/*
   tio.c - timed io functions
   This file is part of the nss-ldapd library.

   Copyright (C) 2007, 2008 Arthur de Jong

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301 USA
*/

#include "config.h"

#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif /* HAVE_STDINT_H */
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <stdio.h>

#include "tio.h"

/* for platforms that don't have ETIME use ETIMEDOUT */
#ifndef ETIME
#define ETIME ETIMEDOUT
#endif /* ETIME */

/* structure that holds a buffer
   the buffer contains the data that is between the application and the
   file descriptor that is used for efficient transfer
   the buffer is built up as follows:
   |.....********......|
         ^start        ^size
         ^--len--^           */
struct tio_buffer {
  uint8_t *buffer;
  size_t size;      /* the size of the buffer */
  size_t maxsize;   /* the maximum size of the buffer */
  size_t start;     /* the start of the data (before start is unused) */
  size_t len;       /* size of the data (from the start) */
};

/* structure that holds all the state for files */
struct tio_fileinfo {
  int fd;
  struct tio_buffer readbuffer;
  struct tio_buffer writebuffer;
  struct timeval readtimeout;
  struct timeval writetimeout;
  int read_resettable; /* whether the tio_reset() function can be called */
#ifdef DEBUG_TIO_STATS
  /* this is used to collect statistics on the use of the streams
     and can be used to tune the buffer sizes */
  size_t byteswritten;
  size_t bytesread;
#endif /* DEBUG_TIO_STATS */
};

/* add the second timeval to the first modifing the first */
static inline void tio_tv_add(struct timeval *tv1, const struct timeval *tv2)
{
  /* BUG: we hope that this does not overflow */
  tv1->tv_usec+=tv2->tv_usec;
  if (tv1->tv_usec>1000000)
  {
    tv1->tv_usec-=1000000;
    tv1->tv_sec+=1;
  }
  tv1->tv_sec+=tv2->tv_sec;
}

/* build a timeval for comparison to when the operation should be finished */
static inline void tio_tv_prepare(struct timeval *deadline, const struct timeval *timeout)
{
  if (gettimeofday(deadline,NULL))
  {
    /* just blank it in case of errors */
    deadline->tv_sec=0;
    deadline->tv_usec=0;
    return;
  }
  tio_tv_add(deadline,timeout);
}

/* update the timeval to the value that is remaining before deadline
   returns non-zero if there is no more time before the deadline */
static inline int tio_tv_remaining(struct timeval *tv, const struct timeval *deadline)
{
  /* get the current time */
  if (gettimeofday(tv,NULL))
  {
    /* 1 second default if gettimeofday() is broken */
    tv->tv_sec=1;
    tv->tv_usec=0;
    return 0;
  }
  /* check if we're too late */
  if ( (tv->tv_sec>deadline->tv_sec) ||
       ( (tv->tv_sec==deadline->tv_sec) && (tv->tv_usec>deadline->tv_usec) ) )
    return -1;
  /* update tv */
  tv->tv_sec=deadline->tv_sec-tv->tv_sec;
  if (tv->tv_usec<deadline->tv_usec)
    tv->tv_usec=deadline->tv_usec-tv->tv_usec;
  else
  {
    tv->tv_sec--;
    tv->tv_usec=1000000+deadline->tv_usec-tv->tv_usec;
  }
  return 0;
}

