c - 我的问题是关于 get_next_line 函数，我应该读取一个文件并使用多个缓冲区大小

Question

我的函数是一个字符一个字符地读取，所以它不能使用多个缓冲区大小，我需要帮助来修复它，以便它可以使用任何缓冲区大小，而不仅仅是 1。

所以主要问题是它应该使用缓冲区大小而不是逐个字符

我试图读取更改缓冲区，但它会跳过一些字符

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>
#define BUFF_SIZE 32
#include <string.h>
#include <ctype.h>
#include <stdbool.h>

int get_next_line(int fd, char **line){

    static char * s_line = NULL;
    static int s_max = 0;
        char character[BUFF_SIZE + 1];

    if(s_line == NULL)
    {
        s_line = (char *)malloc((BUFF_SIZE + 1) * sizeof(char));
        s_max = BUFF_SIZE;
    }
    int len = 0;
    int ret;

    while ((ret = read(fd, character, BUFF_SIZE)) > 0)
    {
        if (character[0] == '\n'){
            break;
        }
        s_line[len] = character[0];
        len = len + 1;
        if (len >= s_max)
        {
            char *tmp;
            s_max = s_max + BUFF_SIZE;
            tmp = (char *) malloc((s_max + 1) * sizeof(char));
            s_line[len] = '\0';
            strcpy(tmp, s_line);
            free(s_line);
            s_line = tmp;
        }
    }
    if (ret < 0) { //read error, free memory and return -1
        free(s_line);
        return -1;
    }
    if (len == 0){
        free(s_line);   //required to release the memory after reading the entire file
        s_line = NULL;
        return 0;
    }
    s_line[len] = '\0';
    *line = s_line;
    return 1;
}
int main(int argc, char **argv)
{
    char *txt;
    int fd;

    fd = open(argv[1], O_RDONLY);
    while (get_next_line(fd, &txt) > 0)
    {
        printf("%s\n", txt);
    }
    printf("Done\n");
    if (txt != NULL)
    {
        free(txt);
    }
    return (0);
}

l 期望读取整个文件的输出，而不是跳过字符 喜欢它在做什么

Answer 1

字符读取大小为 BUFF_SIZE 的字符串。因此，如果 BUFF_SIZE > 1，您需要遍历字符串中的每个元素，并且必须将其复制到 s_line 数组中以复制完整的字符串。否则字符将被跳过。

while ((ret = read(fd, character, BUFF_SIZE)) > 0)
{
  for(i=0;i<BUFF_SIZE;i++){ // for loop is added to visit every element of the character array
    if (character[i] == '\n'){
    s_line[len] = '\n';
    break;
    }
    s_line[len] = character[i];
    len = len + 1;
    if (len >= s_max)
    {
        char *tmp;
        s_max = s_max + BUFF_SIZE;
        tmp = (char *) malloc((s_max + 1) * sizeof(char));
        s_line[len] = '\0';
        strcpy(tmp, s_line);
        free(s_line);
        s_line = tmp;
    }
}}