text: /*
   * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   *   * Redistributions of source code must retain the above copyright notice,
   *     this list of conditions and the following disclaimer.
   *   * Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   *   * Neither the name of Redis nor the names of its contributors may be used
   *     to endorse or promote products derived from this software without
   *     specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
   * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include "server.h"
  #include <math.h> /* isnan(), isinf() */
  
  /*-----------------------------------------------------------------------------
   * String Commands
   *----------------------------------------------------------------------------*/
  
  static int checkStringLength(client *c, long long size) {
      if (size > 512*1024*1024) {
          addReplyError(c,"string exceeds maximum allowed size (512MB)");
          return C_ERR;
      }
      return C_OK;
  }
  
  /* The setGenericCommand() function implements the SET operation with different
   * options and variants. This function is called in order to implement the
   * following commands: SET, SETEX, PSETEX, SETNX.
   *
   * 'flags' changes the behavior of the command (NX or XX, see belove).
   *
   * 'expire' represents an expire to set in form of a Redis object as passed
   * by the user. It is interpreted according to the specified 'unit'.
   *
   * 'ok_reply' and 'abort_reply' is what the function will reply to the client
   * if the operation is performed, or when it is not because of NX or
   * XX flags.
   *
   * If ok_reply is NULL "+OK" is used.
   * If abort_reply is NULL, "$-1" is used. */
  
  #define OBJ_SET_NO_FLAGS 0
  #define OBJ_SET_NX (1<<0)     /* Set if key not exists. */
  #define OBJ_SET_XX (1<<1)     /* Set if key exists. */
  #define OBJ_SET_EX (1<<2)     /* Set if time in seconds is given */
  #define OBJ_SET_PX (1<<3)     /* Set if time in ms in given */
  
  void setGenericCommand(client *c, int flags, robj *key, robj *val, robj *expire, int unit, robj *ok_reply, robj *abort_reply) {
      long long milliseconds = 0; /* initialized to avoid any harmness warning */
  
      if (expire) {//是否有设置expire过期时间
          if (getLongLongFromObjectOrReply(c, expire, &milliseconds, NULL) != C_OK)//expire对象类型转换成long long类型是否成功 必须保证跟在ex或px后面的参数是整数
              return;
          if (milliseconds <= 0) { //必须是正整数
              addReplyErrorFormat(c,"invalid expire time in %s",c->cmd->name);
              return;
          }
          if (unit == UNIT_SECONDS) milliseconds *= 1000;//如果是ex 是秒类型 自乘1000
      }
  
      if ((flags & OBJ_SET_NX && lookupKeyWrite(c->db,key) != NULL) ||    //setnx 是否存在 存在返回
          (flags & OBJ_SET_XX && lookupKeyWrite(c->db,key) == NULL))      //setxx 是否存在 不存在返回
      {
          addReply(c, abort_reply ? abort_reply : shared.nullbulk);
          return;
      }
      setKey(c->db,key,val);//往db插入元素
      server.dirty++;
      if (expire) setExpire(c,c->db,key,mstime()+milliseconds);//是否有设置expire过期时间 有的话添加过期时间
      notifyKeyspaceEvent(NOTIFY_STRING,"set",key,c->db->id);//如果设置了set监听的话 发送此次set消息
      if (expire) notifyKeyspaceEvent(NOTIFY_GENERIC,
          "expire",key,c->db->id);                            //如果设置了expire监听的话 发送此次expire消息
      addReply(c, ok_reply ? ok_reply : shared.ok);
  }
  
