hush: fix interactive input handling of backslash+newline

function                                             old     new   delta
fgetc_interactive                                      -     258    +258
i_peek_and_eat_bkslash_nl                             43      93     +50
static_peek2                                           7       -      -7
setup_string_in_str                                   46      39      -7
setup_file_in_str                                     47      40      -7
file_peek                                             72      52     -20
expand_vars_to_list                                 1167    1143     -24
file_peek2                                            74       -     -74
file_get                                             326      65    -261
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 1/5 up/down: 308/-400)          Total: -92 bytes

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

1 files changed, 89 insertions, 74 deletions

diff --git a/shell/hush.c b/shell/hush.c
index d0b53339d..1674598b6 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -470,11 +470,9 @@ typedef struct in_str {
         FILE *file;
         int (*get) (struct in_str *) FAST_FUNC;
         int (*peek) (struct in_str *) FAST_FUNC;
-        int (*peek2) (struct in_str *) FAST_FUNC;
 } in_str;
 #define i_getch(input) ((input)->get(input))
 #define i_peek(input)  ((input)->peek(input))
-#define i_peek2(input) ((input)->peek2(input))
 
 /* The descrip member of this structure is only used to make
  * debugging output pretty */
@@ -2129,6 +2127,14 @@ static void reinit_unicode_for_hush(void)
  */
 
 #if ENABLE_HUSH_INTERACTIVE
+/* To test correct lineedit/interactive behavior, type from command line:
+ *      echo $P\
+ *      \
+ *      AT\
+ *      H\
+ *      \
+ * It excercises a lot of corner cases.
+ */
 static void cmdedit_update_prompt(void)
 {
         if (ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
@@ -2159,7 +2165,7 @@ static const char *setup_prompt_string(int promptmode)
                         prompt_str = G.PS2;
         } else
                 prompt_str = (promptmode == 0) ? G.PS1 : G.PS2;
-        debug_printf("result '%s'\n", prompt_str);
+        debug_printf("prompt_str '%s'\n", prompt_str);
         return prompt_str;
 }
 static int get_user_input(struct in_str *i)
@@ -2169,8 +2175,6 @@ static int get_user_input(struct in_str *i)
 
         prompt_str = setup_prompt_string(i->promptmode);
 # if ENABLE_FEATURE_EDITING
-        /* Enable command line editing only while a command line
-         * is actually being read */
         do {
                 reinit_unicode_for_hush();
                 G.flag_SIGINT = 0;
@@ -2183,13 +2187,13 @@ static int get_user_input(struct in_str *i)
                 /* catch *SIGINT* etc (^C is handled by read_line_input) */
                 check_and_run_traps();
         } while (r == 0 || G.flag_SIGINT); /* repeat if ^C or SIGINT */
-        i->p = G.user_input_buf;
         if (r < 0) {
                 /* EOF/error detected */
-                G.user_input_buf[0] = '\0';
-                i->peek_buf[1] = i->peek_buf[0] = r = EOF;
+                i->p = NULL;
+                i->peek_buf[0] = r = EOF;
                 return r;
         }
+        i->p = G.user_input_buf;
         return (unsigned char)*i->p++;
 # else
         do {
@@ -2209,18 +2213,45 @@ static int get_user_input(struct in_str *i)
         return r;
 # endif
 }
-#endif  /* INTERACTIVE */
-
 /* This is the magic location that prints prompts
  * and gets data back from the user */
+static int fgetc_interactive(struct in_str *i)
+{
+        int ch;
+        /* If it's interactive stdin, get new line. */
+        if (G_interactive_fd && i->file == stdin) {
+                /* Returns first char (or EOF), the rest is in i->p[] */
+                ch = get_user_input(i);
+                i->promptmode = 1; /* PS2 */
+        } else {
+                /* Not stdin: script file, sourced file, etc */
+                do ch = fgetc(i->file); while (ch == '\0');
+        }
+        return ch;
+}
+#else
+static inline int fgetc_interactive(struct in_str *i)
+{
+        int ch;
+        do ch = fgetc(i->file); while (ch == '\0');
+        return ch;
+}
+#endif  /* INTERACTIVE */
+
 static int FAST_FUNC file_get(struct in_str *i)
 {
         int ch;
 
-        /* If there is data waiting, eat it up */
+#if ENABLE_FEATURE_EDITING
+        /* This can be stdin, check line editing char[] buffer */
+        if (i->p && *i->p != '\0') {
+                ch = (unsigned char)*i->p++;
+                goto out;
+        }
+#endif
         /* peek_buf[] is an int array, not char. Can contain EOF. */
         ch = i->peek_buf[0];
-        if (ch != '\0') {
+        if (ch != 0) {
                 int ch2 = i->peek_buf[1];
                 i->peek_buf[0] = ch2;
                 if (ch2 == 0) /* very likely, avoid redundant write */
@@ -2229,86 +2260,46 @@ static int FAST_FUNC file_get(struct in_str *i)
                 goto out;
         }
 
-#if ENABLE_HUSH_INTERACTIVE
-        /* This can be stdin, check line editing char[] buffer */
-        if (i->p && *i->p != '\0') {
-                ch = (unsigned char)*i->p++;
-                goto out;
-        }
-        /* It's empty.
-         * If it's interactive stdin, get new line.
-         */
-        if (G_interactive_fd && i->file == stdin) {
-                /* Returns first char (or EOF), the rest are in i->p[] */
-                ch = get_user_input(i);
-                i->promptmode = 1; /* PS2 */
-                goto out;
-        }
-        /* Not stdin: script file */
-#endif
-        do ch = fgetc(i->file); while (ch == '\0');
+        ch = fgetc_interactive(i);
  out:
         debug_printf("file_get: got '%c' %d\n", ch, ch);
         i->last_char = ch;
         return ch;
 }
 
