cJSON学习

1、JSON简介

JSON(JavaScript Object Notation, JS 对象标记) 是一种轻量级的数据交换格式。它采用完全独立于编程语言的文本格式来存储和表示数据。简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。 易于人阅读和编写，同时也易于机器解析和生成，并有效地提升网络传输效率。

2、cJSON解析器下载

https://sourceforge.net/projects/cjson/

3、cJSON分析

3.1、cJSON简介

cJSON是用C语言写的用于解析json字符串和生成json字符串的库，他只有一个头文件和源文件。使用它只需要在自己的项目中加入cJSON.c和cJSON.h文件

3.2、cJSON分析

3.2.1. cJSON的机构体

typedef struct cJSON {
    //后继和前驱指针
    struct cJSON *next,*prev;   /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */
    //子对象指针
    struct cJSON *child;        /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */
    //cJSON的类型
    int type;                   /* The type of the item, as above. */
    //item的值【string、int、double】
    char *valuestring;          /* The item's string, if type==cJSON_String */
    int valueint;               /* The item's number, if type==cJSON_Number */
    double valuedouble;         /* The item's number, if type==cJSON_Number */
    //item的名字
    char *string;               /* The item's name string, if this item is the child of, or is in the list of subitems of an object. */
} cJSON;

3.2.2 cJSON的类型

#define cJSON_False 0
#define cJSON_True 1
#define cJSON_NULL 2
#define cJSON_Number 3
#define cJSON_String 4
#define cJSON_Array 5
#define cJSON_Object 6

#define cJSON_IsReference 256
#define cJSON_StringIsConst 512

3.2.3 使用cJSON解析json字符串
使用到函数：

//解析
extern cJSON *cJSON_Parse(const char *value);
//打印
extern char  *cJSON_Print(cJSON *item);

例子：来源于https://www.cnblogs.com/catgatp/p/6379955.html：

{
    "semantic": {
        "slots":    {
            "name": "张三"
        }
    },
    "rc":   0,
    "operation":    "CALL",
    "service":  "telephone",
    "text": "打电话给张三"
}

#include <stdio.h>
#include <stdlib.h>
#include "cJSON.h"

void printJson(cJSON * root)//以递归的方式打印json的最内层键值对
{
    for(int i=0; i<cJSON_GetArraySize(root); i++)   //遍历最外层json键值对
    {
        cJSON * item = cJSON_GetArrayItem(root, i);        
        if(cJSON_Object == item->type)      //如果对应键的值仍为cJSON_Object就递归调用printJson
            printJson(item);
        else                                //值不为json对象就直接打印出键和值
        {
            printf("%s->", item->string);
            printf("%s\n", cJSON_Print(item));
        }
    }
}

int main()
{
    char * jsonStr = "{\"semantic\":{\"slots\":{\"name\":\"张三\"}}, \"rc\":0, \"operation\":\"CALL\", \"service\":\"telephone\", \"text\":\"打电话给张三\"}";
    cJSON * root = NULL;
    cJSON * item = NULL;//cjson对象

    root = cJSON_Parse(jsonStr);     
    if (!root) 
    {
        printf("Error before: [%s]\n",cJSON_GetErrorPtr());
    }
    else
    {
        printf("%s\n", "有格式的方式打印Json:");           
        printf("%s\n\n", cJSON_Print(root));
        printf("%s\n", "无格式方式打印json：");
        printf("%s\n\n", cJSON_PrintUnformatted(root));

        printf("%s\n", "一步一步的获取name 键值对:");
        printf("%s\n", "获取semantic下的cjson对象:");
        item = cJSON_GetObjectItem(root, "semantic");//
        printf("%s\n", cJSON_Print(item));
        printf("%s\n", "获取slots下的cjson对象");
        item = cJSON_GetObjectItem(item, "slots");
        printf("%s\n", cJSON_Print(item));
        printf("%s\n", "获取name下的cjson对象");
        item = cJSON_GetObjectItem(item, "name");
        printf("%s\n", cJSON_Print(item));

        printf("%s:", item->string);   //看一下cjson对象的结构体中这两个成员的意思
        printf("%s\n", item->valuestring);


        printf("\n%s\n", "打印json所有最内层键值对:");
        printJson(root);
    }
    return 0;    
}

cJSON创建的结构体如下图所示：

root = cJSON_Parse(jsonStr);  
传入jsonStr的json字符串cJSON_Parse返回一个指向双向链表的指针。
注意！！！！头结点不是双向链表的第一个节点的prev，第一个节点的前驱为NULL，这在cJSON的源代码中多处有判断。

3.3 源码分析

/*
  Copyright (c) 2009 Dave Gamble

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
*/

#ifndef cJSON__h
#define cJSON__h

#ifdef __cplusplus
extern "C"
{
#endif
/*********************************************************************************
        cJSON的类型
        cJSON Types:
*********************************************************************************/
#define cJSON_False 0
#define cJSON_True 1
#define cJSON_NULL 2
#define cJSON_Number 3
#define cJSON_String 4
#define cJSON_Array 5
#define cJSON_Object 6

#define cJSON_IsReference 256
#define cJSON_StringIsConst 512

/*********************************************************************************
*            cJSON的结构体
*            The cJSON structure:
*********************************************************************************/
typedef struct cJSON {
    //后继和前驱指针
    struct cJSON *next,*prev;   /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */
    //子对象指针
    struct cJSON *child;        /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */
    //cJSON的类型
    int type;                   /* The type of the item, as above. */
    //item的值【string、int、double】
    char *valuestring;          /* The item's string, if type==cJSON_String */
    int valueint;               /* The item's number, if type==cJSON_Number */
    double valuedouble;         /* The item's number, if type==cJSON_Number */
    //item的名字
    char *string;               /* The item's name string, if this item is the child of, or is in the list of subitems of an object. */
} cJSON;

typedef struct cJSON_Hooks {
      void *(*malloc_fn)(size_t sz);
      void (*free_fn)(void *ptr);
} cJSON_Hooks;

/* Supply malloc, realloc and free functions to cJSON */
extern void cJSON_InitHooks(cJSON_Hooks* hooks);


