path: root/camel/camel-seekable-substream.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/* camel-stream-fs.c : file system based stream */

/* inspired by gnome-stream-fs.c in bonobo by Miguel de Icaza */
/* 
 *
 * Author : 
 *  Bertrand Guiheneuf <bertrand@helixcode.com>
 *
 * Copyright 1999, 2000 Helix Code, Inc. (http://www.helixcode.com)
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */
#include <config.h>
#include "camel-seekable-substream.h"
#include "camel-log.h"

static CamelSeekableStreamClass *parent_class=NULL;


/* Returns the class for a CamelSeekableSubStream */
#define CSS_CLASS(so) CAMEL_SEEKABLE_SUBSTREAM_CLASS (GTK_OBJECT(so)->klass)




static  gint           _read                  (CamelStream *stream, 
                               gchar *buffer, gint n);
static  gint           _write                 (CamelStream *stream, 
                               const gchar *buffer, 
                               gint n);
static  void           _flush                 (CamelStream *stream);
static  gint           _available             (CamelStream *stream);
static  gboolean       _eos               (CamelStream *stream);
static  void           _close                 (CamelStream *stream);
static  gint           _seek                  (CamelSeekableStream *stream, 
                               gint offset, 
                               CamelStreamSeekPolicy policy);

static  void           _finalize              (GtkObject *object);
static  void           _destroy               (GtkObject *object);

static  void           _init_with_seekable_stream_and_bounds     (CamelSeekableSubstream *seekable_substream, 
                                  CamelSeekableStream *parent_stream,
                                  guint32 inf_bound, 
                                  gint64  sup_bound);




static void
camel_seekable_substream_class_init (CamelSeekableSubstreamClass *camel_seekable_substream_class)
{
    CamelSeekableStreamClass *camel_seekable_stream_class = CAMEL_SEEKABLE_STREAM_CLASS (camel_seekable_substream_class);
    CamelStreamClass *camel_stream_class = CAMEL_STREAM_CLASS (camel_seekable_substream_class);
    GtkObjectClass *gtk_object_class = GTK_OBJECT_CLASS (camel_seekable_substream_class);

    parent_class = gtk_type_class (camel_seekable_stream_get_type ());
    
    /* virtual method definition */
    camel_seekable_substream_class->init_with_seekable_stream_and_bounds = _init_with_seekable_stream_and_bounds;
    
    /* virtual method overload */
    camel_stream_class->read = _read;
    camel_stream_class->write = _write;
    camel_stream_class->flush = _flush;
    camel_stream_class->available = _available;
    camel_stream_class->eos = _eos;
    camel_stream_class->close = _close;

    camel_seekable_stream_class->seek = _seek;

    gtk_object_class->finalize = _finalize;
    gtk_object_class->destroy = _destroy;

}

static void
camel_seekable_substream_init (gpointer   object,  gpointer   klass)
{
    /* does nothing */
}




GtkType
camel_seekable_substream_get_type (void)
{
    static GtkType camel_seekable_substream_type = 0;
    
    if (!camel_seekable_substream_type) {
        GtkTypeInfo camel_seekable_substream_info = 
        {
            "CamelSeekableSubstream",
            sizeof (CamelSeekableSubstream),
            sizeof (CamelSeekableSubstreamClass),
            (GtkClassInitFunc) camel_seekable_substream_class_init,
            (GtkObjectInitFunc) camel_seekable_substream_init,
                /* reserved_1 */ NULL,
                /* reserved_2 */ NULL,
            (GtkClassInitFunc) NULL,
        };
        
        camel_seekable_substream_type = gtk_type_unique (camel_seekable_stream_get_type (), &camel_seekable_substream_info);
    }
    
    return camel_seekable_substream_type;
}






static void           
_destroy (GtkObject *object)
{
    
    CAMEL_LOG_FULL_DEBUG ("Entering CamelSeekableSubstream::destroy\n");
    
    /* does nothing for the moment */
    GTK_OBJECT_CLASS (parent_class)->destroy (object);
    
    CAMEL_LOG_FULL_DEBUG ("Leaving CamelSeekableSubstream::destroy\n");
}


static void           
_finalize (GtkObject *object)
{
    CamelSeekableStream *seekable_stream;
    CamelSeekableSubstream *seekable_substream;
    CAMEL_LOG_FULL_DEBUG ("Entering CamelSeekableSubstream::finalize\n");
    
    seekable_stream = CAMEL_SEEKABLE_STREAM (object);
    seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (object);

    if (seekable_substream->parent_stream)
        gtk_object_unref (GTK_OBJECT (seekable_substream->parent_stream));

    GTK_OBJECT_CLASS (parent_class)->finalize (object);
    CAMEL_LOG_FULL_DEBUG ("Leaving CamelSeekableSubstream::finalize\n");
}



static void 
_set_bounds (CamelSeekableSubstream *seekable_substream, guint32 inf_bound, gint64 sup_bound)
{
    CAMEL_LOG_FULL_DEBUG ("CamelSeekableSubstream::_set_bounds entering\n");

    g_assert (seekable_substream);
    g_assert (seekable_substream->parent_stream);
    
