74 lines
2.8 KiB
C
74 lines
2.8 KiB
C
/* NRJ (NOR and Reference Jump) OISC ANSI C emulator
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* Created by Luxferre, 2022, public domain
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* Build with: cc -Os -std=c89 -o nrj nrj.c */
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#include <stdlib.h>
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#include <stdio.h>
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#include <termios.h>
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#include <unistd.h>
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#include <sys/select.h>
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#ifndef NRJWORD /* we emulate NRJ16 by default but this can be overridden */
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#define NRJWORD unsigned short
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#endif
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#define NRJWSIZE (sizeof(NRJWORD) << 3)
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#define NRJSIZE (1 << NRJWSIZE)
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#define MAXADDR ((NRJWORD) (NRJSIZE - 1))
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int kbhit() { /* our best attempt to detect a keypress on a POSIX system */
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struct timeval tv = { 0L, 0L };
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fd_set fds;
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FD_ZERO(&fds);
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FD_SET(0, &fds);
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return select(1, &fds, NULL, NULL, &tv) > 0;
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}
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void nrj_in(NRJWORD *ctxid, NRJWORD *val) { /* context-dependent input handler */
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unsigned char c;
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if(*ctxid == (NRJWORD) 0) /* for now, only emulate standard context id */
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*val = (NRJWORD) ((kbhit() && read(0, &c, 1) > -1) ? c : 0);
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}
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void nrj_out(NRJWORD *ctxid, NRJWORD *val) { /* context-dependent output handler */
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if(*ctxid == (NRJWORD) 0) /* for now, only emulate standard context id */
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putchar((unsigned char) *val);
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}
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void nrj_run(NRJWORD *mem, NRJWORD pc) { /* Main NRJ engine - just 12 lines of C within this function */
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while(pc != MAXADDR) { /* halt if jumped to the last word */
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if(mem[0]) { /* handle input if word 0 is set */
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nrj_in(&mem[2], &mem[mem[0]]); /* input a value to the location specified in word 0 */
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mem[0] = (NRJWORD) 0; /* clear word 0 */
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}
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mem[mem[pc]] = (~(mem[mem[pc]] | mem[mem[pc+1]])) & MAXADDR; /* then perform the NOR operation */
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pc = mem[mem[pc+2]]; /* then perform the reference jump operation */
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if(mem[1]) { /* then handle output if word 1 is set */
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nrj_out(&mem[2], &mem[1]); /* output the value from the word 1 */
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mem[1] = (NRJWORD) 0; /* clear word 1 */
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}
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}
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}
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struct termios tty_opts_backup, tty_opts_raw; /* terminal I/O helper definitions */
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void restore_term() {tcsetattr(0, TCSANOW, &tty_opts_backup);}
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int main(int argc, char* argv[]) { /* emulator entry point: nrj program.bin */
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if(argc > 1) {
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FILE *prog = fopen(argv[1], "rb");
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if(prog) { /* load the program and prepare the terminal */
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NRJWORD mem[NRJSIZE]; /* NRJ memory: word 0 - input, 1 - output, 2 - I/O context, 3 - program start */
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fseek(prog, 0, SEEK_END);
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int flen = ftell(prog);
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fseek(prog, 0, SEEK_SET);
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fread(mem, sizeof(NRJWORD), flen/sizeof(NRJWORD), prog);
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fclose(prog);
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tcgetattr(0, &tty_opts_backup);
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atexit(&restore_term);
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cfmakeraw(&tty_opts_raw);
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tcsetattr(0, TCSANOW, &tty_opts_raw);
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nrj_run(mem, 3); /* now, start the engine */
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return 0; /* return the successful status to the outer OS */
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}
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} /* otherwise bail out with an error */
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printf("NRJ%u: no valid program binary specified\r\n", (unsigned int) NRJWSIZE);
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return 1;
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}
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