//解析
/* Supply a block of JSON, and this returns a cJSON object you can interrogate. Call cJSON_Delete when finished. */
extern cJSON *cJSON_Parse(const char *value);
/* Render a cJSON entity to text for transfer/storage. Free the char* when finished. */
//打印
extern char  *cJSON_Print(cJSON *item);
/* Render a cJSON entity to text for transfer/storage without any formatting. Free the char* when finished. */
extern char  *cJSON_PrintUnformatted(cJSON *item);
/* Render a cJSON entity to text using a buffered strategy. prebuffer is a guess at the final size. guessing well reduces reallocation. fmt=0 gives unformatted, =1 gives formatted */
extern char *cJSON_PrintBuffered(cJSON *item,int prebuffer,int fmt);
/* Delete a cJSON entity and all subentities. */
extern void   cJSON_Delete(cJSON *c);

//返回cJSON中item的个数
/* Returns the number of items in an array (or object). */
extern int    cJSON_GetArraySize(cJSON *array);
//返回索引为item的cJSON对象
/* Retrieve item number "item" from array "array". Returns NULL if unsuccessful. */
extern cJSON *cJSON_GetArrayItem(cJSON *array,int item);
//返回item为string的cJSON对象【大小写不敏感】
/* Get item "string" from object. Case insensitive. */
extern cJSON *cJSON_GetObjectItem(cJSON *object,const char *string);

//返回解析cJSON对象错误时对应的字符串
/* For analysing failed parses. This returns a pointer to the parse error. 
You'll probably need to look a few chars back to make sense of it.
Defined when cJSON_Parse() returns 0. 0 when cJSON_Parse() succeeds. */
extern const char *cJSON_GetErrorPtr(void);


/*********************************************************************************
*           返回创建的对应cJSON对象
*           These calls create a cJSON item of the appropriate type. 
*********************************************************************************/
extern cJSON *cJSON_CreateNull(void);
extern cJSON *cJSON_CreateTrue(void);
extern cJSON *cJSON_CreateFalse(void);
extern cJSON *cJSON_CreateBool(int b);
extern cJSON *cJSON_CreateNumber(double num);
extern cJSON *cJSON_CreateString(const char *string);
extern cJSON *cJSON_CreateArray(void);
extern cJSON *cJSON_CreateObject(void);


/*********************************************************************************
*           创建count个数组cJSON对象
*           These utilities create an Array of count items.
*********************************************************************************/
extern cJSON *cJSON_CreateIntArray(const int *numbers,int count);
extern cJSON *cJSON_CreateFloatArray(const float *numbers,int count);
extern cJSON *cJSON_CreateDoubleArray(const double *numbers,int count);
extern cJSON *cJSON_CreateStringArray(const char **strings,int count);

/*********************************************************************************
            添加item到特定的数组/对象cJSON中
            Append item to the specified array/object.
*********************************************************************************/
extern void cJSON_AddItemToArray(cJSON *array, cJSON *item);
extern void cJSON_AddItemToObject(cJSON *object,const char *string,cJSON *item);
extern void cJSON_AddItemToObjectCS(cJSON *object,const char *string,cJSON *item);  /* Use this when string is definitely const (i.e. a literal, or as good as), and will definitely survive the cJSON object */
/* Append reference to item to the specified array/object. Use this when you want to add an existing cJSON to a new cJSON, but don't want to corrupt your existing cJSON. */
extern void cJSON_AddItemReferenceToArray(cJSON *array, cJSON *item);
extern void cJSON_AddItemReferenceToObject(cJSON *object,const char *string,cJSON *item);

/*********************************************************************************
            从数组或者对象中移除/删除item
            Remove/Detatch items from Arrays/Objects.
*********************************************************************************/
extern cJSON *cJSON_DetachItemFromArray(cJSON *array,int which);
extern void   cJSON_DeleteItemFromArray(cJSON *array,int which);
extern cJSON *cJSON_DetachItemFromObject(cJSON *object,const char *string);
extern void   cJSON_DeleteItemFromObject(cJSON *object,const char *string);
/*********************************************************************************
            插入或者替换双向链表中的节点
            Update array items.
*********************************************************************************/
extern void cJSON_InsertItemInArray(cJSON *array,int which,cJSON *newitem); /* Shifts pre-existing items to the right. */
extern void cJSON_ReplaceItemInArray(cJSON *array,int which,cJSON *newitem);
extern void cJSON_ReplaceItemInObject(cJSON *object,const char *string,cJSON *newitem);

/* Duplicate a cJSON item */
extern cJSON *cJSON_Duplicate(cJSON *item,int recurse);
/* Duplicate will create a new, identical cJSON item to the one you pass, in new memory that will
need to be released. With recurse!=0, it will duplicate any children connected to the item.
The item->next and ->prev pointers are always zero on return from Duplicate. */

/* ParseWithOpts allows you to require (and check) that the JSON is null terminated, and to retrieve the pointer to the final byte parsed. */
extern cJSON *cJSON_ParseWithOpts(const char *value,const char **return_parse_end,int require_null_terminated);

extern void cJSON_Minify(char *json);
/*********************************************************************************
            快速创建对象的宏
            Macros for creating things quickly.
*********************************************************************************/
#define cJSON_AddNullToObject(object,name)      cJSON_AddItemToObject(object, name, cJSON_CreateNull())
#define cJSON_AddTrueToObject(object,name)      cJSON_AddItemToObject(object, name, cJSON_CreateTrue())
#define cJSON_AddFalseToObject(object,name)     cJSON_AddItemToObject(object, name, cJSON_CreateFalse())
#define cJSON_AddBoolToObject(object,name,b)    cJSON_AddItemToObject(object, name, cJSON_CreateBool(b))
#define cJSON_AddNumberToObject(object,name,n)  cJSON_AddItemToObject(object, name, cJSON_CreateNumber(n))
#define cJSON_AddStringToObject(object,name,s)  cJSON_AddItemToObject(object, name, cJSON_CreateString(s))

/*********************************************************************************
            设置对象值的宏
            When assigning an integer value, it needs to be propagated to valuedouble too.
*********************************************************************************/
#define cJSON_SetIntValue(object,val)           ((object)?(object)->valueint=(object)->valuedouble=(val):(val))
#define cJSON_SetNumberValue(object,val)        ((object)?(object)->valueint=(object)->valuedouble=(val):(val))

