一、JSON数据表示
JSON(JavaScript Object Notation(JavaScript 对象表示法))，是存储和交换文本信息的语法，类似 XML，但JSON 比 XML 更小、更快，更易解析。
{
"sites": [
{ "name":"菜鸟教程" , "url":"www.runoob.com" },
{ "name":"google" , "url":"www.google.com" },
{ "name":"微博" , "url":"www.weibo.com" }
]
}大括号保存对象，中括号保存数组，键值对以":"分隔，其中键只能是字符串，值可以是数字（整数或浮点数）、字符串、逻辑值（true 或 false）、数组、对象或null，不同的键值对之间以","分隔。
二、CJSON数据结构和函数
cJSON是一个C语言编写的JSON格式数据解析器，他把JSON数据看成是层次树，同级之间用双向链表相连，上下级用指针形成树形结构。
1.cJSON结构体定义
typedef struct cJSON {
struct cJSON *next,*prev; /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */
struct cJSON *child; /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */
int type; /* The type of the item, as above. */
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 */
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;成员变量type包括cJSON_Object、cJSON_Array、cJSON_Number、cJSON_String、cJSON_True、cJSON_False、cJSON_NULL。
成员变量valuestring表示type为cJSON_String时string的值，valueint表示type为cJSON_Number时int的值，或是double被截断为int的值，valuedouble表示type为cJSON_Number时double的值。
成员变量string表示cJSON节点的名称。
2.创建空节点
static cJSON *cJSON_New_Item(void)
{
cJSON* node = (cJSON*)cJSON_malloc(sizeof(cJSON));
if (node) memset(node,0,sizeof(cJSON));
return node;
}3.创建相应type节点
都是先创建一个空节点，然后设置type，有的节点还需要给相应的value赋值。
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;}
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;}4.创建节点数组
根据普通数组创建不同类型指定大小的cJSON数组，所谓数组即存放的是相同类型的数据。
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;//数组节点的孩子节点是数组第一个元素
else suffix_object(p,n);
//static void suffix_object(cJSON *prev,cJSON *item) {prev->next=item;item->prev=prev;}
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;
}5.添加孩子节点到Array，Object上
添加孩子节点都是调用cJSON_AddItemToObject函数。
#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))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);//将item添加到object数组上
}
void cJSON_AddItemToArray(cJSON *array, cJSON *item){
cJSON *c=array->child;
if (!item) return;
if (!c) {array->child=item;}//如果array没有孩子，item是其第一个孩子
else {
while (c && c->next) c=c->next; //如果array有孩子，将item插入到数组末尾
//static void suffix_object(cJSON *prev,cJSON *item) {prev->next=item;item->prev=prev;}
suffix_object(c,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);
}6.创建引用节点
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;
}7.添加引用节点到Array，Object上
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));
}8.获取Array、Object
int cJSON_GetArraySize(cJSON *array){
cJSON *c=array->child;
int i=0;
while(c)i++,c=c->next;
return i;
}
cJSON *cJSON_GetArrayItem(cJSON *array,int item){
cJSON *c=array->child;
while (c && item>0) item--,c=c->next;
return c;
}
cJSON *cJSON_GetObjectItem(cJSON *object,const char *string){
cJSON *c=object->child;
while (c && cJSON_strcasecmp(c->string,string)) c=c->next;
return c;
}9.插入/替换节点
void cJSON_InsertItemInArray(cJSON *array,int which,cJSON *newitem){
cJSON *c=array->child;
while (c && which>0) c=c->next,which--;
if (!c) {
cJSON_AddItemToArray(array,newitem);
return;
}
newitem->next=c;
newitem->prev=c->prev;
c->prev=newitem;
if (c==array->child) array->child=newitem;
else newitem->prev->next=newitem;
}
void cJSON_ReplaceItemInArray(cJSON *array,int which,cJSON *newitem){
cJSON *c=array->child;
while (c && which>0) c=c->next,which--;
if (!c) return;
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;
c->next=c->prev=0;
cJSON_Delete(c);
}
void cJSON_ReplaceItemInObject(cJSON *object,const char *string,cJSON *newitem){
int i=0;
cJSON *c=object->child;
while(c && cJSON_strcasecmp(c->string,string))i++,c=c->next;
if(c){
newitem->string=cJSON_strdup(string);
cJSON_ReplaceItemInArray(object,i,newitem);
}
}10.删除孩子节点
cJSON *cJSON_DetachItemFromArray(cJSON *array,int which){
cJSON *c=array->child;
while (c && which>0) c=c->next,which--;
if (!c) return 0;
