我一定是做错了什么。。。或者这可能是YAJL中的一个bug，但我非常怀疑。
我无法从json对象中检索第一个元素。我回到YAJL源代码，用parse_config.c示例测试它，结果也失败了。
使用sample.config
/*
* The configuration file for Yahoo! BrowserPlus, included in the YAJL
* tree as a sample configuration file for parsing.
*
* This is the configuration file for BrowserPlus
*/
{
// The type of build this is, which is accessible to JavaScript via
// BrowserPlus.getPlatformInfo();
// Different build types should only differ in signatures accepted
// (BrowserPlus.crt) and configured distribution servers.
"BuildType": "ephemeral",
// the base url for the "primary" distribution server. This server will
// be the single source of truth for Permissions, and will used to
// attain services
"DistServer": "http://browserplus.yahoo.com",
// An array of "secondary" distribution servers, which will be checked
// in order for services if the primary server has no components
// available which match an issued require statement.
"SecondaryDistServers": [
"http://first.fictional.server",
"http://second.fictional.server"
],
// Logging Setup
"Logging" :
{
// Log level. Values: "debug"|"info"|"warn"|"error"|"fatal"|"off"
"level": "BP_LOG_LEVEL",
// Destination. Values: "file"|"console"|"win32"
"dest": "BP_LOG_DEST",
// Log message layout. Values: "standard"|"source"|"raw"
"layout": "standard",
// Time format. Values: "utc"|"local"|"msec"
"timeFormat": "utc",
// File size in KB which will trigger a rollover
"fileRolloverKB": 2048,
// Whether to send file logging from each service to a distinct file.
// Values: "combined"|"separate"
"serviceLogMode": "combined"
},
// Daemon setup
// Syntax: "Options": "option1 option2 etc"
// -fg run in foreground, log to console
"Options":"",
// Auto-shutdown daemon if idle for this time. Use 0 for no auto-shutdown.
"MaxIdleSecs": 5,
// At the end of each BrowserPlus session a small web request is made
// to yahoo to indicate that BrowserPlus was used. This report includes
// * information about the browser being used
// * an "installation id", which is a unique token that's generated
// the first time BrowserPlus runs.
//
// By design, there is *no information* in this request that gives
// Yahoo! information about:
// a) the site that the user is visiting (see, "url": false)
// b) who the user is (the installation token cannot be tracked to a
// specific user).
//
// This information is primarily captured to help Yahoo! understand
// adoption and usage of the BrowserPlus platform.
"UsageReporting":
{
"enabled": true,
"url": false,
"id": true
},
// "Breakpoints" is an array of strings holding named breakpoints.
// Platform code checks for specific entries at certain key points, and if
// a matching entry is found here a DebugBreak will be performed.
// For developers with Visual Studio installed, the DebugBreak will cause an
// opportunity to perform just-in-time attachment of an existing or new
// debugger instance.
// The currently-defined breakpoints are listed below:
// runServiceProcess - A DebugBreak is performed in the service
// "harness" just prior to service load.
// ax.FinalConstruct - A DebugBreak is performed at entry to
// FinalConstruct of the ActiveX plugin.
// PluginInit - Very early in the NPAPI plugin initialization.
// A wonderful spot to stop and set more
// breakpoints.
//"Breakpoints": ["runServiceProcess"],
// How often we check for service updates. We guarantee at least this
// much time will pass between checks, though the true time may be
// much more if sites which use browserplus are not visited.
// The time is in seconds.
"ServiceUpdatePollPeriod": 86400
}
我尝试检索“BuildType”我更改了parse_config.c文件来执行此操作。。。代码如下：
int
main(void)
{
size_t rd;
yajl_val node;
char errbuf[1024];
/* null plug buffers */
fileData[0] = errbuf[0] = 0;
/* read the entire config file */
rd = fread((void *) fileData, 1, sizeof(fileData) - 1, stdin);
/* file read error handling */
if (rd == 0 && !feof(stdin)) {
fprintf(stderr, "error encountered on file read\n");
return 1;
} else if (rd >= sizeof(fileData) - 1) {
fprintf(stderr, "config file too big\n");
return 1;
}
/* we have the whole config file in memory. let's parse it ... */
node = yajl_tree_parse((const char *) fileData, errbuf, sizeof(errbuf));
/* parse error handling */
if (node == NULL) {
fprintf(stderr, "parse_error: ");
if (strlen(errbuf)) fprintf(stderr, " %s", errbuf);
else fprintf(stderr, "unknown error");
fprintf(stderr, "\n");
return 1;
}
/* ... and extract a nested value from the config file */
{
//const char * path[] = { "Logging", "timeFormat", (const char *) 0 };
注意：如果我尝试获取“DistServer”，它工作得很好，但是“BuildType”返回空值。
const char * path[] = { "BuildType", (const char *) 0 };
//const char * path[] = { "DistServer", (const char *) 0 };
yajl_val v = yajl_tree_get(node, path, yajl_t_string);
if (v) printf("%s: %s\n", path[0], YAJL_GET_STRING(v));
else printf("no such node: %s\n", path[0] );
//if (v) printf("%s/%s: %s\n", path[0], path[1], YAJL_GET_STRING(v));
//else printf("no such node: %s/%s\n", path[0], path[1]);
}
yajl_tree_free(node);
return 0;
}
我正在使用最新的YAJL版本：2.0.2。
提前谢谢！
编辑：
以下是我的命令输出：
./parse_config < ../../example/sample.config
no such node: BuildType
注意，我运行的parse_配置在build/example目录中
我的gcc版本是：
GCC4.4.5版（Ubuntu/Linaro 4.4.4-14ubuntu 5）
编辑2
作为记录，这是YAJL附带的示例代码。我特意用它来代替我自己的代码，以确保问题不仅仅与我的应用程序有关。同时，我通过使用库提供的回调机制和使用
yajl_parse()
and
yajl_complete_parse()
但我还是想知道为什么原始代码不起作用。
最佳答案
我刚用2.0.2版碰到了同样的错误。它似乎是yajl中的一个错误，并已在github中修复（“验证yajl树get中正确对象的长度”，提交9c2948a33165c65012d131f31110c15321908f5）。
我已经应用了这个补丁，现在我可以很好地阅读第一条了。
关于c - 在C中用YAJL解析json，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/7309992/