如何让我的缓冲区大小根据输入文件动态变化？

Question

现在我的 set 函数有一个预定义的缓冲区大小，这会导致某些内容无法写入或额外的 NULL 被写入文件。

#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

#define BUFFER_SIZE 1024

void handle_get_command(const char *fileName) {
    int fileDescriptor = open(fileName, O_RDONLY);
    if (fileDescriptor < 0) {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
        return;
    }

    char fileBuffer[BUFFER_SIZE];
    ssize_t fileBytesRead;
    while ((fileBytesRead = read(fileDescriptor, fileBuffer, BUFFER_SIZE)) > 0) {
        write(STDOUT_FILENO, fileBuffer, fileBytesRead);
    }

    if (fileBytesRead < 0) {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
    }

    close(fileDescriptor);
}

void handle_set_command(const char *fileName, size_t contentLength, const char *content) {
    if (!fileName) {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
    }\

    int fileDescriptor = open(fileName, O_WRONLY | O_CREAT | O_TRUNC, 0666);
    if (fileDescriptor < 0) {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
    }

    if (contentLength > 0 && content) {
        ssize_t bytesWritten = write(fileDescriptor, content, contentLength);
        if (bytesWritten < 0 || (size_t)bytesWritten != contentLength) {
            fprintf(stderr, "Invalid Command\n");
            close(fileDescriptor);
            exit(1);
        }
    }
    
    close(fileDescriptor);
    write(STDOUT_FILENO, "OK\n", 3);
}

int main(void) {
    char inputBuffer[BUFFER_SIZE];

    ssize_t bytesRead = read(STDIN_FILENO, inputBuffer, BUFFER_SIZE - 1);
    if (bytesRead <= 0) {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
    }
    inputBuffer[bytesRead] = '\0';

    int x = 0;
    if (inputBuffer[bytesRead - 1] != '\n') {
        x = 9;
    }
    

    char *command = strtok(inputBuffer, "\n");
    char *fileName = strtok(NULL, "\n");

    if (strcmp(command, "get") == 0) {
        if ((strtok(NULL, "\n") != NULL) || (x==9)) {
            fprintf(stderr, "Invalid Command\n");
            exit(1);
        }
        handle_get_command(fileName);
    } else if (strcmp(command, "set") == 0) {
        char *contentLengthStr = strtok(NULL, "\n");
        char *content = strtok(NULL, "");

        if (!fileName) {
                fprintf(stderr, "Invalid Command\n");
                exit(1);
        }

        size_t contentLength = strtoul(contentLengthStr, NULL, 10);

        handle_set_command(fileName, contentLength, content);
    } else {
        fprintf(stderr, "Invalid Command\n");
        exit(1);
    }

    return 0;
}

我需要将主函数中的 BUFFER_SIZE 设置为 STDIN 的大小，而我该如何做到这一点中的 BUFFER_SIZE 。我也尝试不使用 fgets 或 put 函数。

预定义的 BUFFER_SIZE 要么切断集合，要么用 NULL 值填充额外的缓冲区。

Answer 1

使用

read ( STDIN_FILENO, inputBuffer, BUFFER_SIZE - 1)  

输入

set<enter>filename<enter>123<enter>stuff<enter>

只会捕获

set\n

 中的 

inputBuffer

输入

set filename 123 stuff<enter>

效果很好，将整条生产线放入

inputBuffer

只要文件名不超过 511 个字符且不包含空格，就可以使用

sscanf

来解析字段。

%n

说明符将给出扫描处理的字符数。它可用于提供指向内容字段开头的指针。

int main ( void) {
    char inputBuffer[BUFFER_SIZE] = "";
    ssize_t bytesRead = 0;

    if ( 0 >= ( bytesRead = read ( STDIN_FILENO, inputBuffer, BUFFER_SIZE - 1))) {
        fprintf ( stderr, "Invalid Command\n");
        exit ( 1);
    }
    inputBuffer[bytesRead] = '\0';

    if ( ( '\n' != inputBuffer[bytesRead - 1])) {
        fprintf ( stderr, "Invalid Command\n");
        exit ( 1);
    }

    char op = 0;
    char fileName[512] = "";
    size_t contentLength = 0;
    int index = 0;

    int fields = sscanf ( inputBuffer, " %cet%511s%zu %n", &op, fileName, &contentLength, &index);

    if ( 'g' == op && 2 == fields) {
        handle_get_command ( fileName);
    }
    else if ( 's' == op && index && 3 == fields) {
        char *content = &inputBuffer[index];
        handle_set_command ( fileName, contentLength, content);
    } else {
        fprintf ( stderr, "Invalid Command\n");
        exit ( 1);
    }
}  

这只扫描

get

或

set

的第一个字符。