source: trunk/third/gnome-vfs/libgnomevfs/gnome-vfs-iobuf.c @ 15497

/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/* gnome-vfs-iobuf.c - Buffered I/O for the GNOME Virtual File System.

   Copyright (C) 1999 Free Software Foundation

   The Gnome Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The Gnome Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the Gnome Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.

   Author: Ettore Perazzoli <ettore@gnu.org>
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <unistd.h>
#include <string.h>

#include "gnome-vfs.h"
#include "gnome-vfs-private.h"


#define BUFFER_SIZE 4096

struct Buffer {
        gchar data[BUFFER_SIZE];
        guint offset;
        guint byte_count;
        GnomeVFSResult last_error;
};
typedef struct Buffer Buffer;

struct GnomeVFSIOBuf {
        gint fd;

        Buffer input_buffer;
        Buffer output_buffer;
};


static void
buffer_init (Buffer *buffer)
{
        buffer->byte_count = 0;
        buffer->offset = 0;
        buffer->last_error = GNOME_VFS_OK;
}

GnomeVFSIOBuf *
gnome_vfs_iobuf_new (gint fd)
{
        GnomeVFSIOBuf *new;

        g_return_val_if_fail (fd >= 0, NULL);

        new = g_new (GnomeVFSIOBuf, 1);

        new->fd = fd;

        buffer_init (&new->input_buffer);
        buffer_init (&new->output_buffer);

        return new;
}

void
gnome_vfs_iobuf_destroy (GnomeVFSIOBuf *iobuf)
{
        g_free (iobuf);
}

static gboolean
refill_input_buffer (GnomeVFSIOBuf *iobuf)
{
        Buffer *input_buffer;
        gint r;

        input_buffer = &iobuf->input_buffer;
        if (input_buffer->last_error != GNOME_VFS_OK
            || input_buffer->byte_count > 0)
                return FALSE;

        input_buffer->offset = 0;

        r = read (iobuf->fd, &input_buffer->data, BUFFER_SIZE);
        if (r == -1) {
                input_buffer->last_error = gnome_vfs_result_from_errno ();
                return FALSE;
        }
        if (r == 0) {
                input_buffer->last_error = GNOME_VFS_ERROR_EOF;
                return FALSE;
        }

        input_buffer->byte_count = r;

        return TRUE;
}

GnomeVFSResult
gnome_vfs_iobuf_read (GnomeVFSIOBuf *iobuf,
                      gpointer buffer,
                      GnomeVFSFileSize bytes,
                      GnomeVFSFileSize *bytes_read)
{
        Buffer *input_buffer;
        GnomeVFSResult result;
        GnomeVFSFileSize n;

        g_return_val_if_fail (iobuf != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);
        g_return_val_if_fail (buffer != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);

        /* Quote from UNIX 98:
           "If nbyte is 0, read() will return 0 and have no other results."
        */
        if (bytes == 0) {
                *bytes_read = 0;
                return GNOME_VFS_OK;
        }
                
        input_buffer = &iobuf->input_buffer;

        result = GNOME_VFS_OK;

        if (input_buffer->byte_count == 0) {
                if (! refill_input_buffer (iobuf)) {
                        /* The buffer is empty but we had an error last time we
                           filled it, so we report the error.  */
                        result = input_buffer->last_error;
                        input_buffer->last_error = GNOME_VFS_OK;
                }
        }

        if (input_buffer->byte_count != 0) {
                n = MIN (bytes, input_buffer->byte_count);
                memcpy (buffer, input_buffer->data + input_buffer->offset, n);
                input_buffer->byte_count -= n;
                input_buffer->offset += n;
                if (bytes_read != NULL)
                        *bytes_read = n;
        } else {
                if (bytes_read != NULL)
                        *bytes_read = 0;
        }

        if (result == GNOME_VFS_ERROR_EOF)
                result = GNOME_VFS_OK;
        return result;
}

GnomeVFSResult
gnome_vfs_iobuf_peekc (GnomeVFSIOBuf *iobuf,
                       gchar *c)
{
        GnomeVFSResult result;
        Buffer *input_buffer;

        g_return_val_if_fail (iobuf != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);
        g_return_val_if_fail (c != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);

        input_buffer = &iobuf->input_buffer;
        result = GNOME_VFS_OK;

        if (input_buffer->byte_count == 0) {
                if (! refill_input_buffer (iobuf)) {
                        /* The buffer is empty but we had an error last time we
                           filled it, so we report the error.  */
                        result = input_buffer->last_error;
                        input_buffer->last_error = GNOME_VFS_OK;
                }
        }

        if (result == GNOME_VFS_OK)
                *c = *input_buffer->data;

        return result;
}

static GnomeVFSResult
flush (GnomeVFSIOBuf *iobuf)
{
        Buffer *output_buffer;
        gint r;

        output_buffer = &iobuf->output_buffer;

        while (output_buffer->byte_count > 0) {
                r = write (iobuf->fd, output_buffer->data,
                           output_buffer->byte_count);
                if (r == -1) {
                        output_buffer->last_error =
                                gnome_vfs_result_from_errno ();
                        return output_buffer->last_error;
                } else {
                        output_buffer->byte_count -= r;
                }
        }

        return GNOME_VFS_OK;
}

GnomeVFSResult
gnome_vfs_iobuf_write (GnomeVFSIOBuf *iobuf,
                       gconstpointer buffer,
                       GnomeVFSFileSize bytes,
                       GnomeVFSFileSize *bytes_written)
{
        Buffer *output_buffer;
        GnomeVFSFileSize write_count;
        GnomeVFSResult result;
        const gchar *p;

        g_return_val_if_fail (iobuf != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);
        g_return_val_if_fail (buffer != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);
        g_return_val_if_fail (bytes_written != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);

        output_buffer = &iobuf->output_buffer;

        result = GNOME_VFS_OK;

        p = buffer;
        write_count = 0;
        while (write_count < bytes) {
                if (output_buffer->byte_count < BUFFER_SIZE) {
                        GnomeVFSFileSize n;

                        n = MIN (BUFFER_SIZE - output_buffer->byte_count,
                                 bytes);
                        memcpy (output_buffer->data + output_buffer->byte_count,
                                p, n);
                        p += n;
                        write_count += n;
                        output_buffer->byte_count += n;
                } else {
                        result = flush (iobuf);
                        if (result != GNOME_VFS_OK)
                                break;
                }
        }

        if (bytes_written != NULL)
                *bytes_written = write_count;

        return result;
}

GnomeVFSResult
gnome_vfs_iobuf_flush (GnomeVFSIOBuf *iobuf)
{
        g_return_val_if_fail (iobuf != NULL, GNOME_VFS_ERROR_BAD_PARAMETERS);

        return flush (iobuf);
}