阅读结构

Question

我正在尝试读取数据包的标头，然后读取有效负载。但不知何故，阅读有效载荷对我来说并不适用。任何帮助都会很棒。感谢。

FILE *inputfile

struct packet {
    unsigned short blocksize;
    unsigned char *payload;
};  

while(!feof(inputfile)) { 
    struct packet p;
    p.payload = malloc(p.blocksize);

    fread(&p, sizeof(p), 1, infp); //reads the header
    fread(p.payload, sizeof(char), p.blocksize, inputfile); //reads the payload
}

Answer 1

第一

fread(&p, sizeof(p), 1, infp); //reads the header

应该是

fread(&p.blocksize, sizeof(short), 1, infp); //reads the header size

---

然后malloc那么多

p.payload = malloc(p.blocksize);

然后读取其有效载荷

fread(p.payload, sizeof(char), p.blocksize, inputfile); //reads the payload

Answer 2

以下是一些事项：

• 您缺少struct声明的结束括号。
• 您malloc()在知道块大小之前。在调用malloc()
之前，您需要从文件中读取块大小

Answer 3

while(!feof(inputfile)) { 
    struct packet p;

    fread(&p.blocksize, sizeof(short), 1, infp); //Now you got the blocksize

    p.payload = malloc(p.blocksize);  // Allocate memory based on blocksize
    if( p.payload == NULL )  return -1 ; // Error...could not allocate mem

    fread(p.payload, sizeof(char), p.blocksize, inputfile); //reads the payload
}

完成所有操作后，请确保您已完成free(p.payload) ;