nrj-oisc

commit 1ce0c339caac58fabba11b8a8e5ff4b7915faf81
parent fc61f19a0758de7429b91c7f49568b7df9085bb6
Author: Luxferre <lux@ferre>
Date:   Tue, 23 Aug 2022 09:30:47 +0300

some more

Diffstat:
M
nrj.c
 | 
41
+++++++++++++++++------------------------

1 file changed, 17 insertions(+), 24 deletions(-)
diff --git a/nrj.c b/nrj.c
@@ -1,14 +1,14 @@
 /*
  * NRJ (NOR and Reference Jump) OISC ANSI C emulator
  * Created by Luxferre, 2022, public domain
- * Build with: cc -Os -o nrj nrj.c
+ * Build with: cc -Os -std=c89 -o nrj nrj.c
  */
 #include <stdlib.h>
 #include <stdio.h>
 #include <termios.h>
 #include <unistd.h>
 #include <sys/select.h>
-#ifndef NRJWORD /* we emulate NRJ16 by default */
+#ifndef NRJWORD /* we emulate NRJ16 by default but this can be overridden */
 #define NRJWORD unsigned short
 #endif
 #define NRJWSIZE (sizeof(NRJWORD) << 3)
@@ -25,11 +25,8 @@ int kbhit() { /* our best attempt to detect a keypress on a POSIX system */
 
 void nrj_in(NRJWORD *ctxid, NRJWORD *val) { /* context-dependent input handler */
   unsigned char c;
-  if(*ctxid == (NRJWORD) 0) { /* for now, only emulate standard context id */
-    *val = (NRJWORD) 0;
-    if(kbhit() && read(0, &c, 1) > -1)
-      *val = (NRJWORD) c;
-  }
+  if(*ctxid == (NRJWORD) 0) /* for now, only emulate standard context id */
+    *val = (NRJWORD) ((kbhit() && read(0, &c, 1) > -1) ? c : 0);
 }
 
 void nrj_out(NRJWORD *ctxid, NRJWORD *val) { /* context-dependent output handler */
@@ -39,42 +36,38 @@ void nrj_out(NRJWORD *ctxid, NRJWORD *val) { /* context-dependent output handler
 
 void nrj_run(NRJWORD *mem, NRJWORD pc) { /* Main NRJ engine - just 12 lines of C within this function */
   while(pc != MAXADDR) { /* halt if jumped to the last word */
-    if(mem[0]) { /* handle input if the first word is set, and clear it */
-      nrj_in(&mem[2], &mem[mem[0]]);
-      mem[0] = (NRJWORD) 0;
+    if(mem[0]) { /* handle input if word 0 is set */
+      nrj_in(&mem[2], &mem[mem[0]]); /* input a value to the location specified in word 0 */
+      mem[0] = (NRJWORD) 0; /* clear word 0 */
     }
     mem[mem[pc]] = (~(mem[mem[pc]] | mem[mem[pc+1]])) & MAXADDR; /* then perform the NOR operation */
     pc = mem[mem[pc+2]]; /* then perform the reference jump operation */
-    if(mem[1]) { /* then handle output if the second word is set, and clear it */
-      nrj_out(&mem[2], &mem[mem[1]]);
-      mem[1] = (NRJWORD) 0;
+    if(mem[1]) { /* then handle output if word 1 is set */
+      nrj_out(&mem[2], &mem[mem[1]]); /* output the value from the location specified in word 1 */
+      mem[1] = (NRJWORD) 0; /* clear word 1 */
     }
   }
 }
 
+/* terminal helper definitions */
 struct termios tty_opts_backup, tty_opts_raw;
-void restore_term() {
-  tcsetattr(STDIN_FILENO, TCSANOW, &tty_opts_backup);
-}
+void restore_term() {tcsetattr(0, TCSANOW, &tty_opts_backup);}
 
-int main(int argc, char* argv[]) {
+int main(int argc, char* argv[]) { /* emulator entry point: nrj program.bin */
   if(argc > 1) {
     NRJWORD mem[NRJSIZE]; /* NRJ memory: word 0 - input, 1 - output, 2 - I/O context, 3 - program start */
     FILE *prog = fopen(argv[1], "rb");
-    if(prog) {
-      /* load the program */
+    if(prog) { /* load the program and prepare the terminal */
       fseek(prog, 0, SEEK_END);
       int flen = ftell(prog);
       fseek(prog, 0, SEEK_SET);
       fread(mem, sizeof(NRJWORD), (flen/sizeof(NRJWORD)) & MAXADDR, prog);
       fclose(prog);
-      /* prepare the terminal */
-      tcgetattr(STDIN_FILENO, &tty_opts_backup);
+      tcgetattr(0, &tty_opts_backup);
       atexit(&restore_term);
       cfmakeraw(&tty_opts_raw);
-      tcsetattr(STDIN_FILENO, TCSANOW, &tty_opts_raw);
-      /* start the engine */
-      nrj_run(mem, 3);
+      tcsetattr(0, TCSANOW, &tty_opts_raw);
+      nrj_run(mem, 3); /* now, start the engine */
     }
     else {
       printf("NRJ%u: could not open the input file %s\r\n", (unsigned int) NRJWSIZE, argv[1]);