[源码分析]-轻量级JSON-cJson
[源码分析]-轻量级JSON-cJson
second60 20180612
1. cJSON简介
cJson是个轻量级的C语言JSON库，速度快，而且代码少，只有两个文件：cJSON.h和cJSON.c。代码只有七百多行。
使用只需引入cJSON文件，一起编译即可，使用了数学库，要添加-lm库
g++ test.c cJSON.c -o test
gcc test.c cJSON.c -o test -lm
2. JSON知识
JSON(JavaScript Object Notation, JS 对象简谱) 是一种轻量级的数据交换格式。它基于 ECMAScript (欧洲计算机协会制定的js规范)的一个子集，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。
2.1 json 语法
在 JS 语言中，一切都是对象。因此，任何支持的类型都可以通过 JSON 来表示，例如字符串、数字、对象、数组等。但是对象和数组是比较特殊且常用的两种类型：
对象表示为键值对
数据由逗号分隔
花括号保存对象
方括号保存数组
对象：JSON最常用的格式是对象的键值对
{"firstName": "Json"}
数组：数组的方式也是使用方括号 []
{
"people":[
{
"firstName": "Brett",
"lastName":"McLaughlin"
},
{
"firstName":"Jason",
"lastName":"Hunter"
}
]
}2.2 json的好处
a) 通用性，任何语言只要按照json格式，都可以互通使用
b) json的转换速度非常快
c) json比xml体积小
d) json的扩展性非常好，新加item只需多加key/value
2.3 json的劣点
a) json体积会比正常的流体积大很多，包括：引号，冒名，键名等，所以比网络中比较浪费流量
b) json递归深度有限制，如果深度很深，那么速度将会变慢，同时占用内存比较大
c) json字符串没有顺序，所以较难读懂
2.4 使用场所景
在大部份的项目中，都会使用json，因为json有语言无关性，只要都是json格式，都可以读取使用。
a) json配置。因为json解析速度比xml要快，要小，所以把配置转成json字符串，程序中读取将会非常快，配置可以放本地，也可以放redis中。
b) 网络格式。虽然json会比较大，但对于网络接口，可以用json格式，目的是json有很好的扩展性，加一个参数或返回值，是非常容易，而且不影响原有逻辑。
c) 跨语言交互。如两个不同语言交互，可以用json来进行交互。
总结，json是一个用途非常广泛，也非常好用的标准。
3. cJSON源码分析
3.1 cJSON数据结构
cJSON中包含两个结构，cJSON结构和cJSON_Hooks结构
// cJson 结构体
typedef struct cJSON {
// 双链表指针
struct cJSON *next,*prev; /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */
// 孩子指什
struct cJSON *child; /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */
// 类型
int type; /* The type of the item, as above. */
// 当类型为cJSON_String,此值有用
char *valuestring; /* The item's string, if type==cJSON_String */
// 当类型为cJSON_Number，下面值有用
int valueint; /* The item's number, if type==cJSON_Number */
double valuedouble; /* The item's number, if type==cJSON_Number */
// item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;
// cJson 函数指针钩子，用来实现不同的函数
typedef struct cJSON_Hooks {
void *(*malloc_fn)(size_t sz);
void (*free_fn)(void *ptr);
} cJSON_Hooks;3.2 cJSON函数库
/* Supply malloc, realloc and free functions to cJSON */
extern void cJSON_InitHooks(cJSON_Hooks* hooks);
/* 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. */
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);
/* Returns the number of items in an array (or object). */
extern int cJSON_GetArraySize(cJSON *array);
/* Retrieve item number "item" from array "array". Returns NULL if unsuccessful. */
extern cJSON *cJSON_GetArrayItem(cJSON *array,int item);
/* Get item "string" from object. Case insensitive. */
extern cJSON *cJSON_GetObjectItem(cJSON *object,const char *string);
/* 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);
/* 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);
/* 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);
/* 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);
/* 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);
/* 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);
/* 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))
/* 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))3.3 cJSON实现
/* cJSON */
/* JSON parser in C. */
#include
#include
#include
#include
#include
#include
#include
#include "cJSON.h"
// 错误指针
static const char *ep;
// 返回错误指针
const char *cJSON_GetErrorPtr(void) { return ep; }
// 字符串大小比较
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);
}
// 初始化malloc和free函数
static void *(*cJSON_malloc)(size_t sz) = malloc;
static void(*cJSON_free)(void *ptr) = free;
// 复制字符串
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;
}
// 初始化犯错钩子函数
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;
}
/* Internal constructor. */
// 创建设一个item
static cJSON *cJSON_New_Item(void)
{
cJSON* node = (cJSON*)cJSON_malloc(sizeof(cJSON));
if (node) memset(node, 0, sizeof(cJSON));
return node;
}
/* Delete a cJSON structure. */
// 遍历删除cJson
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;
}
}
/* Parse the input text to generate a number, and populate the result into item. */
// 把num转成整型放到item中
static const char *parse_number(cJSON *item, const char *num)
{
double n = 0, sign = 1, scale = 0; int subscale = 0, signsubscale = 1;
// 把num转成整型
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 */
