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diff --git a/src/viewer/datasource.c b/src/viewer/datasource.c
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+/*
+ Internal file viewer for the Midnight Commander
+ Functions for datasources
+
+ Copyright (C) 1994-2022
+ Free Software Foundation, Inc.
+
+ Written by:
+ Miguel de Icaza, 1994, 1995, 1998
+ Janne Kukonlehto, 1994, 1995
+ Jakub Jelinek, 1995
+ Joseph M. Hinkle, 1996
+ Norbert Warmuth, 1997
+ Pavel Machek, 1998
+ Roland Illig <roland.illig@gmx.de>, 2004, 2005
+ Slava Zanko <slavazanko@google.com>, 2009
+ Andrew Borodin <aborodin@vmail.ru>, 2009
+ Ilia Maslakov <il.smind@gmail.com>, 2009
+
+ This file is part of the Midnight Commander.
+
+ The Midnight Commander 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 3 of the License,
+ or (at your option) any later version.
+
+ The Midnight Commander 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ The data source provides the viewer with data from either a file, a
+ string or the output of a command. The mcview_get_byte() function can be
+ used to get the value of a byte at a specific offset. If the offset
+ is out of range, -1 is returned. The function mcview_get_byte_indexed(a,b)
+ returns the byte at the offset a+b, or -1 if a+b is out of range.
+
+ The mcview_set_byte() function has the effect that later calls to
+ mcview_get_byte() will return the specified byte for this offset. This
+ function is designed only for use by the hexedit component after
+ saving its changes. Inspect the source before you want to use it for
+ other purposes.
+
+ The mcview_get_filesize() function returns the current size of the
+ data source. If the growing buffer is used, this size may increase
+ later on. Use the mcview_may_still_grow() function when you want to
+ know if the size can change later.
+ */
+
+#include <config.h>
+
+#include "lib/global.h"
+#include "lib/vfs/vfs.h"
+#include "lib/util.h"
+#include "lib/widget.h" /* D_NORMAL, D_ERROR */
+
+#include "internal.h"
+
+/*** global variables ****************************************************************************/
+
+/*** file scope macro definitions ****************************************************************/
+
+/*** file scope type declarations ****************************************************************/
+
+/*** file scope variables ************************************************************************/
+
+/* --------------------------------------------------------------------------------------------- */
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+mcview_set_datasource_stdio_pipe (WView * view, mc_pipe_t * p)
+{
+ p->out.len = MC_PIPE_BUFSIZE;
+ p->out.null_term = FALSE;
+ p->err.len = MC_PIPE_BUFSIZE;
+ p->err.null_term = TRUE;
+ view->datasource = DS_STDIO_PIPE;
+ view->ds_stdio_pipe = p;
+ view->pipe_first_err_msg = TRUE;
+
+ mcview_growbuf_init (view);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_set_datasource_none (WView * view)
+{
+ view->datasource = DS_NONE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+off_t
+mcview_get_filesize (WView * view)
+{
+ switch (view->datasource)
+ {
+ case DS_STDIO_PIPE:
+ case DS_VFS_PIPE:
+ return mcview_growbuf_filesize (view);
+ case DS_FILE:
+ return view->ds_file_filesize;
+ case DS_STRING:
+ return view->ds_string_len;
+ default:
+ return 0;
+ }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_update_filesize (WView * view)
+{
+ if (view->datasource == DS_FILE)
+ {
+ struct stat st;
+ if (mc_fstat (view->ds_file_fd, &st) != -1)
+ view->ds_file_filesize = st.st_size;
+ }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+char *
+mcview_get_ptr_file (WView * view, off_t byte_index)
+{
+ g_assert (view->datasource == DS_FILE);
+
+ mcview_file_load_data (view, byte_index);
+ if (mcview_already_loaded (view->ds_file_offset, byte_index, view->ds_file_datalen))
+ return (char *) (view->ds_file_data + (byte_index - view->ds_file_offset));
+ return NULL;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/* Invalid UTF-8 is reported as negative integers (one for each byte),
+ * see ticket 3783. */
+gboolean
+mcview_get_utf (WView * view, off_t byte_index, int *ch, int *ch_len)
+{
+ gchar *str = NULL;
+ int res;
+ gchar utf8buf[UTF8_CHAR_LEN + 1];
+
+ switch (view->datasource)
+ {
+ case DS_STDIO_PIPE:
+ case DS_VFS_PIPE:
+ str = mcview_get_ptr_growing_buffer (view, byte_index);
+ break;
+ case DS_FILE:
+ str = mcview_get_ptr_file (view, byte_index);
+ break;
+ case DS_STRING:
+ str = mcview_get_ptr_string (view, byte_index);
+ break;
+ case DS_NONE:
+ default:
+ break;
+ }
+
+ *ch = 0;
+
+ if (str == NULL)
+ return FALSE;
+
+ res = g_utf8_get_char_validated (str, -1);
+
+ if (res < 0)
+ {
+ /* Retry with explicit bytes to make sure it's not a buffer boundary */
+ int i;
+
+ for (i = 0; i < UTF8_CHAR_LEN; i++)
+ {
+ if (mcview_get_byte (view, byte_index + i, &res))
+ utf8buf[i] = res;
+ else
+ {
+ utf8buf[i] = '\0';
+ break;
+ }
+ }
