From c8f41912a0c3cfb28a27df2e6f570b2117fb42c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Kochma=C5=84ski?= <daniel@turtleware.eu>
Date: Fri, 25 Jul 2025 20:56:42 +0200
Subject: [PATCH] streams: echo-stream treats last_byte as a flag

Instead of remembering the last unread object and its type, it simply yots down
the fact that something has been unread (and clears on read), and delegates the
question to the input stream.
---
 src/c/streams/strm_composite.d | 37 ++++++++++++++--------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/src/c/streams/strm_composite.d b/src/c/streams/strm_composite.d
index bbd688c7f..f4aad0056 100644
--- a/src/c/streams/strm_composite.d
+++ b/src/c/streams/strm_composite.d
@@ -443,13 +443,13 @@ static cl_object
 echo_read_byte(cl_object strm)
 {
   cl_object byte = strm->stream.last_byte;
-  if (byte == OBJNULL) {
+  if (byte != OBJNULL) {
+    strm->stream.last_byte = OBJNULL;
+    byte = ecl_read_byte(ECHO_STREAM_INPUT(strm));
+  } else {
     byte = ecl_read_byte(ECHO_STREAM_INPUT(strm));
     if (byte != OBJNULL)
       ecl_write_byte(byte, ECHO_STREAM_OUTPUT(strm));
-  } else {
-    strm->stream.last_byte = OBJNULL;
-    byte = ecl_read_byte(ECHO_STREAM_INPUT(strm));
   }
   return byte;
 }
@@ -466,31 +466,28 @@ echo_unread_byte(cl_object strm, cl_object byte)
   unlikely_if (strm->stream.last_byte != OBJNULL) {
     ecl_unread_twice(strm);
   }
-  strm->stream.last_byte = byte;
+  strm->stream.last_byte = ECL_T;
   ecl_unread_byte(byte, ECHO_STREAM_INPUT(strm));
 }
 
 static cl_object
 echo_peek_byte(cl_object strm)
 {
-  cl_object byte = strm->stream.last_byte;
-  if (byte == OBJNULL) {
-    byte = ecl_peek_byte(ECHO_STREAM_INPUT(strm));
-  }
-  return byte;
+  return ecl_peek_byte(ECHO_STREAM_INPUT(strm));
 }
 
 static ecl_character
 echo_read_char(cl_object strm)
 {
-  ecl_character c = strm->stream.last_code[0];
-  if (c == EOF) {
+  cl_object byte = strm->stream.last_byte;
+  ecl_character c;
+  if (byte != OBJNULL) {
+    strm->stream.last_byte = OBJNULL;
+    c = ecl_read_char(ECHO_STREAM_INPUT(strm));
+  } else {
     c = ecl_read_char(ECHO_STREAM_INPUT(strm));
     if (c != EOF)
       ecl_write_char(c, ECHO_STREAM_OUTPUT(strm));
-  } else {
-    strm->stream.last_code[0] = EOF;
-    ecl_read_char(ECHO_STREAM_INPUT(strm));
   }
   return c;
 }
@@ -504,21 +501,17 @@ echo_write_char(cl_object strm, ecl_character c)
 static void
 echo_unread_char(cl_object strm, ecl_character c)
 {
-  unlikely_if (strm->stream.last_code[0] != EOF) {
+  unlikely_if (strm->stream.last_byte != OBJNULL) {
     ecl_unread_twice(strm);
   }
-  strm->stream.last_code[0] = c;
+  strm->stream.last_byte = ECL_T;;
   ecl_unread_char(c, ECHO_STREAM_INPUT(strm));
 }
 
 static ecl_character
 echo_peek_char(cl_object strm)
 {
-  ecl_character c = strm->stream.last_code[0];
-  if (c == EOF) {
-    c = ecl_peek_char(ECHO_STREAM_INPUT(strm));
-  }
-  return c;
+  return ecl_peek_char(ECHO_STREAM_INPUT(strm));
 }
 
 static int