hush: support ${var:EXPR:EXPR}!

function                                             old     new   delta
handle_dollar                                        574     681    +107
expand_and_evaluate_arith                              -      77     +77
expand_vars_to_list                                 2302    2374     +72
add_till_closing_bracket                             359     368      +9
builtin_exit                                          48      47      -1
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 3/1 up/down: 265/-1)            Total: 264 bytes

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

3 files changed, 152 insertions, 86 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 0f0151a21..41d5fcab2 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -171,6 +171,7 @@
 #define debug_printf_env(...)    do {} while (0)
 #define debug_printf_jobs(...)   do {} while (0)
 #define debug_printf_expand(...) do {} while (0)
+#define debug_printf_varexp(...) do {} while (0)
 #define debug_printf_glob(...)   do {} while (0)
 #define debug_printf_list(...)   do {} while (0)
 #define debug_printf_subst(...)  do {} while (0)
@@ -743,6 +744,10 @@ static const struct built_in_command bltins2[] = {
 # define DEBUG_EXPAND 0
 #endif
 
+#ifndef debug_printf_varexp
+# define debug_printf_varexp(...) (indent(), fprintf(stderr, __VA_ARGS__))
+#endif
+
 #ifndef debug_printf_glob
 # define debug_printf_glob(...) (indent(), fprintf(stderr, __VA_ARGS__))
 # define DEBUG_GLOB 1
@@ -1817,11 +1822,11 @@ static void o_addblock(o_string *o, const char *str, int len)
         o->data[o->length] = '\0';
 }
 