#ifdef __cplusplus
}
#endif

#endif

/*
  Copyright (c) 2009 Dave Gamble

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.
*/

/* cJSON */
/* JSON parser in C. */
#define _CRT_SECURE_NO_WARNINGS
#include <string.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <float.h>
#include <limits.h>
#include <ctype.h>
#include "cJSON.h"

static const char *ep;

const char *cJSON_GetErrorPtr(void) {return ep;}

//无大小字符串比较
static int cJSON_strcasecmp(const char *s1,const char *s2)
{
    if (!s1) return (s1==s2)?0:1;if (!s2) return 1;
    for(; tolower(*s1) == tolower(*s2); ++s1, ++s2) if(*s1 == 0)    return 0;
    return tolower(*(const unsigned char *)s1) - tolower(*(const unsigned char *)s2);
}

//cJSON的内存申请释放赋初值
static void *(*cJSON_malloc)(size_t sz) = malloc;
static void (*cJSON_free)(void *ptr) = free;

//字符串深拷贝【string_duplicate】
static char* cJSON_strdup(const char* str)
{
      size_t len;
      char* copy;

      len = strlen(str) + 1;
      if (!(copy = (char*)cJSON_malloc(len))) return 0;
      memcpy(copy,str,len);
      return copy;
}

//初始化cJSON的malloc和free
void cJSON_InitHooks(cJSON_Hooks* hooks)
{
    if (!hooks) { /* Reset hooks */
        cJSON_malloc = malloc;
        cJSON_free = free;
        return;
    }

    cJSON_malloc = (hooks->malloc_fn)?hooks->malloc_fn:malloc;
    cJSON_free   = (hooks->free_fn)?hooks->free_fn:free;
}

//构造cJSON结构体并初始化为0
/* Internal constructor. */
static cJSON *cJSON_New_Item(void)
{
    cJSON* node = (cJSON*)cJSON_malloc(sizeof(cJSON));
    if (node) memset(node,0,sizeof(cJSON));
    return node;
}

//删除cJSON结构体
/* Delete a cJSON structure. */
void cJSON_Delete(cJSON *c)
{
    cJSON *next;
    while (c)
    {
        next=c->next;
        //不是引用且有孩子则递归删除
        if (!(c->type&cJSON_IsReference) && c->child) cJSON_Delete(c->child);
        //不是引用且为字符串值
        if (!(c->type&cJSON_IsReference) && c->valuestring) cJSON_free(c->valuestring);
        //不是应有且有名称
        if (!(c->type&cJSON_StringIsConst) && c->string) cJSON_free(c->string);
        //释放节点内存
        cJSON_free(c);
        c=next;
    }
}

//解析数值
/* Parse the input text to generate a number, and populate the result into item. */
static const char *parse_number(cJSON *item,const char *num)
{
    double n=0,sign=1,scale=0;int subscale=0,signsubscale=1;

    if (*num=='-') sign=-1,num++;   /* Has sign? */
    if (*num=='0') num++;           /* is zero */
    if (*num>='1' && *num<='9') do  n=(n*10.0)+(*num++ -'0');   while (*num>='0' && *num<='9'); /* Number? */
    if (*num=='.' && num[1]>='0' && num[1]<='9') {num++;        do  n=(n*10.0)+(*num++ -'0'),scale--; while (*num>='0' && *num<='9');}  /* Fractional part? */
    if (*num=='e' || *num=='E')     /* Exponent? */
    {   num++;if (*num=='+') num++; else if (*num=='-') signsubscale=-1,num++;      /* With sign? */
        while (*num>='0' && *num<='9') subscale=(subscale*10)+(*num++ - '0');   /* Number? */
    }

    n=sign*n*pow(10.0,(scale+subscale*signsubscale));   /* number = +/- number.fraction * 10^+/- exponent */

    item->valuedouble=n;
    item->valueint=(int)n;
    item->type=cJSON_Number;
    return num;
}

static int pow2gt (int x)   {   --x;    x|=x>>1;    x|=x>>2;    x|=x>>4;    x|=x>>8;    x|=x>>16;   return x+1; }

typedef struct {
    char *buffer; 
    int length;
    int offset; 
} printbuffer;

static char* ensure(printbuffer *p,int needed)
{
    char *newbuffer;int newsize;
    if (!p || !p->buffer) return 0;
    needed+=p->offset;
    if (needed<=p->length) return p->buffer+p->offset;

    newsize=pow2gt(needed);
    newbuffer=(char*)cJSON_malloc(newsize);
    if (!newbuffer) {cJSON_free(p->buffer);p->length=0,p->buffer=0;return 0;}
    if (newbuffer) memcpy(newbuffer,p->buffer,p->length);
    cJSON_free(p->buffer);
    p->length=newsize;
    p->buffer=newbuffer;
    return newbuffer+p->offset;
}

static int update(printbuffer *p)
{
    char *str;
    if (!p || !p->buffer) return 0;
    str=p->buffer+p->offset;
    return p->offset+strlen(str);
}

//打印数值
/* Render the number nicely from the given item into a string. */
static char *print_number(cJSON *item,printbuffer *p)
{
    char *str=0;
    double d=item->valuedouble;
    //0
    if (d==0)
    {
        if (p)  str=ensure(p,2);
        else    str=(char*)cJSON_malloc(2); /* special case for 0. */
        if (str) strcpy(str,"0");
    }
    //整数
    else if (fabs(((double)item->valueint)-d)<=DBL_EPSILON && d<=INT_MAX && d>=INT_MIN)
    {
        if (p)  str=ensure(p,21);
        else    str=(char*)cJSON_malloc(21);    /* 2^64+1 can be represented in 21 chars. */
        if (str)    sprintf(str,"%d",item->valueint);
    }
    //浮点数
    else
    {
        if (p)  str=ensure(p,64);
        else    str=(char*)cJSON_malloc(64);    /* This is a nice tradeoff. */
        if (str)
        {
            if (fabs(floor(d)-d)<=DBL_EPSILON && fabs(d)<1.0e60)sprintf(str,"%.0f",d);
            else if (fabs(d)<1.0e-6 || fabs(d)>1.0e9)           sprintf(str,"%e",d);
            else                                                sprintf(str,"%f",d);
        }
    }
    return str;
}