  /* SET key value [NX] [XX] [EX <seconds>] [PX <milliseconds>] */
  void setCommand(client *c) {
      int j;
      robj *expire = NULL;
      int unit = UNIT_SECONDS;
      int flags = OBJ_SET_NO_FLAGS;
  
      for (j = 3; j < c->argc; j++) {//处理长度大于3的参数
          char *a = c->argv[j]->ptr;
          robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];
  
          if ((a[0] == 'n' || a[0] == 'N') &&
              (a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
              !(flags & OBJ_SET_XX))
          {
              flags |= OBJ_SET_NX;
          } else if ((a[0] == 'x' || a[0] == 'X') &&
                     (a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
                     !(flags & OBJ_SET_NX))
          {
              flags |= OBJ_SET_XX;
          } else if ((a[0] == 'e' || a[0] == 'E') &&
                     (a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
                     !(flags & OBJ_SET_PX) && next)
          {
              flags |= OBJ_SET_EX;
              unit = UNIT_SECONDS;
              expire = next;
              j++;
          } else if ((a[0] == 'p' || a[0] == 'P') &&
                     (a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
                     !(flags & OBJ_SET_EX) && next)
          {
              flags |= OBJ_SET_PX;
              unit = UNIT_MILLISECONDS;
              expire = next;
              j++;
          } else {
              addReply(c,shared.syntaxerr);
              return;
          }
      }
  
      c->argv[2] = tryObjectEncoding(c->argv[2]);
      setGenericCommand(c,flags,c->argv[1],c->argv[2],expire,unit,NULL,NULL);
  }
  
  void setnxCommand(client *c) {
      c->argv[2] = tryObjectEncoding(c->argv[2]);
      setGenericCommand(c,OBJ_SET_NX,c->argv[1],c->argv[2],NULL,0,shared.cone,shared.czero);
  }
  
  void setexCommand(client *c) {
      c->argv[3] = tryObjectEncoding(c->argv[3]);
      setGenericCommand(c,OBJ_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_SECONDS,NULL,NULL);
  }
  
  void psetexCommand(client *c) {
      c->argv[3] = tryObjectEncoding(c->argv[3]);
      setGenericCommand(c,OBJ_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_MILLISECONDS,NULL,NULL);
  }
  
  int getGenericCommand(client *c) {
      robj *o;
  
      if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL)
          return C_OK;
  
      if (o->type != OBJ_STRING) {
          addReply(c,shared.wrongtypeerr);
          return C_ERR;
      } else {
          addReplyBulk(c,o);
          return C_OK;
      }
  }
  
  void getCommand(client *c) {
      getGenericCommand(c);
  }
  
  void getsetCommand(client *c) {
      if (getGenericCommand(c) == C_ERR) return;
      c->argv[2] = tryObjectEncoding(c->argv[2]);
      setKey(c->db,c->argv[1],c->argv[2]);
      notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[1],c->db->id);
      server.dirty++;
  }
  
  void setrangeCommand(client *c) {
      robj *o;
      long offset;
      sds value = c->argv[3]->ptr;
  
      if (getLongFromObjectOrReply(c,c->argv[2],&offset,NULL) != C_OK)
          return;
  
      if (offset < 0) {
          addReplyError(c,"offset is out of range");
          return;
      }
  
      o = lookupKeyWrite(c->db,c->argv[1]);
      if (o == NULL) {
          /* Return 0 when setting nothing on a non-existing string */
          if (sdslen(value) == 0) {
              addReply(c,shared.czero);
              return;
          }
  
          /* Return when the resulting string exceeds allowed size */
          if (checkStringLength(c,offset+sdslen(value)) != C_OK)
              return;
  
          o = createObject(OBJ_STRING,sdsnewlen(NULL, offset+sdslen(value)));
          dbAdd(c->db,c->argv[1],o);
      } else {
          size_t olen;
  
          /* Key exists, check type */
          if (checkType(c,o,OBJ_STRING))
              return;
  
          /* Return existing string length when setting nothing */
          olen = stringObjectLen(o);
          if (sdslen(value) == 0) {
              addReplyLongLong(c,olen);
              return;
          }
  
          /* Return when the resulting string exceeds allowed size */
          if (checkStringLength(c,offset+sdslen(value)) != C_OK)
              return;
  