-#if !BB_MMU
 static void o_addstr(o_string *o, const char *str)
 {
         o_addblock(o, str, strlen(str));
 }
+#if !BB_MMU
 static void nommu_addchr(o_string *o, int ch)
 {
         if (o)
@@ -2597,12 +2602,19 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg, char
                         } else {
                                 /* maybe handle parameter expansion */
                                 exp_saveptr = var + strcspn(var, "%#:-=+?");
-                                exp_save = *exp_saveptr;
-                                if (exp_save) {
-                                        exp_word = exp_saveptr;
-                                        if (exp_save == ':')
-                                                exp_word++;
-                                        exp_op = *exp_word++;
+                                exp_op = exp_save = *exp_saveptr;
+                                if (exp_op) {
+                                        exp_word = exp_saveptr + 1;
+                                        if (exp_op == ':') {
+                                                exp_op = *exp_word++;
+                                                if (ENABLE_HUSH_BASH_COMPAT
+                                                 && (exp_op == '\0' || !strchr("%#:-=+?"+3, exp_op))
+                                                ) {
+                                                        /* oops... it's ${var:N[:M]}, not ${var:?xxx} or some such */
+                                                        exp_op = ':';
+                                                        exp_word--;
+                                                }
+                                        }
                                         *exp_saveptr = '\0';
                                 }
                         }
@@ -2656,39 +2668,42 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg, char
                                                                 *loc = '\0';
                                                 }
                                         }
-                                } else if (!strchr("%#:-=+?"+3, exp_op)) {
+                                } else if (exp_op == ':') {
 #if ENABLE_HUSH_BASH_COMPAT
-        /* exp_op is ':' and next char isn't a subst operator.
-         * Assuming it's ${var:[N][:M]} bashism.
-         * TODO: N, M can be expressions similar to $((EXPR)): 2+2, 2+var etc
+        /* It's ${var:N[:M]} bashism.
+         * Note that in encoded form it has TWO parts:
+         * var:N<SPECIAL_VAR_SYMBOL>M<SPECIAL_VAR_SYMBOL>
          */
-                                        char *end;
-                                        unsigned len = INT_MAX;
-                                        unsigned beg = 0;
-                                        end = --exp_word;
-                                        if (*exp_word != ':') /* not ${var::...} */
-                                                beg = bb_strtou(exp_word, &end, 0);
-                                        //bb_error_msg("beg:'%s'=%u end:'%s'", exp_word, beg, end);
-                                        if (*end == ':') {
-                                                if (end[1] != '\0') /* not ${var:NUM:} */
-                                                        len = bb_strtou(end + 1, &end, 0);
-                                                else {
-                                                        len = 0;
-                                                        end++;
-                                                }
-                                                //bb_error_msg("len:%u end:'%s'", len, end);
-                                        }
-                                        if (*end == '\0') {
-                                                //bb_error_msg("from val:'%s'", val);
+                                        arith_t beg, len;
+                                        int errcode = 0;
+
+                                        beg = expand_and_evaluate_arith(exp_word, &errcode);
+                                        debug_printf_varexp("beg:'%s'=%lld\n", exp_word, (long long)beg);
+                                        *p++ = SPECIAL_VAR_SYMBOL;
+                                        exp_word = p;
+                                        p = strchr(p, SPECIAL_VAR_SYMBOL);
+                                        *p = '\0';
+                                        len = expand_and_evaluate_arith(exp_word, &errcode);
+                                        debug_printf_varexp("len:'%s'=%lld\n", exp_word, (long long)len);
+
+                                        if (errcode >= 0 && len >= 0) { /* bash compat: len < 0 is illegal */
+                                                if (beg < 0) /* bash compat */
+                                                        beg = 0;
+                                                debug_printf_varexp("from val:'%s'\n", val);
                                                 if (len == 0 || !val || beg >= strlen(val))
                                                         val = "";
-                                                else
+                                                else {
+                                                        /* Paranoia. What if user entered 9999999999999
+                                                         * which fits in arith_t but not int? */
+                                                        if (len >= INT_MAX)
+                                                                len = INT_MAX;
                                                         val = to_be_freed = xstrndup(val + beg, len);
-                                                //bb_error_msg("val:'%s'", val);
+                                                }
+                                                debug_printf_varexp("val:'%s'\n", val);
                                         } else
 #endif
                                         {
-                                                die_if_script("malformed ${%s...}", var);
+                                                die_if_script("malformed ${%s:...}", var);
                                                 val = "";
                                         }
                                 } else { /* one of "-=+?" */
@@ -5891,21 +5906,28 @@ static void add_till_backquote(o_string *dest, struct in_str *input)
  * echo $(echo 'TEST)' BEST)            TEST) BEST
  * echo $(echo \(\(TEST\) BEST)         ((TEST) BEST
  *
- * Also adapted to eat ${var%...} constructs, since ... part
+ * Also adapted to eat ${var%...} and $((...)) constructs, since ... part
  * can contain arbitrary constructs, just like $(cmd).
+ * In bash compat mode, it needs to also be able to stop on '}' or ':'
+ * for ${var:N[:M]} parsing.
  */
 #define DOUBLE_CLOSE_CHAR_FLAG 0x80
-static void add_till_closing_bracket(o_string *dest, struct in_str *input, char end_ch)
+static int add_till_closing_bracket(o_string *dest, struct in_str *input, unsigned end_ch)
 {
+        int ch;
         char dbl = end_ch & DOUBLE_CLOSE_CHAR_FLAG;
-        end_ch &= (DOUBLE_CLOSE_CHAR_FLAG-1);
+#if ENABLE_HUSH_BASH_COMPAT
+        char end_char2 = end_ch >> 8;
+#endif
+        end_ch &= (DOUBLE_CLOSE_CHAR_FLAG - 1);
+
         while (1) {
-                int ch = i_getch(input);
+                ch = i_getch(input);
                 if (ch == EOF) {
                         syntax_error_unterm_ch(end_ch);
                         /*xfunc_die(); - redundant */
                 }
-                if (ch == end_ch) {
+                if (ch == end_ch  IF_HUSH_BASH_COMPAT( || ch == end_char2)) {
                         if (!dbl)
                                 break;
                         /* we look for closing )) of $((EXPR)) */
@@ -5947,6 +5969,7 @@ static void add_till_closing_bracket(o_string *dest, struct in_str *input, char
                         continue;
                 }
         }
+        return ch;
 }
 #endif /* ENABLE_HUSH_TICK || ENABLE_SH_MATH_SUPPORT */
 
@@ -6033,22 +6056,45 @@ static int handle_dollar(o_string *as_string,
                                 break;
 
