optimize config_read() (by Timo Teras <timo.teras AT iki.fi>)

function                                             old     new   delta
bb_get_chunk_with_continuation                         -     176    +176
find_pair                                            169     187     +18
...
process_stdin                                        443     433     -10
config_read                                          549     456     -93
bb_get_chunk_from_file                               139       7    -132
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 7/7 up/down: 215/-254)          Total: -39 bytes

1 files changed, 67 insertions, 108 deletions

diff --git a/libbb/parse_config.c b/libbb/parse_config.c
index ace6f3ad3..a0599d4b4 100644
--- a/libbb/parse_config.c
+++ b/libbb/parse_config.c
@@ -123,137 +123,96 @@ mintokens > 0 make config_read() print error message if less than mintokens
 #undef config_read
 int FAST_FUNC config_read(parser_t *parser, char **tokens, unsigned flags, const char *delims)
 {
-        char *line, *q;
-        char comment;
-        int ii;
-        int ntokens;
-        int mintokens;
+        char *line;
+        int ntokens, mintokens;
+        int t, len;
 
-        comment = *delims++;
         ntokens = flags & 0xFF;
         mintokens = (flags & 0xFF00) >> 8;
 
- again:
-        memset(tokens, 0, sizeof(tokens[0]) * ntokens);
-        if (!parser)
+        if (parser == NULL)
                 return 0;
+
+again:
+        memset(tokens, 0, sizeof(tokens[0]) * ntokens);
         config_free_data(parser);
 
-        while (1) {
-//TODO: speed up xmalloc_fgetline by internally using fgets, not fgetc
-                line = xmalloc_fgetline(parser->fp);
-                if (!line)
-                        return 0;
+        /* Read one line (handling continuations with backslash) */
+        line = bb_get_chunk_with_continuation(parser->fp, &len, &parser->lineno);
+        if (line == NULL)
+                return 0;
+        parser->line = line;
 
-                parser->lineno++;
-                // handle continuations. Tito's code stolen :)
-                while (1) {
-                        ii = strlen(line);
-                        if (!ii)
-                                goto next_line;
-                        if (line[ii - 1] != '\\')
-                                break;
-                        // multi-line object
-                        line[--ii] = '\0';
-//TODO: add xmalloc_fgetline-like iface but with appending to existing str
-                        q = xmalloc_fgetline(parser->fp);
-                        if (!q)
-                                break;
-                        parser->lineno++;
-                        line = xasprintf("%s%s", line, q);
-                        free(q);
-                }
-                // discard comments
-                if (comment) {
-                        q = strchrnul(line, comment);
-                        *q = '\0';
-                        ii = q - line;
-                }
-                // skip leading and trailing delimiters
-                if (flags & PARSE_TRIM) {
-                        // skip leading
-                        int n = strspn(line, delims);
-                        if (n) {
-                                ii -= n;
-                                overlapping_strcpy(line, line + n);
-                        }
-                        // cut trailing
-                        if (ii) {
-                                while (strchr(delims, line[--ii]))
-                                        continue;
-                                line[++ii] = '\0';
-                        }
-                }
-                // if something still remains -> return it
-                if (ii)
-                        break;
+        /* Strip trailing line-feed if any */
+        if (len && line[len-1] == '\n')
+                line[len-1] = '\0';
 
- next_line:
-                // skip empty line
-                free(line);
-        }
-        // non-empty line found, parse and return the number of tokens
+        /* Skip token in the start of line? */
+        if (flags & PARSE_TRIM)
+                line += strspn(line, delims + 1);
 
-        // store line
-        parser->line = line = xrealloc(line, ii + 1);
-        if (flags & PARSE_KEEP_COPY) {
+        if (line[0] == '\0' || line[0] == delims[0])
+                goto again;
+
+        if (flags & PARSE_KEEP_COPY)
                 parser->data = xstrdup(line);
-        }
 
-        // split line to tokens
-        ntokens--; // now it's max allowed token no
-        // N.B. non-empty remainder is also a token,
-        // so if ntokens <= 1, we just return the whole line
-        // N.B. if PARSE_GREEDY is set the remainder of the line is stuck to the last token
-        ii = 0;
-        while (*line && ii <= ntokens) {
-                //bb_info_msg("L[%s]", line);
-                // get next token
-                // at last token and need greedy token ->
-                if ((flags & PARSE_GREEDY) && (ii == ntokens)) {
-                        // skip possible delimiters
-                        if (flags & PARSE_COLLAPSE)
-                                line += strspn(line, delims);
-                        // don't cut the line
-                        q = line + strlen(line);
+        /* Tokenize the line */
+        for (t = 0; *line && *line != delims[0] && t < ntokens; t++) {
+                /* Pin token */
+                tokens[t] = line;
+
+                /* Combine remaining arguments? */
+                if ((t != (ntokens-1)) || !(flags & PARSE_GREEDY)) {
+                        /* Vanilla token, find next delimiter */
+                        line += strcspn(line, delims[0] ? delims : delims + 1);
                 } else {
-                        // vanilla token. cut the line at the first delim
-                        q = line + strcspn(line, delims);
-                        if (*q) // watch out: do not step past the line end!
-                                *q++ = '\0';
+                        /* Combining, find comment char if any */
+                        line = strchrnul(line, delims[0]);
+
+                        /* Trim any extra delimiters from the end */
+                        if (flags & PARSE_TRIM) {
+                                while (strchr(delims + 1, line[-1]) != NULL)
+                                        line--;
+                        }
                 }
-                // pin token
-                if (!(flags & (PARSE_COLLAPSE | PARSE_TRIM)) || *line) {
-                        //bb_info_msg("N[%d] T[%s]", ii, line);
-                        tokens[ii++] = line;
-                        // process escapes in token
-#if 0 // unused so far
-                        if (flags & PARSE_ESCAPE) {
-                                char *s = line;
-                                while (*s) {
-                                        if (*s == '\\') {
-                                                s++;
-                                                *line++ = bb_process_escape_sequence((const char **)&s);
-                                        } else {
-                                                *line++ = *s++;
-                                        }
+
+                /* Token not terminated? */
+                if (line[0] == delims[0])
+                        *line = '\0';
+                else if (line[0] != '\0')
+                        *(line++) = '\0';
+
+#if 0 /* unused so far */
+                if (flags & PARSE_ESCAPE) {
+                        const char *from;
+                        char *to;
+
+                        from = to = tokens[t];
+                        while (*from) {
+                                if (*from == '\\') {
+                                        from++;
+                                        *to++ = bb_process_escape_sequence(&from);
+                                } else {
+                                        *to++ = *from++;
                                 }
-                                *line = '\0';
                         }
-#endif
+                        *to = '\0';
                 }
-                line = q;
-                //bb_info_msg("A[%s]", line);
+#endif
+
+                /* Skip possible delimiters */
+                if (flags & PARSE_COLLAPSE)
+                        line += strspn(line, delims + 1);
         }
 
-        if (ii < mintokens) {
+        if (t < mintokens) {
                 bb_error_msg("bad line %u: %d tokens found, %d needed",
-                                parser->lineno, ii, mintokens);
+                                parser->lineno, t, mintokens);
                 if (flags & PARSE_MIN_DIE)
                         xfunc_die();
-                ntokens++;
                 goto again;
         }
 
-        return ii;
+        return t;
 }