implement support for parameter substitution via #/% operators

6 files changed, 243 insertions, 25 deletions

diff --git a/shell/Kbuild b/shell/Kbuild
index 2b461b3bd..8b693ecc3 100644
--- a/shell/Kbuild
+++ b/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
diff --git a/shell/hush.c b/shell/hush.c
index 792886944..1740187d4 100644
--- a/shell/hush.c
+++ b/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;
-
-                                        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);
+                                                *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);
+                                                        }
                                                 }
                                         }
                                 }
+
                                 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 */
diff --git a/shell/hush_test/hush-vars/var_posix1.right b/shell/hush_test/hush-vars/var_posix1.right
new file mode 100644
index 000000000..55f35798a
--- /dev/null
+++ b/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
diff --git a/shell/hush_test/hush-vars/var_posix1.tests b/shell/hush_test/hush-vars/var_posix1.tests
new file mode 100755
index 000000000..4139e2cc3
--- /dev/null
+++ b/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
diff --git a/shell/match.c b/shell/match.c
new file mode 100644
index 000000000..0810fd8f6
--- /dev/null
+++ b/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
diff --git a/shell/match.h b/shell/match.h
new file mode 100644
index 000000000..863f52539
--- /dev/null
+++ b/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;
+        }
+}