if (c->prev) c->prev->next=c->next;
if (c->next) c->next->prev=c->prev;
if (c==array->child) array->child=c->next;
c->prev=c->next=0;
return c;
}
void cJSON_DeleteItemFromArray(cJSON *array,int which){
cJSON_Delete(cJSON_DetachItemFromArray(array,which));
}
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;
}
void cJSON_DeleteItemFromObject(cJSON *object,const char *string){
cJSON_Delete(cJSON_DetachItemFromObject(object,string));
}11.解析层次树
cJSON *cJSON_Parse(const char *value) {return cJSON_ParseWithOpts(value,0,0);}
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));//skip去除value前面的控制字符（asc值小于33）
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;
}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; }
if (*value=='\"') { return parse_string(item,value); }
if (*value=='-' || (*value>='0' && *value<='9')) { return parse_number(item,value); }
if (*value=='[') { return (item,value); }
if (*value=='{') { return parse_object(item,value); }
ep=value;return 0; /* failure. */
}解析函数的第一个参数都是空节点，用于解析后填充信息，第二个参数是之前解析剩余的字符串，所有的\n\r会被过滤掉。
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! *///c语言中\"是一个字符
//ptr没有到字符串末尾，len记录string的长度
while (*ptr!='\"' && *ptr && ++len) if (*ptr++ == '\\') ptr++; /* Skip escaped quotes. 转义字符*/
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++;//进行string赋值
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;
}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 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 */
value=skip(parse_value(child,skip(value))); /* 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_value(child,skip(value+1)));
if (!value) return 0; /* memory fail */
}
if (*value==']') return value+1; /* end of array */
ep=value;return 0; /* malformed. */
}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. */
//非空Object肯定有孩子节点，创建一个空节点作为孩子节点
item->child=child=cJSON_New_Item();
if (!item->child) return 0;
value=skip(parse_string(child,skip(value)));//Object的key肯定是string，所以紧接着是解析string
if (!value) return 0;
//第一次解析得到的valuestring作为节点名称，并且重置valuestring
child->string=child->valuestring;child->valuestring=0;
if (*value!=':') {ep=value;return 0;} /* fail! */
//值可以是很多类型，所以这里又调用parse_value
value=skip(parse_value(child,skip(value+1))); /* skip any spacing, get the value. */
//第二次解析到的child就没有执行置换valuestring的操作，因为：后面的是值，不需要置换
if (!value) return 0;
//，说明之后的内容都属于同一个Object，并且是同一级别
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;
//第一次解析得到的valuestring作为节点名称，并且重置valuestring
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. */
}12.打印层次树
将解析后的JSON格式数据再还原成JSON格式数据打印。
char *cJSON_Print(cJSON *item) {return print_value(item,0,1,0);}
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;
}
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)//不同的值类型对应不同的编号
{
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;
}static char *print_number(cJSON *item,printbuffer *p)
{
char *str=0;
double d=item->valuedouble;
if (d==0)
{
if (p) str=ensure(p,2);
else str=(char*)cJSON_malloc(2); /* special case for 0. */
if (str) strcpy(str,"0");
}
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);
}
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;
}static char *print_string_ptr(const char *str,printbuffer *p)
{
const char *ptr;char *ptr2,*out;int len=0,flag=0;unsigned char token;
//ptr移至str后
for (ptr=str;*ptr;ptr++) flag|=((*ptr>0 && *ptr<32)||(*ptr=='\"')||(*ptr=='\\'))?1:0;
if (!flag)
{
len=ptr-str;
if (p) out=ensure(p,len+3);
else out=(char*)cJSON_malloc(len+3);
if (!out) return 0;
ptr2=out;*ptr2++='\"';//ptr2的位置赋值\"，之后指针++
strcpy(ptr2,str);
ptr2[len]='\"';
ptr2[len+1]=0;//将字符串构造成\"string\"
return out;
}
if (!str)
{
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++; else if (token<32) len+=5;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);}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;
