Hi,
the file less/line.c currently contains three copies of code to
step one multibyte character to the left in a char * buffer, and
cleaning up the file less/cmdbuf.c will require similar functionality
in the future. So let's introduce a new function for that purpose.
Keep it as similar as possible to the ANSI C function mbtowc(3).
Then again, there is no need to handle the case of the input char *
being NULL; for resetting, people should use mbtowc(3) itself, not
the new function.
The logic in less/cmdbuf.c is so contorted that cleaning that up
will still be challenging, but this at least provides one piece to
help with the puzzle.
Behaviour may change in LC_CTYPE=C mode if linebuf[curr-1] contains
an explicit '\0' byte. I think in that case, jumping out of the
backc() function, just like it is already done for UTF-8 mode, i.e.
not trying to back up across the NUL byte, is more robust behaviour.
Either way, linebuf[] is not supposed to contain NUL bytes except
in -r mode, and -r mode is almost unusable in the first place.
No other functional change is intended.
Minus 16 lines of code, by the way...
OK?
Ingo
Index: charset.c
===================================================================
RCS file: /cvs/src/usr.bin/less/charset.c,v
retrieving revision 1.24
diff -u -p -r1.24 charset.c
--- charset.c 15 May 2019 19:36:20 -0000 1.24
+++ charset.c 30 Aug 2019 13:02:01 -0000
@@ -146,6 +146,27 @@ init_charset(void)
}
/*
+ * Like mbtowc(3), except that it converts the multibyte character
+ * preceding ps rather than the one starting at ps.
+ */
+int
+mbtowc_left(wchar_t *pwc, const char *ps, size_t psz)
+{
+ size_t sz = 0;
+ int len;
+
+ do {
+ if (++sz > psz)
+ return -1;
+ } while (utf_mode && IS_UTF8_TRAIL(ps[-sz]));
+ if ((len = mbtowc(pwc, ps - sz, sz)) == -1) {
+ (void)mbtowc(NULL, NULL, 0);
+ return -1;
+ }
+ return len == sz || (len == 0 && sz == 1) ? len : -1;
+}
+
+/*
* Is a given character a "control" character?
*/
static int
Index: funcs.h
===================================================================
RCS file: /cvs/src/usr.bin/less/funcs.h,v
retrieving revision 1.23
diff -u -p -r1.23 funcs.h
--- funcs.h 15 May 2019 19:36:20 -0000 1.23
+++ funcs.h 30 Aug 2019 13:02:02 -0000
@@ -55,6 +55,7 @@ void ch_set_eof(void);
void ch_init(int, int);
void ch_close(void);
int ch_getflags(void);
+int mbtowc_left(wchar_t *, const char *, size_t);
void init_charset(void);
char *prchar(LWCHAR);
char *prutfchar(LWCHAR);
Index: line.c
===================================================================
RCS file: /cvs/src/usr.bin/less/line.c,v
retrieving revision 1.31
diff -u -p -r1.31 line.c
--- line.c 15 May 2019 19:06:01 -0000 1.31
+++ line.c 30 Aug 2019 13:02:02 -0000
@@ -437,44 +437,20 @@ backc(void)
wchar_t ch, prev_ch;
int i, len, width;
- i = curr - 1;
- if (utf_mode) {
- while (i >= lmargin && IS_UTF8_TRAIL(linebuf[i]))
- i--;
- }
- if (i < lmargin)
+ if ((len = mbtowc_left(&ch, linebuf + curr, curr)) <= 0)
return (0);
- if (utf_mode) {
- len = mbtowc(&ch, linebuf + i, curr - i);
- if (len == -1 || i + len < curr) {
- (void)mbtowc(NULL, NULL, MB_CUR_MAX);
- return (0);
- }
- } else
- ch = linebuf[i];
+ curr -= len;
/* This assumes that there is no '\b' in linebuf. */
- while (curr > lmargin && column > lmargin &&
- (!(attr[curr - 1] & (AT_ANSI|AT_BINARY)))) {
- curr = i--;
- if (utf_mode) {
- while (i >= lmargin && IS_UTF8_TRAIL(linebuf[i]))
- i--;
- }
- if (i < lmargin)
+ while (curr >= lmargin && column > lmargin &&
+ !(attr[curr] & (AT_ANSI|AT_BINARY))) {
+ if ((len = mbtowc_left(&prev_ch, linebuf + curr, curr)) <= 0)
prev_ch = L'\0';
- else if (utf_mode) {
- len = mbtowc(&prev_ch, linebuf + i, curr - i);
- if (len == -1 || i + len < curr) {
- (void)mbtowc(NULL, NULL, MB_CUR_MAX);
- prev_ch = L'\0';
- }
- } else
- prev_ch = linebuf[i];
width = pwidth(ch, attr[curr], prev_ch);
column -= width;
if (width > 0)
return (1);
+ curr -= len;
if (prev_ch == L'\0')
return (0);
ch = prev_ch;
@@ -554,21 +530,8 @@ store_char(LWCHAR ch, char a, char *rep,
}
if (w == -1) {
wchar_t prev_ch;
-
- if (utf_mode) {
- for (i = curr - 1; i >= 0; i--)
- if (!IS_UTF8_TRAIL(linebuf[i]))
- break;
- if (i >= 0) {
- w = mbtowc(&prev_ch, linebuf + i, curr - i);
- if (w == -1 || i + w < curr) {
- (void)mbtowc(NULL, NULL, MB_CUR_MAX);
- prev_ch = L' ';
- }
- } else
- prev_ch = L' ';
- } else
- prev_ch = curr > 0 ? linebuf[curr - 1] : L' ';
+ if (mbtowc_left(&prev_ch, linebuf + curr, curr) <= 0)
+ prev_ch = L' ';
w = pwidth(ch, a, prev_ch);
}
