1.普通的小文件打开，就用正常的：
open， read， write，lseek，close即可。
2.经过测试，如果lseek大于2GB，那么就要用lseek64，对应地，open也改成open64
3.更大的文件的seek，尤其是大 > 4GB的，可以参考如下makefile以及C源码：
【makefile】
# Makefile
# version: 1.0
# Author: Crifan
#CC = arm-linux-uclibc-gcc
CC = arm-linux-gcc
DEFINES = __KERNEL__
#DEFINES =
CFLAGS= -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_LARGE_FILE
#CFLAGS= -D_LARGE_FILE
#CFLAGS=
SRC_FILE = as352x_lba_test.c
OUT_FILE = lba_test
all:
$(CC) -D$(DEFINES) $(CFLAGS) -o $(OUT_FILE) $(SRC_FILE)
clean:
rm -f $(patsubst %.c,%.o,$(filter %.c, $(SRC_FILE))) $(OUT_FILE)
【C源码】
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include "as352x_lba_test.h"
/* if lseek > 2GB, then should use lseek64 */
/* follow define is equal with include -D */
//#define _FILE_OFFSET_BITS 64 /* == -D_LARGEFILE64_SOURCE while compile */
//#define _LARGEFILE64_SOURCE /* == -D_LARGEFILE64_SOURCE */
#include <unistd.h>
static int lba_file = 0;
/*******************************************************/
#define BUFFER_SIZE 1024
#define LINE_WIDTH 16
void lba_print_buf(unsigned char *buf, int len)
{
int idx;
printf("buffer=0x%p, len=%d :n", buf, len);
for(idx = 0; idx < len ; idx ++)
{
printf( " %02x", buf[idx]);
if(0==((idx+1)%(LINE_WIDTH/2)))
printf( " ");
if(0==((idx+1)%LINE_WIDTH))
printf( "n");
}
printf( "n");
}
/*******************************************************/
int main(void)
{
unsigned long long pos;
unsigned char buffer[BUFFER_SIZE];
unsigned char pattern;
printf("Now will open ");
printf(AS352X_LBA_DEVICE_NAME);
printf(".n");
if(lba_file)
close(lba_file);
lba_file = open64(AS352X_LBA_DEVICE_NAME, O_RDWR);
if(lba_file == -1)
{
printf(AS352X_LBA_DEVICE_NAME);
printf("open failed.n");
return -1;
}
else
{
printf("open OK: file =%d.n", lba_file);
}
#if 0
read(lba_file, buffer, BUFFER_SIZE);
lba_print_buf(buffer, BUFFER_SIZE);
#endif
//pos = (unsigned long long)0xE0000000; /* 3.5GB */
pos = (unsigned long long)0x10000 * 0x10000; /* 4GB */
// pos = 0x500000; /* 50M */
// pos = 0xA00000; /* 100M */
#if 0
lseek64(lba_file, pos, SEEK_SET);
read(lba_file, buffer, BUFFER_SIZE);
lba_print_buf(buffer, BUFFER_SIZE);
#endif
#if 1
/* write */
lseek64(lba_file, pos, SEEK_SET);
printf("…..seek to 0x%x…n", pos);
pattern = 0x35;
memset(buffer, pattern, BUFFER_SIZE);
printf("pattern = 0x%xn", pattern);
write(lba_file, buffer, BUFFER_SIZE);
printf("write done………………….n");
#endif
#if 1
/* read out */
lseek64(lba_file, pos, SEEK_SET);
printf("…..seek to 0x%x…n", pos);
read(lba_file, buffer, BUFFER_SIZE);
lba_print_buf(buffer, BUFFER_SIZE);
printf("read done………………….n");
#endif
close(lba_file);
printf("Now has close ");
printf(AS352X_LBA_DEVICE_NAME);
printf("……….n");
return 0;
}