读写文件试例

debug.h

#ifndef __DEBUG_H__
#define __DEBUG_H__

#define DEBUG 1

#if DEBUG
#include <stdio.h>
#include <stdarg.h>

#define DebugWhere() \
    printf("FILENAME:%s,FUNCTION:%s,LINE:%d\n",\
            __FILE__,__FUNCTION__,__LINE__):

static inline void debug_p(const char *format,...)
{
    va_list args;

    va_start(args,format);
    vprintf(format,args);
    va_end(args);
}
#else
#define DebugWhere()
static inline void debug_p(const char *format,...)
{

}
#endif

#endif

main.c

/* Copyright(C) 2012
 * It's for free
 */
/**
 * @file main.c
 * @synopsis  读写文件
 * @author sense, [e-mail]
 * @version 1.0
 * @date 2012-06-20
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "debug.h"

/* --------------------------------------------------------------------------*/
/**
 * @synopsis  open_file 打开文件
 *
 * @param filename 要打开的文件名
 * @param mode 打开文件的方式
 *
 * @returns  文件流指针
 */
/* --------------------------------------------------------------------------*/
FILE *open_file(char *filename,char *mode)
{
    FILE *fp = NULL;

    fp = fopen(filename,mode);
    if (NULL == fp) {
        perror("open failure");
        return NULL;
    }

    return fp;
}

/* --------------------------------------------------------------------------*/
/**
 * @synopsis  get_file_size 获取文件的大小
 *
 * @param fp 文件流指针
 *
 * @returns 文件的大小
 */
/* --------------------------------------------------------------------------*/
long get_file_size(FILE *fp)
{
    long len1 = 0;
    long len2 = 0;
    long length = 0;

    fseek(fp,0,SEEK_SET);
    len1 = ftell(fp);
    fseek(fp,0,SEEK_END);
    len2 = ftell(fp);

    length = len2 - len1;
    debug_p("len1:%ld,len2:%ld,length:%ld\n",len1,len2,length);
    return length;
}

/* --------------------------------------------------------------------------*/
/**
 * @synopsis  read_file 读指定文件的数据
 *
 * @param fp 文件流指针
 * @param buf 存放读取的数据
 *
 * @returns  最后读入的字节数
 */
/* --------------------------------------------------------------------------*/
int read_file(FILE *fp,char *buf)
{
    int nread = -1;

    while (nread != 0) {
        nread = fread(buf,1,4096,fp); //unix高编上说一次写入4K/8K的数据，效率较高
        buf += nread;
    }
    debug_p("nread: %d\n",nread);
    return nread;
}

/* --------------------------------------------------------------------------*/
/**
 * @synopsis  write_file 将数据写入文件
 *
 * @param fp 文件流指针
 * @param buf 要写入的数据
 * @param size 写入数据的大小
 *
 * @returns  写入的字节数
 */
/* --------------------------------------------------------------------------*/
int write_file(FILE *fp,char *buf,int size)
{
    int nwrite = 0;

    nwrite = fwrite(buf,1,size,fp);
    debug_p("nwrite: %d\n",nwrite);

    return nwrite;
}

int main(int argc,char *argv[])
{
    char *in_filename = "test.yuv";
    char *in_mode = "r";
    char *out_filename = "test.jpg";
    char *out_mode = "w";
    char *data = NULL;
    FILE *in_fp = NULL;
    FILE *out_fp = NULL;
    long file_size = 0;

    in_fp = open_file(in_filename,in_mode);
    file_size = get_file_size(in_fp);
    data = (char *)malloc(file_size);
    if (NULL == data) {
        perror("malloc failure");
        exit(1);
    }
    read_file(in_fp,data);
    out_fp = open_file(out_filename,out_mode);
    write_file(out_fp,data,file_size);

    free(data);
    data = NULL;

    return 0;
}

Makefile

#mips=1    ##将此项打开则编译为mipsel 格式的
ifdef mips
PREFIX=mipsel-linux-
else
PREFIX=
endif

CC=$(PREFIX)gcc
AR=${PREFIX}ar

TARGET=test
CFLAGS=-g -Wall -O2
Conditional_Compilation_CFLAGS=-D DEBUG=1
LIBS=

RM=rm -f

SRC=$(wildcard *.c)
OBJS=$(patsubst %.c,%.o, $(SRC))

%.o:%.c
    $(CC) $(CFLAGS) $(Conditional_Compilation_CFLAGS) -c $< -o $@
$(TARGET):$(OBJS)
    $(CC) -o $@ $^ ${LIBS}

clean:
    ${RM} $(wildcard *.o) $(TARGET)