-/* All callers guarantee this routine will never
- * be used right after a newline, so prompting is not needed.
- */
 static int FAST_FUNC file_peek(struct in_str *i)
 {
         int ch;
 
-        /* peek_buf[] is an int array, not char. Can contain EOF. */
-        ch = i->peek_buf[0];
-        if (ch != '\0')
-                return ch;
-
-#if ENABLE_HUSH_INTERACTIVE
+#if ENABLE_FEATURE_EDITING && ENABLE_HUSH_INTERACTIVE
         /* This can be stdin, check line editing char[] buffer */
         if (i->p && *i->p != '\0')
                 return (unsigned char)*i->p;
 #endif
+        /* peek_buf[] is an int array, not char. Can contain EOF. */
+        ch = i->peek_buf[0];
+        if (ch != 0)
+                return ch;
 
-        do ch = fgetc(i->file); while (ch == '\0');
-        i->peek_buf[0] = ch;
-        i->peek_buf[1] = 0;
+        /* Need to get a new char */
+        ch = fgetc_interactive(i);
         debug_printf("file_peek: got '%c' %d\n", ch, ch);
-        return ch;
-}
 
-/* Only ever called if i_peek() was called, and did not return EOF */
-static int FAST_FUNC file_peek2(struct in_str *i)
-{
-        int ch;
-
-        /* peek_buf[] is an int array, not char. Can contain EOF. */
-        ch = i->peek_buf[0];
-        if (ch != 0) {
-                /* peek_buf[] is not empty. Is there 2nd char? */
-                ch = i->peek_buf[1];
-                if (ch == 0) {
-                        /* We did not read it yet, get it now */
-                        do ch = fgetc(i->file); while (ch == '\0');
-                        i->peek_buf[1] = ch;
-                }
-                goto out;
+        /* Save it by either rolling back line editing buffer, or in i->peek_buf[0] */
+#if ENABLE_FEATURE_EDITING && ENABLE_HUSH_INTERACTIVE
+        if (i->p) {
+                i->p -= 1;
+                return ch;
         }
-
-#if ENABLE_HUSH_INTERACTIVE
-        /* This can be stdin, check line editing char[] buffer */
-        if (i->p && i->p[0] != '\0')
-                ch = i->p[1];
 #endif
- out:
-        debug_printf("file_peek2: got '%c' %d\n", ch, ch);
+        i->peek_buf[0] = ch;
+        /*i->peek_buf[1] = 0; - already is */
         return ch;
 }
 
 static int FAST_FUNC static_get(struct in_str *i)
 {
-        int ch = *i->p;
+        int ch = (unsigned char)*i->p;
         if (ch != '\0') {
                 i->p++;
                 i->last_char = ch;
@@ -2320,13 +2311,39 @@ static int FAST_FUNC static_get(struct in_str *i)
 static int FAST_FUNC static_peek(struct in_str *i)
 {
         /* Doesn't report EOF on NUL. None of the callers care. */
-        return *i->p;
+        return (unsigned char)*i->p;
 }
 
-/* Only ever called if i_peek() was called, and did not return EOF */
-static int FAST_FUNC static_peek2(struct in_str *i)
+/* Only ever called if i_peek() was called, and did not return EOF.
+ * IOW: we know the previous peek saw an ordinary char, not EOF, not NUL,
+ * not end-of-line. Therefore we never need to read a new editing line here.
+ */
+static int i_peek2(struct in_str *i)
 {
-        return i->p[1];
+        int ch;
+
+        /* There are two cases when i->p[] buffer exists.
+         * (1) it's a string in_str.
+         * (2) It's a file, and we have s saved line editing buffer.
+         * In both cases, we know that i->p[0] exists and not NUL, and
+         * the peek2 result is in i->p[1].
+         */
+        if (i->p)
+                return (unsigned char)i->p[1];
+
+        /* Now we know it is a file-based in_str. */
+
+        /* peek_buf[] is an int array, not char. Can contain EOF. */
+        /* Is there 2nd char? */
+        ch = i->peek_buf[1];
+        if (ch == 0) {
+                /* We did not read it yet, get it now */
+                do ch = fgetc(i->file); while (ch == '\0');
+                i->peek_buf[1] = ch;
+        }
+
+        debug_printf("file_peek2: got '%c' %d\n", ch, ch);
+        return ch;
 }
 
 static void setup_file_in_str(struct in_str *i, FILE *f)
@@ -2334,7 +2351,6 @@ static void setup_file_in_str(struct in_str *i, FILE *f)
         memset(i, 0, sizeof(*i));
         i->get = file_get;
         i->peek = file_peek;
-        i->peek2 = file_peek2;
         /* i->promptmode = 0; - PS1 (memset did it) */
         i->file = f;
         /* i->p = NULL; */
@@ -2345,7 +2361,6 @@ static void setup_string_in_str(struct in_str *i, const char *s)
         memset(i, 0, sizeof(*i));
         i->get = static_get;
         i->peek = static_peek;
-        i->peek2 = static_peek2;
         /* i->promptmode = 0; - PS1 (memset did it) */
         i->p = s;
 }