From c56c347d6d5e93e518d5f72fa7310d9e4279dcfb Mon Sep 17 00:00:00 2001
From: markw <markw@69ca8d6d-28ef-0310-b511-8ec308f3f277>
Date: Mon, 17 Jul 2000 20:06:42 +0000
Subject: - Added support for backreferences in substitution expressions up to
nine (\1, \2...\9). This touched a lot of places in this file and I added
a new function 'print_subst_w_backrefs' in order to keep
'do_subst_command' a little more tidy.
* I tested this good 'n hard, but will always appreciate more testing from
other, willing folks.
- Noticed that the index_of_next_unescaped_slash was subtly wrong so I
changed both the functionality and behavior (it used to skip over the first
char in the string you passed it, assuming it was a leading '/'--this
assumption is no longer made) this necessitated changing the lines that
call this function just slightly.
git-svn-id: svn://busybox.net/trunk/busybox@869 69ca8d6d-28ef-0310-b511-8ec308f3f277
---
sed.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 76 insertions(+), 18 deletions(-)
(limited to 'sed.c')
diff --git a/sed.c b/sed.c
index 4d4886e19..195175e88 100644
--- a/sed.c
+++ b/sed.c
@@ -27,6 +27,7 @@
- address matching: num|/matchstr/[,num|/matchstr/|$]command
- commands: (p)rint, (d)elete, (s)ubstitue (with g & I flags)
- edit commands: (a)ppend, (i)nsert, (c)hange
+ - backreferences in substitution expressions (\1, \2...\9)
(Note: Specifying an address (range) to match is *optional*; commands
default to the whole pattern space if no specific address match was
@@ -73,6 +74,9 @@ struct sed_cmd {
/* substitution command specific fields */
regex_t *sub_match; /* sed -e 's/sub_match/replace/' */
char *replace; /* sed -e 's/sub_match/replace/' XXX: who will hold the \1 \2 \3s? */
+ unsigned int num_backrefs:4; /* how many back references (\1..\9) */
+ /* Note: GNU/POSIX sed does not save more than nine backrefs, so
+ * we only use 4 bits to hold the number */
unsigned int sub_g:1; /* sed -e 's/foo/bar/g' (global) */
/* edit command (a,i,c) speicific field */
@@ -166,19 +170,19 @@ static size_t strrspn(const char *s, const char *accept)
#endif
/*
- * index_of_unescaped_slash - walks left to right through a string beginning
- * at a specified index and returns the index of the next unescaped slash.
+ * index_of_next_unescaped_slash - walks left to right through a string
+ * beginning at a specified index and returns the index of the next forward
+ * slash ('/') not preceeded by a backslash ('\').
*/
static int index_of_next_unescaped_slash(const char *str, int idx)
{
- do {
- idx++;
- /* test if we've hit the end */
- if (str[idx] == 0)
- return -1;
- } while (str[idx] != '/' && str[idx - 1] != '\\');
+ for ( ; str[idx]; idx++) {
+ if (str[idx] == '/' && str[idx-1] != '\\')
+ return idx;
+ }
- return idx;
+ /* if we make it to here, we've hit the end of the string */
+ return -1;
}
/*
@@ -201,7 +205,7 @@ static int get_address(const char *str, int *line, regex_t **regex)
idx++;
}
else if (my_str[idx] == '/') {
- idx = index_of_next_unescaped_slash(my_str, idx);
+ idx = index_of_next_unescaped_slash(my_str, ++idx);
if (idx == -1)
fatalError("unterminated match expression\n");
my_str[idx] = '\0';
@@ -233,6 +237,7 @@ static int parse_subst_cmd(struct sed_cmd *sed_cmd, const char *substr)
int oldidx, cflags = REG_NEWLINE;
char *match;
int idx = 0;
+ int j;
/*
* the string that gets passed to this function should look like this:
@@ -249,14 +254,26 @@ static int parse_subst_cmd(struct sed_cmd *sed_cmd, const char *substr)
/* save the match string */
oldidx = idx+1;
- idx = index_of_next_unescaped_slash(substr, idx);
+ idx = index_of_next_unescaped_slash(substr, ++idx);
if (idx == -1)