//将4字节的16进制转化为无符号整型
static unsigned parse_hex4(const char *str)
{
    unsigned h=0;
    if (*str>='0' && *str<='9') h+=(*str)-'0';
    else if (*str>='A' && *str<='F') h+=10+(*str)-'A';
    else if (*str>='a' && *str<='f') h+=10+(*str)-'a';
    else return 0;
    h=h<<4;str++;
    if (*str>='0' && *str<='9') h+=(*str)-'0'; else if (*str>='A' && *str<='F') h+=10+(*str)-'A'; else if (*str>='a' && *str<='f') h+=10+(*str)-'a'; else return 0;
    h=h<<4;str++;
    if (*str>='0' && *str<='9') h+=(*str)-'0'; else if (*str>='A' && *str<='F') h+=10+(*str)-'A'; else if (*str>='a' && *str<='f') h+=10+(*str)-'a'; else return 0;
    h=h<<4;str++;
    if (*str>='0' && *str<='9') h+=(*str)-'0'; else if (*str>='A' && *str<='F') h+=10+(*str)-'A'; else if (*str>='a' && *str<='f') h+=10+(*str)-'a'; else return 0;
    return h;
}

/* Parse the input text into an unescaped cstring, and populate item. */
static const unsigned char firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

//解析字符串
static const char *parse_string(cJSON *item,const char *str)
{
    const char *ptr=str+1;
    char *ptr2;
    char *out;
    int len=0;
    unsigned uc,uc2;
    if (*str!='\"') {ep=str;return 0;}  /* not a string! */

    //\"与\"之间的字符个数
    while (*ptr!='\"' && *ptr && ++len) 
        if (*ptr++ == '\\')
            ptr++;  /* Skip escaped quotes. */

    out=(char*)cJSON_malloc(len+1); /* This is how long we need for the string, roughly. */
    if (!out) return 0;

    ptr=str+1;
    ptr2=out;
    while (*ptr!='\"' && *ptr)
    {
        if (*ptr!='\\') *ptr2++=*ptr++;
        else
        {
            ptr++;
            switch (*ptr)
            {
                case 'b': *ptr2++='\b'; break;
                case 'f': *ptr2++='\f'; break;
                case 'n': *ptr2++='\n'; break;
                case 'r': *ptr2++='\r'; break;
                case 't': *ptr2++='\t'; break;
                case 'u':    /* transcode utf16 to utf8. */
                    uc=parse_hex4(ptr+1);ptr+=4;    /* get the unicode char. */

                    if ((uc>=0xDC00 && uc<=0xDFFF) || uc==0)    break;  /* check for invalid.   */

                    if (uc>=0xD800 && uc<=0xDBFF)   /* UTF16 surrogate pairs.   */
                    {
                        if (ptr[1]!='\\' || ptr[2]!='u')    break;  /* missing second-half of surrogate.    */
                        uc2=parse_hex4(ptr+3);ptr+=6;
                        if (uc2<0xDC00 || uc2>0xDFFF)       break;  /* invalid second-half of surrogate.    */
                        uc=0x10000 + (((uc&0x3FF)<<10) | (uc2&0x3FF));
                    }

                    len=4;if (uc<0x80) len=1;else if (uc<0x800) len=2;else if (uc<0x10000) len=3; ptr2+=len;

                    switch (len) {
                        case 4: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
                        case 3: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
                        case 2: *--ptr2 =((uc | 0x80) & 0xBF); uc >>= 6;
                        case 1: *--ptr2 =(uc | firstByteMark[len]);
                    }
                    ptr2+=len;
                    break;
                default:  *ptr2++=*ptr; break;
            }
            ptr++;
        }
    }
    *ptr2=0;
    if (*ptr=='\"') ptr++;
    item->valuestring=out;
    item->type=cJSON_String;
    return ptr;
}

//打印字符串
/* Render the cstring provided to an escaped version that can be printed. */
static char *print_string_ptr(const char *str,printbuffer *p)
{
    const char *ptr;
    char *ptr2,*out;
    int len=0,flag=0;
    unsigned char token;

    for (ptr=str;*ptr;ptr++)
        flag|=((*ptr>0 && *ptr<32)||(*ptr=='\"')||(*ptr=='\\'))?1:0;
    if (!flag)//没有\"和\\和>32的字符
    {
        len=ptr-str;
        if (p) out=ensure(p,len+3);
        else        out=(char*)cJSON_malloc(len+3);
        if (!out) return 0;
        ptr2=out;*ptr2++='\"';
        strcpy(ptr2,str);
        ptr2[len]='\"';
        ptr2[len+1]=0;
        return out;
    }

    if (!str)//空字符串
    {
        if (p)  out=ensure(p,3);
        else    out=(char*)cJSON_malloc(3);
        if (!out) return 0;
        strcpy(out,"\"\"");
        return out;
    }
    ptr=str;
    while ((token=*ptr) && ++len) {
        if (strchr("\"\\\b\f\n\r\t",token)) 
            len++; //有"\"\\\b\f\n\r\t"当中的字符 
        else if (token<32)
            len+=5;//为什么加5：因该是和下面的case的default对应
        ptr++;
    }

    if (p)  out=ensure(p,len+3);
    else    out=(char*)cJSON_malloc(len+3);
    if (!out) return 0;

    ptr2=out;ptr=str;
    *ptr2++='\"';
    while (*ptr)
    {
        if ((unsigned char)*ptr>31 && *ptr!='\"' && *ptr!='\\') *ptr2++=*ptr++;
        else
        {
            *ptr2++='\\';
            switch (token=*ptr++)
            {
                case '\\':  *ptr2++='\\';   break;
                case '\"':  *ptr2++='\"';   break;
                case '\b':  *ptr2++='b';    break;
                case '\f':  *ptr2++='f';    break;
                case '\n':  *ptr2++='n';    break;
                case '\r':  *ptr2++='r';    break;
                case '\t':  *ptr2++='t';    break;
                default: sprintf(ptr2,"u%04x",token);ptr2+=5;   break;  /* escape and print */
            }
        }
    }
    *ptr2++='\"';*ptr2++=0;
    return out;
}
/* Invote print_string_ptr (which is useful) on an item. */
static char *print_string(cJSON *item,printbuffer *p)   {
    return print_string_ptr(item->valuestring,p);
}

