任何人都知道基于 C 的 JSON 解析器，它允许我访问用于数字字段的字符串表示形式？我的意思的例子：
json_t * dist = json_object_get(coord, "accuracy");
snprintf(dataOut->distance, MAX_COORD_LEN, "%f", json_number_value(dist));
这是愚蠢且难以编写单元测试的。我宁愿简单地调用json_string_value(dist)并准确获取该号码的字符串。我更希望它不会费心将该字符串转换为数字。这样，当我为我的例程提供一个包含“54.6045”的测试字符串时，我会得到“54.6045”而不是一些填充或舍入的值......而且我不需要解析这个数字，因为我永远不会去将其用作一个。
据我所知，没有这样的事情......在我看来这很愚蠢。上面的示例来自 Jansson，使用字符串值函数返回 null。
我真的不想因为这个而不必自己写。
In case you didn't already know this, http://www.json.org/ maintains a list of JSON libraries written in a wide variety of languages, including 12 of them in C.
I'm using jsmn for a resource-constrained, embedded platform. All it does is tokenize JSON strings, so you could get what you need from that library, but you would need to construct a little more logic around it to do anything useful.
Similarly, you could probably adapt JSON_checker to do what you want.
If you can't find one that does what you want, it's not that hard to parse yourself.
您可以使用https://github.com/cesanta/frozen
自述文件中有一个示例，可以准确显示您的要求，这是一个简短版本：
static const char *str = " { foo: { bar: [ 80, 443 ], baz: 1.2e-21 } } ";
struct json_token tokens[50];
int size = sizeof(tokens) / sizeof(tokens[0]);
const struct json_token *tok = NULL;
parse_json(str, strlen(str), tokens, size);
tok = find_json_token(tokens, "foo.bar[1]");
printf("My number is: [%.*s]\n", tok->len, tok->ptr)
Tiny-json 是一个 C 解析器，它允许您以最简单的方式访问数字字段的字符串表示形式。只需请求一个 JSON 属性，它就会返回一个指向以空值结尾的指针。 https://github.com/rafagafe/tiny-json
#include <stdio.h>
#include "tiny-json.h"
int main( int argc, char** argv ) {
char str[] = "{\"accuracy\":654,\"real\":2.54e-3}";
// In the example only 3 is needed. For root and two fields.
json_t mem[ 3 ];
json_t const* root = json_create( str, mem, sizeof mem / sizeof *mem );
if ( !root ) {
fputs( "Cannot create a JSON.\n", stderr );
return 1;
}
{ // You can get the primitive values as text format:
char const* accuracy = json_getPropertyValue( root, "accuracy" );
if ( !accuracy ) {
fputs( "The filed 'accuracy' is not found.\n", stderr );
return 1;
}
printf( "The accuracy value: %s\n", accuracy );
char const* real = json_getPropertyValue( root, "real" );
if ( !real ) {
fputs( "The filed 'real' is not found.\n", stderr );
return 1;
}
printf( "The real value: %s\n", real );
}
{ // You can check the type of a field and get its value in binary format:
json_t const* accuracy = json_getProperty( root, "accuracy" );
if ( !accuracy ) {
fputs( "The filed 'accuracy' is not found.\n", stderr );
return 1;
}
if( json_getType( accuracy ) != JSON_INTEGER ) {
fputs( "The filed 'accuracy' is not an integer.\n", stderr );
return 1;
}
// Get the value in binary format:
long long accuracyVal = json_getInteger( accuracy );
printf( "The accuracy value: %lld\n", accuracyVal );
// Get the value in text format:
char const* accuracyTxt = json_getValue( accuracy );
printf( "The accuracy value: %s\n", accuracyTxt );
json_t const* real = json_getProperty( root, "real" );
if ( !accuracy ) {
fputs( "The filed 'real' is not found.\n", stderr );
return 1;
}
if( json_getType( real ) != JSON_REAL ) {
fputs( "The filed 'real' is not a real.\n", stderr );
return 1;
}
// Get the value in binary format:
double realVal = json_getReal( real );
printf( "The real value: %f\n", realVal );
// Get the value in text format:
char const* realTxt = json_getValue( real );
printf( "The real value: %s\n", realTxt );
}
return 0;
}
Jansson 是一个很棒的库，如果基于单元测试选择另一个库，那就太可惜了。我不确定你为什么反对解析数值——你能解释一下吗？
就您的代码片段而言，您可能会对从结构中检索数值所涉及的样板文件感到有些恼火。我建议你学会爱上 json_pack / json_unpack 函数。您可以从字典中检索整数元素，如下所示：
double d;
json_unpack(coord, "{s:f}", "accuracy", &d);
使用此调用，您不必使用表示浮点值的 (json_t *) 对象。当然，您应该检查 json_unpack() 调用的返回码以了解错误情况。