6

我正在尝试在 linux 服务器上使用 C 解析 YAML 文件（这是对现有应用程序的修改，因此不能选择更改语言）。

我已经阅读了http://wpsoftware.net/andrew/pages/libyaml.html和 libyaml wiki 上的教程。

我想要做的是将这个应用程序的数据库配置从头文件中移到 YAML 中，以便我可以作为单独的步骤进行编译和配置，从而允许我使用 Chef 来管理配置。

这是yaml：

---
db_server: "localhost"
db_password: "wibble"
db_username: "test"
national_rail_username: test
national_rail_password: wibble

我想要做的是遍历文件并根据键名设置变量。

伪代码如下：

config = YAML::load("file.yaml")
DBUSER = config['db_username']
DBPASS = config['db_password']
DBSERVER = config['db_server']
NATIONAL_RAIL_USERNAME = config['national_rail_username']
NATIONAL_RAIL_PASSWORD = config['national_rail_password']

（如果上面看起来有点像 ruby​​/python，那是因为我习惯使用这些语言！）

我设法让一个使用 YAML-cpp 的测试设置工作，然后我意识到我已经在错误的树上吠了三个小时，因为主要应用程序是用 C 编写的，而不是 C++。

编辑：这是我到目前为止的代码。它是上面教程网站的剪切和粘贴，但是我不认为这是正确的方法，并且它似乎没有为我提供一种将 YAML“键”分配给 C 代码中的变量的方法。

#include <stdio.h>
#include <yaml.h>

int main(void)
{
  FILE *fh = fopen("config.yaml", "r");
  yaml_parser_t parser;
  yaml_token_t  token;   /* new variable */

  /* Initialize parser */
  if(!yaml_parser_initialize(&parser))
    fputs("Failed to initialize parser!\n", stderr);
  if(fh == NULL)
    fputs("Failed to open file!\n", stderr);

  /* Set input file */
  yaml_parser_set_input_file(&parser, fh);

  /* BEGIN new code */
  do {
    yaml_parser_scan(&parser, &token);
    switch(token.type)
    {
    /* Stream start/end */
    case YAML_STREAM_START_TOKEN: puts("STREAM START"); break;
    case YAML_STREAM_END_TOKEN:   puts("STREAM END");   break;
    /* Token types (read before actual token) */
    case YAML_KEY_TOKEN:   printf("(Key token)   "); break;
    case YAML_VALUE_TOKEN: printf("(Value token) "); break;
    /* Block delimeters */
    case YAML_BLOCK_SEQUENCE_START_TOKEN: puts("<b>Start Block (Sequence)</b>"); break;
    case YAML_BLOCK_ENTRY_TOKEN:          puts("<b>Start Block (Entry)</b>");    break;
    case YAML_BLOCK_END_TOKEN:            puts("<b>End block</b>");              break;
    /* Data */
    case YAML_BLOCK_MAPPING_START_TOKEN:  puts("[Block mapping]");            break;
    case YAML_SCALAR_TOKEN:  printf("scalar %s \n", token.data.scalar.value); break;
    /* Others */
    default:
      printf("Got token of type %d\n", token.type);
    }
    if(token.type != YAML_STREAM_END_TOKEN)
      yaml_token_delete(&token);
  } while(token.type != YAML_STREAM_END_TOKEN);
  yaml_token_delete(&token);
  /* END new code */

  /* Cleanup */
  yaml_parser_delete(&parser);
  fclose(fh);
  return 0;
}
4

2 回答 2

5

我从该教程中获取了大量示例代码并对其进行了破解。警告购买者，自从我上次写 C 以来已经有一段时间了！

我使用了令牌 API，事件 API 实际上看起来更简单。

#include <stdio.h>
#include <yaml.h>

typedef struct Conf {
  char* db_server;
  char* db_pass;
  char* db_user;
  char* rail_user;
  char* rail_pass;
}