/* Predeclare these prototypes. */
static const char *parse_value(cJSON *item,const char *value);
static char *print_value(cJSON *item,int depth,int fmt,printbuffer *p);
static const char *parse_array(cJSON *item,const char *value);
static char *print_array(cJSON *item,int depth,int fmt,printbuffer *p);
static const char *parse_object(cJSON *item,const char *value);
static char *print_object(cJSON *item,int depth,int fmt,printbuffer *p);

//跳过空白
/* Utility to jump whitespace and cr/lf */
static const char *skip(const char *in) {
    while (in && *in && (unsigned char)*in<=32) 
        in++; 
    return in;
}

//解析对象、创建带头结点的双向链表
/* Parse an object - create a new root, and populate. */
cJSON *cJSON_ParseWithOpts(const char *value,const char **return_parse_end,int require_null_terminated)
{
    const char *end=0;
    cJSON *c=cJSON_New_Item();
    ep=0;
    if (!c) return 0;       /* memory fail */

    end=parse_value(c,skip(value));
    //解析失败
    if (!end)   {cJSON_Delete(c);return 0;} /* parse failure. ep is set. */

    /* if we require null-terminated JSON without appended garbage, skip and then check for a null terminator */
    if (require_null_terminated) {
        end=skip(end);
        if (*end) {
            cJSON_Delete(c);
            ep=end;
            return 0;
        }
    }
    if (return_parse_end) 
        *return_parse_end=end;
    return c;
}
/* Default options for cJSON_Parse */
cJSON *cJSON_Parse(const char *value) {
    return cJSON_ParseWithOpts(value,0,0);
}

//有格式打印
/* Render a cJSON item/entity/structure to text. */
char *cJSON_Print(cJSON *item)              {
    return print_value(item,0,1,0);
}
//无格式打印
char *cJSON_PrintUnformatted(cJSON *item)   {
    return print_value(item,0,0,0);
}

char *cJSON_PrintBuffered(cJSON *item,int prebuffer,int fmt)
{
    printbuffer p;
    p.buffer=(char*)cJSON_malloc(prebuffer);
    p.length=prebuffer;
    p.offset=0;
    return print_value(item,0,fmt,&p);
    return p.buffer;
}

//解析JSON字符串的核心函数，返回最后一个字符指针
/* Parser core - when encountering text, process appropriately. */
static const char *parse_value(cJSON *item,const char *value)
{
    if (!value)                     return 0;   /* Fail on null. */
    if (!strncmp(value,"null",4))   { item->type=cJSON_NULL;  return value+4; }
    if (!strncmp(value,"false",5))  { item->type=cJSON_False; return value+5; }
    if (!strncmp(value,"true",4))   { item->type=cJSON_True; item->valueint=1;  return value+4; }
    //字符串
    if (*value=='\"')               { return parse_string(item,value); }
    //数值
    if (*value=='-' || (*value>='0' && *value<='9'))    { return parse_number(item,value); }
    //数组
    if (*value=='[')                { return parse_array(item,value); }
    //对象
    if (*value=='{')                { return parse_object(item,value); }
    //字符串错误
    ep=value;return 0;  /* failure. */
}

//根据cJSON对象的类型打印其值
//非常重要的一个函数
/* Render a value to text. */
static char *print_value(cJSON *item,int depth,int fmt,printbuffer *p)
{
    char *out=0;
    if (!item) return 0;
    if (p)
    {
        switch ((item->type)&255)
        {
            case cJSON_NULL:    {out=ensure(p,5);   if (out) strcpy(out,"null");    break;}
            case cJSON_False:   {out=ensure(p,6);   if (out) strcpy(out,"false");   break;}
            case cJSON_True:    {out=ensure(p,5);   if (out) strcpy(out,"true");    break;}
            case cJSON_Number:  out=print_number(item,p);break;
            case cJSON_String:  out=print_string(item,p);break;
            case cJSON_Array:   out=print_array(item,depth,fmt,p);break;
            case cJSON_Object:  out=print_object(item,depth,fmt,p);break;
        }
    }
    else
    {
        switch ((item->type)&255)
        {
            case cJSON_NULL:    out=cJSON_strdup("null");   break;
            case cJSON_False:   out=cJSON_strdup("false");break;
            case cJSON_True:    out=cJSON_strdup("true"); break;
            case cJSON_Number:  out=print_number(item,0);break;
            case cJSON_String:  out=print_string(item,0);break;
            case cJSON_Array:   out=print_array(item,depth,fmt,0);break;
            case cJSON_Object:  out=print_object(item,depth,fmt,0);break;
        }
    }
    return out;
}

//构建一个数组的带头结点的双向链表
/* Build an array from input text. */
static const char *parse_array(cJSON *item,const char *value)
{
    cJSON *child;
    if (*value!='[')    {ep=value;return 0;}    /* not an array! */

    item->type=cJSON_Array;
    value=skip(value+1);
    if (*value==']') return value+1;    /* empty array. */

    item->child=child=cJSON_New_Item();
    if (!item->child) return 0;      /* memory fail */
    //第一个数组元素
    value=skip(parse_value(child,skip(value))); /* skip any spacing, get the value. */
    if (!value) return 0;
    //剩下的数组元素
    while (*value==',')
    {
        cJSON *new_item;
        if (!(new_item=cJSON_New_Item())) return 0;     /* memory fail */
        child->next=new_item;new_item->prev=child;child=new_item;
        value=skip(parse_value(child,skip(value+1)));
        if (!value) return 0;   /* memory fail */
    }

    if (*value==']') return value+1;    /* end of array */
    ep=value;return 0;  /* malformed. */
}

//打印数组
/* Render an array to text */
static char *print_array(cJSON *item,int depth,int fmt,printbuffer *p)
{
    char **entries;
    char *out=0,*ptr,*ret;int len=5;
    cJSON *child=item->child;
    int numentries=0,i=0,fail=0;
    size_t tmplen=0;