// 会同时设置两个值，一个整型，一个浮点型
item->valuedouble = n;
item->valueint = (int)n;
item->type = cJSON_Number;
return num;
}
//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;
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);
}
/* Render the number nicely from the given item into a string. */
// 把数据转换成字符串
static char *print_number(cJSON *item, printbuffer *p)
{
char *str = 0;
double d = item->valuedouble;
// 0分配两位
// 这里d==0会不会有问题呢 d是一个double类型
if (d == 0)
{
if (p) str = ensure(p, 2);
else str = (char*)cJSON_malloc(2); /* special case for 0. */
if (str) strcpy(str, "0");
}
// 2^64+1 占21个字符
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);
}
// 科学计数 64位
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;
}
// 解析四位十六进制数 "ffff"
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 };
// 把str字符串解析放入item中
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! */
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;
}
/* 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)
{
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)
{
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); }
/* 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);
/* Utility to jump whitespace and cr/lf */
static const char *skip(const char *in) { while (in && *in && (unsigned char)*in <= 32) in++; return in; }
/* 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));
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); }
/* Render a cJSON item/entity/structure to text. */
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;
}
/* Parser core - when encountering text, process appropriately. */
// 解析value的值到item中
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 parse_array(item, value); }
if (*value == '{') { return parse_object(item, value); }
ep = value; return 0; /* failure. */
}
/* 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;
}
/* Build an array from input text. */
// 解析数组 []
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. */
}
/* Render an array to text */
// 将数据转换成字符
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; itype = 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! */
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. */
// 将对象转换成字符
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;
/* Count the number of entries. */
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; ioffset;
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; joffset += 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; ibuffer) + 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)
{
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; ichild; 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; }
/* Utility for array list handling. */
static void suffix_object(cJSON *prev, cJSON *item) { prev->next = item; item->prev = prev; }
/* 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; }
/* 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)); }
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)); }
/* Replace array/object items with new ones. */
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); } }
/* 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; }
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; }
/* Create Arrays: */
cJSON *cJSON_CreateIntArray(const int *numbers, int count) { int i; cJSON *n = 0, *p = 0, *a = cJSON_CreateArray(); for (i = 0; a && ichild = 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 && ichild = 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 && ichild = 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 && ichild = n; else suffix_object(p, n); p = n; }return a; }
/* Duplication */
// 复制item 是否递归recurse
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;
}
// json 缩进
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. */
} 3.4 cJSON使用
#include
#include
#include "cJSON.h"
/* Parse text to JSON, then render back to text, and print! */
// 把文本转找成json格式
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: */
doit(text1);
doit(text2);
doit(text3);
doit(text4);
doit(text5);
/* Now some samplecode for building objects concisely: */
create_objects();
return 0;
}