[U-Boot] [PATCH v2 07/11] setexpr: add regex substring matching and substitution

Wolfgang Denk
2013-03-24T09:50:34Z

Add "setexpr name gsub r s [t]" and "setexpr name sub r s [t]"
commands which implement substring matching for the regular
expression <r> in the string <t>, and substitution of the string .
The result is assigned to the environment variable <name>. If <t> is
not supplied, the previous value of <name> is used instead. "gsub"
performs global substitution, while "sub" will replace only the first
substring.

Both commands are closely modeled after the gawk functions with the
same names.

Examples:

- Generate broadcast address by substituting the last two numbers of
the IP address by "255.255":

=> print ipaddr
ipaddr=192.168.1.104
=> setexpr broadcast sub "(.*\\.).*\\..*" "\\1255.255" $ipaddr
broadcast=192.168.255.255

- Depending on keyboard configuration (German vs. US keyboard) a
barcode scanner may initialize the MAC address as C0:E5:4E:02:06:DC
or as C0>E5>4E>02>06>DC. Make sure we always have a correct value:

=> print ethaddr
ethaddr=C0>E5>4E>02>06>DC
=> setexpr ethaddr gsub > :
ethaddr=C0:E5:4E:02:06:DC

- Do the same, but substitute one step at a time in a loop until no
futher matches:

=> setenv ethaddr C0>E5>4E>02>06>DC
=> while setexpr ethaddr sub > :
> do
> echo -----
> done
ethaddr=C0:E5>4E>02>06>DC
-----
ethaddr=C0:E5:4E>02>06>DC
-----
ethaddr=C0:E5:4E:02>06>DC
-----
ethaddr=C0:E5:4E:02:06>DC
-----
ethaddr=C0:E5:4E:02:06:DC
-----
C0:E5:4E:02:06:DC: No match
=> print ethaddr
ethaddr=C0:E5:4E:02:06:DC

etc.

To enable this feature, the CONFIG_REGEX option has to be defined in
the board config file.

Signed-off-by: Wolfgang Denk <wd@denx.de>

---
Changes in v2:
- fix "No space is necessary after a cast" checks
- fix "space prohibited before semicolon" and "space required after
that ';'" errors (but I consider the result less readable :-( )
- Note: the remaining warnings ("line over 80 characters") and checks
("Alignment should match open parenthesis") are intentionally left
as is.

common/cmd_setexpr.c | 280 ++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 277 insertions(+), 3 deletions(-)

diff --git a/common/cmd_setexpr.c b/common/cmd_setexpr.c
index ccd87f4..93cb255 100644
--- a/common/cmd_setexpr.c
+++ b/common/cmd_setexpr.c
@@ -1,5 +1,6 @@
/*
* Copyright 2008 Freescale Semiconductor, Inc.
+ * Copyright 2013 Wolfgang Denk <wd@denx.de>
*
* See file CREDITS for list of people who contributed to this
* project.
@@ -50,13 +51,263 @@ static ulong get_arg(char *s, int w)
}
}

