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List:       busybox
Subject:    [BusyBox] the patch applet
From:       Glenn McGrath <bug1 () optushome ! com ! au>
Date:       2003-06-21 20:40:37
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Attached is a minimal patch applet to handle unified diff format.

Im pretty sure i have the logic correct, it correctly applies a linux
kernel diff which is a pretty good test.

I thought it would be pretty simple, but it was painfull for a number of
reasons,
 - Unified diff is standard practice as far as ive seen
 - The posix standard for patch doesnt mention the unified diff format.
 - Unified diff is GNU standard, but the source to GNU patch is ugly
enough that its not worth looking at.
 - The patches for the linux kernel use /dev/null when the source or
destination file doesnt exist, but it doesnt do it consistently, the
real filename is still in the diff command. What diff program do they
use ?
 - Why is there even two filenames in the diff format anyway, who cares
what the filename used to be, we just need to know what file it applies
to.

I nearly gave up in frustration. I still have some optimising to do,
this is just the first working version.

Issues
 - Only handles unified diff format.
 - Only option it accepts is -p<num>
 - Doesnt save the .rej files, im not even sure what they are... but it
does save the .orig though if a hunk fails.
 - The patch has to apply cleanly or the hunk will fail, no fuzz factor.
 - non interactive.

I will use it to apply patches before building a proper toolchain in a
linux from scratc htype environment. It would be more usefull with a
diff command as well, then it could be used on dpkg configure files, but
im not in a hurry to do that.

If i dont hear any objections i will apply a slightly improved version
in a few days.


Glenn 

["patch.diff" (application/octet-stream)]

Index: editors/Config.in
===================================================================
RCS file: /var/cvs/busybox/editors/Config.in,v
retrieving revision 1.2
diff -u -b -B -w -p -u -r1.2 Config.in
--- editors/Config.in	30 Mar 2003 03:41:53 -0000	1.2
+++ editors/Config.in	21 Jun 2003 19:51:34 -0000
@@ -18,6 +18,12 @@ config CONFIG_FEATURE_AWK_MATH
 	help
 	  Please submit a patch to add help text for this item.
 
+config CONFIG_PATCH
+	bool "patch"
+	default n
+	help
+	  Apply a context type diff
+
 config CONFIG_SED
 	bool "sed"
 	default n
Index: editors/Makefile.in
===================================================================
RCS file: /var/cvs/busybox/editors/Makefile.in,v
retrieving revision 1.2
diff -u -b -B -w -p -u -r1.2 Makefile.in
--- editors/Makefile.in	11 Nov 2002 06:20:56 -0000	1.2
+++ editors/Makefile.in	21 Jun 2003 19:51:34 -0000
@@ -24,6 +24,7 @@ endif
 
