c++ - NSPropertyListSerialization propertyListWithData 因二进制 plist 而失败

Question

更新:已解决。代码已更新。

我正在编写一些代码来处理 Objective-C++ 中的 plist。

当我向函数传递一个到 XML plist 的路径时，一切正常，输出显示:

2014-08-12 17:06:47.932 plist_tests[96368:507] plist was in xml format

当我向函数传递二进制 plist 的路径时，出现以下错误:

2014-08-12 17:02:23.598 plist_tests[95709:507] could not deserialize plist: Error Domain=NSCocoaErrorDomain Code=3840 "The data couldn’t be read because it isn’t in the correct format." (Unexpected character b at line 1) UserInfo=0x7f9f2040cd60 {NSDebugDescription=Unexpected character b at line 1, kCFPropertyListOldStyleParsingError=The data couldn’t be read because it isn’t in the correct format.}

这是代码。请注意，我不能将 dictionaryWithContentsOfFile 用于我的用例。

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>

#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/path.hpp>

#import <Foundation/Foundation.h>

class Status {
public:
  Status(int c, std::string m) : code_(c), message_(m) {}
public:
  int getCode() { return code_; }
  std::string getMessage() { return message_; }
  bool ok() { return getCode() == 0; }
  std::string toString() { return getMessage(); }
private:
    int code_;
    std::string message_;
};

Status readFile(const std::string& path, std::string& content) {
  if (!boost::filesystem::exists(path)) {
    return Status(1, "File not found");
  }

  std::ifstream file_h(path);
  if (file_h) {
     file_h.seekg (0, file_h.end);
     int len = file_h.tellg();
     file_h.seekg (0, file_h.beg);
     char *buffer = new char [len];
     file_h.read(buffer, len);
     if (!file_h) {
      return Status(1, "Could not entire file");
     }
     content.assign(buffer, len);
  } else {
    return Status(1, "Could not open file for reading");
  }

  return Status(0, "OK");
}

void parsePlist(const std::string& path) {
  std::string file_content;
  Status readFileStatus = readFile(path, file_content);
  if (!readFileStatus.ok()) {
    NSLog(@"Couldn't read file");
    return;
  }
  NSData *plist_content = [NSData dataWithBytes:file_content.c_str()
                                         length:file_content.size()];

  NSError *error;
  NSPropertyListFormat plist_format;
  id plist = [NSPropertyListSerialization propertyListWithData:plist_content
                                                       options:NSPropertyListImmutable
                                                        format:&plist_format
                                                         error:&error];

  if (plist == nil) {
    NSLog(@"could not deserialize plist: %@", error);
  } else {
    switch (plist_format) {
    case NSPropertyListOpenStepFormat:
      NSLog(@"plist was in openstep format");
      break;
    case NSPropertyListXMLFormat_v1_0:
      NSLog(@"plist was in xml format");
      break;
    case NSPropertyListBinaryFormat_v1_0:
      NSLog(@"plist was in binary format");
      break;
    default:
      NSLog(@"plist was in unknown format");
      break;
    }
  }
}

int main(int argc, char *argv[]) {
  if (argc < 2) {
    std::cout << "Usage: plist <filename>" << std::endl;
    return 1;
  }
  parsePlist(argv[1]);
  return 0;
}

要编译:g++ -lboost_system -lboost_filesystem -lglog -fobjc-arc -fobjc-link-runtime -framework Foundation plist.mm -o plist

我之所以头疼是因为如果我在二进制 plist 上执行 plutil -convert xml1 file.plist -o -，它工作得很好。

Answer 1

将数据转换为 NSString 然后再转换为 NSData 的方式对 XML 有点不利，对二进制数据则非常不利。而是这样做:

NSData *plist_content = [NSData dataWithBytes: file_content.c_str()
                                length: file_content.size() ];

您的readFile 函数也有问题。考虑这条线

content = std::string(buffer);

std::string 如何知道缓冲区的长度？它寻找一个 NUL 字节，但这是对二进制数据的错误处理。您可以将该行替换为

content.assign( buffer, len );

或者如果你的路径是绝对路径，你可以去掉 readFile 并说

NSData *plist_content = [NSData dataWithContentsOfFile:
                                [NSString stringWithUTF8String: path.c_str() ];