06.memory_stream_write_operation.c

/***************************************************
* 
* 描述：内存流的写入操作
* 
* **************************************************
*/

#include <stdio.h>
#include <string.h>

#define BSZ 48

int main()
{
    FILE *fp;
    char buf[BSZ];

    memset(buf, 'a', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';

    if ((fp = fmemopen(buf, BSZ, "w+")) == NULL) {
        printf("fmemopen error");
    }

    printf("initial buffer contents: %s\n", buf);
    fprintf(fp, "hello, world");
    printf("before flush : %s\n", buf);
    fflush(fp);
    printf("after flush : %s\n",buf);
    printf("len of string in buf = %ld\n", (long)strlen(buf));

    memset(buf, 'b', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';
    fprintf(fp, "hello, world");
    printf("before fseek : %s\n", buf);
    fseek(fp, 0, SEEK_SET);
    printf("after fseek : %s\n",buf);
    printf("len of string in buf = %ld\n", (long)strlen(buf));

    memset(buf, 'c', BSZ - 2);
    buf[BSZ - 2] = '\0';
    buf[BSZ - 1] = 'X';
    fprintf(fp, "hello, world");
    printf("before fclose : %s\n", buf);
    fclose(fp);
    printf("after fclose : %s\n",buf);
    printf("len of string in buf = %ld\n", (long)strlen(buf));

    return 0;
}