+#ifdef CONFIG_REGEX
+
+#include <slre.h>
+
+#define SLRE_BUFSZ 16384
+#define SLRE_PATSZ 4096
+
+/*
+ * memstr - Find the first substring in memory
+ * @s1: The string to be searched
+ * @s2: The string to search for
+ *
+ * Similar to and based on strstr(),
+ * but strings do not need to be NUL terminated.
+ */
+static char *memstr(const char *s1, int l1, const char *s2, int l2)
+{
+ if (!l2)
+ return (char *)s1;
+
+ while (l1 >= l2) {
+ l1--;
+ if (!memcmp(s1, s2, l2))
+ return (char *)s1;
+ s1++;
+ }
+ return NULL;
+}
+
+static char *substitute(char *string, /* string buffer */
+ int *slen, /* current string length */
+ int ssize, /* string bufer size */
+ const char *old,/* old (replaced) string */
+ int olen, /* length of old string */
+ const char *new,/* new (replacement) string */
+ int nlen) /* length of new string */
+{
+ char *p = memstr(string, *slen, old, olen);
+
+ if (p == NULL)
+ return NULL;
+
+ debug("## Match at pos %ld: match len %d, subst len %d\n",
+ (long)(p - string), olen, nlen);
+
+ /* make sure replacement matches */
+ if (*slen + nlen - olen > ssize) {
+ printf("## error: substitution buffer overflow\n");
+ return NULL;
+ }
+
+ /* move tail if needed */
+ if (olen != nlen) {
+ int tail, len;
+
+ len = (olen > nlen) ? olen : nlen;
+
+ tail = ssize - (p + len - string);
+
+ debug("## tail len %d\n", tail);
+
+ memmove(p + nlen, p + olen, tail);
+ }
+
+ /* insert substitue */
+ memcpy(p, new, nlen);
+
+ *slen += nlen - olen;
+
+ return p + nlen;
+}
+
+/*
+ * Perform regex operations on a environment variable
+ *
+ * Returns 0 if OK, 1 in case of errors.
+ */
+static int regex_sub(const char *name,
+ const char *r, const char *s, const char *t,
+ int global)
+{
+ struct slre slre;
+ char data[SLRE_BUFSZ];
+ char *datap = data;
+ const char *value;
+ int res, len, nlen, loop;
+
+ if (name == NULL)
+ return 1;
+
+ if (slre_compile(&slre, r) == 0) {
+ printf("Error compiling regex: %s\n", slre.err_str);
+ return 1;
+ }
+
+ if (t == NULL) {
+ value = getenv(name);
+
+ if (value == NULL) {
+ printf("## Error: variable \"%s\" not defined\n", name);
+ return 1;
+ }
+ t = value;
+ }
+
+ debug("REGEX on %s=%s\n", name, t);
+ debug("REGEX=\"%s\", SUBST=\"%s\", GLOBAL=%d\n",
+ r, s ? s : "<NULL>", global);
+
+ len = strlen(t);
+ if (len + 1 > SLRE_BUFSZ) {
+ printf("## error: subst buffer overflow: have %d, need %d\n",
+ SLRE_BUFSZ, len + 1);
+ return 1;
+ }
+
+ strcpy(data, t);
+
+ if (s == NULL)
+ nlen = 0;
+ else
+ nlen = strlen(s);
+
+ for (loop = 0;; loop++) {
+ struct cap caps[slre.num_caps + 2];
+ char nbuf[SLRE_PATSZ];
+ const char *old;
+ char *np;
+ int i, olen;
+
+ (void) memset(caps, 0, sizeof(caps));
+
+ res = slre_match(&slre, datap, len, caps);
+
+ debug("Result: %d\n", res);
+
+ for (i = 0; i < slre.num_caps; i++) {
+ if (caps[i].len > 0) {
+ debug("Substring %d: [%.*s]\n", i,
+ caps[i].len, caps[i].ptr);
+ }
+ }
+
+ if (res == 0) {
+ if (loop == 0) {
+ printf("%s: No match\n", t);
+ return 1;
+ } else {
+ break;
+ }
+ }
+
+ debug("## MATCH ## %s\n", data);
+
+ if (s == NULL) {
+ printf("%s=%s\n", name, t);
+ return 1;
+ }
+
+ old = caps[0].ptr;
+ olen = caps[0].len;
+
+ if (nlen + 1 >= SLRE_PATSZ) {
+ printf("## error: pattern buffer overflow: have %d, need %d\n",
+ SLRE_BUFSZ, nlen + 1);
+ return 1;
+ }
+ strcpy(nbuf, s);
+
+ debug("## SUBST(1) ## %s\n", nbuf);
+
+ /*
+ * Handle back references
+ *
+ * Support for \0 ... \9, where \0 is the
+ * whole matched pattern (similar to &).
+ *
+ * Implementation is a bit simpleminded as
+ * backrefs are substituted sequentially, one
+ * by one. This will lead to somewhat
+ * unexpected results if the replacement
+ * strings contain any \N strings then then
+ * may get substitued, too. We accept this
+ * restriction for the sake of simplicity.
+ */
+ for (i = 0; i < 10; ++i) {
+ char backref[2] = {
+ '\\',
+ '0',
+ };
+
+ if (caps[i].len == 0)
+ break;
+
+ backref[1] += i;
+
+ debug("## BACKREF %d: replace \"%.*s\" by \"%.*s\" in \"%s\"\n",
+ i,
+ 2, backref,
+ caps[i].len, caps[i].ptr,
+ nbuf);
+
+ for (np = nbuf;;) {
+ char *p = memstr(np, nlen, backref, 2);
+
+ if (p == NULL)
+ break;
+
+ np = substitute(np, &nlen,
+ SLRE_PATSZ,
+ backref, 2,
+ caps[i].ptr, caps[i].len);
+
+ if (np == NULL)
+ return 1;
+ }
+ }
+ debug("## SUBST(2) ## %s\n", nbuf);
+
+ datap = substitute(datap, &len, SLRE_BUFSZ,
+ old, olen,
+ nbuf, nlen);
+
+ if (datap == NULL)
+ return 1;
+
+ debug("## REMAINDER: %s\n", datap);
+
+ debug("## RESULT: %s\n", data);
+
+ if (!global)
+ break;
+ }
+ debug("## FINAL (now setenv()) : %s\n", data);
+
+ printf("%s=%s\n", name, data);
+
+ return setenv(name, data);
+}
+#endif
+
static int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
ulong a, b;
ulong value;
int w;

