错误而用C

Question

修正错误我有一个.c文件和两个头。我不知道为什么会出现这些错误。我试图在网络中找到解决方案，但无法将其应用于我的代码。

Structs.h

#ifndef STRUCTS_H 
#define STRUCTS_H 

typedef struct stream 
{ 
    char* enc; //binary string 
    int pos; 
}stream; 

typedef struct tag 
{ 
    int tagClass; 
    char tagConstructed; 
    char tagNumber; 
}tag; 

#endif 

Funcs.h错误：

Error 22 error C2143: syntax error : missing '{' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 26 error C2143: syntax error : missing '{' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 21 error C2143: syntax error : missing ')' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 25 error C2143: syntax error : missing ')' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 15 error C2061: syntax error : identifier 'isUniversal' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 18 error C2061: syntax error : identifier 'isEOC' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 17 error C2059: syntax error : 'type' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 20 error C2059: syntax error : 'type' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 16 error C2059: syntax error : ';' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 19 error C2059: syntax error : ';' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 24 error C2059: syntax error : ')' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 28 error C2059: syntax error : ')' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 23 error C2059: syntax error : '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 27 error C2059: syntax error : '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 


#ifndef FUNCS_H 
#define FUNCS_H 

#include "Structs.h" 

bool isUniversal(tag curTag); 
bool isEOC(tag curTag); 
char getByte(stream curStream); 
void parseTag(stream & str, tag & tag); 
char parseLength(stream & str); 

#endif 

Functions.c错误：

Error 22 error C2143: syntax error : missing '{' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 26 error C2143: syntax error : missing '{' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 21 error C2143: syntax error : missing ')' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 25 error C2143: syntax error : missing ')' before '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 15 error C2061: syntax error : identifier 'isUniversal' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 18 error C2061: syntax error : identifier 'isEOC' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 17 error C2059: syntax error : 'type' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 20 error C2059: syntax error : 'type' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 16 error C2059: syntax error : ';' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 3 1 asn1 
Error 19 error C2059: syntax error : ';' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 7 1 asn1 
Error 24 error C2059: syntax error : ')' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 28 error C2059: syntax error : ')' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 
Error 23 error C2059: syntax error : '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 15 1 asn1 
Error 27 error C2059: syntax error : '&' c:\users\natasha\documents\visual studio 2012\projects\asn1\asn1\functions.c 36 1 asn1 


#include "Funcs.h" 

bool isUniversal(tag curTag) { 
    return curTag.tagClass == 0x00; 
} 

bool isEOC(tag curTag) { 
    return (curTag.tagClass == 0x00) && (curTag.tagNumber == 0x00); 
} 

char getByte(stream curStream) { 
    return curStream.enc[curStream.pos]; 
} 

void parseTag(stream & str, tag & tag) 
{ 
    char buf, tempNumber; 
    buf = getByte(str); 
    tempNumber = 0x00; 
    tag.tagClass = buf >> 6; 
    tag.tagConstructed = ((buf & 0x20) != 0); 
    tag.tagNumber = buf & 0x1F; 
    if (tag.tagNumber == 0x1F) 
    { 
     do 
     { 
      str.pos++; 
      buf = getByte(str); 
      tempNumber = (tempNumber << 7) | (buf & 0x7F); 
     }while(buf & 0x80); 

     tag.tagNumber = tempNumber; 
    } 
} 

char parseLength(stream & str) { 
    char buf, len; 
    int numberOfOctets, i; 
    buf = getByte(str); 
    len = 0x00; 
    numberOfOctets = 0; 
    if (buf < 0x80) { 
     len = buf; //short form 
    } else { //long form 
     numberOfOctets = buf & 0x7F; 
     for (i = 0; i < numberOfOctets; ++i) { 
      len = (len * 256) + getByte(str); 
      str.pos++; 
     } 
    } 

    return len; 
} 

Answer 1

C没有引用像C++一样。由于&，void parseLength(stream & str);是无效的语法。不过，您可以改用指针。

例如，转换您的parseLength()功能使用指针（和改变返回类型相匹配的定义），原型变为：

char parseLength(stream *str); 

而在函数体则需要取消引用根据需要，这样的指针：

char parseLength(stream *str) { 
    char buf, len; 
    int numberOfOctets, i; 
    buf = getByte(*str); /* use "*" to get the object from the pointer */ 
    len = 0x00; 
    numberOfOctets = 0; 
    if (buf < 0x80) { 
     len = buf; //short form 
    } else { //long form 
     numberOfOctets = buf & 0x7F; 
     for (i = 0; i < numberOfOctets; ++i) { 
      len = (len * 256) + getByte(*str); 
      str->pos++; /* Use "->" to access struct members from the pointer */ 
     } 
    } 

    return len; 
} 

此外，你需要传递一个地址（指针），而不是实际的对象，所以你也只需要修改从如函数调用。 parseLength(str)至parseLength(&str)。

你当然需要做出类似的改变为parseTag()并尝试使用引用其他任何代码。

可能的一些像getByte()其它功能应该采取一个指针，而不是实际的结构，以及...例如，如果getByte()需要修改stream参数的pos成员它的传递，使得它影响从对象来电者，而不只是它的副本。

此外，parseLength()或许应该返回int或size_t代替char - len看起来像它需要一个更大的范围比的char。