c - 链表: Reading in txt file,节点不保存

Question

我在编码方面相当陌生，并且被赋予了使用链表和结构的艰巨任务。任务是创建一个音乐数据库，以便您可以读取艺术家的专辑和轨道，并将它们存储在节点中。

目前，当我运行该程序时，当我从 .txt 文件读取数据时，不会存储任何节点。最终，我开始怀疑我对某些指针的使用是否正确，因为我遇到了段错误。我做错了什么，我可以修复它以使其正常工作吗？

我的代码(所需的库已包含):

结构体和宏定义:

#define LINEBUFFERSIZE 256

struct song
{
    char *songName_p;
    int trackNumber;
    struct song *nextSong_p;
};

struct disc
{
    char *discName_p;
    int year;
    struct song *song_p;
    struct disc *nextDisc_p;

};

struct artist
{
    char name[20];
    char *artistName_p;
    struct disc *disc_p;
    struct artist *nextArtist_p;
};
struct artist *end = (struct artist *) NULL;   //NEW
struct artist *startPtr = (struct artist *) NULL; //NEW
struct artist *find(struct artist *, char * );//NEW
//NEW

类型定义:

typedef struct artist artist_t;
typedef struct disc disc_t;
typedef struct song song_t;

typedef struct artist *artistNodePtr;
typedef struct disc *discNodePtr;
typedef struct song *songNodePtr;

函数定义:

void InsertArtist(struct artist *New);
artistNodePtr initializenode(char *name);
artistNodePtr findOrInsertArtist(artistNodePtr *sPtr, char *name);
discNodePtr  findOrInsertDisc(discNodePtr *sPtr, char *discID, int releaseYear);
void  findOrInsertSong(songNodePtr *sPtr, char *songID, int trackID);
void getNextLine(char buffer[], int bufferSize, FILE *fptr);
void printlist( struct artist *ptr );
void printnode(struct artist *ptr);

主要方法:

int main(int argc, char *argv[])
{
    char name[20];
    struct artist *newNodePointer;
    char lineBuffer[LINEBUFFERSIZE];
    artistNodePtr startPtr = NULL; /* initially the artist list is empty */
    FILE *musicFile;
    char *artistTemp, *discTemp, *yearTemp, *trackTemp, *songTemp;
    int year, track, menu = 1;
    artistNodePtr theArtist;
    // discNodePtr theDisc;

    if (argc==1)
    {
        printf(" Must supply a file name as command line argument/n");
        return 0;
    }

    if ((musicFile = fopen(argv[1], "r")) == NULL)
    {
        printf ("Error opening music file.  Program terminated/n");
        return 0;
    }

    getNextLine(lineBuffer, LINEBUFFERSIZE, musicFile);
    while (!feof(musicFile))
    {
        artistTemp = strtok(lineBuffer,";");
        if (artistTemp == NULL)
        {
            printf("Error parsing input file; Program is terminated\n");
            return 0;
        }
        discTemp = strtok(NULL ,";");
        if (discTemp == NULL)
        {
            printf("Error parsing input file; Program is terminated\n");
            return 0;
        }
        yearTemp  = strtok(NULL ,";");
        if (yearTemp == NULL)
        {
            printf("Error parsing input file; Program is terminated\n");
            return 0;
        }
        trackTemp = strtok(NULL ,";");
        if (trackTemp == NULL)
        {
            printf("Error parsing input file; Program is terminated\n");
            return 0;
         }
        songTemp = strtok(NULL ,"\n");
        if (songTemp == NULL)
        {
            printf("Error parsing input file; Program is terminated\n");
            return 0;
        }
        year = atoi(yearTemp);
        track = atoi(trackTemp);
        theArtist = findOrInsertArtist(&startPtr, artistTemp);
  //    theDisc = findOrInsertDisc(&(theArtist->disc_p), discTemp, year);
        //findOrInsertSong(&(theDisc->song_p), songTemp, track);
        getNextLine(lineBuffer, LINEBUFFERSIZE, musicFile);
    }  /* end of while loop */

    while (menu != 0)
    {
        printf("1 to display entire catalog \n");
        printf("2 to display alls songs by a given artist\n");
        printf("3 to display all songs on a given disc\n");
        printf("0 to exit the library\n ");
        scanf("%d", &menu);
        switch (menu){
        case 1: printlist(startPtr);
            break;

        case 2:
            printf("enter an artist name");
            scanf("%s", name );
            newNodePointer = find(startPtr, name );
            if (newNodePointer==NULL)
            {
                newNodePointer = initializenode(name );
                InsertArtist(newNodePointer);
            }