/* open a new TFILE based on the file descriptor */
TFILE *tio_fdopen(int fd,struct timeval *readtimeout,struct timeval *writetimeout,
                  size_t initreadsize,size_t maxreadsize,
                  size_t initwritesize,size_t maxwritesize)
{
  struct tio_fileinfo *fp;
  fp=(struct tio_fileinfo *)malloc(sizeof(struct tio_fileinfo));
  if (fp==NULL)
    return NULL;
  fp->fd=fd;
  /* initialize read buffer */
  fp->readbuffer.buffer=(uint8_t *)malloc(initreadsize);
  if (fp->readbuffer.buffer==NULL)
  {
    free(fp);
    return NULL;
  }
  fp->readbuffer.size=initreadsize;
  fp->readbuffer.maxsize=maxreadsize;
  fp->readbuffer.start=0;
  fp->readbuffer.len=0;
  /* initialize write buffer */
  fp->writebuffer.buffer=(uint8_t *)malloc(initwritesize);
  if (fp->writebuffer.buffer==NULL)
  {
    free(fp->readbuffer.buffer);
    free(fp);
    return NULL;
  }
  fp->writebuffer.size=initwritesize;
  fp->writebuffer.maxsize=maxwritesize;
  fp->writebuffer.start=0;
  fp->writebuffer.len=0;
  /* initialize other attributes */
  fp->readtimeout.tv_sec=readtimeout->tv_sec;
  fp->readtimeout.tv_usec=readtimeout->tv_usec;
  fp->writetimeout.tv_sec=writetimeout->tv_sec;
  fp->writetimeout.tv_usec=writetimeout->tv_usec;
  fp->read_resettable=0;
#ifdef DEBUG_TIO_STATS
  fp->byteswritten=0;
  fp->bytesread=0;
#endif /* DEBUG_TIO_STATS */
  return fp;
}

/* wait for any activity on the specified file descriptor using
   the specified deadline */
static int tio_select(int fd, int readfd, const struct timeval *deadline)
{
  struct timeval tv;
  fd_set fdset;
  int rv;
  while (1)
  {
    /* prepare our filedescriptorset */
    FD_ZERO(&fdset);
    FD_SET(fd,&fdset);
    /* figure out the time we need to wait */
    if (tio_tv_remaining(&tv,deadline))
    {
      errno=ETIME;
      return -1;
    }
    /* wait for activity */
    if (readfd)
      rv=select(FD_SETSIZE,&fdset,NULL,NULL,&tv);
    else
      rv=select(FD_SETSIZE,NULL,&fdset,NULL,&tv);
    if (rv>0)
      return 0; /* we have activity */
    else if (rv==0)
    {
      /* no file descriptors were available within the specified time */
      errno=ETIME;
      return -1;
    }
    else if (errno!=EINTR)
      /* some error ocurred */
      return -1;
    /* we just try again on EINTR */
  }
}

/* do a read on the file descriptor, returning the data in the buffer
   if no data was read in the specified time an error is returned */
int tio_read(TFILE *fp, void *buf, size_t count)
{
  struct timeval deadline;
  int rv;
  uint8_t *tmp;
  size_t newsz;
  /* have a more convenient storage type for the buffer */
  uint8_t *ptr=(uint8_t *)buf;
  /* build a time by which we should be finished */
  tio_tv_prepare(&deadline,&(fp->readtimeout));
  /* loop until we have returned all the needed data */
  while (1)
  {
    /* check if we have enough data in the buffer */
    if (fp->readbuffer.len >= count)
    {
      if (count>0)
      {
        if (ptr!=NULL)
          memcpy(ptr,fp->readbuffer.buffer+fp->readbuffer.start,count);
        /* adjust buffer position */
        fp->readbuffer.start+=count;
        fp->readbuffer.len-=count;
      }
      return 0;
    }
    /* empty what we have and continue from there */
    if (fp->readbuffer.len>0)
    {
      if (ptr!=NULL)
      {
        memcpy(ptr,fp->readbuffer.buffer+fp->readbuffer.start,fp->readbuffer.len);
        ptr+=fp->readbuffer.len;
      }
      count-=fp->readbuffer.len;
      fp->readbuffer.start+=fp->readbuffer.len;
      fp->readbuffer.len=0;
    }
    /* after this point until the read fp->readbuffer.len is 0 */
    if (!fp->read_resettable)
    {
      /* the stream is not resettable, re-use the buffer */
      fp->readbuffer.start=0;
    }
    else if (fp->readbuffer.start>=(fp->readbuffer.size-4))
    {
      /* buffer is running empty, try to grow buffer */
      if (fp->readbuffer.size<fp->readbuffer.maxsize)
      {
        newsz=fp->readbuffer.size*2;
        if (newsz>fp->readbuffer.maxsize)
          newsz=fp->readbuffer.maxsize;
        tmp=realloc(fp->readbuffer.buffer,newsz);
        if (tmp!=NULL)
        {
          fp->readbuffer.buffer=tmp;
          fp->readbuffer.size=newsz;
        }
      }
      /* if buffer still does not contain enough room, clear resettable */
      if (fp->readbuffer.start>=(fp->readbuffer.size-4))
      {
        fp->readbuffer.start=0;
        fp->read_resettable=0;
      }
    }
    /* wait until we have input */
    if (tio_select(fp->fd,1,&deadline))
      return -1;
    /* read the input in the buffer */
    rv=read(fp->fd,fp->readbuffer.buffer+fp->readbuffer.start,fp->readbuffer.size-fp->readbuffer.start);
    /* check for errors */
    if ((rv==0)||((rv<0)&&(errno!=EINTR)&&(errno!=EAGAIN)))
      return -1; /* something went wrong with the read */
    /* skip the read part in the buffer */
    fp->readbuffer.len=rv;
#ifdef DEBUG_TIO_STATS
    fp->bytesread+=rv;
#endif /* DEBUG_TIO_STATS */
  }
}