- if (argc < 3)
+ /*
+ * We take 3, 5, or 6 arguments:
+ * 3 : setexpr name value
+ * 5 : setexpr name val1 op val2
+ * setexpr name [g]sub r s
+ * 6 : setexpr name [g]sub r s t
+ */
+
+ /* > 6 already tested by max command args */
+ if ((argc < 3) || (argc == 4))
return CMD_RET_USAGE;

w = cmd_get_data_size(argv[0], 4);
@@ -69,6 +320,19 @@ static int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
return 0;
}

+ /* 5 or 6 args (6 args only with [g]sub) */
+#ifdef CONFIG_REGEX
+ /*
+ * rexep handling: "setexpr name [g]sub r s [t]"
+ * with 5 args, "t" will be NULL
+ */
+ if (strcmp(argv[2], "gsub") == 0)
+ return regex_sub(argv[1], argv[3], argv[4], argv[5], 1);
+
+ if (strcmp(argv[2], "sub") == 0)
+ return regex_sub(argv[1], argv[3], argv[4], argv[5], 0);
+#endif
+
/* standard operators: "setexpr name val1 op val2" */
if (argc != 5)
return CMD_RET_USAGE;
@@ -114,13 +378,23 @@ static int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
}

U_BOOT_CMD(
- setexpr, 5, 0, do_setexpr,
+ setexpr, 6, 0, do_setexpr,
"set environment variable as the result of eval expression",
"[.b, .w, .l] name [*]value1 <op> [*]value2\n"
" - set environment variable 'name' to the result of the evaluated\n"
- " express specified by <op>. <op> can be &, |, ^, +, -, *, /, %\n"
+ " expression specified by <op>. <op> can be &, |, ^, +, -, *, /, %\n"
" size argument is only meaningful if value1 and/or value2 are\n"
" memory addresses (*)\n"
"setexpr[.b, .w, .l] name [*]value\n"
" - load a value into a variable"
+#ifdef CONFIG_REGEX
+ "\n"
+ "setexpr name gsub r s [t]\n"
+ " - For each substring matching the regular expression <r> in the\n"
+ " string <t>, substitute the string . The result is\n"
+ " assigned to <name>. If <t> is not supplied, use the old\n"
+ " value of <name>\n"
+ "setexpr name sub r s [t]\n"
+ " - Just like gsub(), but replace only the first matching substring"
+#endif
);
--
1.8.1.4