    //计算数组元素的个数
    /* How many entries in the array? */
    while (child) numentries++,child=child->next;
    /* Explicitly handle numentries==0 */
    if (!numentries)
    {
        if (p)  out=ensure(p,3);
        else    out=(char*)cJSON_malloc(3);
        if (out) strcpy(out,"[]");
        return out;
    }

    if (p)
    {
        /* Compose the output array. */
        i=p->offset;
        ptr=ensure(p,1);if (!ptr) return 0; *ptr='[';   p->offset++;
        child=item->child;
        while (child && !fail)
        {
            print_value(child,depth+1,fmt,p);
            p->offset=update(p);
            if (child->next) {len=fmt?2:1;ptr=ensure(p,len+1);if (!ptr) return 0;*ptr++=',';if(fmt)*ptr++=' ';*ptr=0;p->offset+=len;}
            child=child->next;
        }
        ptr=ensure(p,2);if (!ptr) return 0; *ptr++=']';*ptr=0;
        out=(p->buffer)+i;
    }
    else
    {
        /* Allocate an array to hold the values for each */
        entries=(char**)cJSON_malloc(numentries*sizeof(char*));
        if (!entries) return 0;
        memset(entries,0,numentries*sizeof(char*));
        //递归输出所有的数组元素
        /* Retrieve all the results: */
        child=item->child;
        while (child && !fail)
        {
            ret=print_value(child,depth+1,fmt,0);
            entries[i++]=ret;
            if (ret) len+=strlen(ret)+2+(fmt?1:0); else fail=1;
            child=child->next;
        }

        /* If we didn't fail, try to malloc the output string */
        if (!fail)  out=(char*)cJSON_malloc(len);
        /* If that fails, we fail. */
        if (!out) fail=1;

        /* Handle failure. */
        if (fail)
        {
            for (i=0;i<numentries;i++) if (entries[i]) cJSON_free(entries[i]);
            cJSON_free(entries);
            return 0;
        }

        /* Compose the output array. */
        *out='[';
        ptr=out+1;*ptr=0;
        for (i=0;i<numentries;i++)
        {
            tmplen=strlen(entries[i]);memcpy(ptr,entries[i],tmplen);ptr+=tmplen;
            if (i!=numentries-1) {*ptr++=',';if(fmt)*ptr++=' ';*ptr=0;}
            cJSON_free(entries[i]);
        }
        cJSON_free(entries);
        *ptr++=']';*ptr++=0;
    }
    return out; 
}

//构建一个带头结点的双向对象链表
/* Build an object from the text. */
static const char *parse_object(cJSON *item,const char *value)
{
    cJSON *child;
    if (*value!='{')    {ep=value;return 0;}    /* not an object! */

    item->type=cJSON_Object;
    value=skip(value+1);
    if (*value=='}') return value+1;    /* empty array. */

    item->child=child=cJSON_New_Item();
    if (!item->child) return 0;
    value=skip(parse_string(child,skip(value)));
    if (!value) return 0;
    child->string=child->valuestring;child->valuestring=0;
    if (*value!=':') {ep=value;return 0;}   /* fail! */
    //第一个对象元素
    value=skip(parse_value(child,skip(value+1)));   /* skip any spacing, get the value. */
    if (!value) return 0;

    while (*value==',')
    {
        cJSON *new_item;
        if (!(new_item=cJSON_New_Item()))   return 0; /* memory fail */
        child->next=new_item;new_item->prev=child;child=new_item;
        value=skip(parse_string(child,skip(value+1)));
        if (!value) return 0;
        child->string=child->valuestring;child->valuestring=0;
        if (*value!=':') {ep=value;return 0;}   /* fail! */
        value=skip(parse_value(child,skip(value+1)));   /* skip any spacing, get the value. */
        if (!value) return 0;
    }

    if (*value=='}') return value+1;    /* end of array */
    ep=value;return 0;  /* malformed. */
}

/* Render an object to text. */
static char *print_object(cJSON *item,int depth,int fmt,printbuffer *p)
{
    char **entries=0,**names=0;
    char *out=0,*ptr,*ret,*str;
    int len=7,i=0,j;
    cJSON *child=item->child;
    int numentries=0,fail=0;
    size_t tmplen=0;
    //计算双向链表中有多少个节点
    /* Count the number of entries. */
    while (child) numentries++,child=child->next;
    /* Explicitly handle empty object case */
    if (!numentries)//空对象
    {
        if (p) out=ensure(p,fmt?depth+4:3);
        else    out=(char*)cJSON_malloc(fmt?depth+4:3);
        if (!out)   return 0;
        ptr=out;*ptr++='{';
        if (fmt) {*ptr++='\n';for (i=0;i<depth-1;i++) *ptr++='\t';}
        *ptr++='}';*ptr++=0;
        return out;
    }
    if (p)
    {
        /* Compose the output: */
        i=p->offset;
        len=fmt?2:1;    ptr=ensure(p,len+1);    if (!ptr) return 0;
        *ptr++='{'; if (fmt) *ptr++='\n';   *ptr=0; p->offset+=len;
        child=item->child;depth++;
        while (child)
        {
            if (fmt)
            {
                ptr=ensure(p,depth);    if (!ptr) return 0;
                for (j=0;j<depth;j++) *ptr++='\t';
                p->offset+=depth;
            }
            print_string_ptr(child->string,p);
            p->offset=update(p);

            len=fmt?2:1;
            ptr=ensure(p,len);  if (!ptr) return 0;
            *ptr++=':';if (fmt) *ptr++='\t';
            p->offset+=len;

            print_value(child,depth,fmt,p);
            p->offset=update(p);

            len=(fmt?1:0)+(child->next?1:0);
            ptr=ensure(p,len+1); if (!ptr) return 0;
            if (child->next) *ptr++=',';
            if (fmt) *ptr++='\n';*ptr=0;
            p->offset+=len;
            child=child->next;
        }
        ptr=ensure(p,fmt?(depth+1):2);   if (!ptr) return 0;
        if (fmt)    for (i=0;i<depth-1;i++) *ptr++='\t';
        *ptr++='}';*ptr=0;
        out=(p->buffer)+i;
    }
    else
    {
        //分配空间给值【entries】、名字【names】
        /* Allocate space for the names and the objects */
        entries=(char**)cJSON_malloc(numentries*sizeof(char*));
        if (!entries) return 0;
        names=(char**)cJSON_malloc(numentries*sizeof(char*));
        if (!names) {cJSON_free(entries);return 0;}
        memset(entries,0,sizeof(char*)*numentries);
        memset(names,0,sizeof(char*)*numentries);

        //收集所有的节点加入到数组names和entries中
        /* Collect all the results into our arrays: */
        child=item->child;depth++;if (fmt) len+=depth;
        while (child)
        {
            names[i]=str=print_string_ptr(child->string,0);
            entries[i++]=ret=print_value(child,depth,fmt,0);
            if (str && ret) len+=strlen(ret)+strlen(str)+2+(fmt?2+depth:0);
            else fail=1;
            child=child->next;
        }