fatalError("bad format in substitution expression\n");
match = strdup_substr(substr, oldidx, idx);
+ /* determine the number of back references in the match string */
+ /* Note: we compute this here rather than in the do_subst_command()
+ * function to save processor time, at the expense of a little more memory
+ * (4 bits) per sed_cmd */
+
+ /* sed_cmd->num_backrefs = 0; */ /* XXX: not needed? --apparently not */
+ for (j = 0; match[j]; j++) {
+ /* GNU/POSIX sed does not save more than nine backrefs */
+ if (match[j] == '\\' && match[j+1] == '(' && sed_cmd->num_backrefs < 9)
+ sed_cmd->num_backrefs++;
+ }
+
/* save the replacement string */
oldidx = idx+1;
- idx = index_of_next_unescaped_slash(substr, idx);
+ idx = index_of_next_unescaped_slash(substr, ++idx);
if (idx == -1)
fatalError("bad format in substitution expression\n");
sed_cmd->replace = strdup_substr(substr, oldidx, idx);
@@ -280,7 +297,7 @@ static int parse_subst_cmd(struct sed_cmd *sed_cmd, const char *substr)
}
out:
- /* compile the regex */
+ /* compile the match string into a regex */
sed_cmd->sub_match = (regex_t *)xmalloc(sizeof(regex_t));
xregcomp(sed_cmd->sub_match, match, cflags);
free(match);
@@ -460,26 +477,64 @@ static void load_cmd_file(char *filename)
}
}
+static void print_subst_w_backrefs(const char *line, const char *replace, regmatch_t *regmatch)
+{
+ int i;
+
+ /* go through the replacement string */
+ for (i = 0; replace[i]; i++) {
+ /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
+ if (replace[i] == '\\' && isdigit(replace[i+1])) {
+ int j;
+ char tmpstr[2];
+ int backref;
+ ++i; /* i now indexes the backref number, instead of the leading slash */
+ tmpstr[0] = replace[i];
+ tmpstr[1] = 0;
+ backref = atoi(tmpstr);
+ /* print out the text held in regmatch[backref] */
+ for (j = regmatch[backref].rm_so; j < regmatch[backref].rm_eo; j++)
+ fputc(line[j], stdout);
+ }
+
+ /* if we find an unescaped '&' print out the whole matched text.
+ * fortunately, regmatch[0] contains the indicies to the whole matched
+ * expression (kinda seems like it was designed for just such a
+ * purpose...) */
+ else if (replace[i] == '&' && replace[i-1] != '\\') {
+ int j;
+ for (j = regmatch[0].rm_so; j < regmatch[0].rm_eo; j++)
+ fputc(line[j], stdout);
+ }
+ /* nothing special, just print this char of the replacement string to stdout */
+ else
+ fputc(replace[i], stdout);
+ }
+}
+
static int do_subst_command(const struct sed_cmd *sed_cmd, const char *line)
{
int altered = 0;
/* we only substitute if the substitution 'search' expression matches */
if (regexec(sed_cmd->sub_match, line, 0, NULL, 0) == 0) {
- regmatch_t regmatch;
+ regmatch_t *regmatch = xmalloc(sizeof(regmatch_t) * (sed_cmd->num_backrefs+1));
int i;
char *ptr = (char *)line;
while (*ptr) {
/* if we can match the search string... */
- if (regexec(sed_cmd->sub_match, ptr, 1, ®match, 0) == 0) {
+ if (regexec(sed_cmd->sub_match, ptr, sed_cmd->num_backrefs+1, regmatch, 0) == 0) {
/* print everything before the match, */
- for (i = 0; i < regmatch.rm_so; i++)
+ for (i = 0; i < regmatch[0].rm_so; i++)
fputc(ptr[i], stdout);
+
/* then print the substitution in its place */
- fputs(sed_cmd->replace, stdout);
+ print_subst_w_backrefs(ptr, sed_cmd->replace, regmatch);
+
/* then advance past the match */
- ptr += regmatch.rm_eo;
+ ptr += regmatch[0].rm_eo;
+
/* and flag that something has changed */
altered++;
@@ -496,6 +551,9 @@ static int do_subst_command(const struct sed_cmd *sed_cmd, const char *line)
/* is there anything left to print? */
if (*ptr)
fputs(ptr, stdout);
+
+ /* cleanup */
+ free(regmatch);
}
return altered;
--
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