prioritise reading over writing in the select loop. (this is another

[rsync/rsync.git] / io.c

/* 
   Copyright (C) Andrew Tridgell 1996
   Copyright (C) Paul Mackerras 1996
   
   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.
   
   This program 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 General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
  Utilities used in rsync 

  tridge, June 1996
  */
#include "rsync.h"

static int io_multiplexing_out;
static int io_multiplexing_in;
static int multiplex_in_fd;
static int multiplex_out_fd;
static time_t last_io;
static int eof_error=1;
extern int verbose;
extern int io_timeout;
extern struct stats stats;

static int buffer_f_in = -1;

void setup_readbuffer(int f_in)
{
	buffer_f_in = f_in;
}

static void check_timeout(void)
{
	time_t t;
	
	if (!io_timeout) return;

	if (!last_io) {
		last_io = time(NULL);
		return;
	}

	t = time(NULL);

	if (last_io && io_timeout && (t-last_io) >= io_timeout) {
		rprintf(FERROR,"io timeout after %d second - exiting\n", 
			(int)(t-last_io));
		exit_cleanup(1);
	}
}


static char *read_buffer;
static char *read_buffer_p;
static int read_buffer_len;
static int read_buffer_size;
static int no_flush;

/* read from a socket with IO timeout. return the number of
   bytes read. If no bytes can be read then exit, never return
   a number <= 0 */
static int read_timeout(int fd, char *buf, int len)
{
	int n, ret=0;

	io_flush();

	while (ret == 0) {
		fd_set fds;
		struct timeval tv;

		FD_ZERO(&fds);
		FD_SET(fd, &fds);
		tv.tv_sec = io_timeout;
		tv.tv_usec = 0;

		if (select(fd+1, &fds, NULL, NULL, 
			   io_timeout?&tv:NULL) != 1) {
			check_timeout();
			continue;
		}

		n = read(fd, buf, len);

		if (n > 0) {
			stats.total_read += n;
			buf += n;
			len -= n;
			ret += n;
			if (io_timeout)
				last_io = time(NULL);
			continue;
		}

		if (n == -1 && errno == EINTR) {
			continue;
		}

		if (n == -1 && 
		    (errno == EAGAIN || errno == EWOULDBLOCK)) {
			/* this shouldn't happen, if it does then
			   sleep for a short time to prevent us
			   chewing too much CPU */
			u_sleep(100);
			continue;
		}

		if (n == 0) {
			if (eof_error) {
				rprintf(FERROR,"EOF in read_timeout\n");
			}
			exit_cleanup(1);
		}

		rprintf(FERROR,"read error: %s\n", strerror(errno));
		exit_cleanup(1);
	}

	return ret;
}

/* continue trying to read len bytes - don't return until len
   has been read */
static void read_loop(int fd, char *buf, int len)
{
	while (len) {
		int n = read_timeout(fd, buf, len);

		buf += n;
		len -= n;
	}
}

/* read from the file descriptor handling multiplexing - 
   return number of bytes read
   never return <= 0 */
static int read_unbuffered(int fd, char *buf, int len)
{
	static int remaining;
	char ibuf[4];
	int tag, ret=0;
	char line[1024];

	if (!io_multiplexing_in || fd != multiplex_in_fd) 
		return read_timeout(fd, buf, len);

	while (ret == 0) {
		if (remaining) {
			len = MIN(len, remaining);
			read_loop(fd, buf, len);
			remaining -= len;
			ret = len;
			continue;
		}

		read_loop(fd, ibuf, 4);
		tag = IVAL(ibuf, 0);

		remaining = tag & 0xFFFFFF;
		tag = tag >> 24;

		if (tag == MPLEX_BASE) continue;

		tag -= MPLEX_BASE;

		if (tag != FERROR && tag != FINFO) {
			rprintf(FERROR,"unexpected tag %d\n", tag);
			exit_cleanup(1);
		}

		if (remaining > sizeof(line)-1) {
			rprintf(FERROR,"multiplexing overflow %d\n\n", 
				remaining);
			exit_cleanup(1);
		}

		read_loop(fd, line, remaining);
		line[remaining] = 0;

		rprintf(tag,"%s", line);
		remaining = 0;
	}

	return ret;
}



/* This function was added to overcome a deadlock problem when using
 * ssh.  It looks like we can't allow our receive queue to get full or
 * ssh will clag up. Uggh.  */
static void read_check(int f)
{
	int n = 8192;

