diff options
Diffstat (limited to 'editors')
| -rw-r--r-- | editors/sed.c | 94 |
1 files changed, 76 insertions, 18 deletions
diff --git a/editors/sed.c b/editors/sed.c index 4d4886e19..195175e88 100644 --- a/editors/sed.c +++ b/editors/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; |