hush: rework input char buffering to allow more than one-deep peek

...this time with actual hush.c changes too :)

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

1 files changed, 125 insertions, 68 deletions

diff --git a/shell/hush.c b/shell/hush.c
index d7d152c10..e3dcf2c38 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -462,19 +462,19 @@ static const char *const assignment_flag[] = {
 
 typedef struct in_str {
         const char *p;
-        /* eof_flag=1: last char in ->p is really an EOF */
-        char eof_flag; /* meaningless if ->p == NULL */
-        char peek_buf[2];
 #if ENABLE_HUSH_INTERACTIVE
         smallint promptmode; /* 0: PS1, 1: PS2 */
 #endif
+        int peek_buf[2];
         int last_char;
         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_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 */
@@ -2122,28 +2122,11 @@ static void reinit_unicode_for_hush(void)
         }
 }
 
-
 /*
- * in_str support
+ * in_str support (strings, and "strings" read from files).
  */
-static int FAST_FUNC static_get(struct in_str *i)
-{
-        int ch = *i->p;
-        if (ch != '\0') {
-                i->p++;
-                i->last_char = ch;
-                return ch;
-        }
-        return EOF;
-}
-
-static int FAST_FUNC static_peek(struct in_str *i)
-{
-        return *i->p;
-}
 
 #if ENABLE_HUSH_INTERACTIVE
-
 static void cmdedit_update_prompt(void)
 {
         if (ENABLE_FEATURE_EDITING_FANCY_PROMPT) {
@@ -2157,7 +2140,6 @@ static void cmdedit_update_prompt(void)
         if (G.PS2 == NULL)
                 G.PS2 = "> ";
 }
-
 static const char *setup_prompt_string(int promptmode)
 {
         const char *prompt_str;
@@ -2178,8 +2160,7 @@ static const char *setup_prompt_string(int promptmode)
         debug_printf("result '%s'\n", prompt_str);
         return prompt_str;
 }
-
-static void get_user_input(struct in_str *i)
+static int get_user_input(struct in_str *i)
 {
         int r;
         const char *prompt_str;
@@ -2197,11 +2178,14 @@ static void 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->eof_flag = (r < 0);
-        if (i->eof_flag) { /* EOF/error detected */
-                G.user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
-                G.user_input_buf[1] = '\0';
+        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;
+                return r;
         }
+        return (unsigned char)*i->p++;
 # else
         do {
                 G.flag_SIGINT = 0;
@@ -2215,14 +2199,11 @@ static void get_user_input(struct in_str *i)
                         fputs(prompt_str, stdout);
                 }
                 fflush_all();
-                G.user_input_buf[0] = r = fgetc(i->file);
-                /*G.user_input_buf[1] = '\0'; - already is and never changed */
-        } while (G.flag_SIGINT);
-        i->eof_flag = (r == EOF);
+                r = fgetc(i->file);
+        } while (G.flag_SIGINT || r == '\0');
+        return r;
 # endif
-        i->p = G.user_input_buf;
 }
-
 #endif  /* INTERACTIVE */
 
 /* This is the magic location that prints prompts
@@ -2232,28 +2213,36 @@ static int FAST_FUNC file_get(struct in_str *i)
         int ch;
 
         /* If there is data waiting, eat it up */
-        if (i->p && *i->p) {
-#if ENABLE_HUSH_INTERACTIVE
- take_cached:
-#endif
-                ch = *i->p++;
-                if (i->eof_flag && !*i->p)
-                        ch = EOF;
-                /* note: ch is never NUL */
-        } else {
-                /* need to double check i->file because we might be doing something
-                 * more complicated by now, like sourcing or substituting. */
+        /* peek_buf[] is an int array, not char. Can contain EOF. */
+        ch = i->peek_buf[0];
+        if (ch != '\0') {
+                int ch2 = i->peek_buf[1];
+                i->peek_buf[0] = ch2;
+                if (ch2 == 0) /* very likely, avoid redundant write */
+                        goto out;
+                i->peek_buf[1] = 0;
+                goto out;
+        }
+
 #if ENABLE_HUSH_INTERACTIVE
-                if (G_interactive_fd && i->file == stdin) {
-                        do {
-                                get_user_input(i);
-                        } while (!*i->p); /* need non-empty line */
-                        i->promptmode = 1; /* PS2 */
-                        goto take_cached;
-                }
-#endif
-                do ch = fgetc(i->file); while (ch == '\0');
+        /* 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');
+ out:
         debug_printf("file_get: got '%c' %d\n", ch, ch);
         i->last_char = ch;
         return ch;
@@ -2265,26 +2254,82 @@ static int FAST_FUNC file_get(struct in_str *i)
 static int FAST_FUNC file_peek(struct in_str *i)
 {
         int ch;
-        if (i->p && *i->p) {
-                if (i->eof_flag && !i->p[1])
-                        return EOF;
-                return *i->p;
-                /* note: ch is never NUL */
-        }
+
+        /* 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
+        /* This can be stdin, check line editing char[] buffer */
+        if (i->p && *i->p != '\0')
+                return (unsigned char)*i->p;
+#endif
+
         do ch = fgetc(i->file); while (ch == '\0');
-        i->eof_flag = (ch == EOF);
         i->peek_buf[0] = ch;
-        i->peek_buf[1] = '\0';
-        i->p = i->peek_buf;
+        i->peek_buf[1] = 0;
         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;
+        }
+
+#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);
+        return ch;
+}
+
+static int FAST_FUNC static_get(struct in_str *i)
+{
+        int ch = *i->p;
+        if (ch != '\0') {
+                i->p++;
+                i->last_char = ch;
+                return ch;
+        }
+        return EOF;
+}
+
+static int FAST_FUNC static_peek(struct in_str *i)
+{
+        /* Doesn't report EOF on NUL. None of the callers care. */
+        return *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)
+{
+        return i->p[1];
+}
+
 static void setup_file_in_str(struct in_str *i, FILE *f)
 {
         memset(i, 0, sizeof(*i));
-        i->peek = file_peek;
         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; */
@@ -2293,11 +2338,11 @@ static void setup_file_in_str(struct in_str *i, FILE *f)
 static void setup_string_in_str(struct in_str *i, const char *s)
 {
         memset(i, 0, sizeof(*i));
-        i->peek = static_peek;
         i->get = static_get;
+        i->peek = static_peek;
+        i->peek2 = static_peek2;
         /* i->promptmode = 0; - PS1 (memset did it) */
         i->p = s;
-        /* i->eof_flag = 0; */
 }
 
 
@@ -4040,9 +4085,21 @@ static int parse_dollar(o_string *as_string,
                         debug_printf_parse(": '%c'\n", ch);
                         o_addchr(dest, ch | quote_mask);
                         quote_mask = 0;
+ next_ch:
                         ch = i_peek(input);
-                        if (!isalnum(ch) && ch != '_')
+                        if (!isalnum(ch) && ch != '_') {
+                                if (ch == '\\') {
+                                        /* If backslash+newline, skip it */
+                                        int ch2 = i_peek2(input);
+                                        if (ch2 == '\n') {
+                                                i_getch(input);
+                                                i_getch(input);
+                                                goto next_ch;
+                                        }
+                                }
+                                /* End of variable name reached */
                                 break;
+                        }
                         ch = i_getch(input);
                         nommu_addchr(as_string, ch);
                 }