	if (f == -1) return;

	if (read_buffer_len == 0) {
		read_buffer_p = read_buffer;
	}

	if (n > MAX_READ_BUFFER/4)
		n = MAX_READ_BUFFER/4;

	if (read_buffer_p != read_buffer) {
		memmove(read_buffer,read_buffer_p,read_buffer_len);
		read_buffer_p = read_buffer;
	}

	if (n > (read_buffer_size - read_buffer_len)) {
		read_buffer_size += n;
		read_buffer = (char *)Realloc(read_buffer,read_buffer_size);
		if (!read_buffer) out_of_memory("read check");      
		read_buffer_p = read_buffer;      
	}

	n = read_unbuffered(f,read_buffer+read_buffer_len,n);
	read_buffer_len += n;
}


/* do a buffered read from fd. don't return until all N bytes
   have been read. If all N can't be read then exit with an error */
static void readfd(int fd,char *buffer,int N)
{
	int  ret;
	int total=0;  
	
	if (read_buffer_len < N && N < 1024) {
		read_check(buffer_f_in);
	}
	
	while (total < N) {
		if (read_buffer_len > 0 && buffer_f_in == fd) {
			ret = MIN(read_buffer_len,N-total);
			memcpy(buffer+total,read_buffer_p,ret);
			read_buffer_p += ret;
			read_buffer_len -= ret;
			total += ret;
			continue;
		} 

		io_flush();

		ret = read_unbuffered(fd,buffer + total,N-total);
		total += ret;
	}
}


int32 read_int(int f)
{
	char b[4];
	readfd(f,b,4);
	return IVAL(b,0);
}

int64 read_longint(int f)
{
	extern int remote_version;
	int64 ret;
	char b[8];
	ret = read_int(f);

	if ((int32)ret != (int32)0xffffffff) return ret;

#ifdef NO_INT64
	rprintf(FERROR,"Integer overflow - attempted 64 bit offset\n");
	exit_cleanup(1);
#else
	if (remote_version >= 16) {
		readfd(f,b,8);
		ret = IVAL(b,0) | (((int64)IVAL(b,4))<<32);
	}
#endif

	return ret;
}

void read_buf(int f,char *buf,int len)
{
	readfd(f,buf,len);
}

void read_sbuf(int f,char *buf,int len)
{
	read_buf(f,buf,len);
	buf[len] = 0;
}

unsigned char read_byte(int f)
{
	unsigned char c;
	read_buf(f,(char *)&c,1);
	return c;
}



/* write len bytes to fd, possibly reading from buffer_f_in if set
   in order to unclog the pipe. don't return until all len
   bytes have been written */
static void writefd_unbuffered(int fd,char *buf,int len)
{
	int total = 0;
	fd_set w_fds, r_fds;
	int fd_count, count;
	struct timeval tv;
	int reading;
	int blocked=0;

	no_flush++;

	while (total < len) {
		FD_ZERO(&w_fds);
		FD_ZERO(&r_fds);
		FD_SET(fd,&w_fds);
		fd_count = fd+1;

		reading = (buffer_f_in != -1 && 
			   read_buffer_len < MAX_READ_BUFFER);

		if (reading) {
			FD_SET(buffer_f_in,&r_fds);
			if (buffer_f_in > fd) 
				fd_count = buffer_f_in+1;
		}

		tv.tv_sec = io_timeout;
		tv.tv_usec = 0;

		count = select(fd_count,
			       reading?&r_fds:NULL,
			       &w_fds,NULL,
			       io_timeout?&tv:NULL);

		if (count <= 0) {
			check_timeout();
			continue;
		}

		if (reading && FD_ISSET(buffer_f_in, &r_fds)) {
			read_check(buffer_f_in);
		}

		if (FD_ISSET(fd, &w_fds)) {
			int n = (len-total)>>blocked;
			int ret = write(fd,buf+total,n?n:1);

			if (ret == -1 && errno == EINTR) {
				continue;
			}

			if (ret == -1 && 
			    (errno == EAGAIN || errno == EWOULDBLOCK)) {
				blocked++;
				continue;
			}

			if (ret <= 0) {
				rprintf(FERROR,"erroring writing %d bytes - exiting\n", len);
				exit_cleanup(1);
			}

			blocked = 0;
			total += ret;
			stats.total_written += ret;

			if (io_timeout)
				last_io = time(NULL);
			continue;
		}
	}

	no_flush--;
}


static char *io_buffer;
static int io_buffer_count;

void io_start_buffering(int fd)
{
	if (io_buffer) return;
	multiplex_out_fd = fd;
	io_buffer = (char *)malloc(IO_BUFFER_SIZE+4);
	if (!io_buffer) out_of_memory("writefd");
	io_buffer_count = 0;