        /* Try to allocate the output string */
        if (!fail)  out=(char*)cJSON_malloc(len);
        if (!out) fail=1;

        /* Handle failure */
        if (fail)
        {
            for (i=0;i<numentries;i++) {
                if (names[i]) cJSON_free(names[i]);
                if (entries[i]) cJSON_free(entries[i]);
            }
            cJSON_free(names);cJSON_free(entries);
            return 0;
        }

        /* Compose the output: */
        *out='{';ptr=out+1;
        if (fmt)*ptr++='\n';*ptr=0;
        for (i=0;i<numentries;i++)
        {
            if (fmt) for (j=0;j<depth;j++) *ptr++='\t';
            tmplen=strlen(names[i]);memcpy(ptr,names[i],tmplen);ptr+=tmplen;
            *ptr++=':';if (fmt) *ptr++='\t';
            strcpy(ptr,entries[i]);ptr+=strlen(entries[i]);
            if (i!=numentries-1) *ptr++=',';
            if (fmt) *ptr++='\n';*ptr=0;
            cJSON_free(names[i]);cJSON_free(entries[i]);
        }

        cJSON_free(names);cJSON_free(entries);
        if (fmt) for (i=0;i<depth-1;i++) *ptr++='\t';
        *ptr++='}';*ptr++=0;
    }
    return out; 
}

/* Get Array size/item / object item. */
//获取数组cJSON对象的个数
int    cJSON_GetArraySize(cJSON *array){
    cJSON *c=array->child;
    int i=0;
    while(c)
        i++,c=c->next;
    return i;
}
//返回索引为item的数组cJSON指针
cJSON *cJSON_GetArrayItem(cJSON *array,int item){
    cJSON *c=array->child;  
    while (c && item>0)
        item--,c=c->next;
    return c;
}
//返回名字为string的对象cJSON指针
cJSON *cJSON_GetObjectItem(cJSON *object,const char *string){
    cJSON *c=object->child;
    while (c && cJSON_strcasecmp(c->string,string)) 
        c=c->next;
    return c;
}

//双向链表的连接辅助函数
/* Utility for array list handling. */
static void suffix_object(cJSON *prev,cJSON *item) {
    prev->next=item;
    item->prev=prev;
}

//创建引用类型的cJSON对象
/* Utility for handling references. */
static cJSON *create_reference(cJSON *item) {
    cJSON *ref=cJSON_New_Item();
    if (!ref) return 0;
    memcpy(ref,item,sizeof(cJSON));
    ref->string=0;
    ref->type|=cJSON_IsReference;
    ref->next=ref->prev=0;
    return ref;
}

//添加item到array/object的cJSON结构中
/* Add item to array/object. */
void   cJSON_AddItemToArray(cJSON *array, cJSON *item){
    cJSON *c=array->child;
    if (!item) return;
    if (!c) {array->child=item;}
    else {
        while (c && c->next) 
            c=c->next; 
        suffix_object(c,item);
    }
}
void   cJSON_AddItemToObject(cJSON *object,const char *string,cJSON *item)  {
    if (!item) return; 
    if (item->string)
        cJSON_free(item->string);
    item->string=cJSON_strdup(string);
    cJSON_AddItemToArray(object,item);
}
void   cJSON_AddItemToObjectCS(cJSON *object,const char *string,cJSON *item)    {if (!item) return; if (!(item->type&cJSON_StringIsConst) && item->string) cJSON_free(item->string);item->string=(char*)string;item->type|=cJSON_StringIsConst;cJSON_AddItemToArray(object,item);}
void    cJSON_AddItemReferenceToArray(cJSON *array, cJSON *item)                        {cJSON_AddItemToArray(array,create_reference(item));}
void    cJSON_AddItemReferenceToObject(cJSON *object,const char *string,cJSON *item){
    cJSON_AddItemToObject(object,string,create_reference(item));
}

//移除【detach】索引为which的节点
cJSON *cJSON_DetachItemFromArray(cJSON *array,int which)            {
    cJSON *c=array->child;
    //找到索引为which的cJSON对象
    while (c && which>0)
        c=c->next,which--;
    if (!c) return 0;
    //双向链表的删除
    if (c->prev) 
        c->prev->next=c->next;
    if (c->next)
        c->next->prev=c->prev;
    //如果删除的是第一个子节点
    if (c==array->child) 
        array->child=c->next;
    c->prev=c->next=0;
    return c;
}
//删除【delete】索引为which的节点
void   cJSON_DeleteItemFromArray(cJSON *array,int which){
    cJSON_Delete(cJSON_DetachItemFromArray(array,which));
}
//移除【detach】字符串为string的节点
cJSON *cJSON_DetachItemFromObject(cJSON *object,const char *string) {
    int i=0;
    cJSON *c=object->child;
    while (c && cJSON_strcasecmp(c->string,string))
        i++,c=c->next;
    if (c)
        return cJSON_DetachItemFromArray(object,i);
    return 0;
}
//删除【delete】字符串为string的节点
void   cJSON_DeleteItemFromObject(cJSON *object,const char *string) {
    cJSON_Delete(cJSON_DetachItemFromObject(object,string));
}

/* Replace array/object items with new ones. */
//在数组cJSON中索引为which之前插入newitem
void   cJSON_InsertItemInArray(cJSON *array,int which,cJSON *newitem){
    cJSON *c=array->child;
    while (c && which>0) 
        c=c->next,which--;
    if (!c) {//which为最后一个
        cJSON_AddItemToArray(array,newitem);
        return;
    }
    //双向链表的连接
    newitem->next=c;
    newitem->prev=c->prev;
    c->prev=newitem;
    if (c==array->child)//如果插入节点为第一个子孩子
        array->child=newitem; 
    else 
        newitem->prev->next=newitem;
}
//将索引为which的节点替换为newitem
void   cJSON_ReplaceItemInArray(cJSON *array,int which,cJSON *newitem){
    cJSON *c=array->child;
    //找索引为which的节点
    while (c && which>0)
        c=c->next,which--;
    if (!c) return;//没有找到则返回
    //双向链表的连接
    newitem->next=c->next;
    newitem->prev=c->prev;
    if (newitem->next)
        newitem->next->prev=newitem;
    if (c==array->child)
        array->child=newitem;
    else
        newitem->prev->next=newitem;
    //释放被替换的节点内存
    c->next=c->prev=0;
    cJSON_Delete(c);
}
//替换名称为string的cJSON对象为newitem
void   cJSON_ReplaceItemInObject(cJSON *object,const char *string,cJSON *newitem){
    int i=0;
    cJSON *c=object->child;
    //找名称为string的对象
    while(c && cJSON_strcasecmp(c->string,string))
        i++,c=c->next;
    if(c){
        newitem->string=cJSON_strdup(string);
        cJSON_ReplaceItemInArray(object,i,newitem);
    }
}