 EDITOR-y:=
 EDITOR-$(CONFIG_AWK)	   += awk.o
+EDITOR-$(CONFIG_PATCH)	   += patch.o
 EDITOR-$(CONFIG_SED)       += sed.o
 EDITOR-$(CONFIG_VI)        += vi.o
 EDITOR_SRC:= $(EDITOR-y)
Index: editors/patch.c
===================================================================
RCS file: editors/patch.c
diff -N editors/patch.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ editors/patch.c	21 Jun 2003 19:51:34 -0000
@@ -0,0 +1,290 @@
+/* vi: set sw=4 ts=4: */
+/*
+ *  busybox patch applet to handle the unified diff format.
+ *  Copyright (C) 2003 Glenn McGrath <bug1@optushome.com.au>
+ *
+ *  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.
+ *
+ *
+ *
+ *  This applet is written to work with patches generated by GNU diff,
+ *  where there is equivalent functionality busybox patch shall behave
+ *  as per GNU patch.
+ *
+ *  There is a SUSv3 specification for patch, however it looks to be
+ *  incomplete, it doesnt even mention unified diff format.
+ *  http://www.opengroup.org/onlinepubs/007904975/utilities/patch.html
+ *
+ *  Issues
+ *   - Non-interactive
+ *   - Patches must apply cleanly or the hunk will fail.
+ *   - Reject file isnt saved
+ *   - 
+ */
+
+#include <getopt.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "busybox.h"
+#include "libbb.h"
+
+static int copy_lines(FILE *src_stream, FILE *dest_stream, const unsigned int \
lines_count) +{
+	int i = 0;
+
+	while (src_stream && (i < lines_count)) {
+		char *line;
+		line = bb_get_line_from_file(src_stream);
+		if (line == NULL) {
+			break;
+		}
+		if (fputs(line, dest_stream) == EOF) {
+			bb_perror_msg_and_die("Error writing to new file");
+		}
+		free(line);
+		
+		i++;
+	}
+	return(i);
+}
+
+/* If patch_level is -1 it will remove all directory names
+ * char *line must be greater than 4 chars
+ * returns NULL if the file doesnt exist or error
+ * returns malloc'ed filename
+ */
+
+static unsigned char *extract_filename(char *line, unsigned short patch_level)
+{
+	char *filename_start_ptr = line + 4;
+	int i;
+
+	/* Terminate string at end of source filename */
+	{
+		char *line_ptr;
+		line_ptr = strchr(filename_start_ptr, '\t');
+		if (!line_ptr) {
+			bb_perror_msg("Malformed line %s", line);
+			return(NULL);
+		}
+		*line_ptr = '\0';
+	}
+
+	/* Skip over (patch_level) number of leading directories */
+	for (i = 0; i < patch_level; i++) {
+		char *dirname_ptr;
+
+		dirname_ptr = strchr(filename_start_ptr, '/');
+		if (!dirname_ptr) {
+			break;
+		}
+		filename_start_ptr = dirname_ptr + 1;
+	}
+
+	return(bb_xstrdup(filename_start_ptr));
+}
+
+static int file_doesnt_exist(const char *filename)
+{
+	struct stat statbuf;
+	return(stat(filename, &statbuf));
+}
+
+extern int patch_main(int argc, char **argv)
+{
+	unsigned int patch_level = -1;
+	char *patch_line;
+	int ret = 0;
+
+	/* Handle 'p' option */
+	if (argv[1] && (argv[1][0] == '-') && (argv[1][1] == 'p')) {
+		patch_level = atoi(&argv[1][2]);
+	}
+
+	patch_line = bb_get_line_from_file(stdin);
+	while (patch_line) {
+		FILE *src_stream;
+		FILE *dst_stream;
+		char *original_filename;
+		char *new_filename;
+		char *backup_filename;
+		unsigned int src_cur_line = 1;
+		unsigned int dest_cur_line = 0;
+		unsigned int dest_beg_line;
+		unsigned int bad_hunk_count = 0;
+		unsigned int hunk_count = 0;
+		char copy_trailing_lines_flag = 0;
+
+		/* Skip everything upto the "---" marker
+		 * No need to parse the lines "Only in <dir>", and "diff <args>"
+		 */
+		while (patch_line && strncmp(patch_line, "--- ", 4) != 0) {
+			free(patch_line);
+			patch_line = bb_get_line_from_file(stdin);
+		}
+
+		/* Extract the filename used before the patch was generated */
+		original_filename = extract_filename(patch_line, patch_level);
+		free(patch_line);
+
+		patch_line = bb_get_line_from_file(stdin);
+		if (strncmp(patch_line, "+++ ", 4) != 0) {
+			ret = 2;
+			bb_error_msg("Invalid patch");
+			continue;
+		}
+		new_filename = extract_filename(patch_line, patch_level);
+		free(patch_line);
+
+		if (file_doesnt_exist(new_filename)) {
+			char *line_ptr;
+			/* Create leading directories */
+			line_ptr = strrchr(new_filename, '/');
+			if (line_ptr) {
+				*line_ptr = '\0';
+				bb_make_directory(new_filename, -1, FILEUTILS_RECUR);
+				*line_ptr = '/';
+			}
+			dst_stream = bb_xfopen(new_filename, "w+");
+			backup_filename = NULL;
+		} else {
+			backup_filename = xmalloc(strlen(new_filename) + 6);
+			strcpy(backup_filename, new_filename);
+			strcat(backup_filename, ".orig");
+			if (rename(new_filename, backup_filename) == -1) {
+				bb_perror_msg_and_die("Couldnt create file %s", backup_filename);
+			}