                         if (!isalnum(ch) && ch != '_') {
+                                unsigned end_ch;
+                                unsigned char last_ch;
                                 /* handle parameter expansions
                                  * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_06_02
                                  */
                                 if (!strchr("%#:-=+?", ch)) /* ${var<bad_char>... */
                                         goto bad_dollar_syntax;
-                                /* Eat everything until closing '}' */
                                 o_addchr(dest, ch);
+
+                                /* Eat everything until closing '}' (or ':') */
+                                end_ch = '}';
+                                if (ENABLE_HUSH_BASH_COMPAT
+                                 && ch == ':'
+                                 && !strchr("%#:-=+?"+3, i_peek(input))
+                                ) {
+                                        /* It's ${var:N[:M]} thing */
+                                        end_ch = '}' * 0x100 + ':';
+                                }
+ again:
                                 if (!BB_MMU)
                                         pos = dest->length;
-                                add_till_closing_bracket(dest, input, '}');
-#if !BB_MMU
+                                last_ch = add_till_closing_bracket(dest, input, end_ch);
                                 if (as_string) {
                                         o_addstr(as_string, dest->data + pos);
-                                        o_addchr(as_string, '}');
+                                        o_addchr(as_string, last_ch);
+                                }
+
+                                if (ENABLE_HUSH_BASH_COMPAT && (end_ch & 0xff00)) {
+                                        /* close the first block: */
+                                        o_addchr(dest, SPECIAL_VAR_SYMBOL);
+                                        /* while parsing N from ${var:N[:M]}... */
+                                        if ((end_ch & 0xff) == last_ch) {
+                                                /* ...got ':' - parse the rest */
+                                                end_ch = '}';
+                                                goto again;
+                                        }
+                                        /* ...got '}', not ':' - it's ${var:N}! emulate :999999999 */
+                                        o_addstr(dest, "999999999");
                                 }
-#endif
                                 break;
                         }
                 }
diff --git a/shell/hush_test/hush-vars/param_expand_bash_substring.right b/shell/hush_test/hush-vars/param_expand_bash_substring.right
index 6e3eb3ba6..53b8836ff 100644
--- a/shell/hush_test/hush-vars/param_expand_bash_substring.right
+++ b/shell/hush_test/hush-vars/param_expand_bash_substring.right
@@ -39,3 +39,13 @@ f:1:2=|12|
 f::2 =|01|
 f:1: =||
 f::  =||
+Substrings with expressions
+f            =|01234567|
+f:1+1:2+2    =|2345|
+f:-1:2+2     =|01234567|
+f:1:f        =|1234567|
+f:1:$f       =|1234567|
+f:1:${f}     =|1234567|
+f:1:${f:3:1} =|123|
+f:1:1`echo 1`=|1|
+Done
diff --git a/shell/hush_test/hush-vars/param_expand_bash_substring.tests b/shell/hush_test/hush-vars/param_expand_bash_substring.tests
index eedd435ed..a80523add 100755
--- a/shell/hush_test/hush-vars/param_expand_bash_substring.tests
+++ b/shell/hush_test/hush-vars/param_expand_bash_substring.tests
@@ -1,8 +1,6 @@
+# first try some invalid patterns
 # do all of these in subshells since it's supposed to error out
-
 export var=0123456789
-
-# first try some invalid patterns
 "$THIS_SH" -c 'echo ${:}'
 "$THIS_SH" -c 'echo ${::}'
 "$THIS_SH" -c 'echo ${:1}'
@@ -15,44 +13,56 @@ export var=0123456789
 # UNFIXED BUG: this should work: "$THIS_SH" -c 'echo ${?:0}'
 