Conf* readConf(char* filename) {
  FILE* fh = fopen(filename, "r");
  yaml_parser_t parser;
  yaml_token_t token;
  Conf* conf = malloc(sizeof(Conf));

  if (!yaml_parser_initialize(&parser))
    fputs("Failed to initialize parser!\n", stderr);
  if (fh == NULL)
    fputs("Failed to open file!\n", stderr);
  yaml_parser_set_input_file(&parser, fh);

  do {
    /* As this is an example, I'll just use:
     *  state = 0 = expect key
     *  state = 1 = expect value
     */
    int state = 0;
    char** datap;
    char* tk;

    yaml_parser_scan(&parser, &token);
    switch(token.type)
    {
    case YAML_KEY_TOKEN:     state = 0; break;
    case YAML_VALUE_TOKEN:   state = 1; break;
    case YAML_SCALAR_TOKEN:
      tk = token.data.scalar.value;
      if (state == 0) {
        /* It's safe to not use strncmp as one string is a literal */
        if (!strcmp(tk, "db_server")) {
          datap = &conf.db_server;
        } else if (!strcmp(tk, "db_password")) {
          datap = &conf.db_pass;
        } else if (!strcmp(tk, "db_username")) {
          datap = &conf.db_user;
        } else if (!strcmp(tk, "national_rail_username")) {
          datap = &conf.rail_user;
        } else if (!strcmp(tk, "national_rail_password")) {
          datap = &conf.rail_pass;
        } else {
          printf("Unrecognised key: %s\n", tk);
        }
      } else {
        *datap = strdup(tk);
      }
      break;
    default: break;
    }
    if (token.type != YAML_STREAM_END_TOKEN)
      yaml_token_delete(&token);
  } while (token.type != YAML_STREAM_END_TOKEN);
  yaml_token_delete(&token);

  yaml_parser_delete(&parser);
  fclose(fh);
  return conf;
}
于 2013-12-17T08:24:56.777 回答
1

我认为 lxs 的答案应该是

int state = 0;
char** datap;
char* tk;

在 do-while 循环和 &conf->key 之前，而不是 &conf.key。

有代码，对我有用：

#include <stdio.h>
#include <string.h>
#include <yaml.h>

typedef struct Conf {
    char* db_server;
    char* db_pass;
    char* db_user;
    char* rail_user;
    char* rail_pass;
}

Conf* readConf(char* filename) {
    FILE* fh = fopen(filename, "r");
    yaml_parser_t parser;
    yaml_token_t token;
    Conf* conf = malloc(sizeof(Conf));

    if (!yaml_parser_initialize(&parser))
        fputs("Failed to initialize parser!\n", stderr);
    if (fh == NULL)
        fputs("Failed to open file!\n", stderr);
    yaml_parser_set_input_file(&parser, fh);


    /* As this is an example, I'll just use:
     *  state = 0 = expect key
     *  state = 1 = expect value
     */
    int state = 0;
    char** datap;
    char* tk;

    do {
        yaml_parser_scan(&parser, &token);
        switch(token.type) {
            case YAML_KEY_TOKEN:     state = 0; break;
            case YAML_VALUE_TOKEN:   state = 1; break;
            case YAML_SCALAR_TOKEN:
                tk = token.data.scalar.value;
                if (state == 0) {
                    /* It's safe to not use strncmp as 
                       one string is a literal */
                    if (!strcmp(tk, "db_server")) {
                        datap = &conf->db_server;
                    } else if (!strcmp(tk, "db_password")) {
                        datap = &conf->db_pass;
                    } else if (!strcmp(tk, "db_username")) {
                        datap = &conf->db_user;
                    } else if (!strcmp(tk, "national_rail_username")) {
                        datap = &conf->rail_user;
                    } else if (!strcmp(tk, "national_rail_password")) {
                        datap = &conf->rail_pass;
                    } else {
                        printf("Unrecognised key: %s\n", tk);
                    }
                } else {
                      *datap = strdup(tk);
                }
                break;
           default: break;
           }
       if (token.type != YAML_STREAM_END_TOKEN)
           yaml_token_delete(&token);
   } while (token.type != YAML_STREAM_END_TOKEN);

   yaml_token_delete(&token);
   yaml_parser_delete(&parser);
   fclose(fh);
   return conf;
 }
于 2015-07-05T22:38:06.483 回答