我有一个简单的网页，它在 <body> 中显示一个 json 对象.我在这里简化了示例，因为每个元素都有很多数据，并且没有必要在这个问题中打印出来。但是，我保留了格式，包括回车。
<body>
callBack({
"resSet":[
{
"results":[
{^M
"res":{"data inside res",^M
"more data",^M
{"and some more"}^M
},^M
{^M
"res":{"data inside res",^M
"more data",^M
{"and some more"}^M
},^M
{^M
"res":{"data inside res",^M
"more data",^M
{"and some more"}^M
}],^M
"other resSet data"^M
}^M
],
})^M
</body>
我在 C 中使用 libcurl 将此数据作为字符串读入内存。我使用 C 和 cURL 来保持可移植性和内存控制。我想要做的是将 "results" 的元素分开数组，这样我就可以根据自己的选择对它们进行重新排序。排序后json写入文件供其他程序使用。
请注意，这可能具有 JSON 对象的结构，但它在内存中被视为字符串。
这是我的代码。
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
struct MemoryStruct {
char *memory;
size_t size;
};
static size_t
WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
// curl callback function (found on
https://curl.haxx.se/libcurl/c/getinmemory.html)
{
size_t realsize = size * nmemb;
struct MemoryStruct *mem = (struct MemoryStruct *)userp;
char *ptr = realloc(mem->memory, mem->size + realsize + 1);
if(ptr == NULL) {
/* out of memory! */
printf("not enough memory (realloc returned NULL)\n");
return 0;
}
mem->memory = ptr;
memcpy(&(mem->memory[mem->size]), contents, realsize);
mem->size += realsize;
mem->memory[mem->size] = 0;
return realsize;
}
int main(int argc, char *argv[]) { // pass query and collection
curl_global_init(CURL_GLOBAL_ALL);
CURL *curl;
CURLcode res;
struct MemoryStruct chunk;
char *url = calloc(1024, 1); // url to maxxcat4.astm.org/query4.cgi, plenty of space for query and collection parameters
char *query = calloc(strlen(argv[1])+1, 1); // +1 so | can be placed in function FetchLine
char *collection = calloc(strlen(argv[2]), 1);
char *order; // not allocated, points to return from function FetchLine
sprintf(query, "%s", argv[1]);
sprintf(collection, "%s", argv[2]);
sprintf(url, "http://maxxcat4.astm.org/query4.cgi?query=%s&collection=%s", query, collection); // query then collection
chunk.memory = malloc(1); // currently using realloc, should change to calloc
chunk.size = 0; // nothing, initially
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, url); // fetch data from url
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION,WriteMemoryCallback); // send the data to the function WriteMemoryCallback (found on https://curl.haxx.se/libcurl/c/getinmemory.html)
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk); // pass the MemoryStruct chunk to the function
curl_easy_setopt(curl, CURLOPT_USERAGENT, "libcurl-agent/1.0"); // set a user agent if the server requests for one
res = curl_easy_perform(curl); // retrieve data
if(res != CURLE_OK) { // make sure things worked
fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
} else {
/*
Sort the data while in memory according to how the file is shuffled
- read file into memory
- take one line at a time, breaking on delimiter (if needed)
- shuffle each res
*/
// order = FetchLine(query);
FILE *fp;
fp = fopen("maxxcat4_data.json", "w");
/* seperate results array elements here */
fclose(fp);
printf("%lu bytes retrieved\n", (unsigned long)chunk.size);
}
/* always cleanup */
curl_easy_cleanup(curl); // clean up handle
free(chunk.memory);
free(url);
free(query);
free(collection);
free(order);
curl_global_cleanup(); // clean up libcurl
}
return 0;
}
我的第一个想法是使用 strtok()但我不知道一种方法来分隔字符串，而不是一组分隔符中的单个字符。我读过 json-c ，但我想尽可能避免这样的依赖。如何分离元素？
最佳答案
I kept the format, however, including the carriage returns.
如果您知道确切的格式，则可以利用这些知识并简化阅读 - e。 G。结果的每个元素在一行的开头以 } 结尾。
下面的代码片段将 chunk.memory 中的字符串分成 head(结果元素之前的部分)，res[nres] ( nres 元素的数组)和 tail(结果元素之后的部分，在结束 ] 之后)；注释与代码内联。
char c, *head, **res = NULL, *tail; // pointers to parts
int nres = 0; // number of results
head = chunk.memory; // it begins here
const char results[] = "\"results\":[";
char *cp = strstr(head, results); // find the results
if (!cp) printf("%s not found\n", results), exit(1);
cp += strlen(results); // skip to the \n
*cp++ = '\0'; // delimit the head
do
{
res = realloc(res, sizeof *res * ++nres);
if (!res) puts("out of memory"), exit(1);
res[nres-1] = cp; // store the result
cp = strstr(cp, "\n}"); // find end of result
if (!cp) puts("} not found"), exit(1);
cp += 2; // skip over the }
c = *cp; // character after } is , or ]
*cp++ = '\0'; // delimit the string
} while (c == ',');
if (c != ']') puts("] not found"), exit(1);
tail = cp; // rest follows here
// output the parts with results rearranged, e. g. backwards
printf("%s\n", head);
while (nres--) printf("%s%c", res[nres], nres ? ',' : ']');
free(res);
printf("%s", tail);
关于c - 在 C 中将 JSON 数组元素分隔为字符串，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/54992132/