/*= -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
 *
 * librsync -- the library for network deltas
 * Id: buf.c,v 1.17 2001/09/14 01:29:40 mbp Exp 
 * 
 * Copyright (C) 2000, 2001 by Martin Pool <mbp@samba.org>
 * 
 * This program 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 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

                              /*
                               | Pick a window, Jimmy, you're leaving.
                               |   -- Martin Schwenke, regularly
                               */


/*
 * buf.c -- Buffers that map between stdio file streams and librsync
 * streams.  As the stream consumes input and produces output, it is
 * refilled from appropriate input and output FILEs.  A dynamically
 * allocated buffer of configurable size is used as an intermediary.
 *
 * TODO: Perhaps be more efficient by filling the buffer on every call
 * even if not yet completely empty.  Check that it's really our
 * buffer, and shuffle remaining data down to the front.
 *
 * TODO: Perhaps expose a routine for shuffling the buffers.
 */


#include <config.h>

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#include "rsync.h"
#include "trace.h"
#include "buf.h"
#include "util.h"

/**
 * File IO buffer sizes.
 */
int rs_inbuflen = 16000, rs_outbuflen = 16000;


struct rs_filebuf {
        FILE *f;
        char            *buf;
        size_t          buf_len;
};



rs_filebuf_t *rs_filebuf_new(FILE *f, size_t buf_len) 
{
    rs_filebuf_t *pf = rs_alloc_struct(rs_filebuf_t);

    pf->buf = rs_alloc(buf_len, "file buffer");
    pf->buf_len = buf_len;
    pf->f = f;

    return pf;
}


void rs_filebuf_free(rs_filebuf_t *fb) 
{
        rs_bzero(fb, sizeof *fb);
        free(fb);
}


/*
 * If the stream has no more data available, read some from F into
 * BUF, and let the stream use that.  On return, SEEN_EOF is true if
 * the end of file has passed into the stream.
 */
rs_result rs_infilebuf_fill(rs_job_t *job, rs_buffers_t *buf,
                            void *opaque)
{
    int                     len;
    rs_filebuf_t            *fb = (rs_filebuf_t *) opaque;
    FILE                    *f = fb->f;
        
    /* This is only allowed if either the buf has no input buffer
     * yet, or that buffer could possibly be BUF. */
    if (buf->next_in != NULL) {
        assert(buf->avail_in <= fb->buf_len);
        assert(buf->next_in >= fb->buf);
        assert(buf->next_in <= fb->buf + fb->buf_len);
    } else {
        assert(buf->avail_in == 0);
    }

    if (buf->eof_in || (buf->eof_in = feof(f))) {
        rs_trace("seen end of file on input");
        buf->eof_in = 1;
        return RS_DONE;
    }

    if (buf->avail_in)
        /* Still some data remaining.  Perhaps we should read
           anyhow? */
        return RS_DONE;
        
    len = fread(fb->buf, 1, fb->buf_len, f);
    if (len <= 0) {
        /* This will happen if file size is a multiple of input block len
         */
        if (feof(f)) {
            rs_trace("seen end of file on input");
            buf->eof_in = 1;
            return RS_DONE;
        }
        if (ferror(f)) {
            rs_error("error filling buf from file: %s",
                     strerror(errno));
            return RS_IO_ERROR;
        } else {
            rs_error("no error bit, but got %d return when trying to read",
                     len);
            return RS_IO_ERROR;
        }
    }
    buf->avail_in = len;
    buf->next_in = fb->buf;

    return RS_DONE;
}


/*
 * The buf is already using BUF for an output buffer, and probably
 * contains some buffered output now.  Write this out to F, and reset
 * the buffer cursor.
 */
rs_result rs_outfilebuf_drain(rs_job_t *job, rs_buffers_t *buf, void *opaque)
{
    int present;
    rs_filebuf_t *fb = (rs_filebuf_t *) opaque;
    FILE *f = fb->f;

    /* This is only allowed if either the buf has no output buffer
     * yet, or that buffer could possibly be BUF. */
    if (buf->next_out == NULL) {
        assert(buf->avail_out == 0);
                
        buf->next_out = fb->buf;
        buf->avail_out = fb->buf_len;
                
        return RS_DONE;
    }
        
    assert(buf->avail_out <= fb->buf_len);
    assert(buf->next_out >= fb->buf);
    assert(buf->next_out <= fb->buf + fb->buf_len);

    present = buf->next_out - fb->buf;
    if (present > 0) {
        int result;
                
        assert(present > 0);

        result = fwrite(fb->buf, 1, present, f);
        if (present != result) {
            rs_error("error draining buf to file: %s",
                     strerror(errno));
            return RS_IO_ERROR;
        }

        buf->next_out = fb->buf;
        buf->avail_out = fb->buf_len;
    }
        
    return RS_DONE;
}


/**
 * Default copy implementation that retrieves a part of a stdio file.
 */
rs_result rs_file_copy_cb(void *arg, off_t pos, size_t *len, void **buf)
{
    int        got;
    FILE       *f = (FILE *) arg;

    if (fseek(f, pos, SEEK_SET)) {
        rs_log(RS_LOG_ERR, "seek failed: %s", strerror(errno));
        return RS_IO_ERROR;
    }

    got = fread(*buf, 1, *len, f);
    if (got == -1) {
        rs_error(strerror(errno));
        return RS_IO_ERROR;
    } else if (got == 0) {
        rs_error("unexpected eof on fd%d", fileno(f));
        return RS_INPUT_ENDED;
    } else {
        *len = got;
        return RS_DONE;
    }
}