peek support

os/charsio.c

@@ -26,6 +26,7 @@ static char SccsId[] = "%W% %G%";
 #include "Yap.h"
 #include "Yatom.h"
 #include "YapHeap.h"
+#include "YapText.h"
 #include "yapio.h"
 #include <stdlib.h>
 #if HAVE_UNISTD_H
@@ -84,18 +85,66 @@ Int Yap_peek(int sno) {
   Int ch;
 
   s = GLOBAL_Stream + sno;
+  if ( s->status & Readline_Stream_f) {
+    ch = Yap_ReadlinePeekChar( sno );
+    if (ch == EOFCHAR) {
+      s->stream_getc = EOFPeek;
+      s->stream_wgetc = EOFWPeek;
+      s->status |= Push_Eof_Stream_f;
+    }
+    return ch;
+  }
   ocharcount = s->charcount;
   olinecount = s->linecount;
   olinepos = s->linepos;
   ch = s->stream_wgetc(sno);
+  s ->och = ch;
+  if (ch == EOFCHAR) {
+    s->stream_getc = EOFPeek;
+    s->stream_wgetc = EOFWPeek;
+    s->status |= Push_Eof_Stream_f;
+   return ch;
+  }
   s->charcount = ocharcount;
   s->linecount = olinecount;
   s->linepos = olinepos;
   /* buffer the character */
   if (s->encoding == LOCAL_encoding) {
     ungetwc(ch, s->file);
-  } else {
+  } else if (s->encoding == ENC_OCTET ||
+      s->encoding == ENC_ISO_LATIN1||
+      s->encoding == ENC_ISO_ASCII) {
+    ungetc(ch, s->file);
+  } else if (s->encoding == ENC_ISO_UTF8) {
+    unsigned char cs[8];
+    size_t n = put_utf8(cs, ch );
+    while (n--) {
+      ungetc(cs[n-1], s->file);
+    }
+  } else if (s->encoding == ENC_UTF16_BE) {
     /* do the ungetc as if a write .. */
+    unsigned long int c = ch;
+    if (c >((1<<16)-1)) {
+      ungetc(c/1<<16, s->file);
+      c %= 1<< 16;
+    }
+    ungetc(c, s->file);
+  } else if (s->encoding == ENC_UTF16_BE) {
+    /* do the ungetc as if a write .. */
+    unsigned long int c = ch;
+    if (c > ((1<<16)-1)) {
+      ungetc(c/1<<16, s->file);
+      c %= 1<< 16;
+    } 
+  } else if (s->encoding == ENC_UTF16_LE) {
+    /* do the ungetc as if a write .. */
+    unsigned long int c = ch;
+    if (c >(( 1<<16)-1)) {
+      ungetc(c%1<<16, s->file);
+      c /= 1<< 16;
+    }
+    ungetc(c, s->file);
+  } else {    
     int (*f)(int, int) = s->stream_putc;
     s->stream_putc = plUnGetc;
     put_wchar(sno, ch);

os/iopreds.h

@@ -301,6 +301,7 @@ void Yap_InitWriteTPreds(void);
 void Yap_InitReadTPreds(void);
 void Yap_socketStream( StreamDesc *s );
 void Yap_ReadlineFlush( int  sno );
+Int Yap_ReadlinePeekChar( int  sno );
 int Yap_ReadlineForSIGINT(void);
 bool Yap_ReadlinePrompt( StreamDesc * s );
 
@@ -327,6 +328,8 @@ int DefaultGets( int,UInt,char*);
 int put_wchar(int sno, wchar_t ch);
 Int GetStreamFd(int sno);
 int ResetEOF(StreamDesc *s);
+int EOFPeek(int sno);
+int EOFWPeek(int sno);
 
 void Yap_SetAlias (Atom arg, int sno);
 bool Yap_AddAlias (Atom arg, int sno);

os/readline.c

@@ -300,6 +300,42 @@ static int ReadlineGetc(int sno) {
   return console_post_process_read_char(ch, s);
 }
 
+
+/** 
+  @brief  Yap_ReadlinePeekChar peeks the next char from the
+  readline buffer, but does not actually grab it.
+
+  The idea is to take advantage of the buffering. Special care must be taken with EOF, though.
+
+*/
+Int Yap_ReadlinePeekChar( int sno) {
+  StreamDesc *s = &GLOBAL_Stream[sno];
+  int ch;
+
+  if (s->u.irl.buf) {
+    const char *ttyptr = s->u.irl.ptr;
+    ch = *ttyptr;
+    if (ch == '\0') {
+       ch = '\n';
+    }
+  } if (getLine(sno, StdErrStream) ) {
+      CACHE_REGS
+    ch = s->u.irl.ptr[0];
+    if (ch == '\0') {
+       ch = '\n';
+    }
+    if (ch == '\n') {
+      LOCAL_newline = true;
+    } else {
+      LOCAL_newline = false;
+    }
+  } else {
+    return EOF;
+  }
+  return ch;
+}
+
+
 int Yap_ReadlineForSIGINT(void) {
   CACHE_REGS
   int ch;

os/streams.c

@@ -140,6 +140,7 @@ int GetFreeStreamD(void) {
   LOCK(GLOBAL_Stream[sno].streamlock);
   UNLOCK(GLOBAL_StreamDescLock);
   GLOBAL_Stream[sno].encoding = LOCAL_encoding;
+  GLOBAL_Stream[sno].och = '\0';
   return sno;
 }