如何以这种方式转换我的char类型的缓冲区，我可以在我的哈希函数中使用它 [英] How do i convert my buffer of type char in such a way i can use it in my hashfunction

问题描述

嘿伙计们！



我正在遵循cs50课程，本周我们有拼写错误。每次我尝试加载我的字典时，都会出现错误：

Hey guys!

I'm currrently following the cs50 course and this week we have the misspellings pset. Everytime i try to load in my dictionary, an error occurs:

dictionary.c:93:30: error: passing 'char [47]' to parameter of type 'unsigned char *' converts between pointers to integer types with
      different sign [-Werror,-Wpointer-sign]
        int wordvalue = hash(buffer);
                             ^~~~~~
dictionary.c:38:21: note: passing argument to parameter 'str' here
hash(unsigned char *str)

^



我不知道为了解决这个问题我必须改变什么。

有谁可以帮帮我？！



这是我的代码到目前为止：

^

I have no clue what i have to change in order to fix this problem.
Could anyone help me out?!

This is my code so far:

/**
 * dictionary.c
 *
 * Computer Science 50
 * Problem Set 5
 *
 * Implements a dictionary's functionality.
 */

#include <stdio.h>
#include <cs50.h>
#include <string.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <stdlib.h>
#include <stdbool.h>

#include "dictionary.h"

// create a node with the word and a pointer to the next node
typedef struct node
{
    char word[46];
    struct node* next;
}
node;

// variable to keep track of number of words that have been loaded
int loadedwords;

// define the hashtable
node* hashtable[27] = {NULL};

// hashfunction obtained from http://www.cse.yorku.ca/~oz/hash.html
unsigned long
hash(unsigned char *str)
{
    unsigned long hash = 5381;
    int c = 0;

    while (c == *str++)
    {
        hash = ((hash << 5) + hash) + c;
    }
    return hash;
}

/**
 * Returns true if word is in dictionary else false.
 */
bool check(const char* word)
{
    // TODO
    return false;
}

/**
 * Loads dictionary into memory.  Returns true if successful else false.
 */
bool load(const char* dictionary)
{
    // open the dictionary file
    FILE* dict = fopen(dictionary, "r");
    
    // check if file is valid and opened correctly
    if (dict == NULL)
    {
        printf("Could not open dictionary\n");
        return -1;
    }
    
    // make buffer to store the loaded word plus the NULL terminator
    char buffer[47];
    
    // go through dictionary
    while(fgets(buffer, sizeof(buffer), dict))
    {
        // change the "\n" to "\0" in order to work with NULL
        buffer[strlen(buffer)-1] = '\0';
        
        // create temporary memory space with the size of node
        node* temporary = malloc(sizeof(node));
        
        // node points to the next node and the word
        // copies the buffer content into the location of the temporary pointer
        // temporary node moves on to next node and clears it
        strncpy(temporary ->word, buffer, 46);
        temporary -> next = NULL;
        
        // put word into hashing function to get it's value
        int wordvalue = hash(buffer);
        
        // put temporary node in hashtable if the worldvalue is not known yet in the hashtable
        if(hashtable[wordvalue] == NULL)
        {
            hashtable[wordvalue] = temporary;
        }
        // move over list and put node at the end
        else
        {
            // make a node that points to the beginning of the list
            node* point = hashtable[wordvalue];
            
            // skip over every node untill the next value is NULL
            while (point -> next != NULL)
            {
                point = point -> next;
            }
            point -> next = temporary;
        }
        loadedwords++;
    }
    return false;
}

/**
 * Returns number of words in dictionary if loaded else 0 if not yet loaded.
 */
unsigned int size(void)
{
    // TODO
    return 0;
}

/**
 * Unloads dictionary from memory.  Returns true if successful else false.
 */
bool unload(void)
{
    // TODO
    return false;
}

谢谢！



什么我试过了：



我尝试修改缓冲区的类型，我尝试使用不同的哈希函数。

Thanks!

What I have tried:

I tried modifying the type of the buffer and i tried to use a different hashfunction.

推荐答案

只需在调用哈希函数时使用强制转换，例如：

Just use a cast on your call to the hash function, something like:

char text[] = "abcdef";
hash((unsigned char *)text);

您可以通过转换为预期类型来解决此问题：

You can solve this by casting to the expected type:

int wordvalue = hash((unsigned char *)buffer);

< br $> b $ b

另一种选择是在你的 hash（）函数中执行强制转换：

Another option is performing the cast inside your hash() function:

unsigned long hash(char *str)
{
    unsigned long hash = 5381;
    unsigned char c = 0;
 
    while (c == (unsigned char)*str++)
    {
        hash = ((hash << 5) + hash) + c;
    }
    return hash;
}

请注意，我已使用类型 unsigned char 作为变量 c 这里也是。虽然这不是必需的，但它更清楚地表明使用了无符号值。

Note that I have used the type unsigned char for the variable c here too. While this is not really necessary it indicates more clear that unsigned values are used.

这篇关于如何以这种方式转换我的char类型的缓冲区，我可以在我的哈希函数中使用它的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！