C语言实现手写JSON解析的方法详解
什么是JSON
JSON（javascript Object Notation）是一种轻量级的数据交换格式，用来传输属性值或者序列性的值组成的数据对象。
JSON是JavaScript的一个子集。
具有良好的可读性和便于快速编写的特性。
JSON是独立于语言的文本格式，并且采用了类似C语言家族的一些习惯。
JSON数据格式与语言无关，是目前网络中主流的数据传输格式之一，使用率几乎为99%。
JSON支持的数据类型
JSON里面的数据以一种键值对的方式存在，即“key”:“value” 类型可以是数据类型中的任意一种：
JSON语法规则
JSON的语法规则非常简单，使用
大括号——{}
中括号——[]
逗号——，
冒号——：
双引号——“” (一般可以不需要)
JSON的解析
在解析JSON是我们会遇到两种情况，其一是解析大括号——{}类型，其二是解析中括号类型——[]，以及这两种类型的组合模式。
JSON基本语法
对象类型（Object）
{
"name" : "佩奇" ,
"age" : "8"
}
数组类型（Array）
[
"喜羊羊","懒羊羊",5,true,null
]
对象组合形
{
"name" : "佩奇" ,
"age" : "8",
"friend" :[{"name" : " 喜羊羊 " , "age" : "5"} , {"name" : " 懒羊羊 " , "age" : "6"}]
//对象类型嵌套数组类型，数组类型嵌套对象类型
}
数组组合型
[ [{"name" : "佩奇" ,"age" : "8"},{"name" : "佩奇" ,"age" : "8"}],[{},{}]]
编写解析器
头文件
//
// Created by huanmin on 2022/9/15.
//
#ifndef STUDY_JSON_H
#define STUDY_JSON_H
#include "../util/str_util.h"
#include <stdio.h>
#include "charHashMap.h"
#include "charlist.h"
#include "../util/assertmy.h"
static char *str_to_json_placeholder(char *string, CharHashMap *map, CharHashMap *list);
static char *querySubstitute(char *string, CharHashMap *map, CharHashMap *list);
BOOL str_is_json(char *string);
CharList *str_to_json_array(char *array);
CharHashMap *str_to_json_map(char *dict);
char *map_to_json_str(CharHashMap *pMap);
char *array_to_json_str(CharList *pCharlist);
BOOL str_is_map(char *str);
BOOL str_is_array(char *str);
#endif //STUDY_JSON_H实现文件
//
// Created by huanmin on 2022/9/15.
//
#include "json.h"
//转换字符串为JSON_先进行占位符替换
static char *str_to_json_placeholder(char *string, CharHashMap *map, CharHashMap *list) {
//判断是否有[],如果有那么提取出来,并且将位置上的内容替换为 @arri
int zi = 0;
int start = -1;
while ((start = str_find(string, "[")) != -1) {
int length = str_length(string);
int jilu = 0;
int end = -1;
for (int i = start; i < length; ++i) {
if (string[i] == '[') {
jilu++;
}
if (string[i] == ']') {
jilu--;
if (jilu == 0) {
end = i;
break;
}
}
}
char *arr_str = str_substring(string, start, end);
char *append = str_concat(3, "@arr", int_to_str(zi), "@");
putCharHashMap(list, append, arr_str);
string = str_replace(string, arr_str, append);
zi++;
}
zi = 0;
start = -1;
//判断是否有{},如果有那么提取出来, 并且将位置上的内容替换为@mapi
while ((start = str_find(string, "{")) != -1) {
int length = str_length(string);
int jilu = 0;
int end = -1;
for (int i = start; i < length; ++i) {
if (string[i] == '{') {
jilu++;
}
if (string[i] == '}') {
jilu--;
if (jilu == 0) {
end = i;
break;
}
}
}
char *map_str = str_substring(string, start, end);
char *append = str_concat(3, "@map", int_to_str(zi), "@");
putCharHashMap(map, append, map_str);
string = str_replace(string, map_str, append);
zi++;
}
return string;
}
static char *querySubstitute(char *string, CharHashMap *map, CharHashMap *list) {
char *str = string;
int start = -1;
//替换
if (str_start_with(string, "@map")) {
while ((start = str_find(str, "@map")) != -1) {
int end = str_find_n(str, "@", start + 1, str_length(str));
char *substring = str_substring(str, start, end);
str = (char *) getCharHashMap(map, substring);
}
} else if (str_start_with(string, "@arr")) {
//替换参数为原来的值
while ((start = str_find(str, "@arr")) != -1) {
int end = str_find_n(str, "@", start + 1, str_length(str));
char *substring = str_substring(str, start, end);
str = (char *) getCharHashMap(list, substring);
}
}
start = -1;
//判断是否还包含@map或者@arr,如果有那么就继续替换
while ((start = str_find(str, "@map")) != -1 || (start = str_find(str, "@arr")) != -1) {
//截取所有的@map@和@arr@,并且将其替换为原来的字符串
CharList *pCharlist = createCharList(10);
while ((str_find_n(str, "@map", start, str_length(str))) != -1 ||
