read_key: ignore unknown keys (do not return them to caller byte-by-byte)

function                                             old     new   delta
read_key                                             568     601     +33

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

diff --git a/libbb/read_key.c b/libbb/read_key.c
index 02c381dd5237235e8f2dc1b66d53b2c689bfe45f..ec1b3a4a846b4c390312086682265bda2d1e6283 100644 (file)
--- a/libbb/read_key.c
+++ b/libbb/read_key.c
@@ -14,7 +14,6 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
        struct pollfd pfd;
        const char *seq;
        int n;
-       int c;
 
        /* Known escape sequences for cursor and function keys */
        static const char esccmds[] ALIGN1 = {
@@ -91,8 +90,11 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
                /* ESC [ Z - Shift-Tab */
        };
 
+       buffer++; /* saved chars counter is in buffer[-1] now */
+
+ start_over:
        errno = 0;
-       n = (unsigned char) *buffer++;
+       n = (unsigned char)buffer[-1];
        if (n == 0) {
                /* If no data, block waiting for input.
                 * It is tempting to read more than one byte here,
@@ -106,15 +108,17 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
                        return -1;
        }
 
-       /* Grab character to return from buffer */
-       c = (unsigned char)buffer[0];
-       n--;
-       if (n)
-               memmove(buffer, buffer + 1, n);
-
-       /* Only ESC starts ESC sequences */
-       if (c != 27)
-               goto ret;
+       {
+               unsigned char c = buffer[0];
+               n--;
+               if (n)
+                       memmove(buffer, buffer + 1, n);
+               /* Only ESC starts ESC sequences */
+               if (c != 27) {
+                       buffer[-1] = n;
+                       return c;
+               }
+       }
 
        /* Loop through known ESC sequences */
        pfd.fd = fd;
@@ -136,17 +140,21 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
                                if (safe_poll(&pfd, 1, 50) == 0) {
                                        /* No more data!
                                         * Array is sorted from shortest to longest,
-                                        * we can't match anything later in array,
-                                        * break out of both loops. */
-                                       goto ret;
+                                        * we can't match anything later in array -
+                                        * anything later is longer than this seq.
+                                        * Break out of both loops. */
+                                       goto got_all;
                                }
                                errno = 0;
                                if (safe_read(fd, buffer + n, 1) <= 0) {
                                        /* If EAGAIN, then fd is O_NONBLOCK and poll lied:
                                         * in fact, there is no data. */
-                                       if (errno != EAGAIN)
-                                               c = -1; /* otherwise it's EOF/error */
-                                       goto ret;
+                                       if (errno != EAGAIN) {
+                                               /* otherwise: it's EOF/error */
+                                               buffer[-1] = 0;
+                                               return -1;
+                                       }
+                                       goto got_all;
                                }
                                n++;
                        }
@@ -162,66 +170,82 @@ int64_t FAST_FUNC read_key(int fd, char *buffer)
                        }
                        if (seq[i] & 0x80) {
                                /* Entire seq matched */
-                               c = (signed char)seq[i+1];
                                n = 0;
                                /* n -= i; memmove(...);
                                 * would be more correct,
                                 * but we never read ahead that much,
                                 * and n == i here. */
-                               goto ret;
+                               buffer[-1] = 0;
+                               return (signed char)seq[i+1];
                        }
                        i++;
                }
        }
-       /* We did not find matching sequence, it was a bare ESC.
-        * We possibly read and stored more input in buffer[] by now. */
+       /* We did not find matching sequence.
+        * We possibly read and stored more input in buffer[] by now.
+        * n = bytes read. Try to read more until we time out.
+        */
+       while (n < KEYCODE_BUFFER_SIZE-1) { /* 1 for count byte at buffer[-1] */
+               if (safe_poll(&pfd, 1, 50) == 0) {
+                       /* No more data! */
+                       break;
+               }
+               errno = 0;
+               if (safe_read(fd, buffer + n, 1) <= 0) {
+                       /* If EAGAIN, then fd is O_NONBLOCK and poll lied:
+                        * in fact, there is no data. */
+                       if (errno != EAGAIN) {
+                               /* otherwise: it's EOF/error */
+                               buffer[-1] = 0;
+                               return -1;
+                       }
+                       break;
+               }
+               n++;
+       }
+ got_all:
+
+       if (n <= 1) {
+               /* Alt-x is usually returned as ESC x.
+                * Report ESC, x is remembered for the next call.
+                */
+               buffer[-1] = n;
+               return 27;
+       }
 
        /* Try to decipher "ESC [ NNN ; NNN R" sequence */
        if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
-        && n != 0
+        && n >= 5
         && buffer[0] == '['
+        && isdigit(buffer[1])
+        && buffer[n-1] == 'R'
        ) {
                char *end;
                unsigned long row, col;
 
-               while (n < KEYCODE_BUFFER_SIZE-1) { /* 1 for cnt */
-                       if (safe_poll(&pfd, 1, 50) == 0) {
-                               /* No more data! */
-                               break;
-                       }
-                       errno = 0;
-                       if (safe_read(fd, buffer + n, 1) <= 0) {
-                               /* If EAGAIN, then fd is O_NONBLOCK and poll lied:
-                                * in fact, there is no data. */
-                               if (errno != EAGAIN)
-                                       c = -1; /* otherwise it's EOF/error */
-                               goto ret;
-                       }
-                       if (buffer[n++] == 'R')
-                               goto got_R;
-               }
-               goto ret;
- got_R:
-               if (!isdigit(buffer[1]))
-                       goto ret;
                row = strtoul(buffer + 1, &end, 10);
                if (*end != ';' || !isdigit(end[1]))
-                       goto ret;
+                       goto not_R;
                col = strtoul(end + 1, &end, 10);
                if (*end != 'R')
-                       goto ret;
+                       goto not_R;
                if (row < 1 || col < 1 || (row | col) > 0x7fff)
-                       goto ret;
+                       goto not_R;
 
                buffer[-1] = 0;
 
                /* Pack into "1 <row15bits> <col16bits>" 32-bit sequence */
-               c = (((-1 << 15) | row) << 16) | col;
+               col |= (((-1 << 15) | row) << 16);
                /* Return it in high-order word */
-               return ((int64_t) c << 32) | (uint32_t)KEYCODE_CURSOR_POS;
+               return ((int64_t) col << 32) | (uint32_t)KEYCODE_CURSOR_POS;
        }
+ not_R:
 
- ret:
-       buffer[-1] = n;
-       return c;
+       /* We were doing "buffer[-1] = n; return c;" here, but this results
+        * in unknown key sequences being interpreted as ESC + garbage.
+        * This was not useful. Pretend there was no key pressed,
+        * go and wait for a new keypress:
+        */
+       buffer[-1] = 0;
+       goto start_over;
 }