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, 23 insertions, 7 deletions

diff --git a/libbb/get_line_from_file.c b/libbb/get_line_from_file.c
index 968d7572d..3cb46d240 100644
--- a/libbb/get_line_from_file.c
+++ b/libbb/get_line_from_file.c
@@ -9,18 +9,22 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-/* for getline() [GNUism] */
+/* for getline() [GNUism]
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE 1
 #endif
+*/
 #include "libbb.h"
 
 /* This function reads an entire line from a text file, up to a newline
  * or NUL byte, inclusive.  It returns a malloc'ed char * which
  * must be free'ed by the caller.  If end is NULL '\n' isn't considered
- * end of line.  If end isn't NULL, length of the chunk read is stored in it.
- * Return NULL if EOF/error */
-char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
+ * end of line.  If end isn't NULL, length of the chunk is stored in it.
+ * If lineno is not NULL, *lineno is incremented for each line,
+ * and also trailing '\' is recognized as line continuation.
+ *
+ * Returns NULL if EOF/error. */
+char* FAST_FUNC bb_get_chunk_with_continuation(FILE *file, int *end, int *lineno)
 {
 	int ch;
 	int idx = 0;
@@ -30,12 +34,20 @@ char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
 	while ((ch = getc(file)) != EOF) {
 		/* grow the line buffer as necessary */
 		if (idx >= linebufsz) {
-			linebufsz += 80;
+			linebufsz += 256;
 			linebuf = xrealloc(linebuf, linebufsz);
 		}
 		linebuf[idx++] = (char) ch;
-		if (!ch || (end && ch == '\n'))
+		if (!ch)
 			break;
+		if (end && ch == '\n') {
+			if (lineno == NULL)
+				break;
+			(*lineno)++;
+			if (idx < 2 || linebuf[idx-2] != '\\')
+				break;
+			idx -= 2;
+		}
 	}
 	if (end)
 		*end = idx;
@@ -52,6 +64,11 @@ char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
 	return linebuf;
 }
 
+char* FAST_FUNC bb_get_chunk_from_file(FILE *file, int *end)
+{
+	return bb_get_chunk_with_continuation(file, end, NULL);
+}
+
 /* Get line, including trailing \n if any */
 char* FAST_FUNC xmalloc_fgets(FILE *file)
 {
@@ -72,7 +89,6 @@ char* FAST_FUNC xmalloc_fgetline(FILE *file)
 }
 
 #if 0
-
 /* GNUism getline() should be faster (not tested) than a loop with fgetc */
 
 /* Get line, including trailing \n if any */