+			dst_stream = bb_xfopen(new_filename, "w");
+		}
+
+		if ((backup_filename == NULL) || file_doesnt_exist(original_filename)) {
+			src_stream = NULL;
+		} else {
+			if (strcmp(original_filename, new_filename) == 0) {
+				src_stream = bb_xfopen(backup_filename, "r");
+			} else {
+				src_stream = bb_xfopen(original_filename, "r");
+			}
+		}
+
+		printf("patching file %s\n", new_filename);
+
+		/* Handle each hunk */
+		patch_line = bb_get_line_from_file(stdin);
+		while (patch_line) {
+			unsigned int count;
+			unsigned int src_beg_line;
+			unsigned int unused;
+			unsigned int hunk_offset_start = 0;
+			int hunk_error = 0;
+
+			/* This bit should be improved */
+			if ((sscanf(patch_line, "@@ -%d,%d +%d,%d @@", &src_beg_line, &unused, \
&dest_beg_line, &unused) != 4) && +				(sscanf(patch_line, "@@ -%d,%d +%d @@", \
&src_beg_line, &unused, &dest_beg_line) != 3) && +				(sscanf(patch_line, "@@ -%d \
+%d,%d @@", &src_beg_line, &dest_beg_line, &unused) != 3)) { +				/* No more hunks \
for this file */ +				break;
+			}
+			free(patch_line);
+			hunk_count++;
+
+			if (src_beg_line && dest_beg_line) {
+				/* Copy unmodified lines upto start of hunk */
+				/* src_beg_line will be 0 if its a new file */
+				count = src_beg_line - src_cur_line;
+				if (copy_lines(src_stream, dst_stream, count) != count) {
+					bb_error_msg_and_die("Bad src file");
+				}
+				src_cur_line += count;
+				dest_cur_line += count;
+				copy_trailing_lines_flag = 1;
+			}
+			hunk_offset_start = src_cur_line;
+
+			while ((patch_line = bb_get_line_from_file(stdin)) != NULL) {
+				if ((*patch_line == '-') || (*patch_line == ' ')) {
+					char *src_line = NULL;
+					if (src_stream) {
+						src_line = bb_get_line_from_file(src_stream);
+						if (!src_line) {
+							hunk_error++;
+							break;
+						} else {
+							src_cur_line++;
+						}
+						if (strcmp(src_line, patch_line + 1) != 0) {
+							bb_error_msg("Hunk #%d FAILED at %d.", hunk_count, hunk_offset_start);
+							hunk_error++;
+							free(patch_line);
+							break;
+						}
+						free(src_line);
+					}
+					if (*patch_line == ' ') {
+						fputs(patch_line + 1, dst_stream);
+						dest_cur_line++;
+					}
+				} else if (*patch_line == '+') {
+					fputs(patch_line + 1, dst_stream);
+					dest_cur_line++;
+				} else {
+					break;
+				}
+				free(patch_line);
+			}
+			if (hunk_error) {
+				bad_hunk_count++;
+			}
+		}
+
+		/* Cleanup last patched file */
+		if (copy_trailing_lines_flag) {
+			copy_lines(src_stream, dst_stream, -1);
+		}
+		if (src_stream) {
+			fclose(src_stream);
+		}
+		if (dst_stream) {
+			fclose(dst_stream);
+		}
+		if (bad_hunk_count) {
+			if (!ret) {
+				ret = 1;
+			}
+			bb_error_msg("%d out of %d hunk FAILED", bad_hunk_count, hunk_count);
+		} else {
+			/* It worked, we can remove the backup */
+			if (backup_filename) {
+				unlink(backup_filename);
+			}
+			if ((dest_cur_line == 0) || (dest_beg_line == 0)) {
+				/* The new patched file is empty, remove it */
+				if (unlink(new_filename) == -1) {
+					bb_perror_msg_and_die("Couldnt remove file %s", new_filename);
+				}
+				if (unlink(original_filename) == -1) {
+					bb_perror_msg_and_die("Couldnt remove original file %s", new_filename);
+				}
+			}
+		}
+	}
+
+	/* 0 = SUCCESS 
+	 * 1 = Some hunks failed
+	 * 2 = More serious problems
+	 */
+	return(ret);
+}
Index: include/applets.h
===================================================================
RCS file: /var/cvs/busybox/include/applets.h,v
retrieving revision 1.97
diff -u -b -B -w -p -u -r1.97 applets.h
--- include/applets.h	10 Jun 2003 17:22:46 -0000	1.97
+++ include/applets.h	21 Jun 2003 19:51:36 -0000
@@ -421,6 +421,9 @@
 #ifdef CONFIG_PASSWD
 	APPLET(passwd, passwd_main, _BB_DIR_USR_BIN, _BB_SUID_ALWAYS)
 #endif
+#ifdef CONFIG_PATCH
+	APPLET(patch, patch_main, _BB_DIR_USR_BIN, _BB_SUID_NEVER)
+#endif
 #ifdef CONFIG_PIDFILEHACK
 	APPLET(pidfilehack, pidfilehack_main, _BB_DIR_BIN, _BB_SUID_NEVER)
 #endif
Index: include/usage.h
===================================================================
RCS file: /var/cvs/busybox/include/usage.h,v
retrieving revision 1.151
diff -u -b -B -w -p -u -r1.151 usage.h
--- include/usage.h	15 Jun 2003 07:00:54 -0000	1.151
+++ include/usage.h	21 Jun 2003 19:51:42 -0000
@@ -1692,6 +1692,11 @@
 	"\t-l\tLocks (disables) the specified user account.\n" \
 	"\t-u\tUnlocks (re-enables) the specified user account."
 
+#define patch_trivial_usage \
+	"blah"
+#define patch_full_usage \
+	"blah blah"
+
 #define pidfilehack_trivial_usage \
 	"[daemon.pid] [daemon]"
 #define pidfilehack_full_usage \


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