          /* Create a copy when the object is shared or encoded. */
          o = dbUnshareStringValue(c->db,c->argv[1],o);
      }
  
      if (sdslen(value) > 0) {
          o->ptr = sdsgrowzero(o->ptr,offset+sdslen(value));
          memcpy((char*)o->ptr+offset,value,sdslen(value));
          signalModifiedKey(c->db,c->argv[1]);
          notifyKeyspaceEvent(NOTIFY_STRING,
              "setrange",c->argv[1],c->db->id);
          server.dirty++;
      }
      addReplyLongLong(c,sdslen(o->ptr));
  }
  
  void getrangeCommand(client *c) {
      robj *o;
      long long start, end;
      char *str, llbuf[32];
      size_t strlen;
  
      if (getLongLongFromObjectOrReply(c,c->argv[2],&start,NULL) != C_OK)
          return;
      if (getLongLongFromObjectOrReply(c,c->argv[3],&end,NULL) != C_OK)
          return;
      if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptybulk)) == NULL ||
          checkType(c,o,OBJ_STRING)) return;
  
      if (o->encoding == OBJ_ENCODING_INT) {
          str = llbuf;
          strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
      } else {
          str = o->ptr;
          strlen = sdslen(str);
      }
  
      /* Convert negative indexes */
      if (start < 0 && end < 0 && start > end) {
          addReply(c,shared.emptybulk);
          return;
      }
      if (start < 0) start = strlen+start;
      if (end < 0) end = strlen+end;
      if (start < 0) start = 0;
      if (end < 0) end = 0;
      if ((unsigned long long)end >= strlen) end = strlen-1;
  
      /* Precondition: end >= 0 && end < strlen, so the only condition where
       * nothing can be returned is: start > end. */
      if (start > end || strlen == 0) {
          addReply(c,shared.emptybulk);
      } else {
          addReplyBulkCBuffer(c,(char*)str+start,end-start+1);
      }
  }
  
  void mgetCommand(client *c) {
      int j;
  
      addReplyMultiBulkLen(c,c->argc-1);
      for (j = 1; j < c->argc; j++) {
          robj *o = lookupKeyRead(c->db,c->argv[j]);
          if (o == NULL) {
              addReply(c,shared.nullbulk);
          } else {
              if (o->type != OBJ_STRING) {
                  addReply(c,shared.nullbulk);
              } else {
                  addReplyBulk(c,o);
              }
          }
      }
  }
  
  void msetGenericCommand(client *c, int nx) {
      int j, busykeys = 0;
  
      if ((c->argc % 2) == 0) {
          addReplyError(c,"wrong number of arguments for MSET");
          return;
      }
      /* Handle the NX flag. The MSETNX semantic is to return zero and don't
       * set nothing at all if at least one already key exists. */
      if (nx) {
          for (j = 1; j < c->argc; j += 2) {
              if (lookupKeyWrite(c->db,c->argv[j]) != NULL) {
                  busykeys++;
              }
          }
          if (busykeys) {
              addReply(c, shared.czero);
              return;
          }
      }
  
      for (j = 1; j < c->argc; j += 2) {
          c->argv[j+1] = tryObjectEncoding(c->argv[j+1]);
          setKey(c->db,c->argv[j],c->argv[j+1]);
          notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[j],c->db->id);
      }
      server.dirty += (c->argc-1)/2;
      addReply(c, nx ? shared.cone : shared.ok);
  }
  
  void msetCommand(client *c) {
      msetGenericCommand(c,0);
  }
  
  void msetnxCommand(client *c) {
      msetGenericCommand(c,1);
  }
  
  void incrDecrCommand(client *c, long long incr) {
      long long value, oldvalue;
      robj *o, *new;
  
      o = lookupKeyWrite(c->db,c->argv[1]);//寻找key对应的val
      if (o != NULL && checkType(c,o,OBJ_STRING)) return;
      if (getLongLongFromObjectOrReply(c,o,&value,NULL) != C_OK) return;//如果val转long不成功返回 自增必须是整数
  
      oldvalue = value;
      if ((incr < 0 && oldvalue < 0 && incr < (LLONG_MIN-oldvalue)) ||
          (incr > 0 && oldvalue > 0 && incr > (LLONG_MAX-oldvalue))) {    //是否越界long范围
          addReplyError(c,"increment or decrement would overflow");
          return;
      }
      value += incr; //累加
  