/* Read and discard the specified number of bytes from the stream. */
int tio_skip(TFILE *fp, size_t count)
{
  return tio_read(fp,NULL,count);
}

/* the caller has assured us that we can write to the file descriptor
   and we give it a shot */
static int tio_writebuf(TFILE *fp)
{
  int rv;
  struct sigaction act,oldact;
  /* FIXME: we have a race condition here (setting and restoring the signal mask), this is a critical region that should be locked */
  /* set up sigaction */
  memset(&act,0,sizeof(struct sigaction));
  act.sa_sigaction=NULL;
  act.sa_handler=SIG_IGN;
  sigemptyset(&act.sa_mask);
  act.sa_flags=SA_RESTART;
  /* ignore SIGPIPE */
  if (sigaction(SIGPIPE,&act,&oldact)!=0)
    return -1; /* error setting signal handler */
  /* write the buffer */
  rv=write(fp->fd,fp->writebuffer.buffer+fp->writebuffer.start,fp->writebuffer.len);
  /* restore the old handler for SIGPIPE */
  if (sigaction(SIGPIPE,&oldact,NULL)!=0)
    return -1; /* error restoring signal handler */
  /* check for errors */
  if ((rv==0)||((rv<0)&&(errno!=EINTR)&&(errno!=EAGAIN)))
    return -1; /* something went wrong with the write */
  /* skip the written part in the buffer */
  if (rv>0)
  {
    fp->writebuffer.start+=rv;
    fp->writebuffer.len-=rv;
#ifdef DEBUG_TIO_STATS
    fp->byteswritten+=rv;
#endif /* DEBUG_TIO_STATS */
    /* reset start if len is 0 */
    if (fp->writebuffer.len==0)
      fp->writebuffer.start=0;
    /* move contents of the buffer to the front if it will save enough room */
    if (fp->writebuffer.start>=(fp->writebuffer.size/4))
    {
      memmove(fp->writebuffer.buffer,fp->writebuffer.buffer+fp->writebuffer.start,fp->writebuffer.len);
      fp->writebuffer.start=0;
    }
  }
  return 0;
}

/* write all the data in the buffer to the stream */
int tio_flush(TFILE *fp)
{
  struct timeval deadline;
  /* build a time by which we should be finished */
  tio_tv_prepare(&deadline,&(fp->writetimeout));
  /* loop until we have written our buffer */
  while (fp->writebuffer.len > 0)
  {
    /* wait until we can write */
    if (tio_select(fp->fd,0,&deadline))
      return -1;
    /* write one block */
    if (tio_writebuf(fp))
      return -1;
  }
  return 0;
}

