implement support for parameter substitution via #/% operators

shell/Kbuild

@@ -6,7 +6,7 @@
 
 lib-y:=
 lib-$(CONFIG_ASH)      += ash.o ash_ptr_hack.o
-lib-$(CONFIG_HUSH)     += hush.o
+lib-$(CONFIG_HUSH)     += hush.o match.o
 lib-$(CONFIG_MSH)      += msh.o
 lib-$(CONFIG_CTTYHACK) += cttyhack.o
 lib-$(CONFIG_SH_MATH_SUPPORT) += math.o

shell/hush.c

@@ -43,7 +43,6 @@
  *      Here Documents ( << word )
  *      Functions
  *      Tilde Expansion
- *      Parameter Expansion for substring processing ${var#word} ${var%word}
  *
  * Bash stuff (maybe optionally enable?):
  *      &> and >& redirection of stdout+stderr
@@ -76,6 +75,7 @@
 #include <fnmatch.h>
 #endif
 #include "math.h"
+#include "match.h"
 
 #ifdef WANT_TO_TEST_NOMMU
 # undef BB_MMU
@@ -1667,8 +1667,9 @@ static int expand_vars_to_list(o_string *output, int n, char *arg, char or_mask)
 	char first_ch, ored_ch;
 	int i;
 	const char *val;
-	char *p;
+	char *dyn_val, *p;
 
+	dyn_val = NULL;
 	ored_ch = 0;
 
 	debug_printf_expand("expand_vars_to_list: arg '%s'\n", arg);
@@ -1844,7 +1845,7 @@ static int expand_vars_to_list(o_string *output, int n, char *arg, char or_mask)
 				++var;
 			} else {
 				/* maybe handle parameter expansion */
-				exp_off = strcspn(var, ":-=+?");
+				exp_off = strcspn(var, ":-=+?%#");
 				if (!var[exp_off])
 					exp_off = 0;
 				if (exp_off) {
@@ -1873,29 +1874,45 @@ static int expand_vars_to_list(o_string *output, int n, char *arg, char or_mask)
 				val = utoa(val ? strlen(val) : 0);
 				debug_printf_expand("%s\n", val);
 			} else if (exp_off) {
-				/* we need to do an expansion */
-				int exp_test = (!val || (exp_null && !val[0]));
-				if (exp_op == '+')
-					exp_test = !exp_test;
-				debug_printf_expand("expand: op:%c (null:%s) test:%i\n", exp_op,
-					exp_null ? "true" : "false", exp_test);
-				if (exp_test) {
-					if (exp_op == '?')
-						maybe_die(var, *exp_word ? exp_word : "parameter null or not set");
+				if (exp_op == '%' || exp_op == '#') {
+					/* we need to do a pattern match */
+					bool zero;
+					char *loc;
+					scan_t scan = pick_scan(exp_op, *exp_word, &zero);
+					if (exp_op == *exp_word)	/* ## or %% */
+						++exp_word;
+					val = dyn_val = xstrdup(val);
+					loc = scan(dyn_val, exp_word, zero);
+					if (zero)
+						val = loc;
 					else
-						val = exp_word;
+						*loc = '\0';
+				} else {
+					/* we need to do an expansion */
+					int exp_test = (!val || (exp_null && !val[0]));
+					if (exp_op == '+')
+						exp_test = !exp_test;
+					debug_printf_expand("expand: op:%c (null:%s) test:%i\n", exp_op,
+						exp_null ? "true" : "false", exp_test);
+					if (exp_test) {
+						if (exp_op == '?')
+							maybe_die(var, *exp_word ? exp_word : "parameter null or not set");
+						else
+							val = exp_word;
 
-					if (exp_op == '=') {
-						if (isdigit(var[0]) || var[0] == '#') {
-							maybe_die(var, "special vars cannot assign in this way");
-							val = NULL;
-						} else {
-							char *new_var = xmalloc(strlen(var) + strlen(val) + 2);
-							sprintf(new_var, "%s=%s", var, val);
-							set_local_var(new_var, -1, 0);
+						if (exp_op == '=') {
+							if (isdigit(var[0]) || var[0] == '#') {
+								maybe_die(var, "special vars cannot assign in this way");
+								val = NULL;
+							} else {
+								char *new_var = xmalloc(strlen(var) + strlen(val) + 2);
+								sprintf(new_var, "%s=%s", var, val);
+								set_local_var(new_var, -1, 0);
+							}
 						}
 					}
 				}
+
 				var[exp_off] = exp_save;
 			}
 