//创建基本的cJSON对象
/* Create basic types: */
cJSON *cJSON_CreateNull(void)                   {cJSON *item=cJSON_New_Item();if(item)item->type=cJSON_NULL;return item;}
cJSON *cJSON_CreateTrue(void)                   {cJSON *item=cJSON_New_Item();if(item)item->type=cJSON_True;return item;}
cJSON *cJSON_CreateFalse(void)                  {cJSON *item=cJSON_New_Item();if(item)item->type=cJSON_False;return item;}
//三目运算法【？：】的优先级 > 赋值运算符【=】
cJSON *cJSON_CreateBool(int b)                  {cJSON *item=cJSON_New_Item();if(item)item->type=b?cJSON_True:cJSON_False;return item;}
cJSON *cJSON_CreateNumber(double num)           {cJSON *item=cJSON_New_Item();if(item){item->type=cJSON_Number;item->valuedouble=num;item->valueint=(int)num;}return item;}
cJSON *cJSON_CreateString(const char *string)   {cJSON *item=cJSON_New_Item();if(item){item->type=cJSON_String;item->valuestring=cJSON_strdup(string);}return item;}
cJSON *cJSON_CreateArray(void)                  {cJSON *item=cJSON_New_Item();if(item)item->type=cJSON_Array;return item;}
cJSON *cJSON_CreateObject(void)                 {cJSON *item=cJSON_New_Item();if(item)item->type=cJSON_Object;return item;}

//创建数组类型的cJSON对象【int float double string】
/* Create Arrays: */
cJSON *cJSON_CreateIntArray(const int *numbers,int count)       {
    int i;
    cJSON *n=0,*p=0,*a=cJSON_CreateArray();
    for(i=0;a && i<count;i++){
        n=cJSON_CreateNumber(numbers[i]);
        if(!i)a->child=n;
        else suffix_object(p,n);
        p=n;
    }
    return a;
}
cJSON *cJSON_CreateFloatArray(const float *numbers,int count)   {int i;cJSON *n=0,*p=0,*a=cJSON_CreateArray();for(i=0;a && i<count;i++){n=cJSON_CreateNumber(numbers[i]);if(!i)a->child=n;else suffix_object(p,n);p=n;}return a;}
cJSON *cJSON_CreateDoubleArray(const double *numbers,int count) {int i;cJSON *n=0,*p=0,*a=cJSON_CreateArray();for(i=0;a && i<count;i++){n=cJSON_CreateNumber(numbers[i]);if(!i)a->child=n;else suffix_object(p,n);p=n;}return a;}
cJSON *cJSON_CreateStringArray(const char **strings,int count)  {
    int i;
    cJSON *n=0,*p=0,*a=cJSON_CreateArray();
    for(i=0;a && i<count;i++){
        n=cJSON_CreateString(strings[i]);
        if(!i)a->child=n;
        else suffix_object(p,n);
        p=n;
    }
    return a;
}

//复制【递归】
/* Duplication */
cJSON *cJSON_Duplicate(cJSON *item,int recurse)
{
    cJSON *newitem,*cptr,*nptr=0,*newchild;
    /* Bail on bad ptr */
    if (!item) return 0;
    /* Create new item */
    newitem=cJSON_New_Item();
    if (!newitem) return 0;

    //拷贝所有的字段
    /* Copy over all vars */
    newitem->type=item->type&(~cJSON_IsReference),newitem->valueint=item->valueint,newitem->valuedouble=item->valuedouble;
    if (item->valuestring)  {newitem->valuestring=cJSON_strdup(item->valuestring);  if (!newitem->valuestring)  {cJSON_Delete(newitem);return 0;}}
    if (item->string)       {newitem->string=cJSON_strdup(item->string);            if (!newitem->string)       {cJSON_Delete(newitem);return 0;}}

    /* If non-recursive, then we're done! */
    if (!recurse) return newitem;
    /* Walk the ->next chain for the child. */
    cptr=item->child;
    while (cptr)
    {
        newchild=cJSON_Duplicate(cptr,1);       /* Duplicate (with recurse) each item in the ->next chain */
        if (!newchild) {cJSON_Delete(newitem);return 0;}
        if (nptr)   {nptr->next=newchild,newchild->prev=nptr;nptr=newchild;}    /* If newitem->child already set, then crosswire ->prev and ->next and move on */
        else        {newitem->child=newchild;nptr=newchild;}                    /* Set newitem->child and move to it */
        //下一个节点
        cptr=cptr->next;
    }
    return newitem;
}
//简化json的表示
//"{//xilo\n/*11*/\"\\ jei\":\"lli\"}"
//=====>
//{"\ jei":"lli"}
void cJSON_Minify(char *json)
{
    char *into=json;
    while (*json)
    {
        if (*json==' ') json++;
        else if (*json=='\t') json++;   /* Whitespace characters. */
        else if (*json=='\r') json++;
        else if (*json=='\n') json++;
        //删除单行注释://
        else if (*json=='/' && json[1]=='/')  while (*json && *json!='\n') json++;  /* double-slash comments, to end of line. */
        //删除多行注释：/**/
        else if (*json=='/' && json[1]=='*') {
            while (*json && !(*json=='*' && json[1]=='/'))
                json++;
            json+=2;
        }   /* multiline comments. */
        else if (*json=='\"'){
            *into++=*json++;
            while (*json && *json!='\"'){
                if (*json=='\\')
                    *into++=*json++;
                *into++=*json++;
            }
            *into++=*json++;
        } /* string literals, which are \" sensitive. */
        else *into++=*json++;           /* All other characters. */
    }
    *into=0;    /* and null-terminate. */
}