/* 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*));
/* 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;
}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;
//找到属于该Object的同一级孩子
while (child) numentries++,child=child->next;
/* Explicitly handle empty object case */
if (!numentries)
{
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
{
/* 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);
/* Collect all the results into our arrays: */
child=item->child;depth++;if (fmt) len+=depth;
while (child)
{
//打印key，值肯定是string，所以调用print_string_ptr
names[i]=str=print_string_ptr(child->string,0);
//打印value，value可以是多种类型，所以调用print_value，ret是复原为解析之前的格式
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;
}
/* 重构输出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;
}13.删除层次树
删除整个cJSON层次树结构。
void cJSON_Delete(cJSON *c)
{
cJSON *next;
while (c)
{
next=c->next;
if (!(c->type&cJSON_IsReference) && c->child) cJSON_Delete(c->child);
if (!(c->type&cJSON_IsReference) && c->valuestring) cJSON_free(c->valuestring);
if (!(c->type&cJSON_StringIsConst) && c->string) cJSON_free(c->string);
cJSON_free(c);
c=next;
}
}14.其他函数
//字符串比较函数（不区分大小写），相同返回0，大于返回正值，小于返回负值
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);
}
//深拷贝，根据str创建了一份拷贝
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;
}
//使用自定义内存分配函数，或者是系统内存分配函数，默认是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;
}
//返回比x大的最小的2的N次方数
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;
//确保读取的大小在字符串的范围内; 如果需要的大小在总长度内,直接范围偏移地址;如果不够,则使用Pow2gt先申请更大的一块
//,复制内容后,释放原来的内存,再返回偏移值;
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);
}
//将字符串转换成16进制格式
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;
}
//跳过控制字符，asc码小于33，包括\r\n
static const char *skip(const char *in) {while (in && *in && (unsigned char)*in<=32) in++; return in;}
//双向链表节点互指
static void suffix_object(cJSON *prev,cJSON *item) {prev->next=item;item->prev=prev;}
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;
/* 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 */
cptr=cptr->next;
}
return newitem;
}
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++;
else if (*json=='/' && json[1]=='/') while (*json && *json!='\n') json++; /* double-slash comments, to end of line. */
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. */
}三、cJSON测试程序
#include <stdio.h>
#include <stdlib.h>
#include "cJSON.h"
/* Parse text to JSON, then render back to text, and print! */
void doit(char *text)
{
char *out;cJSON *json;
json=cJSON_Parse(text);
if (!json) {printf("Error before: [%s]\n",cJSON_GetErrorPtr());}
else
{
out=cJSON_Print(json);
cJSON_Delete(json);
printf("%s\n",out);
free(out);
}
}
/* Read a file, parse, render back, etc. */
void dofile(char *filename)
{
FILE *f;long len;char *data;
f=fopen(filename,"rb");fseek(f,0,SEEK_END);len=ftell(f);fseek(f,0,SEEK_SET);
data=(char*)malloc(len+1);fread(data,1,len,f);fclose(f);
doit(data);
free(data);
}
/* Used by some code below as an example datatype. */
struct record {const char *precision;double lat,lon;const char *address,*city,*state,*zip,*country; };
/* Create a bunch of objects as demonstration. */
void create_objects()
{
cJSON *root,*fmt,*img,*thm,*fld;char *out;int i; /* declare a few. */
/* Our "days of the week" array: */
const char *strings[7]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
/* Our matrix: */
int numbers[3][3]={{0,-1,0},{1,0,0},{0,0,1}};
/* Our "gallery" item: */
int ids[4]={116,943,234,38793};
/* Our array of "records": */
struct record fields[2]={
{"zip",37.7668,-1.223959e+2,"","SAN FRANCISCO","CA","94107","US"},
{"zip",37.371991,-1.22026e+2,"","SUNNYVALE","CA","94085","US"}};
/* Here we construct some JSON standards, from the JSON site. */
