Hi,
yesterday i downloaded and installed the newest maemo sdk and scratchbox
4.1 from maemo.org to port a database library (hamsterdb).
after some pondering, i found out that pwrite() usually succeeds, but
only writes zeroes to the file. When replacing pwrite() with
seek()/write(), everything works.
To reproduce, i wrote a small test program which allocates 3 pages (each
of size 16kb), fills them and then writes them with pwrite(). But
hexdump shows that only the first page is written, all other pages are
zeroes.
I have attached my test program - it compiles with "gcc -g iotest.c",
and creates an iotest.bin file with the broken pages. On my host system
(Ubuntu 8 x64) it works.
Regards
Christoph
PS: i tried to search bugzilla, but the web interface seems to be broken
(mysql returns SQL errors when querying the database).
PPS: in my configure script i will disable pread/pwrite if the target is
arm-*-linux-gnu. If someone has a better test for broken pread/pwrite
implementations, or a better test for scratchbox environments, please
tell me.
/**
* Copyright (C) 2005-2008 Christoph Rupp ([EMAIL PROTECTED]).
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* See files COPYING.* for License information.
*
*/
#define _GNU_SOURCE 1 /* for O_LARGEFILE */
#define __USE_XOPEN2K 1 /* for ftruncate() */
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <fcntl.h>
#include <unistd.h>
#include <assert.h>
typedef unsigned long long ham_offset_t;
typedef unsigned ham_size_t;
static void
my_enable_largefile(int fd)
{
/*
* not available on cygwin...
*/
int oflag=fcntl(fd, F_GETFL, 0);
fcntl(fd, F_SETFL, oflag|O_LARGEFILE);
}
static void
my_lock_exclusive(int fd, int lock)
{
int r, flags;
if (lock)
flags=LOCK_EX|LOCK_NB;
else
flags=LOCK_UN;
r=flock(fd, flags);
assert(r==0);
}
void
os_pread(int fd, ham_offset_t addr, void *buffer, ham_size_t bufferlen)
{
int r;
ham_size_t total=0;
while (total<bufferlen) {
r=pread(fd, buffer+total, bufferlen-total, addr+total);
assert(r>=0);
if (r==0)
break;
total+=r;
}
assert(total==bufferlen);
}
void
os_seek(int fd, ham_offset_t offset, int whence)
{
int r=lseek(fd, offset, whence);
assert(r!=-1);
}
void
os_pwrite(int fd, ham_offset_t addr, const void *buffer, ham_size_t bufferlen)
{
ssize_t s;
ham_size_t total=0;
while (total<bufferlen) {
s=pwrite(fd, buffer, bufferlen, addr);
assert(s>=0);
if (s==0)
break;
total+=s;
}
assert(total==bufferlen);
}
void
os_truncate(int fd, ham_offset_t newsize)
{
int r=ftruncate(fd, newsize);
assert(r==0);
}
void
os_create(const char *filename, unsigned mode, int *fd)
{
int osflags=O_CREAT|O_RDWR|O_TRUNC;
*fd=open(filename, osflags, mode);
assert(*fd>0);
my_enable_largefile(*fd);
my_lock_exclusive(*fd, 1);
}
void
os_close(int fd)
{
my_lock_exclusive(fd, 0);
close(fd);
}
void
os_tell(int fd, ham_offset_t *offset)
{
*offset=lseek(fd, 0, SEEK_CUR);
assert(*offset!=-1);
}
void
os_get_filesize(int fd, ham_offset_t *size)
{
os_seek(fd, 0, SEEK_END);
os_tell(fd, size);
}
int main()
{
const char *fname="iotest.bin";
char page[1024*16];
int fd;
ham_offset_t address;
int i;
os_create(fname, 0644, &fd);
for (i=0; i<3; i++) {
printf("%u: line %d\n", i, __LINE__);
os_get_filesize(fd, &address);
printf("next page: %llu\n", address);
printf("%u: line %d\n", i, __LINE__);
os_truncate(fd, address+sizeof(page));
printf("%u: line %d\n", i, __LINE__);
os_pread(fd, address, page, sizeof(page));
printf("%u: line %d\n", i, __LINE__);
memset(page, 'a'+i, sizeof(page));
printf("%u: line %d\n", i, __LINE__);
os_pwrite(fd, address, page, sizeof(page));
}
os_close(fd);
return (0);
}
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