      if (o && o->refcount == 1 && o->encoding == OBJ_ENCODING_INT &&
          (value < 0 || value >= OBJ_SHARED_INTEGERS) &&
          value >= LONG_MIN && value <= LONG_MAX)//不在共享范围内 不是共享对象 在long范围内
      {
          new = o;
          o->ptr = (void*)((long)value);//long类型情况下 指针8字节 long8字节 指针等于值直接存储
      } else {
          new = createStringObjectFromLongLongForValue(value);//新建个long robj对象插入或覆盖
          if (o) {
              dbOverwrite(c->db,c->argv[1],new);
          } else {
              dbAdd(c->db,c->argv[1],new);
          }
      }
      signalModifiedKey(c->db,c->argv[1]);
      notifyKeyspaceEvent(NOTIFY_STRING,"incrby",c->argv[1],c->db->id);
      server.dirty++;
      addReply(c,shared.colon);
      addReply(c,new);
      addReply(c,shared.crlf);
  }
  
  void incrCommand(client *c) {
      incrDecrCommand(c,1);//自增加1
  }
  
  void decrCommand(client *c) {
      incrDecrCommand(c,-1);
  }
  
  void incrbyCommand(client *c) {
      long long incr;
  
      if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
      incrDecrCommand(c,incr);//加一定数量
  }
  
  void decrbyCommand(client *c) {
      long long incr;
  
      if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
      incrDecrCommand(c,-incr);
  }
  
  void incrbyfloatCommand(client *c) {
      long double incr, value;
      robj *o, *new, *aux;
  
      o = lookupKeyWrite(c->db,c->argv[1]);
      if (o != NULL && checkType(c,o,OBJ_STRING)) return;
      if (getLongDoubleFromObjectOrReply(c,o,&value,NULL) != C_OK ||
          getLongDoubleFromObjectOrReply(c,c->argv[2],&incr,NULL) != C_OK)
          return;
  
      value += incr;
      if (isnan(value) || isinf(value)) {
          addReplyError(c,"increment would produce NaN or Infinity");
          return;
      }
      new = createStringObjectFromLongDouble(value,1);
      if (o)
          dbOverwrite(c->db,c->argv[1],new);
      else
          dbAdd(c->db,c->argv[1],new);
      signalModifiedKey(c->db,c->argv[1]);
      notifyKeyspaceEvent(NOTIFY_STRING,"incrbyfloat",c->argv[1],c->db->id);
      server.dirty++;
      addReplyBulk(c,new);
  
      /* Always replicate INCRBYFLOAT as a SET command with the final value
       * in order to make sure that differences in float precision or formatting
       * will not create differences in replicas or after an AOF restart. */
      aux = createStringObject("SET",3);
      rewriteClientCommandArgument(c,0,aux);
      decrRefCount(aux);
      rewriteClientCommandArgument(c,2,new);
  }
  
  void appendCommand(client *c) {
      size_t totlen;
      robj *o, *append;
  
      o = lookupKeyWrite(c->db,c->argv[1]);
      if (o == NULL) {
          /* Create the key */
          c->argv[2] = tryObjectEncoding(c->argv[2]);
          dbAdd(c->db,c->argv[1],c->argv[2]);
          incrRefCount(c->argv[2]);
          totlen = stringObjectLen(c->argv[2]);
      } else {
          /* Key exists, check type */
          if (checkType(c,o,OBJ_STRING))
              return;
  
          /* "append" is an argument, so always an sds */
          append = c->argv[2];
          totlen = stringObjectLen(o)+sdslen(append->ptr);
          if (checkStringLength(c,totlen) != C_OK)
              return;
  
          /* Append the value */
          o = dbUnshareStringValue(c->db,c->argv[1],o);
          o->ptr = sdscatlen(o->ptr,append->ptr,sdslen(append->ptr));
          totlen = sdslen(o->ptr);
      }
      signalModifiedKey(c->db,c->argv[1]);
      notifyKeyspaceEvent(NOTIFY_STRING,"append",c->argv[1],c->db->id);
      server.dirty++;
      addReplyLongLong(c,totlen);
  }
  
  void strlenCommand(client *c) {
      robj *o;
      if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
          checkType(c,o,OBJ_STRING)) return;
      addReplyLongLong(c,stringObjectLen(o));
  }
  