    /* store the bounds */
    seekable_substream->inf_bound = inf_bound;
    seekable_substream->sup_bound = sup_bound;


    seekable_substream->cur_pos = 0;
    seekable_substream->eos = FALSE;
    
    CAMEL_LOG_FULL_DEBUG ("In CamelSeekableSubstream::_set_bounds (%p), "
                  "setting inf bound to %lu, "
                  "sup bound to %lld, current position to %lu from %lu\n"
                  "Parent stream = %p\n", 
                  seekable_substream,
                  seekable_substream->inf_bound, seekable_substream->sup_bound,
                  seekable_substream->cur_pos, inf_bound,
                  seekable_substream->parent_stream);
    
    CAMEL_LOG_FULL_DEBUG ("CamelSeekableSubstream::_set_bounds Leaving\n");
}

static void
_reemit_parent_signal (CamelStream *parent_stream, gpointer user_data)
{
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (user_data);

    gtk_signal_emit_by_name (GTK_OBJECT (seekable_substream), "data_available");
    
}


static void        
_init_with_seekable_stream_and_bounds    (CamelSeekableSubstream *seekable_substream, 
                      CamelSeekableStream    *parent_stream,
                      guint32                 inf_bound, 
                      gint64                  sup_bound)
{
    /* sanity checks */
    g_assert (seekable_substream);
    g_assert (!seekable_substream->parent_stream);
    g_assert (parent_stream);
    
    /* store the parent stream */
    seekable_substream->parent_stream = parent_stream;
    gtk_object_ref (GTK_OBJECT (parent_stream));

    /* set the bound of the substream */
    _set_bounds (seekable_substream, inf_bound, sup_bound);

    /* 
     *  connect to the parent stream "data_available"
     *  stream so that we can reemit the signal on the 
     *  seekable substream in case some data would 
     *  be available for us 
     */
    gtk_signal_connect (GTK_OBJECT (parent_stream),
                "data_available", 
                _reemit_parent_signal,
                seekable_substream);

    gtk_signal_emit_by_name (GTK_OBJECT (seekable_substream), "data_available");

}



CamelStream *
camel_seekable_substream_new_with_seekable_stream_and_bounds (CamelSeekableStream    *parent_stream,
                                  guint32                 inf_bound, 
                                  gint64                  sup_bound)
{
    CamelSeekableSubstream *seekable_substream;

    /* create the seekable substream */
    seekable_substream = gtk_type_new (camel_seekable_substream_get_type ());

    /* initialize it */
    CSS_CLASS (seekable_substream)->init_with_seekable_stream_and_bounds (seekable_substream,
                                          parent_stream,
                                          inf_bound,
                                          sup_bound);
    return CAMEL_STREAM (seekable_substream);
}





/**
 * _read: read bytes from a stream
 * @stream: stream
 * @buffer: buffer where bytes are stored
 * @n: max number of bytes to read
 * 
 * 
 * 
 * Return value: number of bytes actually read.
 **/
static gint
_read (CamelStream *stream, gchar *buffer, gint n)
{
    CamelSeekableStream *seekable_stream = CAMEL_SEEKABLE_STREAM (stream);
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (stream);
    gint v;
    gint nb_to_read;
    guint32 parent_stream_current_position;
    guint32 position_in_parent;
    
    g_assert (stream);
    g_assert (seekable_substream->parent_stream);

    g_assert (n);


    /* 
       we are doing something quite infefficient : 
       
       each time we want to read a block, we store
       the parent stream position so that we can 
       change it, and restore it before returning 

       This may change. I don't know yet. 
       It may be useless to reseek every time
       and is incompatible with buffering. 
    */


    parent_stream_current_position = 
        camel_seekable_stream_get_current_position (seekable_substream->parent_stream);

    /* compute the position in the parent stream */
    position_in_parent =  
        seekable_stream->cur_pos + seekable_substream->inf_bound;
        
    /* compute how much byte should be read */
    if (seekable_substream->sup_bound != -1)
        nb_to_read = 
            MIN (seekable_substream->sup_bound - position_in_parent, n);
    else
        nb_to_read = n;
    //printf ("Nb to read = %d\n", n); 
    if (!nb_to_read) {
        
        seekable_substream->eos = TRUE;
        return 0;
    }

    /*printf ("In SeekableSubstream(%p)::read, the position has to be changed\n", stream);
    printf ("--- parent_stream_current_position=%d,  position_in_parent=%d\n", 
        parent_stream_current_position, position_in_parent);
    printf ("--- seekable_substream->inf_bound=%d\n", seekable_substream->inf_bound);
    printf ("--- seekable_substream->sup_bound=%d\n", seekable_substream->sup_bound);
    printf ("--- seekable_substream->parent_stream=%p\n", seekable_substream->parent_stream);
    */
    /* go to our position in the parent stream */
    if (parent_stream_current_position != position_in_parent) {
        
        
    camel_seekable_stream_seek (seekable_substream->parent_stream, 
                        position_in_parent,
                        CAMEL_STREAM_SET);
    }

    /* check if we were able to set the position in the parent */
    parent_stream_current_position = 
        camel_seekable_stream_get_current_position (seekable_substream->parent_stream);

    if (parent_stream_current_position != position_in_parent) {
        seekable_substream->eos = TRUE;
        return 0;
    }

    
    /* Read the data */
    if (nb_to_read >0 )
        v = camel_stream_read ( CAMEL_STREAM (seekable_substream->parent_stream), 
                    buffer, 
                    nb_to_read);
    else 
        v = 0;

    /* if the return value is negative, an error occured, 
       we must do something  FIXME : handle exception */ 
    if (v<0)
        CAMEL_LOG_FULL_DEBUG ("CamelSeekableSubstream::read v=%d\n", v);
    else 
        seekable_stream->cur_pos += v;


    /* printf ("Nb Bytes Read : %d\n",v); */
    /* return the number of bytes read */
    return v;
}


/**
 * _write: write bytes to a stream
 * @stream: the stream
 * @buffer: byte buffer
 * @n: number of bytes to write
 * 
 * 
 * 
 * Return value: the number of bytes actually written
 *  in the stream.
 **/
static gint
_write (CamelStream *stream, const gchar *buffer, gint n)
{
    /* NOT VALID ON SEEKABLE SUBSTREAM */
    g_warning ("CamelSeekableSubstream:: seekable substream don't have a write method\n");
    CAMEL_LOG_WARNING ( "CamelSeekableSubstream:: seekable substream don't have a write method\n");
    return -1;
}



/**
 * _flush: flush pending changes 
 * @stream: the stream
 * 
 * 
 **/
static void
_flush (CamelStream *stream)
{
    /* NOT VALID ON SEEKABLE SUBSTREAM */
    g_warning ("CamelSeekableSubstream:: seekable substream don't have a flush method\n");
    CAMEL_LOG_WARNING ( "CamelSeekableSubstream:: seekable substream don't have a flush method\n");
}



/**
 * _available: return the number of bytes available for reading
 * @stream: the stream
 * 
 * Return the number of bytes available without blocking.
 * 
 * Return value: the number of bytes available
 **/
static gint 
_available (CamelStream *stream)
{
    g_warning ("not implemented\n");
    return -1;
}


/**
 * _eos: test if there are bytes left to read
 * @stream: the stream
 * 
 * 
 * 
 * Return value: true if all stream has been read
 **/
static gboolean
_eos (CamelStream *stream)
{
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (stream);
    CamelSeekableStream *seekable_stream = CAMEL_SEEKABLE_STREAM (stream);
    guint32 substream_len;
    gboolean eos;
    
    g_assert (stream);

    if (seekable_substream->eos)
        eos = TRUE;
    else {

        /* first check that the parent stream is ok */
        eos = camel_stream_eos (CAMEL_STREAM (seekable_substream->parent_stream));
        if ((!eos) && (seekable_substream->sup_bound != -1)) {
            substream_len = seekable_substream->sup_bound - seekable_substream->inf_bound;      
            eos = ( seekable_stream->cur_pos >= substream_len);
        } 
    }

    
    return eos;
}


/**
 * _close: close a stream
 * @stream: the stream
 * 
 * 
 **/
static void
_close (CamelStream *stream)
{
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (stream);

    g_assert (stream);
    seekable_substream->open = FALSE;
}


static gint
_seek (CamelSeekableStream *stream, gint offset, CamelStreamSeekPolicy policy)
{
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (stream);
    CamelSeekableStream *seekable_stream = CAMEL_SEEKABLE_STREAM (stream);
    gint64 real_offset = 0; 
    guint32 substream_len;
    guint32 parent_pos;
    gboolean seek_done = FALSE;

    substream_len = seekable_substream->sup_bound - seekable_substream->inf_bound;
    
    seekable_substream->eos = FALSE;

    switch  (policy) {

    case CAMEL_STREAM_SET:
        real_offset = offset;
        
        break;

    case CAMEL_STREAM_CUR:
        real_offset = seekable_stream->cur_pos + offset;
        
        break;

    case CAMEL_STREAM_END:
        if (seekable_substream->sup_bound != -1)
            real_offset = substream_len - offset;
        else {
            parent_pos = camel_seekable_stream_seek (seekable_substream->parent_stream, 
                                 offset, 
                                 CAMEL_STREAM_END);
            seekable_stream->cur_pos = parent_pos - seekable_substream->inf_bound;
            seek_done = TRUE;
        }

        break;

    default:
        return -1;
    }

    if (!seek_done) {
        if (real_offset > 0) {
            seekable_stream->cur_pos = MIN (real_offset, substream_len);
        } else 
            seekable_stream->cur_pos = 0;
    }
    

    return seekable_stream->cur_pos;
}