1 files changed, 43 insertions, 34 deletions

diff --git a/shell/ash.c b/shell/ash.c
index a31cee259..a63d40d7e 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -1168,6 +1168,12 @@ struct strpush {
         struct alias *ap;       /* if push was associated with an alias */
 #endif
         char *string;           /* remember the string since it may change */
+
+        /* Remember last two characters for pungetc. */
+        int lastc[2];
+
+        /* Number of outstanding calls to pungetc. */
+        int unget;
 };
 
 struct parsefile {
@@ -1180,6 +1186,12 @@ struct parsefile {
         char *buf;              /* input buffer */
         struct strpush *strpush; /* for pushing strings at this level */
         struct strpush basestrpush; /* so pushing one is fast */
+
+        /* Remember last two characters for pungetc. */
+        int lastc[2];
+
+        /* Number of outstanding calls to pungetc. */
+        int unget;
 };
 
 static struct parsefile basepf;        /* top level input file */
@@ -9715,6 +9727,8 @@ pushstring(char *s, struct alias *ap)
         g_parsefile->strpush = sp;
         sp->prev_string = g_parsefile->next_to_pgetc;
         sp->prev_left_in_line = g_parsefile->left_in_line;
+        sp->unget = g_parsefile->unget;
+        memcpy(sp->lastc, g_parsefile->lastc, sizeof(sp->lastc));
 #if ENABLE_ASH_ALIAS
         sp->ap = ap;
         if (ap) {
@@ -9724,6 +9738,7 @@ pushstring(char *s, struct alias *ap)
 #endif
         g_parsefile->next_to_pgetc = s;
         g_parsefile->left_in_line = len;
+        g_parsefile->unget = 0;
         INT_ON;
 }
 
@@ -9751,6 +9766,8 @@ popstring(void)
 #endif
         g_parsefile->next_to_pgetc = sp->prev_string;
         g_parsefile->left_in_line = sp->prev_left_in_line;
+        g_parsefile->unget = sp->unget;
+        memcpy(g_parsefile->lastc, sp->lastc, sizeof(sp->lastc));
         g_parsefile->strpush = sp->prev;
         if (sp != &(g_parsefile->basestrpush))
                 free(sp);
@@ -9846,13 +9863,14 @@ preadfd(void)
  */
 //#define pgetc_debug(...) bb_error_msg(__VA_ARGS__)
 #define pgetc_debug(...) ((void)0)
+static int pgetc(void);
 static int
 preadbuffer(void)
 {
         char *q;
         int more;
 
-        while (g_parsefile->strpush) {
+        if (g_parsefile->strpush) {
 #if ENABLE_ASH_ALIAS
                 if (g_parsefile->left_in_line == -1
                  && g_parsefile->strpush->ap
@@ -9864,13 +9882,7 @@ preadbuffer(void)
                 }
 #endif
                 popstring();
-                /* try "pgetc" now: */
-                pgetc_debug("preadbuffer internal pgetc at %d:%p'%s'",
-                                g_parsefile->left_in_line,
-                                g_parsefile->next_to_pgetc,
-                                g_parsefile->next_to_pgetc);
-                if (--g_parsefile->left_in_line >= 0)
-                        return (unsigned char)(*g_parsefile->next_to_pgetc++);
+                return pgetc();
         }
         /* on both branches above g_parsefile->left_in_line < 0.
          * "pgetc" needs refilling.
@@ -9949,27 +9961,28 @@ preadbuffer(void)
         return (unsigned char)*g_parsefile->next_to_pgetc++;
 }
 
-#define pgetc_as_macro() \
-        (--g_parsefile->left_in_line >= 0 \
-        ? (unsigned char)*g_parsefile->next_to_pgetc++ \
-        : preadbuffer() \
-        )
-
 static int
 pgetc(void)
 {
-        pgetc_debug("pgetc_fast at %d:%p'%s'",
+        int c;
+
+        pgetc_debug("pgetc at %d:%p'%s'",
                         g_parsefile->left_in_line,
                         g_parsefile->next_to_pgetc,
                         g_parsefile->next_to_pgetc);
-        return pgetc_as_macro();
-}
+        if (g_parsefile->unget)
+                return g_parsefile->lastc[--g_parsefile->unget];
 
-#if ENABLE_ASH_OPTIMIZE_FOR_SIZE
-# define pgetc_fast() pgetc()
-#else
-# define pgetc_fast() pgetc_as_macro()
-#endif
+        if (--g_parsefile->left_in_line >= 0)
+                c = (signed char)*g_parsefile->next_to_pgetc++;
+        else
+                c = preadbuffer();
+
+        g_parsefile->lastc[1] = g_parsefile->lastc[0];
+        g_parsefile->lastc[0] = c;
+
+        return c;
+}
 
 #if ENABLE_ASH_ALIAS
 static int
@@ -9977,11 +9990,11 @@ pgetc_without_PEOA(void)
 {
         int c;
         do {
-                pgetc_debug("pgetc_fast at %d:%p'%s'",
+                pgetc_debug("pgetc at %d:%p'%s'",
                                 g_parsefile->left_in_line,
                                 g_parsefile->next_to_pgetc,
                                 g_parsefile->next_to_pgetc);
-                c = pgetc_fast();
+                c = pgetc();
         } while (c == PEOA);
         return c;
 }
@@ -10015,18 +10028,13 @@ pfgets(char *line, int len)
 }
 
 /*
- * Undo the last call to pgetc.  Only one character may be pushed back.
+ * Undo a call to pgetc.  Only two characters may be pushed back.
  * PEOF may be pushed back.
  */
 static void
 pungetc(void)
 {
-        g_parsefile->left_in_line++;
-        g_parsefile->next_to_pgetc--;
-        pgetc_debug("pushed back to %d:%p'%s'",
-                        g_parsefile->left_in_line,
-                        g_parsefile->next_to_pgetc,
-                        g_parsefile->next_to_pgetc);
+        g_parsefile->unget++;
 }
 
 /*
@@ -10043,6 +10051,7 @@ pushfile(void)
         pf->pf_fd = -1;
         /*pf->strpush = NULL; - ckzalloc did it */
         /*pf->basestrpush.prev = NULL;*/
+        /*pf->unget = 0;*/
         g_parsefile = pf;
 }
 
@@ -11451,7 +11460,7 @@ readtoken1(int c, int syntax, char *eofmark, int striptabs)
                         IF_ASH_ALIAS(if (c != PEOA))
                                 USTPUTC(c, out);
                 }
-                c = pgetc_fast();
+                c = pgetc();
         } /* for (;;) */
  endword:
 
@@ -11945,7 +11954,7 @@ xxreadtoken(void)
         setprompt_if(needprompt, 2);
         startlinno = g_parsefile->linno;
         for (;;) {                      /* until token or start of word found */
-                c = pgetc_fast();
+                c = pgetc();
                 if (c == ' ' || c == '\t' IF_ASH_ALIAS( || c == PEOA))
                         continue;
 
@@ -12008,7 +12017,7 @@ xxreadtoken(void)
         setprompt_if(needprompt, 2);
         startlinno = g_parsefile->linno;
         for (;;) {      /* until token or start of word found */
-                c = pgetc_fast();
+                c = pgetc();
                 switch (c) {
                 case ' ': case '\t':
                 IF_ASH_ALIAS(case PEOA:)