Improve quoting performance

If features or users have added a large number of files or directories
to pack into an image, then quoting a very long string takes too much
time.

Quoting variables is necessary for the correct processing of paths with
spaces.

The problem is that if we need to process a very large string,
character-by-character parsing takes a long time. It so happens that
there is no quick way to parse a string character by character in the
POSIX shell. But in bash, such a way exists.

Since we always use bash, the quoting process can be significantly
accelerated by simply reading a single character in a string.

Before:

[   2.55ms ] Config file: /etc/initrd.mk
[     5.3m ] Used features: runtime add-modules add-udev-rules cleanup compress depmod-image gpu-drm locales plymouth rdshell rootfs system-glibc ucode
[     5.3m ] Unpacked size: 36M
[     5.3m ] Image size: 16M
[     5.3m ] Image is saved as /boot/initrd-6.16.0.img

After:

[   2.47ms ] Config file: /etc/initrd.mk
[    9.43s ] Used features: runtime add-modules add-udev-rules cleanup compress depmod-image gpu-drm locales plymouth rdshell rootfs system-glibc ucode
[    9.43s ] Unpacked size: 36M
[    9.44s ] Image size: 16M
[    9.49s ] Image is saved as /boot/initrd-6.16.0.img

Signed-off-by: Alexey Gladkov <[email protected]>

Author: legionus

tools/create-rootfs

@@ -15,6 +15,84 @@ DIRS=()
 LIB_PATHS=()
 BIN_PATHS=()
 
+quote_bash_args()
+{
+### This is an internal function to avoid the use of ugly namespace.
+__quote_bash_args_toggle() {
+	### toggle $1 value
+	eval [ -n \"\$$1\" ] && eval "$1=" || eval "$1=\$$2"
+}
+__quote_bash_args() {
+	local i=0 c=''
+	### backslash/double/single quote mode
+	local bq='' dq='' sq=''
+
+	__quote_bash_args_out=''
+
+	for (( i=0; i<${#1}; i++ )); do
+		c="${1:i:1}"
+
+		case "$c" in
+			\")
+				### toggle double quote mode unless
+				### in backslash or single quote mode
+				[ -n "$bq$sq" ] || __quote_bash_args_toggle dq c
+				;;
+			\')
+				### toggle single quote mode unless
+				### in backslash or double quote mode
+				[ -n "$bq$dq" ] || __quote_bash_args_toggle sq c
+				;;
+			\$|\`)
+				### quote special character unless
+				### in backslash or single quote mode
+				[ -n "$bq$sq" ] || bq=\\
+				;;
+			\\)
+				### toggle backslash quote mode unless
+				### in single quote mode
+				if [ -z "$sq" ]; then
+					if [ -z "$bq" ]; then
+						### enter backslash quote mode
+						bq=\\
+						continue
+					else
+						### leave backslash quote mode
+						__quote_bash_args_out+="\\"
+						bq=
+					fi
+				fi
+				;;
+			[!A-Za-z0-9_\ \	])
+				### quote non-regular character unless
+				### in any quote mode
+				[ -n "$bq$dq$sq" ] || bq=\\
+				;;
+		esac
+		__quote_bash_args_out+="$bq$c"
+		### leave backslash quote mode if any
+		bq=
+	done
+
+	[ -z "$bq$dq$sq" ] ||
+		{ message "unmatched character ($bq$dq$sq) found"; return 1; }
+}
+	local __quote_bash_args_rc=0
+
+	if [[ "$2" =~ [\"\'\$\`\\\\] ]]; then
+		local __quote_bash_args_out=''
+		__quote_bash_args "$2" || __quote_bash_args_rc=1
+		eval "$1=\"\$__quote_bash_args_out\""
+	else
+		eval "$1=\"\$2\""
+	fi
+
+	### Remove internal functions from user namespace.
+	unset -f __quote_bash_args __quote_bash_args_toggle
+
+	return $__quote_bash_args_rc
+}
+
 in_runtimedir()
 {
 	local f="${1#$LOCALBUILDDIR}"
@@ -34,7 +112,7 @@ append_progs()
 	[ -n "$1" ] ||
 		return 0
 
-	quote_shell_args args "$1"
+	quote_bash_args args "$1"
 	eval "set -- $args"
 
 	for n; do
@@ -113,7 +191,7 @@ append_libs()
 	[ -n "$1" ] ||
 		return 0
 
-	quote_shell_args args "$1"
+	quote_bash_args args "$1"
 	eval "set -- $args"
 
 	for n; do
@@ -158,7 +236,7 @@ append_libs()
 get_bin_paths
 get_lib_paths
 
-quote_shell_args args "${PUT_FEATURE_DIRS-} $PUT_DIRS"
+quote_bash_args args "${PUT_FEATURE_DIRS-} $PUT_DIRS"
 eval "set -- $args"
 
 for n in \
@@ -184,7 +262,7 @@ append_libs required "${PUT_FEATURE_LIBS-}"
 append_libs optional "${PUT_FEATURE_OPTIONAL_LIBS-}"
 
 if [ -n "${PUT_FEATURE_PROGS_WILDCARD-}" ]; then
-	quote_shell_args args "$PUT_FEATURE_PROGS_WILDCARD"
+	quote_bash_args args "$PUT_FEATURE_PROGS_WILDCARD"
 	eval "set -- $args"
 
 	while read -d: -r n; do
@@ -209,7 +287,7 @@ if [ -n "${PUT_FEATURE_PROGS_WILDCARD-}" ]; then
 fi
 
 if [ -n "${PUT_FEATURE_FILES-}" ] || [ -n "${PUT_FILES-}" ]; then
-	quote_shell_args args "${PUT_FEATURE_FILES-} ${PUT_FILES-}"
+	quote_bash_args args "${PUT_FEATURE_FILES-} ${PUT_FILES-}"
 	eval "set -- $args"
 
 	for n in "$@"; do