(str_find_n(str, "@arr", start, str_length(str))) != -1) {
int end = str_find_n(str, "@", start + 1, str_length(str));
char *substring = str_substring(str, start, end);
addCharList(pCharlist, substring);
start = end;
}
CharListIterator *pIterator = createCharListIterator(pCharlist);
while (hasNextCharListIterator(pIterator)) {
char *key = nextCharListIterator(pIterator);
if (str_start_with(key, "@map")) {
char *value = (char *) getCharHashMap(map, key);
str = str_replace(str, key, value);
} else if (str_start_with(key, "@arr")) {
char *value = (char *) getCharHashMap(list, key);
str = str_replace(str, key, value);
}
}
}
return str;
}
//将字符串数组格式[1,2,3]或者[{a:b,c:d},{a:b,c:d}]转换为List ,(没有任何格式验证,全靠自己规范编写)
CharList *str_to_json_array(char *array) {
if (array == NULL || str_length(array) == 0) {
return NULL;
}
char *trim = str_trim(array);
char *string = str_substring(trim, 1, str_length(trim) - 2);
CharHashMap *map = createCharHashMap(10);
CharHashMap *list = createCharHashMap(10);
char *string1 = str_to_json_placeholder(string, map, list);
CharList *pCharlist = str_split(string1, ",");
for (int i = 0; i < pCharlist->len; ++i) {
char *v = pCharlist->str[i];
pCharlist->str[i] = querySubstitute(v, map, list);
}
return pCharlist;
}
//将json对象字符串{a:b,c:d},转换为hashMap ,(没有任何格式验证,全靠自己规范编写)
CharHashMap *str_to_json_map(char *dict) {
if (dict == NULL || str_length(dict) == 0) {
return NULL;
}
char *trim = str_trim(dict);
char *string = str_substring(trim, 1, str_length(trim) - 2);
CharHashMap *map = createCharHashMap(10);
CharHashMap *list = createCharHashMap(10);
char *string1 = str_to_json_placeholder(string, map, list);
CharList *pCharlist = str_split(string1, ",");
int str_len = pCharlist->len;
if (str_len == 0) {
return NULL;
}
//分割key和value
CharHashMap *pMap = createCharHashMap(str_len);
for (int i = 0; i < str_len; i++) {
char *str = pCharlist->str[i];
CharList *pList = str_split(str, ":");
char *key = str_trim(pList->str[0]);
char *value = str_trim(pList->str[1]);
putCharHashMap(pMap, key, querySubstitute(value, map, list));
}
return pMap;
}
//将hashMap转换为json对象{a:b,c:d,v:[1,2],f:{a:b,c:d}} ,(没有任何格式验证,全靠自己规范编写)
char *map_to_json_str(CharHashMap *pMap) {
if (pMap == NULL) {
return NULL;
}
char *string = str_create("{");
int len = pMap->size;
//创建迭代器
CharHashMapIterator *pIterator = createCharHashMapIterator(pMap);
while (hasNextCharHashMapIterator(pIterator)) {
CharKvLinkednode *pNode = nextCharHashMapIterator(pIterator);
string = str_append(string, pNode->key);
string = str_append(string, ":");
string = str_append(string, pNode->value);
if (len != 1) {
string = str_append(string, ",");
}
len--;
}
string = str_append(string, "}");
return string;
}
//将CharList转换为json数组格式[1,2,[1,2,3]]或者[{},{}] ,(没有任何格式验证,全靠自己规范编写)
char *array_to_json_str(CharList *pCharlist) {
if (pCharlist == NULL) {
return NULL;
}
char *string = str_create("[");
for (int i = 0; i < pCharlist->len; ++i) {
string = str_append(string, pCharlist->str[i]);
if (i != pCharlist->len - 1) {
string = str_append(string, ",");
}
}
string = str_append(string, "]");
return string;
}
//判断是否是json对象
BOOL str_is_map(char *str) {
if (str == NULL) {
return FALSE;
}
if (str_length(str) < 2) {
return FALSE;
}
if (str_start_with(str, "{") && str_end_with(str, "}")) {
return TRUE;
}
return FALSE;
}
//判断是否是数组
BOOL str_is_array(char *str) {
if (str == NULL) {
return FALSE;
}
if (str_length(str) < 2) {
return FALSE;
}
if (str_start_with(str, "[") && str_end_with(str, "]")) {
return TRUE;
}
return FALSE;
}
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