bbconfig: add COMPRESS_BBCONFIG option

function                                             old     new   delta
bbconfig_config_bz2                                    -    4905   +4905
bbconfig_main                                         13      70     +57
bbconfig_config                                    21811       -  -21811
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/0 up/down: 4962/-21811)    Total: -16849 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

Makefile

@@ -842,7 +842,7 @@ export CPPFLAGS_busybox.lds += -P -C -U$(ARCH)
 
 # 	Split autoconf.h into include/linux/config/*
 quiet_cmd_gen_bbconfigopts = GEN     include/bbconfigopts.h
-      cmd_gen_bbconfigopts = $(srctree)/scripts/mkconfigs > include/bbconfigopts.h
+      cmd_gen_bbconfigopts = $(srctree)/scripts/mkconfigs include/bbconfigopts.h include/bbconfigopts_bz2.h
 quiet_cmd_split_autoconf   = SPLIT   include/autoconf.h -> include/config/*
       cmd_split_autoconf   = scripts/basic/split-include include/autoconf.h include/config
 #bbox# piggybacked generation of few .h files

archival/libunarchive/Kbuild.src

@@ -54,6 +54,7 @@ lib-$(CONFIG_FEATURE_SEAMLESS_BZ2)      += open_transformer.o decompress_bunzip2
 lib-$(CONFIG_FEATURE_SEAMLESS_LZMA)     += open_transformer.o decompress_unlzma.o get_header_tar_lzma.o
 lib-$(CONFIG_FEATURE_SEAMLESS_XZ)       += open_transformer.o decompress_unxz.o
 lib-$(CONFIG_FEATURE_COMPRESS_USAGE)    += decompress_bunzip2.o
+lib-$(CONFIG_FEATURE_COMPRESS_BBCONFIG) += decompress_bunzip2.o
 lib-$(CONFIG_FEATURE_TAR_TO_COMMAND)    += data_extract_to_command.o
 
 ifneq ($(lib-y),)

miscutils/Config.src

@@ -22,6 +22,20 @@ config BBCONFIG
 	  The bbconfig applet will print the config file with which
 	  busybox was built.
 
+config FEATURE_COMPRESS_BBCONFIG
+	bool "Compress bbconfig data"
+	default y
+	depends on BBCONFIG
+	help
+	  Store bbconfig data in compressed form, uncompress them on-the-fly
+	  before output.
+
+	  If you have a really tiny busybox with few applets enabled (and
+	  bunzip2 isn't one of them), the overhead of the decompressor might
+	  be noticeable. Also, if you run executables directly from ROM
+	  and have very little memory, this might not be a win. Otherwise,
+	  you probably want this.
+
 config BEEP
 	bool "beep"
 	default y

miscutils/bbconfig.c

@@ -3,10 +3,32 @@
  */
 #include "libbb.h"
 #include "bbconfigopts.h"
+#if ENABLE_FEATURE_COMPRESS_BBCONFIG
+# include "unarchive.h"
+# include "bbconfigopts_bz2.h"
+#endif
 
 int bbconfig_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int bbconfig_main(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 {
+#if ENABLE_FEATURE_COMPRESS_BBCONFIG
+	bunzip_data *bd;
+	int i = start_bunzip(&bd,
+			/* src_fd: */ -1,
+			/* inbuf:  */ (void *)bbconfig_config_bz2,
+			/* len:    */ sizeof(bbconfig_config_bz2));
+	/* read_bunzip can longjmp to start_bunzip, and ultimately
+	 * end up here with i != 0 on read data errors! Not trivial */
+	if (!i) {
+		/* Cannot use xmalloc: will leak bd in NOFORK case! */
+		char *outbuf = malloc_or_warn(sizeof(bbconfig_config));
+		if (outbuf) {
+			read_bunzip(bd, outbuf, sizeof(bbconfig_config));
+			full_write1_str(outbuf);
+		}
+	}
+#else
 	full_write1_str(bbconfig_config);
+#endif
 	return 0;
 }

scripts/mkconfigs

@@ -26,12 +26,9 @@
 #      - Retain lines that begin with "# CONFIG_"
 #      - lines that use double-quotes must \\-escape-quote them
 
-config="$1"
-if [ $# -lt 1 ]
-then
 config=.config
-fi
 
+{
 echo "\
 #ifndef _BBCONFIGOPTS_H
 #define _BBCONFIGOPTS_H
@@ -43,9 +40,36 @@ echo "\
  * This file is generated automatically by scripts/mkconfigs.
  * Do not edit.
  */
-static const char bbconfig_config[] ="
+static const char bbconfig_config[] ALIGN1 ="
 
-sed 's/\"/\\\"/g' $config | grep "^#\? \?CONFIG_" | awk '{print "\"" $0 "\\n\"";}'
+grep '^#\? \?CONFIG_' "$config" \
+| sed -e 's/\"/\\\"/g' -e 's/^/"/' -e 's/$/\\n"/'
 
 echo ";"
-echo "#endif /* _BBCONFIGOPTS_H */"
+echo "#endif"
+} >"$1"
+
+{
+echo "\
+#ifndef _BBCONFIGOPTS_BZ2_H
+#define _BBCONFIGOPTS_BZ2_H
+/*
+ * busybox configuration settings.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ *
+ * This file is generated automatically by scripts/mkconfigs.
+ * Do not edit.
+ */
+static const char bbconfig_config_bz2[] ALIGN1 = {"
+
+grep '^#\? \?CONFIG_' "$config" \
+| bzip2 -1 | tee z.bz2 | dd bs=2 skip=1 2>/dev/null | od -v -t x1 \
+| sed -e 's/^[^ ]*//' \
+        -e 's/ //g' \
+        -e '/^$/d' \
+        -e 's/\(..\)/0x\1,/g'
+
+echo "};"
+echo "#endif"
+} >"$2"