+ utf8buf[UTF8_CHAR_LEN] = '\0';
+ str = utf8buf;
+ res = g_utf8_get_char_validated (str, -1);
+ }
+
+ if (res < 0)
+ {
+ /* Implicit conversion from signed char to signed int keeps negative values. */
+ *ch = *str;
+ *ch_len = 1;
+ }
+ else
+ {
+ gchar *next_ch = NULL;
+
+ *ch = res;
+ /* Calculate UTF-8 char length */
+ next_ch = g_utf8_next_char (str);
+ *ch_len = next_ch - str;
+ }
+
+ return TRUE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+char *
+mcview_get_ptr_string (WView * view, off_t byte_index)
+{
+ g_assert (view->datasource == DS_STRING);
+
+ if (byte_index >= 0 && byte_index < (off_t) view->ds_string_len)
+ return (char *) (view->ds_string_data + byte_index);
+ return NULL;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+gboolean
+mcview_get_byte_string (WView * view, off_t byte_index, int *retval)
+{
+ char *p;
+
+ if (retval != NULL)
+ *retval = -1;
+
+ p = mcview_get_ptr_string (view, byte_index);
+ if (p == NULL)
+ return FALSE;
+
+ if (retval != NULL)
+ *retval = (unsigned char) (*p);
+ return TRUE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+gboolean
+mcview_get_byte_none (WView * view, off_t byte_index, int *retval)
+{
+ (void) &view;
+ (void) byte_index;
+
+ g_assert (view->datasource == DS_NONE);
+
+ if (retval != NULL)
+ *retval = -1;
+ return FALSE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_set_byte (WView * view, off_t offset, byte b)
+{
+ (void) &b;
+
+ g_assert (offset < mcview_get_filesize (view));
+ g_assert (view->datasource == DS_FILE);
+
+ view->ds_file_datalen = 0; /* just force reloading */
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/*static */
+void
+mcview_file_load_data (WView * view, off_t byte_index)
+{
+ off_t blockoffset;
+ ssize_t res;
+ size_t bytes_read;
+
+ g_assert (view->datasource == DS_FILE);
+
+ if (mcview_already_loaded (view->ds_file_offset, byte_index, view->ds_file_datalen))
+ return;
+
+ if (byte_index >= view->ds_file_filesize)
+ return;
+
+ blockoffset = mcview_offset_rounddown (byte_index, view->ds_file_datasize);
+ if (mc_lseek (view->ds_file_fd, blockoffset, SEEK_SET) == -1)
+ goto error;
+
+ bytes_read = 0;
+ while (bytes_read < view->ds_file_datasize)
+ {
+ res =
+ mc_read (view->ds_file_fd, view->ds_file_data + bytes_read,
+ view->ds_file_datasize - bytes_read);
+ if (res == -1)
+ goto error;
+ if (res == 0)
+ break;
+ bytes_read += (size_t) res;
+ }
+ view->ds_file_offset = blockoffset;
+ if ((off_t) bytes_read > view->ds_file_filesize - view->ds_file_offset)
+ {
+ /* the file has grown in the meantime -- stick to the old size */
+ view->ds_file_datalen = view->ds_file_filesize - view->ds_file_offset;
+ }
+ else
+ {
+ view->ds_file_datalen = bytes_read;
+ }
+ return;
+
+ error:
+ view->ds_file_datalen = 0;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_close_datasource (WView * view)
+{
+ switch (view->datasource)
+ {
+ case DS_NONE:
+ break;
+ case DS_STDIO_PIPE:
+ if (view->ds_stdio_pipe != NULL)
+ {
+ mcview_growbuf_done (view);
+ mcview_display (view);
+ }
+ mcview_growbuf_free (view);
+ break;
+ case DS_VFS_PIPE:
+ if (view->ds_vfs_pipe != -1)
+ mcview_growbuf_done (view);
+ mcview_growbuf_free (view);
+ break;
+ case DS_FILE:
+ (void) mc_close (view->ds_file_fd);
+ view->ds_file_fd = -1;
+ MC_PTR_FREE (view->ds_file_data);
+ break;
+ case DS_STRING:
+ MC_PTR_FREE (view->ds_string_data);
+ break;
+ default:
+ break;
+ }
+ view->datasource = DS_NONE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_set_datasource_file (WView * view, int fd, const struct stat *st)
+{
+ view->datasource = DS_FILE;
+ view->ds_file_fd = fd;
+ view->ds_file_filesize = st->st_size;
+ view->ds_file_offset = 0;
+ view->ds_file_data = g_malloc (4096);
+ view->ds_file_datalen = 0;
+ view->ds_file_datasize = 4096;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+gboolean
+mcview_load_command_output (WView * view, const char *command)
+{
+ mc_pipe_t *p;
+ GError *error = NULL;
+
+ mcview_close_datasource (view);
+
+ p = mc_popen (command, TRUE, TRUE, &error);
+ if (p == NULL)
+ {
+ mcview_display (view);
+ mcview_show_error (view, error->message);
+ g_error_free (error);
+ return FALSE;
+ }
+
+ /* Check if filter produced any output */
+ mcview_set_datasource_stdio_pipe (view, p);
+ if (!mcview_get_byte (view, 0, NULL))
+ {
+ mcview_close_datasource (view);
+ mcview_display (view);
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_set_datasource_vfs_pipe (WView * view, int fd)
+{
+ g_assert (fd != -1);
+
+ view->datasource = DS_VFS_PIPE;
+ view->ds_vfs_pipe = fd;
+
+ mcview_growbuf_init (view);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+mcview_set_datasource_string (WView * view, const char *s)
+{
+ view->datasource = DS_STRING;
+ view->ds_string_len = strlen (s);
+ view->ds_string_data = (byte *) g_strndup (s, view->ds_string_len);
+}
+
+/* --------------------------------------------------------------------------------------------- */
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