/* try a single write of data in the buffer if the file descriptor
   will accept data */
static int tio_flush_nonblock(TFILE *fp)
{
  struct timeval tv;
  fd_set fdset;
  int rv;
  /* prepare our filedescriptorset */
  FD_ZERO(&fdset);
  FD_SET(fp->fd,&fdset);
  /* set the timeout to 0 to poll */
  tv.tv_sec=0;
  tv.tv_usec=0;
  /* wait for activity */
  rv=select(FD_SETSIZE,NULL,&fdset,NULL,&tv);
  /* check if any file descriptors were ready (timeout) or we were
     interrupted */
  if ((rv==0)||((rv<0)&&(errno==EINTR)))
    return 0;
  /* any other errors? */
  if (rv<0)
    return -1;
  /* so file descriptor will accept writes */
  return tio_writebuf(fp);
}

int tio_write(TFILE *fp, const void *buf, size_t count)
{
  size_t fr;
  uint8_t *tmp;
  size_t newsz;
  const uint8_t *ptr=(const uint8_t *)buf;
  /* keep filling the buffer until we have bufferred everything */
  while (count>0)
  {
    /* figure out free size in buffer */
    fr=fp->writebuffer.size-(fp->writebuffer.start+fp->writebuffer.len);
    if (count <= fr)
    {
      /* the data fits in the buffer */
      memcpy(fp->writebuffer.buffer+fp->writebuffer.start+fp->writebuffer.len,ptr,count);
      fp->writebuffer.len+=count;
      return 0;
    }
    else if (fr > 0)
    {
      /* fill the buffer with data that will fit */
      memcpy(fp->writebuffer.buffer+fp->writebuffer.start+fp->writebuffer.len,ptr,fr);
      fp->writebuffer.len+=fr;
      ptr+=fr;
      count-=fr;
    }
    /* try to flush some of the data that is in the buffer */
    if (tio_flush_nonblock(fp))
      return -1;
    /* if we have room now, try again */
    if (fp->writebuffer.size>(fp->writebuffer.start+fp->writebuffer.len))
      continue;
    /* try to grow the buffer */
    if (fp->writebuffer.size<fp->writebuffer.maxsize)
    {
      newsz=fp->writebuffer.size*2;
      if (newsz>fp->writebuffer.maxsize)
        newsz=fp->writebuffer.maxsize;
      tmp=realloc(fp->writebuffer.buffer,newsz);
      if (tmp!=NULL)
      {
        fp->writebuffer.buffer=tmp;
        fp->writebuffer.size=newsz;
        continue; /* try again */
      }
    }
    /* write the buffer to the stream */
    if (tio_flush(fp))
      return -1;
  }
  return 0;
}

int tio_close(TFILE *fp)
{
  int retv;
  /* write any buffered data */
  retv=tio_flush(fp);
#ifdef DEBUG_TIO_STATS
  /* dump statistics to stderr */
  fprintf(stderr,"DEBUG_TIO_STATS READ=%d WRITTEN=%d\n",fp->bytesread,fp->byteswritten);
#endif /* DEBUG_TIO_STATS */
  /* close file descriptor */
  if (close(fp->fd))
    retv=-1;
  /* free any allocated buffers */
  free(fp->readbuffer.buffer);
  free(fp->writebuffer.buffer);
  /* free the tio struct itself */
  free(fp);
  /* return the result of the earlier operations */
  return retv;
}

void tio_mark(TFILE *fp)
{
  /* move any data in the buffer to the start of the buffer */
  if ((fp->readbuffer.start>0)&&(fp->readbuffer.len>0))
  {
    memmove(fp->readbuffer.buffer,fp->readbuffer.buffer+fp->readbuffer.start,fp->readbuffer.len);
    fp->readbuffer.start=0;
  }
  /* mark the stream as resettable */
  fp->read_resettable=1;
}

int tio_reset(TFILE *fp)
{
  /* check if the stream is (still) resettable */
  if (!fp->read_resettable)
    return -1;
  /* reset the buffer */
  fp->readbuffer.len+=fp->readbuffer.start;
  fp->readbuffer.start=0;
  return 0;
}
