Add support for enabling/disabling utf - st - Simple Terminal

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---

commit f0e2d28732549690466df995981698173daf39c0

parent 078337d7457f7869a85f4ec364be92b79e93c502

Author: Roberto E. Vargas Caballero 

Date:   Tue, 13 Sep 2016 14:01:18 +0200

Add support for enabling/disabling utf

There are some ocasions where we want to disable the enconding/decoding of utf8, mainly
because it adds an important overhead. This is partial patch for ESC % G and ESC % @,
where they modified the way that st reads and write from/to the serial line, but it does
not modifies how it interacts with the X window part.

Diffstat:
  st.c                                |      79 ++++++++++++++++++++++++-------

1 file changed, 62 insertions(+), 17 deletions(-)
---

diff --git a/st.c b/st.c

@@ -137,6 +137,7 @@ enum term_mode {
         MODE_MOUSEMANY   = 1 << 18,
         MODE_BRCKTPASTE  = 1 << 19,
         MODE_PRINT       = 1 << 20,
+        MODE_UTF8        = 1 << 21,
         MODE_MOUSE       = MODE_MOUSEBTN|MODE_MOUSEMOTION|MODE_MOUSEX10\
                           |MODE_MOUSEMANY,
 };
@@ -158,6 +159,7 @@ enum escape_state {
         ESC_ALTCHARSET = 8,
         ESC_STR_END    = 16, /* a final string was encountered */
         ESC_TEST       = 32, /* Enter in test mode */
+        ESC_UTF8       = 64,
 };
 
 enum window_state {
@@ -412,6 +414,7 @@ static void tfulldirt(void);
 static void techo(Rune);
 static void tcontrolcode(uchar );
 static void tdectest(char );
+static void tdefutf8(char);
 static int32_t tdefcolor(int *, int *, int);
 static void tdeftran(char);
 static inline int match(uint, uint);
@@ -1478,17 +1481,29 @@ ttyread(void)
         if ((ret = read(cmdfd, buf+buflen, LEN(buf)-buflen)) < 0)
                 die("Couldn't read from shell: %s\n", strerror(errno));
 
-        /* process every complete utf8 char */
         buflen += ret;
         ptr = buf;
-        while ((charsize = utf8decode(ptr, &unicodep, buflen))) {
-                tputc(unicodep);
-                ptr += charsize;
-                buflen -= charsize;
-        }
 
+        for (;;) {
+                if (IS_SET(MODE_UTF8)) {
+                        /* process a complete utf8 char */
+                        charsize = utf8decode(ptr, &unicodep, buflen);
+                        if (charsize == 0)
+                                break;
+                        tputc(unicodep);
+                        ptr += charsize;
+                        buflen -= charsize;
+
+                } else {
+                        if (buflen <= 0)
+                                break;
+                        tputc(*ptr++ & 0xFF);
+                        buflen--;
+                }
+        }
         /* keep any uncomplete utf8 char for the next call */
-        memmove(buf, ptr, buflen);
+        if (buflen > 0)
+                memmove(buf, ptr, buflen);
 
         return ret;
 }
@@ -1554,15 +1569,26 @@ void
 tttysend(char *s, size_t n)
 {
         int len;
+        char *t, *lim;
         Rune u;
 
         ttywrite(s, n);
-        if (IS_SET(MODE_ECHO))
-                while ((len = utf8decode(s, &u, n)) > 0) {
-                        techo(u);
-                        n -= len;
-                        s += len;
+        if (!IS_SET(MODE_ECHO))
+                return;
+
+        lim = &s[n];
+        for (t = s; t < lim; t += len) {
+                if (IS_SET(MODE_UTF8)) {
+                        len = utf8decode(t, &u, n);
+                } else {
+                        u = *t & 0xFF;
+                        len = 1;
                 }
+                if (len <= 0)
+                        break;
+                techo(u);
+                n -= len;
+        }
 }
 
 void
@@ -1656,7 +1682,7 @@ treset(void)
                 term.tabs[i] = 1;
         term.top = 0;
         term.bot = term.row - 1;
-        term.mode = MODE_WRAP;
+        term.mode = MODE_WRAP|MODE_UTF8;
         memset(term.trantbl, CS_USA, sizeof(term.trantbl));
         term.charset = 0;
 
@@ -2690,6 +2716,15 @@ techo(Rune u)
 }
 
 void
+ttdefutf8(char ascii)
+{
+        if (ascii == 'G')
+                term.mode |= MODE_UTF8;
+        else if (ascii == '@')
+                term.mode &= ~MODE_UTF8;
+}
+
+void
 ttdeftran(char ascii)
 {
         static char cs[] = "0B";
@@ -2851,6 +2886,9 @@ eschandle(uchar ascii)
         case '#':
                 term.esc |= ESC_TEST;
                 return 0;
+        case '%':
+                term.esc |= ESC_UTF8;
+                return 0;
         case 'P': /* DCS -- Device Control String */
         case '_': /* APC -- Application Program Command */
         case '^': /* PM -- Privacy Message */
@@ -2930,10 +2968,15 @@ tputc(Rune u)
         Glyph *gp;
 
         control = ISCONTROL(u);
-        len = utf8encode(u, c);
-        if (!control && (width = wcwidth(u)) == -1) {
-                memcpy(c, "\357\277\275", 4); /* UTF_INVALID */
-                width = 1;
+        if (!IS_SET(MODE_UTF8)) {
+                c[0] = u;
+                width = len = 1;
+        } else {
+                len = utf8encode(u, c);
+                if (!control && (width = wcwidth(u)) == -1) {
+                        memcpy(c, "\357\277\275", 4); /* UTF_INVALID */
+                        width = 1;
+                }
         }
 
         if (IS_SET(MODE_PRINT))
@@ -2994,6 +3037,8 @@ tputc(Rune u)
                                 csihandle();
                         }
                         return;
+                } else if (term.esc & ESC_UTF8) {
+                        tdefutf8(u);
                 } else if (term.esc & ESC_ALTCHARSET) {
                         tdeftran(u);
                 } else if (term.esc & ESC_TEST) {