Question

问题：我无法从.csv文件中获取输入并将其粘贴到结构数组中。我的问题是编译器不允许我从我的char变量字中分配G.word。我不知道为什么不是因为我的结构和初始占位符变量都包含相同的类型。谢谢。它必须在C中，但赋值允许我们使用C ++函数来处理文件。除此之外，我被C卡住了。

/*Sample of the data being read. 
airport 2007    175702  32788
airport 2008    173294  31271
request 2005    646179  81592
request 2006    677820  86967
request 2007    697645  92342
request 2008    795265  125775
*/

struct NGram{
char *nword;
int year;
int wordCount;
int uText;
};

char fileName[]="very_short.csv";

int main() {
char word[81];
int year;
int wordCount;
int uniqueTextCount;
int i = 0;
int j = 0;

int size = 100000; //initialize array at 100000
struct NGram G[size];

FILE *inFile;    // declare file pointer
inFile = fopen( fileName,"r");

while( fscanf( inFile, "%s %d %d %d", word, &year, &wordCount, &uniqueTextCount) != EOF) {
    //printf("%s %d %d %d\n", word, year, wordCount, uniqueTextCount);

        if (year > 1800 && year < 2000) { //store values in struct only if between these dates
        G[j].nword = word;
        G[j].year = year;
        G[j].wordCount = wordCount;
        G[j].uText = uniqueTextCount;
            j++;
        }

}
return 0;
}

Answer 1

将数组复制到指针的错误方法。需要分配内存，然后使用memcpy()进行复制。

// char *nword;
// char word[81];
// G[j].nword = word;

size_t wsize = strlen(word) + 1;
G[j].nword = (char *) malloc(wsize);  // drop cast if compiling in C, could add NULL check
memcpy(G[j].nword, word, wsize);

读取面向行的文件的简单C方法是读取1 行，然后解析它。使用fgets()而不是fscanf()。使用"%n"注意扫描停止的位置。

// Zero fill G.  Not truly needed but simplifies debugging.
struct NGram G[size] = { 0 }; 

char buf[200];
size_t j = 0;
while (fgets(buf, sizeof buf,  inFile) != NULL) {
  if (j >= size) break;  // Too many
  char word[81];
  NGram Nbuf;
  int n = 0;
  sscanf(buf, "%80s %d %d %d %n", word, &Nbuf.year, &Nbuf.wordCount, &Nbuf.uText, &n);
  // If all fields were not scanned or something left at the end ...
  if (n == 0 || buf[n]) {
    puts("Bad Input");
    break;
  }
  if (Nbuf.year > 1800 && Nbuf.year < 2000) {
    size_t wsize = strlen(word) + 1;
    Nbuf.nword = (char *) malloc(wsize);  // drop cast if compiling in C
    memcpy(Nbuf.nword, word, wsize);
    G[j] = Nbuf;
    j++
  }
}

// Do something with G[0] to G[j-1]

// free each ( 0 to j-1) G[].nword when done.

无法从文件读取并将值放入结构数组中

1 个答案: