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
 *
 * Authors: Bertrand Guiheneuf <bertrand@helixcode.com>
 *      Michael Zucchi <notzed@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"

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           stream_read        (CamelStream *stream,
                           gchar *buffer, gint n);
static  gint           stream_write       (CamelStream *stream,
                           const gchar *buffer,
                           gint n);
static  void           stream_flush       (CamelStream *stream);
static  gboolean       eos            (CamelStream *stream);
static  off_t          stream_seek        (CamelSeekableStream *stream,
                           off_t offset,
                           CamelStreamSeekPolicy policy);
static  void           finalize           (GtkObject *object);

static  void           init_with_seekable_stream_and_bounds  (CamelSeekableSubstream *seekable_substream,
                                  CamelSeekableStream *parent_stream,
                                  off_t start, off_t end);

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 */

    /* virtual method overload */
    camel_stream_class->read = stream_read;
    camel_stream_class->write = stream_write;
    camel_stream_class->flush = stream_flush;
    camel_stream_class->eos = eos;

    camel_seekable_stream_class->seek = stream_seek;

    gtk_object_class->finalize = finalize;
}


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) NULL,
                /* 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
finalize (GtkObject *object)
{
    CamelSeekableSubstream *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);
}

static void
init_with_seekable_stream_and_bounds (CamelSeekableSubstream *seekable_substream,
                      CamelSeekableStream *parent_stream,
                      off_t start, off_t end)
{
    /* Store the parent stream. */
    seekable_substream->parent_stream = parent_stream;
    gtk_object_ref (GTK_OBJECT (parent_stream));
    gtk_object_sink (GTK_OBJECT (parent_stream));

    /* Set the bound of the substream. */
    camel_seekable_stream_set_bounds ((CamelSeekableStream *)seekable_substream, start, end);
}

/**
 * camel_seekable_substream_new_with_seekable_stream_and_bounds:
 * @parent_stream: a seekable parent stream
 * @inf_bound: a lower bound
 * @sup_bound: an upper bound
 *
 * Creates a new CamelSeekableSubstream that references the portion
 * of @parent_stream from @inf_bound to @sup_bound. (If @sup_bound is
 * #CAMEL_STREAM_UNBOUND, it references to the end of stream, even if
 * the stream grows.)
 *
 * While the substream is open, the caller cannot assume anything about
 * the current position of @parent_stream. After the substream has been
 * closed, @parent_stream will stabilize again.
 *
 * Return value: the substream
 **/
CamelStream *
camel_seekable_substream_new_with_seekable_stream_and_bounds (CamelSeekableStream *parent_stream,
                                  off_t start, off_t end)
{
    CamelSeekableSubstream *seekable_substream;

    g_return_val_if_fail (CAMEL_IS_SEEKABLE_STREAM (parent_stream), NULL);

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

    /* Initialize it. */
    init_with_seekable_stream_and_bounds (seekable_substream,
                          parent_stream,
                          start, end);
    return CAMEL_STREAM (seekable_substream);
}

static gboolean
parent_reset (CamelSeekableSubstream *seekable_substream)
{
    CamelSeekableStream *parent, *seekable_stream = CAMEL_SEEKABLE_STREAM (seekable_substream);

    parent = seekable_substream->parent_stream;

    g_return_val_if_fail (parent != NULL, FALSE);

    if (camel_seekable_stream_tell(parent) != seekable_stream->position) {
        return camel_seekable_stream_seek(parent, seekable_stream->position, CAMEL_STREAM_SET)
            == seekable_stream->position;
    } else {
        return TRUE;
    }
}

static gint
stream_read (CamelStream *stream, gchar *buffer, gint n)
{
    CamelSeekableStream *seekable_stream = CAMEL_SEEKABLE_STREAM (stream);
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (stream);
    int v;

    if (n == 0)
        return 0;

    /* Go to our position in the parent stream. */
    if (!parent_reset (seekable_substream)) {   
        stream->eos = TRUE;
        return 0;
    }

    /* Compute how much byte should be read. */
    if (seekable_stream->bound_end != CAMEL_STREAM_UNBOUND)
        n = MIN (seekable_stream->bound_end -  seekable_stream->position, n);

    if (n == 0) {
        stream->eos = TRUE;
        return 0;
    }

    v = camel_stream_read (CAMEL_STREAM (seekable_substream->parent_stream), buffer, n);

    /* ignore <0 - its an error, let the caller deal */
    if (v > 0)
        seekable_stream->position += v;

    return v;
}

static gint
stream_write (CamelStream *stream, const gchar *buffer, gint n)
{
    /* NOT VALID ON SEEKABLE SUBSTREAM */
    /* Well, its entirely valid, just not implemented */
    g_warning ("CamelSeekableSubstream:: seekable substream doesn't "
           "have a write method\n");
    return -1;
}

static void
stream_flush (CamelStream *stream)
{
    /* NOT VALID ON SEEKABLE SUBSTREAM */
    g_warning ("CamelSeekableSubstream:: seekable substream doesn't "
           "have a flush method\n");
}

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 (stream->eos) {
        eos = TRUE;
    } else {
        parent_reset (seekable_substream);

        eos = camel_stream_eos (CAMEL_STREAM (seekable_substream->parent_stream));
        if ((!eos) && (seekable_stream->bound_end != CAMEL_STREAM_UNBOUND)) {
            substream_len = seekable_stream->bound_start - seekable_stream->bound_end;
            eos = ( seekable_stream->position >= substream_len);
        }
    }

    return eos;
}

/* seeks within a seekable substream follow the bound limits ... dont start at 0 */
static off_t
stream_seek (CamelSeekableStream *seekable_stream, off_t offset,
         CamelStreamSeekPolicy policy)
{
    CamelSeekableSubstream *seekable_substream = CAMEL_SEEKABLE_SUBSTREAM (seekable_stream);
    CamelStream *stream = (CamelStream *)seekable_stream;
    off_t real_offset = 0;
    off_t parent_pos;

    stream->eos = FALSE;

    switch (policy) {
    case CAMEL_STREAM_SET:
        real_offset = offset;
        break;

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

    case CAMEL_STREAM_END:
        if (seekable_stream->bound_end != CAMEL_STREAM_UNBOUND)
            real_offset = seekable_stream->bound_end + offset;
        else {
            parent_pos = camel_seekable_stream_seek (seekable_substream->parent_stream,
                                 offset,
                                 CAMEL_STREAM_END);
            if (parent_pos == -1)
                return -1;
            real_offset = parent_pos;
        }
        break;

    default:
        return -1;
    }

    if (seekable_stream->bound_end != CAMEL_STREAM_UNBOUND)
        real_offset = MIN (real_offset, seekable_stream->bound_end);

    if (real_offset<seekable_stream->bound_start)
        real_offset = seekable_stream->bound_start;

    seekable_stream->position = real_offset;
    return real_offset;
}