 # now some valid ones
-"$THIS_SH" -c 'set --; echo "1    =|${1}|"'
-"$THIS_SH" -c 'set --; echo "1:1  =|${1:1}|"'
-"$THIS_SH" -c 'set --; echo "1:1:2=|${1:1:2}|"'
-"$THIS_SH" -c 'set --; echo "1::2 =|${1::2}|"'
-"$THIS_SH" -c 'set --; echo "1:1: =|${1:1:}|"'
-"$THIS_SH" -c 'set --; echo "1::  =|${1::}|"'
-
-"$THIS_SH" -c 'set -- 0123; echo "1    =|${1}|"'
-"$THIS_SH" -c 'set -- 0123; echo "1:1  =|${1:1}|"'
-"$THIS_SH" -c 'set -- 0123; echo "1:1:2=|${1:1:2}|"'
-"$THIS_SH" -c 'set -- 0123; echo "1::2 =|${1::2}|"'
-"$THIS_SH" -c 'set -- 0123; echo "1:1: =|${1:1:}|"'
-"$THIS_SH" -c 'set -- 0123; echo "1::  =|${1::}|"'
-
-"$THIS_SH" -c 'unset f; echo "f    =|$f|"'
-"$THIS_SH" -c 'unset f; echo "f:1  =|${f:1}|"'
-"$THIS_SH" -c 'unset f; echo "f:1:2=|${f:1:2}|"'
-"$THIS_SH" -c 'unset f; echo "f::2 =|${f::2}|"'
-"$THIS_SH" -c 'unset f; echo "f:1: =|${f:1:}|"'
-"$THIS_SH" -c 'unset f; echo "f::  =|${f::}|"'
-
-"$THIS_SH" -c 'f=; echo "f    =|$f|"'
-"$THIS_SH" -c 'f=; echo "f:1  =|${f:1}|"'
-"$THIS_SH" -c 'f=; echo "f:1:2=|${f:1:2}|"'
-"$THIS_SH" -c 'f=; echo "f::2 =|${f::2}|"'
-"$THIS_SH" -c 'f=; echo "f:1: =|${f:1:}|"'
-"$THIS_SH" -c 'f=; echo "f::  =|${f::}|"'
-
-"$THIS_SH" -c 'f=a; echo "f    =|$f|"'
-"$THIS_SH" -c 'f=a; echo "f:1  =|${f:1}|"'
-"$THIS_SH" -c 'f=a; echo "f:1:2=|${f:1:2}|"'
-"$THIS_SH" -c 'f=a; echo "f::2 =|${f::2}|"'
-"$THIS_SH" -c 'f=a; echo "f:1: =|${f:1:}|"'
-"$THIS_SH" -c 'f=a; echo "f::  =|${f::}|"'
-
-"$THIS_SH" -c 'f=0123456789; echo "f    =|$f|"'
-"$THIS_SH" -c 'f=0123456789; echo "f:1  =|${f:1}|"'
-"$THIS_SH" -c 'f=0123456789; echo "f:1:2=|${f:1:2}|"'
-"$THIS_SH" -c 'f=0123456789; echo "f::2 =|${f::2}|"'
-"$THIS_SH" -c 'f=0123456789; echo "f:1: =|${f:1:}|"'
-"$THIS_SH" -c 'f=0123456789; echo "f::  =|${f::}|"'
+set --; echo "1    =|${1}|"
+set --; echo "1:1  =|${1:1}|"
+set --; echo "1:1:2=|${1:1:2}|"
+set --; echo "1::2 =|${1::2}|"
+set --; echo "1:1: =|${1:1:}|"
+set --; echo "1::  =|${1::}|"
+
+set -- 0123; echo "1    =|${1}|"
+set -- 0123; echo "1:1  =|${1:1}|"
+set -- 0123; echo "1:1:2=|${1:1:2}|"
+set -- 0123; echo "1::2 =|${1::2}|"
+set -- 0123; echo "1:1: =|${1:1:}|"
+set -- 0123; echo "1::  =|${1::}|"
+
+unset f; echo "f    =|$f|"
+unset f; echo "f:1  =|${f:1}|"
+unset f; echo "f:1:2=|${f:1:2}|"
+unset f; echo "f::2 =|${f::2}|"
+unset f; echo "f:1: =|${f:1:}|"
+unset f; echo "f::  =|${f::}|"
+
+f=; echo "f    =|$f|"
+f=; echo "f:1  =|${f:1}|"
+f=; echo "f:1:2=|${f:1:2}|"
+f=; echo "f::2 =|${f::2}|"
+f=; echo "f:1: =|${f:1:}|"
+f=; echo "f::  =|${f::}|"
+
+f=a; echo "f    =|$f|"
+f=a; echo "f:1  =|${f:1}|"
+f=a; echo "f:1:2=|${f:1:2}|"
+f=a; echo "f::2 =|${f::2}|"
+f=a; echo "f:1: =|${f:1:}|"
+f=a; echo "f::  =|${f::}|"
+
+f=0123456789; echo "f    =|$f|"
+f=0123456789; echo "f:1  =|${f:1}|"
+f=0123456789; echo "f:1:2=|${f:1:2}|"
+f=0123456789; echo "f::2 =|${f::2}|"
+f=0123456789; echo "f:1: =|${f:1:}|"
+f=0123456789; echo "f::  =|${f::}|"
+
+echo "Substrings with expressions"
+f=01234567; echo 'f            '"=|$f|"
+f=01234567; echo 'f:1+1:2+2    '"=|${f:1+1:2+2}|"
+f=01234567; echo 'f:-1:2+2     '"=|${f:-1:2+2}|"
+f=01234567; echo 'f:1:f        '"=|${f:1:f}|"
+f=01234567; echo 'f:1:$f       '"=|${f:1:$f}|"
+f=01234567; echo 'f:1:${f}     '"=|${f:1:${f}}|"
+f=01234567; echo 'f:1:${f:3:1} '"=|${f:1:${f:3:1}}|"
+f=01234567; echo 'f:1:1`echo 1`'"=|${f:1:`echo 1`}|"
+
+echo Done