	/* leave room for the multiplex header in case it's needed */
	io_buffer += 4;
}

void io_flush(void)
{
	int fd = multiplex_out_fd;
	if (!io_buffer_count || no_flush) return;

	if (io_multiplexing_out) {
		SIVAL(io_buffer-4, 0, (MPLEX_BASE<<24) + io_buffer_count);
		writefd_unbuffered(fd, io_buffer-4, io_buffer_count+4);
	} else {
		writefd_unbuffered(fd, io_buffer, io_buffer_count);
	}
	io_buffer_count = 0;
}

void io_end_buffering(int fd)
{
	io_flush();
	if (!io_multiplexing_out) {
		free(io_buffer-4);
		io_buffer = NULL;
	}
}

static void writefd(int fd,char *buf,int len)
{
	if (!io_buffer) {
		writefd_unbuffered(fd, buf, len);
		return;
	}

	while (len) {
		int n = MIN(len, IO_BUFFER_SIZE-io_buffer_count);
		if (n > 0) {
			memcpy(io_buffer+io_buffer_count, buf, n);
			buf += n;
			len -= n;
			io_buffer_count += n;
		}
		
		if (io_buffer_count == IO_BUFFER_SIZE) io_flush();
	}
}


void write_int(int f,int32 x)
{
	char b[4];
	SIVAL(b,0,x);
	writefd(f,b,4);
}

void write_longint(int f, int64 x)
{
	extern int remote_version;
	char b[8];

	if (remote_version < 16 || x <= 0x7FFFFFFF) {
		write_int(f, (int)x);
		return;
	}

	write_int(f, -1);
	SIVAL(b,0,(x&0xFFFFFFFF));
	SIVAL(b,4,((x>>32)&0xFFFFFFFF));

	writefd(f,b,8);
}

void write_buf(int f,char *buf,int len)
{
	writefd(f,buf,len);
}

/* write a string to the connection */
void write_sbuf(int f,char *buf)
{
	write_buf(f, buf, strlen(buf));
}


void write_byte(int f,unsigned char c)
{
	write_buf(f,(char *)&c,1);
}

int read_line(int f, char *buf, int maxlen)
{
	eof_error = 0;

	while (maxlen) {
		buf[0] = 0;
		read_buf(f, buf, 1);
		if (buf[0] == 0) return 0;
		if (buf[0] == '\n') {
			buf[0] = 0;
			break;
		}
		if (buf[0] != '\r') {
			buf++;
			maxlen--;
		}
	}
	if (maxlen == 0) {
		*buf = 0;
		return 0;
	}

	eof_error = 1;

	return 1;
}


void io_printf(int fd, const char *format, ...)
{
	va_list ap;  
	char buf[1024];
	int len;
	
	va_start(ap, format);
	len = vslprintf(buf, sizeof(buf)-1, format, ap);
	va_end(ap);

	if (len < 0) exit_cleanup(1);

	write_sbuf(fd, buf);
}


/* setup for multiplexing an error stream with the data stream */
void io_start_multiplex_out(int fd)
{
	multiplex_out_fd = fd;
	io_flush();
	io_start_buffering(fd);
	io_multiplexing_out = 1;
}

/* setup for multiplexing an error stream with the data stream */
void io_start_multiplex_in(int fd)
{
	multiplex_in_fd = fd;
	io_flush();
	if (read_buffer_len) {
		fprintf(stderr,"ERROR: data in read buffer at mplx start\n");
		exit_cleanup(1);
	}

	io_multiplexing_in = 1;
}

/* write an message to the error stream */
int io_multiplex_write(int f, char *buf, int len)
{
	if (!io_multiplexing_out) return 0;

	io_flush();

	SIVAL(io_buffer-4, 0, ((MPLEX_BASE + f)<<24) + len);
	memcpy(io_buffer, buf, len);

	writefd_unbuffered(multiplex_out_fd, io_buffer-4, len+4);
	return 1;
}

void io_close_input(int fd)
{
	buffer_f_in = -1;
}