[ソース分析]-軽量級JSON-cJson


[ソース分析]-軽量級JSON-cJson
second60 20180612
1.cJSON概要
cJsonは軽量級のC言語JSONライブラリで、速度が速くて、しかもコードが少なくて、2つのファイルしかありません:cJSON.hとcJSON.c.コードは700行以上しかありません.
 
使用はcJSONファイルを導入するだけで、一緒にコンパイルすればいいです.数学ライブラリを使用して、-lmライブラリを追加します.
g++ test.c cJSON.c -o test
gcc test.c cJSON.c -o test -lm
2.JSON知識
JSON(JavaScript Object Notation,JSオブジェクトプロファイル)は、軽量レベルのデータ交換フォーマットです.ECMAScript(欧州コンピュータ協会が制定したjs仕様)のサブセットに基づいて、プログラミング言語とは完全に独立したテキストフォーマットを用いてデータを格納し、表す.簡潔で明確な階層はJSONを理想的なデータ交換言語にした.読み取りと作成が容易であり、同時に機械の解析と生成が容易であり、ネットワーク伝送効率を効果的に向上させる.
2.1 json構文
JS言語では、すべてが対象です.したがって、文字列、数字、オブジェクト、配列など、サポートされるタイプはJSONで表すことができます.ただし、オブジェクトと配列は比較的特殊で一般的な2つのタイプです.
オブジェクトはキー値ペアとして表示されます
カンマで区切られたデータ
かっこでオブジェクトを保存
かっこ保存配列
 
オブジェクト:JSONで最も一般的なフォーマットは、オブジェクトのキー値ペアです.
{"firstName": "Json"}
配列:配列の仕方もかっこ[]を使う
{
    "people":[
    {
        "firstName": "Brett",
        "lastName":"McLaughlin"
    },
    {  
        "firstName":"Jason",
        "lastName":"Hunter"
    }
    ]
}

2.2 jsonのメリット
a)共通性、いかなる言語もjson形式であれば、互いに通じ合うことができる.
b)jsonの変換速度は非常に速い
c)jsonはxmlより体積が小さい
d)jsonの拡張性は非常に良く、itemを追加するにはkey/valueを追加するだけです.
 
2.3 jsonの劣化点
a)jsonボリュームは通常のストリームボリュームよりも大きく、引用符、偽名、キー名などが含まれているため、ネットワークよりもトラフィックを浪費している.
b)json再帰深さには制限があり、深さが深いと速度が遅くなり、メモリの消費量が大きい
c)json文字列は順番がないので読みづらい
 
2.4使用場所景
ほとんどのプロジェクトでは、jsonが使用されます.jsonには言語に関係なく、json形式であれば、読み取り使用できます.
 
a)json構成.json解析速度はxmlよりも速く、小さいので、構成をjson文字列に変換すると、プログラムの読み取りが非常に速くなり、構成はローカルに置くこともredisに置くこともできます.
b)ネットワークフォーマット.jsonは比較的大きいが,ネットワークインタフェースではjsonフォーマットを用いることができ,jsonが良好な拡張性を有し,パラメータや戻り値を加えることが容易であり,従来の論理に影響を及ぼさないことを目的とする.
c)言語間インタラクション.2つの異なる言語が対話するように、jsonで対話することができます.
 
まとめて、jsonは用途が非常に広く、非常に使いやすい基準です.
3.cJSONソース分析
3.1 cJSONデータ構造
cJSONには2つの構造が含まれており、cJSON構造とcJSON_Hooks構造
// cJson    
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. */
  //     cJSON_String,    
char *valuestring;	/* The item's string, if type==cJSON_String */
  //     cJSON_Number,     
int valueint;	/* The item's number, if type==cJSON_Number */
double valuedouble;	/* The item's number, if type==cJSON_Number */
  // item  
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       ,         
typedef struct cJSON_Hooks {
      void *(*malloc_fn)(size_t sz);
      void (*free_fn)(void *ptr);
} cJSON_Hooks;

3.2 cJSON関数ライブラリ
/* 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実現
/* cJSON */
/* JSON parser in C. */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "cJSON.h"

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

//    malloc free  
static void *(*cJSON_malloc)(size_t sz) = malloc;
static void(*cJSON_free)(void *ptr) = free;

//      
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;
}

//          
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. */
//      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. */
//     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. */
//  num      item 
static const char *parse_number(cJSON *item, const char *num)
{
	double n = 0, sign = 1, scale = 0; int subscale = 0, signsubscale = 1;
	//  num    
	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;
}

//   x     2 N   
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. */
//          
static char *print_number(cJSON *item, printbuffer *p)
{
	char *str = 0;
	double d = item->valuedouble;
	// 0    
	//   d==0        d   double  
	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  21   
	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);
	}
	//      64 
	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;
}

//           "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 };

//  str       item 
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++ = '
'; 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
\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 '
': *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. */ // value item 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. */ // [] 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 */ // 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. */ // 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++ = '
'; for (i = 0; ioffset; len = fmt ? 2 : 1; ptr = ensure(p, len + 1); if (!ptr) return 0; *ptr++ = '{'; if (fmt) *ptr++ = '
'; *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++ = '
'; *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 */ // item 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 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 == '
') json++; else if (*json == '/' && json[1] == '/') while (*json && *json != '
') 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! */
//       json  
void doit(char *text)
{
	char *out; cJSON *json;
	json = cJSON_Parse(text);
	if (!json) { printf("Error before: [%s]
", cJSON_GetErrorPtr()); } else { out = cJSON_Print(json); cJSON_Delete(json); printf("%s
", 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
", 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
", 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
", 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
", 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
", out); free(out); } int main(int argc, const char * argv[]) { /* a bunch of json: */ char text1[] = "{
\"name\": \"Jack (\\\"Bee\\\") Nimble\",
\"format\": {\"type\":       \"rect\",
\"width\":      1920,
\"height\":     1080,
\"interlace\":  false,\"frame rate\": 24
}
}"; char text2[] = "[\"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\"]"; char text3[] = "[
    [0, -1, 0],
    [1, 0, 0],
    [0, 0, 1]
]
"; char text4[] = "{
\"Image\": {
\"Width\":  800,
\"Height\": 600,
\"Title\":  \"View from 15th Floor\",
\"Thumbnail\": {
\"Url\":    \"http:/*www.example.com/image/481989943\",
\"Height\": 125,
\"Width\":  \"100\"
},
\"IDs\": [116, 943, 234, 38793]
}
}"; char text5[] = "[
{
\"precision\": \"zip\",
\"Latitude\":  37.7668,
\"Longitude\": -122.3959,
\"Address\":   \"\",
\"City\":      \"SAN FRANCISCO\",
\"State\":     \"CA\",
\"Zip\":       \"94107\",
\"Country\":   \"US\"
  },
{
\"precision\": \"zip\",
\"Latitude\":  37.371991,
\"Longitude\": -122.026020,
\"Address\":   \"\",
  \"City\":      \"SUNNYVALE\",
\"State\":     \"CA\",
\"Zip\":       \"94085\",
\"Country\":   \"US\"
}
]"; /* 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; }