emit.c

rsync的核心代码库。主要作用是比较二进制文件

/*=                    -*- c-basic-offset: 4; indent-tabs-mode: nil; -*-
 *
 * librsync -- dynamic caching and delta update in HTTP
 * $Id: emit.c,v 1.49 2004/09/10 02:48:58 mbp Exp $
 * 
 * Copyright (C) 2000, 2001, 2004 by Martin Pool <[e-mail]>
 * 
 * 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.
 */


/*
 * TODO: Pluggable encoding formats:
 *
 *  - gdiff-style
 *  - rsync 24
 *  - ed (text)
 *  - Delta HTTP
 */


#include <config.h>

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

#include "librsync.h"
#include "command.h"
#include "protocol.h"
#include "trace.h"
#include "emit.h"
#include "prototab.h"
#include "netint.h"
#include "sumset.h"
#include "job.h"


/*
 * Write the magic for the start of a delta.
 */
void
rs_emit_delta_header(rs_job_t *job)
{
    rs_trace("emit DELTA magic");
    rs_squirt_n4(job, RS_DELTA_MAGIC);
}



/* Write a LITERAL command. */
void
rs_emit_literal_cmd(rs_job_t *job, int len)
{
    int cmd;
    int param_len;

    switch (param_len = rs_int_len(len)) {
    case 1:
        cmd = RS_OP_LITERAL_N1;
        break;
    case 2:
        cmd = RS_OP_LITERAL_N2;
        break;
    case 4:
        cmd = RS_OP_LITERAL_N4;
        break;
    default:
        rs_fatal("What?");
    }
    
    rs_trace("emit LITERAL_N%d(len=%d), cmd_byte=%#x", param_len, len, cmd);
    rs_squirt_byte(job, cmd);
    rs_squirt_netint(job, len, param_len);

    job->stats.lit_cmds++;
    job->stats.lit_bytes += len;
    job->stats.lit_cmdbytes += 1 + param_len;
}


/** Write a COPY command for given offset and length.
 *
 * There is a choice of variable-length encodings, depending on the
 * size of representation for the parameters. */
void
rs_emit_copy_cmd(rs_job_t *job, rs_long_t where, rs_long_t len)
{
    int            cmd;
    rs_stats_t     *stats = &job->stats;
    const int where_bytes = rs_int_len(where);
    const int len_bytes   = rs_int_len(len);

    /* Commands ascend (1,1), (1,2), ... (8, 8) */
    if (where_bytes == 8) 
        cmd = RS_OP_COPY_N8_N1;
    else if (where_bytes == 4)
        cmd = RS_OP_COPY_N4_N1;
    else if (where_bytes == 2)
        cmd = RS_OP_COPY_N2_N1;
    else if (where_bytes == 1)
        cmd = RS_OP_COPY_N1_N1;
    else {
        rs_fatal("can't encode copy command with where_bytes=%d",
                 where_bytes);
    }

    if (len_bytes == 1)
        ;
    else if (len_bytes == 2)
        cmd += 1;
    else if (len_bytes == 4)
        cmd += 2;
    else if (len_bytes == 8)
        cmd += 3;
    else {
        rs_fatal("can't encode copy command with len_bytes=%d",
                 len_bytes);
    }       

    rs_trace("emit COPY_N%d_N%d(where=" PRINTF_FORMAT_U64
             ", len=" PRINTF_FORMAT_U64 "), cmd_byte=%#x",
             where_bytes, len_bytes, PRINTF_CAST_U64(where), PRINTF_CAST_U64(len), cmd);
    rs_squirt_byte(job, cmd);
    rs_squirt_netint(job, where, where_bytes);
    rs_squirt_netint(job, len, len_bytes);

    stats->copy_cmds++;
    stats->copy_bytes += len;
    stats->copy_cmdbytes += 1 + where_bytes + len_bytes;

    /* TODO: All the stats */
}


/** Write an END command. */
void
rs_emit_end_cmd(rs_job_t *job)
{
    int cmd = RS_OP_END;
    
    rs_trace("emit END, cmd_byte=%#x", cmd);
    rs_squirt_byte(job, cmd);
}