        }
    } /* end main */
}

函数定义:

artistNodePtr findOrInsertArtist(artistNodePtr *sPtr, char *name )
   {

sPtr = initializenode(name);
    InsertArtist(sPtr);

    if(!sPtr)
        sPtr = find(startPtr, name);
    return sPtr;
}
void printlist( struct artist *ptr ){
    while(ptr!= NULL){
    printnode(ptr);
    ptr = ptr->nextArtist_p;
    }
    }
void printnode(struct artist *ptr)
{
    printf("Name %s\n", ptr->name);

}

artistNodePtr initializenode(char *name)
{

    struct artist *newNodePtr = (artistNodePtr)malloc(sizeof(artist_t));
    if (newNodePtr != NULL)
    {
        newNodePtr->artistName_p = (char*)malloc((strlen(name)+1)*sizeof(char));
        if (newNodePtr->artistName_p != NULL)
        {
           strcpy(newNodePtr->artistName_p, name);
            newNodePtr->nextArtist_p = NULL;
            newNodePtr->disc_p = NULL;

            return newNodePtr;
        }   
    }
}

void InsertArtist(struct artist *New)
   {
    //NEW
    struct artist *temp, *prev;

    if(startPtr == NULL)
    {
        startPtr = New;
        end = New;
       startPtr->nextArtist_p = NULL;
        return;
    }
    temp = startPtr;

    while(strcmp(temp->name, New->name) < 0)
    {
        temp = temp->nextArtist_p;
        if(temp == NULL)
            break;
     }
    if(temp == startPtr)
    {
        New->nextArtist_p = startPtr;
        startPtr = New;
    }
    else
    {
       prev = startPtr;
        while(prev->nextArtist_p != temp)
        {
            prev = prev->nextArtist_p;
        }
        prev->nextArtist_p = New;
        New-> nextArtist_p = temp;
            if(end == prev)
            end = New;
    }
}

 struct artist *find(struct artist *newNodePointer, char *name)
{
    //NEW
    while (strcmp(name, newNodePointer->name )!=0)
    {
        newNodePointer = newNodePointer->nextArtist_p;
        if (newNodePointer == NULL)
            break;
    }
    return newNodePointer;
}


void getNextLine(char buffer[], int bufferSize, FILE *fptr)
{
    char temp;
    int i = 0;

    buffer[0] = fgetc(fptr);
    while ( (!feof(fptr)) && (buffer[i] != '\n') &&  i<(bufferSize-1))
    {
        i = i +1;
        buffer[i]=fgetc(fptr);
    }

    if ((i == (bufferSize-1)) && (buffer[i] != '\n'))
    {
        temp = fgetc(fptr);
        while (temp != '\n')
        {
            temp = fgetc(fptr);
        }
     }

    buffer[i] = '\0';
}    

Answer 1

有很多类型错误会通过 -Wall 溢出(如 @user120115 所建议)。

一些立即跳出来的事情:

• 不要强制转换 malloc(在 C 中；甚至不要在 C++ 中使用 malloc，除非有充分的理由避免新)
• 任何 while (!feof(stream)) 形式的循环都可能是错误的，因为 feof 不会预测 future 的 EOF，它只会告诉您为什么之前的 EOF 会发生变化。读取尝试失败(例如，为什么 getchar 返回 EOF)。 feof 的要点是区分由于文件末尾导致的“正常”读取失败和由于磁盘驱动器着火或其他原因导致的“异常”(ferror)读取失败.
• InsertArtist 需要修改列表，因此它要么必须返回新列表，要么获取指向旧列表指针的指针，但它两者都没有。 (但是各种 findOrInsert 函数都可以!)

我也同意 @sarnold 的观点，即限制 typedef 的使用，尽管这确实是一个品味问题。