e00\u6b21\u5185\u5b58\u5206\u914d\uff0c\u800c\u5bf9\u4e8eraw\u6765\u8bf4\uff0cSDS\u548credisObject\u5206\u79bb\uff0c\u9700\u8981\u4e24\u6b21\u5185\u5b58\u5206\u914d\uff0c\u800c\u4e14\u5360\u7528\u66f4\u591a\u7684\u5185\u5b58\u7a7a\u95f4\u3002<\/p>\n
<\/p>\n
\u53ef\u4ee5\u770b\u5230embstr\u57283.2+\u4e2d\u4f7f\u7528\u4e86\u53ebsdshdr8\u7684\u7ed3\u6784\uff0c\u5728\u8be5\u7ed3\u6784\u4e0b\uff0c\u5143\u6570\u636e\u53ea\u9700\u89813\u4e2a\u5b57\u8282\uff0c\u800cRedis\u9700\u89818\u4e2a\u5b57\u8282\uff0c\u6240\u4ee5\u603b\u517164\u4e2a\u5b57\u8282\uff0c\u51cf\u53bbredisObject(16\u5b57\u8282)\uff0c\u518d\u51cf\u53bbSDS\u7684\u539f\u4fe1\u606f\uff0c\u6700\u540e\u7684\u5b9e\u9645\u5185\u5bb9\u5c31\u53d8\u6210\u4e8644\u5b57\u8282\u548c39\u5b57\u8282\u3002<\/p>\n
<\/p>\n
\u5f53\u5b57\u7b26\u4e32\u5c0f\u4e8e\u7b49\u4e8e 44 \u5b57\u8282\u65f6\uff0cRedis \u5c31\u4f7f\u7528\u4e86\u5d4c\u5165\u5f0f\u5b57\u7b26\u4e32\u7684\u521b\u5efa\u65b9\u6cd5\uff0c\u4ee5\u6b64\u51cf\u5c11\u5185\u5b58\u5206\u914d\u548c\u5185\u5b58\u788e\u7247\u3002<\/p>\n
\u4e0b\u9762\u8fd9\u5f20\u56fe\u5c55\u793a\u4e86 createEmbeddedStringObject \u521b\u5efa\u5d4c\u5165\u5f0f\u5b57\u7b26\u4e32\u7684\u8fc7\u7a0b\uff1a<\/p>\n
 <\/p>\n
\u603b\u4e4b\uff0c\u53ea\u8981\u8bb0\u4f4f\uff0cRedis \u4f1a\u901a\u8fc7\u8bbe\u8ba1\u5b9e\u73b0\u4e00\u5757\u8fde\u7eed\u7684\u5185\u5b58\u7a7a\u95f4\uff0c\u628a redisObject \u7ed3\u6784\u4f53\u548c SDS \u7ed3\u6784\u4f53\u7d27\u51d1\u5730\u653e\u7f6e\u5728\u4e00\u8d77\u3002<\/p>\n
\u8fd9\u6837\u4e00\u6765\uff0c\u5bf9\u4e8e\u4e0d\u8d85\u8fc7 44 \u5b57\u8282\u7684\u5b57\u7b26\u4e32\u6765\u8bf4\uff0c\u5c31\u53ef\u4ee5\u907f\u514d\u5185\u5b58\u788e\u7247\u548c\u4e24\u6b21\u5185\u5b58\u5206\u914d\u7684\u5f00\u9500\u4e86\u3002<\/p>\n
SDS\u662fRedis\u4e2d\u4e00\u79cd\u9ad8\u6548\u7684\u5b57\u7b26\u4e32\u5b9e\u73b0\u65b9\u5f0f\uff0c\u5b83\u5177\u6709\u81ea\u52a8\u6269\u5bb9\u3001\u4e8c\u8fdb\u5236\u5b89\u5168\u3001O(1)\u957f\u5ea6\u83b7\u53d6\u548c\u4fee\u6539\u7b49\u4f18\u70b9\u3002\u5728\u5b9e\u9645\u7684\u5e94\u7528\u4e2d\uff0cSDS\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5b9e\u73b0\u9ad8\u6548\u7684\u5b57\u7b26\u4e32\u64cd\u4f5c\uff0c\u540c\u65f6\u4e5f\u53ef\u4ee5\u907f\u514d\u4e00\u4e9b\u5e38\u89c1\u7684\u5b57\u7b26\u4e32\u64cd\u4f5c\u95ee\u9898\uff0c\u6bd4\u5982\u7f13\u51b2\u533a\u6ea2\u51fa\u7b49\u3002\u901a\u8fc7\u6df1\u5165\u4e86\u89e3SDS\u7684\u5185\u90e8\u7ed3\u6784\u548c\u5b9e\u73b0\u539f\u7406\uff0c\u6211\u4eec\u53ef\u4ee5\u66f4\u597d\u5730\u7406\u89e3Redis\u7684\u5e95\u5c42\u673a\u5236\uff0c\u8fdb\u4e00\u6b65\u63d0\u5347\u6211\u4eec\u7684Redis\u5e94\u7528\u80fd\u529b\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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