telnet: speed up processing of network input

function                                             old     new   delta
telnet_main                                         1482    1492     +10

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/networking/telnet.c b/networking/telnet.c
index 7f65ff3e69e9e0521e8acddd40767d3723032757..0ee65c5321ea19be8267deeb1f7a804a7dce3143 100644 (file)
--- a/networking/telnet.c
+++ b/networking/telnet.c
@@ -94,19 +94,19 @@ enum {
        IACBUFSIZE  = 128,
 
        CHM_TRY = 0,
-       CHM_ON = 1,
+       CHM_ON  = 1,
        CHM_OFF = 2,
 
        UF_ECHO = 0x01,
-       UF_SGA = 0x02,
+       UF_SGA  = 0x02,
 
        TS_NORMAL = 0,
        TS_COPY = 1,
-       TS_IAC = 2,
-       TS_OPT = 3,
+       TS_IAC  = 2,
+       TS_OPT  = 3,
        TS_SUB1 = 4,
        TS_SUB2 = 5,
-       TS_CR = 6,
+       TS_CR   = 6,
 };
 
 typedef unsigned char byte;
@@ -244,25 +244,34 @@ static void handle_net_output(int len)
 
 static void handle_net_input(int len)
 {
+       byte c;
        int i;
-       int cstart = 0;
-
-       for (i = 0; i < len; i++) {
-               byte c = G.buf[i];
-
-               if (G.telstate == TS_NORMAL) { /* most typical state */
-                       if (c == IAC) {
-                               cstart = i;
-                               G.telstate = TS_IAC;
-                       }
-                       else if (c == '\r') {
-                               cstart = i + 1;
-                               G.telstate = TS_CR;
-                       }
-                       /* No IACs were seen so far, no need to copy
-                        * bytes within G.buf: */
-                       continue;
+       int cstart;
+
+       i = 0;
+       //bb_error_msg("[%u,'%.*s']", G.telstate, len, G.buf);
+       if (G.telstate == TS_NORMAL) { /* most typical state */
+               while (i < len) {
+                       c = G.buf[i];
+                       i++;
+                       if (c == IAC) /* unlikely */
+                               goto got_IAC;
+                       if (c != '\r') /* likely */
+                               continue;
+                       G.telstate = TS_CR;
+                       cstart = i;
+                       goto got_special;
                }
+               full_write(STDOUT_FILENO, G.buf, len);
+               return;
+ got_IAC:
+               G.telstate = TS_IAC;
+               cstart = i - 1;
+ got_special: ;
+       }
+
+       for (; i < len; i++) {
+               c = G.buf[i];
 
                switch (G.telstate) {
                case TS_CR:
@@ -278,20 +287,19 @@ static void handle_net_input(int len)
                        /* Similar to NORMAL, but in TS_COPY we need to copy bytes */
                        if (c == IAC)
                                G.telstate = TS_IAC;
-                       else
+                       else {
                                G.buf[cstart++] = c;
-                       if (c == '\r')
-                               G.telstate = TS_CR;
+                               if (c == '\r')
+                                       G.telstate = TS_CR;
+                       }
                        break;
 
                case TS_IAC: /* Prev char was IAC */
-                       if (c == IAC) { /* IAC IAC -> one IAC */
+                       switch (c) {
+                       case IAC: /* IAC IAC -> one IAC */
                                G.buf[cstart++] = c;
                                G.telstate = TS_COPY;
                                break;
-                       }
-                       /* else */
-                       switch (c) {
                        case SB:
                                G.telstate = TS_SUB1;
                                break;
@@ -320,17 +328,12 @@ static void handle_net_input(int len)
                }
        }
 
-       if (G.telstate != TS_NORMAL) {
-               /* We had some IACs, or CR */
-               if (G.iaclen)
-                       iac_flush();
-               if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
-                       G.telstate = TS_NORMAL;
-               len = cstart;
-       }
-
-       if (len)
-               full_write(STDOUT_FILENO, G.buf, len);
+       /* We had some IACs, or CR */
+       iac_flush();
+       if (G.telstate == TS_COPY) /* we aren't in the middle of IAC */
+               G.telstate = TS_NORMAL;
+       if (cstart != 0)
+               full_write(STDOUT_FILENO, G.buf, cstart);
 }
 
 static void put_iac(int c)