/* Our "Video" datatype: */
root=cJSON_CreateObject();
cJSON_AddItemToObject(root, "name", cJSON_CreateString("Jack (\"Bee\") Nimble"));
cJSON_AddItemToObject(root, "format", fmt=cJSON_CreateObject());
cJSON_AddStringToObject(fmt,"type", "rect");
cJSON_AddNumberToObject(fmt,"width", 1920);
cJSON_AddNumberToObject(fmt,"height", 1080);
cJSON_AddFalseToObject (fmt,"interlace");
cJSON_AddNumberToObject(fmt,"frame rate", 24);
out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out); /* Print to text, Delete the cJSON, print it, release the string. */
/* Our "days of the week" array: */
root=cJSON_CreateStringArray(strings,7);
out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out);
/* Our matrix: */
root=cJSON_CreateArray();
for (i=0;i<3;i++) cJSON_AddItemToArray(root,cJSON_CreateIntArray(numbers[i],3));
/* cJSON_ReplaceItemInArray(root,1,cJSON_CreateString("Replacement")); */
out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out);
/* Our "gallery" item: */
root=cJSON_CreateObject();
cJSON_AddItemToObject(root, "Image", img=cJSON_CreateObject());
cJSON_AddNumberToObject(img,"Width",800);
cJSON_AddNumberToObject(img,"Height",600);
cJSON_AddStringToObject(img,"Title","View from 15th Floor");
cJSON_AddItemToObject(img, "Thumbnail", thm=cJSON_CreateObject());
cJSON_AddStringToObject(thm, "Url", "http:/*www.example.com/image/481989943");
cJSON_AddNumberToObject(thm,"Height",125);
cJSON_AddStringToObject(thm,"Width","100");
cJSON_AddItemToObject(img,"IDs", cJSON_CreateIntArray(ids,4));
out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out);
/* Our array of "records": */
root=cJSON_CreateArray();
for (i=0;i<2;i++)
{
cJSON_AddItemToArray(root,fld=cJSON_CreateObject());
cJSON_AddStringToObject(fld, "precision", fields[i].precision);
cJSON_AddNumberToObject(fld, "Latitude", fields[i].lat);
cJSON_AddNumberToObject(fld, "Longitude", fields[i].lon);
cJSON_AddStringToObject(fld, "Address", fields[i].address);
cJSON_AddStringToObject(fld, "City", fields[i].city);
cJSON_AddStringToObject(fld, "State", fields[i].state);
cJSON_AddStringToObject(fld, "Zip", fields[i].zip);
cJSON_AddStringToObject(fld, "Country", fields[i].country);
}
/* cJSON_ReplaceItemInObject(cJSON_GetArrayItem(root,1),"City",cJSON_CreateIntArray(ids,4)); */
out=cJSON_Print(root); cJSON_Delete(root); printf("%s\n",out); free(out);
}
int main (int argc, const char * argv[]) {
/* a bunch of json: */
char text1[]="{\n\"name\": \"Jack (\\\"Bee\\\") Nimble\", \n\"format\": {\"type\": \"rect\", \n\"width\": 1920, \n\"height\": 1080, \n\"interlace\": false,\"frame rate\": 24\n}\n}";
char text2[]="[\"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\"]";
char text3[]="[\n [0, -1, 0],\n [1, 0, 0],\n [0, 0, 1]\n ]\n";
char text4[]="{\n \"Image\": {\n \"Width\": 800,\n \"Height\": 600,\n \"Title\": \"View from 15th Floor\",\n \"Thumbnail\": {\n \"Url\": \"http:/*www.example.com/image/481989943\",\n \"Height\": 125,\n \"Width\": \"100\"\n },\n \"IDs\": [116, 943, 234, 38793]\n }\n }";
char text5[]="[\n {\n \"precision\": \"zip\",\n \"Latitude\": 37.7668,\n \"Longitude\": -122.3959,\n \"Address\": \"\",\n \"City\": \"SAN FRANCISCO\",\n \"State\": \"CA\",\n \"Zip\": \"94107\",\n \"Country\": \"US\"\n },\n {\n \"precision\": \"zip\",\n \"Latitude\": 37.371991,\n \"Longitude\": -122.026020,\n \"Address\": \"\",\n \"City\": \"SUNNYVALE\",\n \"State\": \"CA\",\n \"Zip\": \"94085\",\n \"Country\": \"US\"\n }\n ]";
/* Process each json textblock by parsing, then rebuilding: */
//解析传入的字符串并以JSON格式数据输出
doit(text1);
doit(text2);
doit(text3);
doit(text4);
doit(text5);
/* Now some samplecode for building objects concisely: */
//根据cJSON提供的接口手动构建层次树并输出
create_objects();
return 0;
}
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