@@ -1921,6 +1938,8 @@ static int expand_vars_to_list(o_string *output, int n, char *arg, char or_mask)
 		if (val) {
 			o_addQstr(output, val, strlen(val));
 		}
+		free(dyn_val);
+		dyn_val = NULL;
 		/* Do the check to avoid writing to a const string */
 		if (*p != SPECIAL_VAR_SYMBOL)
 			*p = SPECIAL_VAR_SYMBOL;
@@ -4428,7 +4447,6 @@ static int handle_dollar(o_string *as_string,
 						break;
 					}
 					goto case_default;
-#if 0 /* not implemented yet :( */
 				case '#': /* remove prefix */
 				case '%': /* remove suffix */
 					if (expansion == 0) {
@@ -4437,7 +4455,6 @@ static int handle_dollar(o_string *as_string,
 						break;
 					}
 					goto case_default;
-#endif
 				case '-': /* default value */
 				case '=': /* assign default */
 				case '+': /* alternative */

shell/hush_test/hush-vars/var_posix1.right

@@ -0,0 +1,17 @@
+abcdcd
+abcdcd
+abcdcd
+cdcd
+babcdcd
+babcdcd
+ababcdcd
+
+ababcd
+ababcd
+ababcd
+abab
+ababcdc
+ababcdc
+ababcdcd
+
+end

shell/hush_test/hush-vars/var_posix1.tests

@@ -0,0 +1,21 @@
+var=ababcdcd
+
+echo ${var#ab}
+echo ${var##ab}
+echo ${var#a*b}
+echo ${var##a*b}
+echo ${var#?}
+echo ${var##?}
+echo ${var#*}
+echo ${var##*}
+
+echo ${var%cd}
+echo ${var%%cd}
+echo ${var%c*d}
+echo ${var%%c*d}
+echo ${var%?}
+echo ${var%%?}
+echo ${var%*}
+echo ${var%%*}
+
+echo end

shell/match.c

@@ -0,0 +1,141 @@
+/*
+ * ##/%% variable matching code ripped out of ash shell for code sharing
+ *
+ * Copyright (c) 1989, 1991, 1993, 1994
+ *      The Regents of the University of California.  All rights reserved.
+ *
+ * Copyright (c) 1997-2005 Herbert Xu <herbert@gondor.apana.org.au>
+ * was re-ported from NetBSD and debianized.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Kenneth Almquist.
+ *
+ * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ *
+ * Original BSD copyright notice is retained at the end of this file.
+ */
+
+#ifdef STANDALONE
+# include <stdbool.h>
+# include <stdio.h>
+# include <stdlib.h>
+# include <string.h>
+# include <unistd.h>
+#else
+# include "busybox.h"
+#endif
+#include <fnmatch.h>
+#include "match.h"
+
+#define pmatch(a, b) !fnmatch((a), (b), 0)
+
+char *scanleft(char *string, char *pattern, bool zero)
+{
+	char c;
+	char *loc = string;
+
+	do {
+		int match;
+		const char *s;
+
+		c = *loc;
+		if (zero) {
+			*loc = '\0';
+			s = string;
+		} else
+			s = loc;
+		match = pmatch(pattern, s);
+		*loc = c;
+
+		if (match)
+			return loc;
+
+		loc++;
+	} while (c);
+
+	return NULL;
+}
+
+char *scanright(char *string, char *pattern, bool zero)
+{
+	char c;
+	char *loc = string + strlen(string);
+
+	while (loc >= string) {
+		int match;
+		const char *s;
+
+		c = *loc;
+		if (zero) {
+			*loc = '\0';
+			s = string;
+		} else
+			s = loc;
+		match = pmatch(pattern, s);
+		*loc = c;
+
+		if (match)
+			return loc;
+
+		loc--;
+	}
+
+	return NULL;
+}
+
+#ifdef STANDALONE
+int main(int argc, char *argv[])
+{
+	char *string;
+	char *op;
+	char *pattern;
+	bool zero;
+	char *loc;
+
+	int i;
+
+	if (argc == 1) {
+		puts(
+			"Usage: match <test> [test...]\n\n"
+			"Where a <test> is the form: <string><op><match>\n"
+			"This is to test the shell ${var#val} expression type.\n\n"
+			"e.g. `match 'abc#a*'` -> bc"
+		);
+		return 1;
+	}
+
+	for (i = 1; i < argc; ++i) {
+		size_t off;
+		scan_t scan;
+
+		printf("'%s': ", argv[i]);
+
+		string = strdup(argv[i]);
+		off = strcspn(string, "#%");
+		if (!off) {
+			printf("invalid format\n");
+			free(string);
+			continue;
+		}
+		op = string + off;
+		scan = pick_scan(op[0], op[1], &zero);
+		pattern = op + 1;
+		if (op[0] == op[1])
+			op[1] = '\0', ++pattern;
+		op[0] = '\0';
+
+		loc = scan(string, pattern, zero);
+
+		if (zero) {
+			printf("'%s'\n", loc);
+		} else {
+			*loc = '\0';
+			printf("'%s'\n", string);
+		}
+
+		free(string);
+	}
+
+	return 0;
+}
+#endif

shell/match.h

@@ -0,0 +1,22 @@
+/* match.h - interface to shell ##/%% matching code */
+
+typedef char *(*scan_t)(char *string, char *match, bool zero);
+
+char *scanleft(char *string, char *match, bool zero);
+char *scanright(char *string, char *match, bool zero);
+
+static inline scan_t pick_scan(char op1, char op2, bool *zero)
+{
+	/* #  - scanleft
+	 * ## - scanright
+	 * %  - scanright
+	 * %% - scanleft
+	 */
+	if (op1 == '#') {
+		*zero = true;
+		return op1 == op2 ? scanright : scanleft;
+	} else {
+		*zero = false;
+		return op1 == op2 ? scanleft : scanright;
+	}
+}