c - 如何将字符串插入缓冲区？

Question

我是 C 编程新手。我想创建将字符串写入文本文件的循环缓冲区。

#include <stdio.h>
#include <malloc.h>

// Buffer writer header files
#include <stdlib.h>

typedef struct { char value; } ElemType;

/* Circular buffer object */
typedef struct {
    int         size;   /* maximum number of elements           */
    int         start;  /* index of oldest element              */
    int         end;    /* index at which to write new element  */
    ElemType   *elems;  /* vector of elements                   */
} CircularBuffer;

void cbInit(CircularBuffer *cb, int size);
void cbFree(CircularBuffer *cb);
int cbIsFull(CircularBuffer *cb);
int cbIsEmpty(CircularBuffer *cb);
void cbWrite(CircularBuffer *cb, ElemType *elem);
void cbRead(CircularBuffer *cb, ElemType *elem);
void writeFile();


void cbInit(CircularBuffer *cb, int size) {
    cb->size  = size + 1; /* include empty elem */
    cb->start = 0;
    cb->end   = 0;
    cb->elems = (ElemType *)calloc(cb->size, sizeof(ElemType));
}

void cbFree(CircularBuffer *cb) {
    free(cb->elems); /* OK if null */ }

int cbIsFull(CircularBuffer *cb) {
    return (cb->end + 1) % cb->size == cb->start; }

int cbIsEmpty(CircularBuffer *cb) {
    return cb->end == cb->start; }

/* Write an element, overwriting oldest element if buffer is full. App can
   choose to avoid the overwrite by checking cbIsFull(). */
void cbWrite(CircularBuffer *cb, ElemType *elem) {
    cb->elems[cb->end] = *elem;
    cb->end = (cb->end + 1) % cb->size;
    if (cb->end == cb->start)
        cb->start = (cb->start + 1) % cb->size; /* full, overwrite */
}

/* Read oldest element. App must ensure !cbIsEmpty() first. */
void cbRead(CircularBuffer *cb, ElemType *elem) {
    *elem = cb->elems[cb->start];
    cb->start = (cb->start + 1) % cb->size;
}

int mainSecond(int argc, char **argv) {
    CircularBuffer cb;
    ElemType elem = {0};

    int testBufferSize = 10; /* arbitrary size */
    cbInit(&cb, testBufferSize);

    /* Fill buffer with test elements 3 times */
    for (elem.value = 0; elem.value < 3 * testBufferSize; ++ elem.value)
        cbWrite(&cb, "AC");

    /* Remove and print all elements */
    while (!cbIsEmpty(&cb)) {
        cbRead(&cb, &elem);
        printf("%d\n", elem.value);
    }

    cbFree(&cb);
    return 0;
}



int main(int argc, char** argv) {

    writeFile();

    return 0;
}

// write to file function

void writeFile() {

    FILE *file;
    file = fopen("file.txt", "a+"); /* apend file (add text to a file or create a file if it does not exist.*/

    CircularBuffer cb;
    ElemType elem = {0};

    int testBufferSize = 10; /* arbitrary size */
    cbInit(&cb, testBufferSize);

    /* Fill buffer with test elements 3 times */
    for (elem.value = 0; elem.value < 3 * testBufferSize; ++ elem.value)
        cbWrite(&cb, "test");

    /* Remove and print all elements */
    while (!cbIsEmpty(&cb)) {
        cbRead(&cb, &elem);
        fprintf(file, "%d\n", elem.value);
       // printf("%d\n", elem.value);      
    }   

    // write something into the file
    fprintf(file, "%s", "Test!\n");
    // close the file
    fclose(file); 
    //getchar(); /* pause and wait for key */
    cbFree(&cb);
}

问题是如何将字符串插入循环缓冲区，然后将它们写入文本文件？此实现仅适用于数字。

Answer 1

有两种方法:

1. 在循环缓冲区中插入指针。您会将字符串存储在内存中的某个位置。然后你就有了一个指向内存中该位置的指针，并将其存储在循环缓冲区中。

2. 将字符存储在循环缓冲区中，以便将它们连接起来形成字符串。这意味着字符串被复制到缓冲区中，并且您需要某种方法从缓冲区中读取足够的字符来组成字符串。