306 lines
8 KiB
Markdown
306 lines
8 KiB
Markdown
Muri is a minimalistic assembler for Nga.
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The standard assembler for Nga is Naje. This is an attempt at
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making a much smaller assembler at a cost of requiring more
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manual knowledge of the Nga virtual machine and its encodings.
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Input syntax
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<directive> <data>
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Directives are a single character. Muri recognizes:
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* **i** for instructions
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* **d** for numeric data
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* **s** for string data
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* **:** for creating a label
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* **r** for references to labels
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Instructions are packed up to four instructions per location.
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You can specify them using the first two characters of the
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instruction name. For a non operation, use '..' instead of
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'no'.
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0 nop 7 jump 14 gt 21 and 28 iquery
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1 lit <v> 8 call 15 fetch 22 or 29 iinteract
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2 dup 9 ccall 16 store 23 xor
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3 drop 10 return 17 add 24 shift
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4 swap 11 eq 18 sub 25 zret
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5 push 12 neq 19 mul 26 end
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6 pop 13 lt 20 divmod 27 ienum
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E.g., for a sequence of dup, multiply, no-op, drop:
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i dupmu..dr
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An example of a small program:
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i liju....
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r main
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: square
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i dumure..
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: main
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i lilica..
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d 12
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r square
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i en......
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As mentioned earlier this requires knowledge of Nga architecture.
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While you can pack up to four instructions per location, you
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should not place anything after an instruction that modifies the
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instruction pointer. These are: ju, ca, cc, re, and zr.
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----
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The code begins with the necessary C headers.
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~~~
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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~~~
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The glibc on Linux does not provide strlcpy or strlcat. I
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include the OpenBSD versions of these if compiling with glibc.
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~~~
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#include "strl.h"
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~~~
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And then a couple of constants that determine overall memory
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usage.
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~~~
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#define KiB * 1024
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#define MAX_NAMES 1024
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#define STRING_LEN 64
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#define IMAGE_SIZE 128 KiB
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~~~
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Next, define the arrays for the reference handling.
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~~~
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char Labels[MAX_NAMES][STRING_LEN];
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int32_t Pointers[MAX_NAMES];
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int32_t np;
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~~~
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And then the variables and array for the target memory and
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source buffer:
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~~~
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char source[1 KiB];
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int32_t target[IMAGE_SIZE];
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int32_t here;
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~~~
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And that's the end of the data part. Now on to routines.
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First up, something to save the generated image file.
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~~~
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void save() {
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FILE *fp;
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if ((fp = fopen("ngaImage", "wb")) == NULL) {
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printf("Unable to save the image!\n");
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exit(2);
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}
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fwrite(&target, sizeof(int32_t), here, fp);
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fclose(fp);
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}
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~~~
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Next, functions related to the reference tables. We have two.
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The `lookup()` searches the tables for a name and returns
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either -1 (if not found) or the address that corresponds to it.
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~~~
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int32_t lookup(char *name) {
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int32_t slice = -1;
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int32_t n = np;
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while (n > 0) {
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n--;
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if (strcmp(Labels[n], name) == 0)
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slice = Pointers[n];
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}
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return slice;
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}
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~~~
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The second, `add_label()` handles adding a new label to the
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table. It also terminates the build if the label already exists.
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~~~
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void add_label(char *name, int32_t slice) {
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if (lookup(name) == -1) {
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strlcpy(Labels[np], name, STRING_LEN);
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Pointers[np] = slice;
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np++;
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} else {
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printf("Fatal error: %s already defined\n", name);
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exit(0);
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}
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}
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~~~
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This next routine reads a line from a file into the input buffer.
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~~~
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void read_line(FILE *file, char *line_buffer) {
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int ch = getc(file);
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int count = 0;
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while ((ch != '\n') && (ch != EOF)) {
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line_buffer[count] = ch;
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count++;
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ch = getc(file);
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}
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line_buffer[count] = '\0';
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}
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~~~
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This one is a little messy. It just checks a source string
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against the list of instructions and returns the corresponding
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opcode. It returns 0 (nop) for anything unrecognized.
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~~~
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int32_t opcode_for(char *s) {
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if (strcmp(s, "..") == 0) return 0; if (strcmp(s, "li") == 0) return 1;
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if (strcmp(s, "du") == 0) return 2; if (strcmp(s, "dr") == 0) return 3;
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if (strcmp(s, "sw") == 0) return 4; if (strcmp(s, "pu") == 0) return 5;
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if (strcmp(s, "po") == 0) return 6; if (strcmp(s, "ju") == 0) return 7;
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if (strcmp(s, "ca") == 0) return 8; if (strcmp(s, "cc") == 0) return 9;
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if (strcmp(s, "re") == 0) return 10; if (strcmp(s, "eq") == 0) return 11;
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if (strcmp(s, "ne") == 0) return 12; if (strcmp(s, "lt") == 0) return 13;
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if (strcmp(s, "gt") == 0) return 14; if (strcmp(s, "fe") == 0) return 15;
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if (strcmp(s, "st") == 0) return 16; if (strcmp(s, "ad") == 0) return 17;
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if (strcmp(s, "su") == 0) return 18; if (strcmp(s, "mu") == 0) return 19;
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if (strcmp(s, "di") == 0) return 20; if (strcmp(s, "an") == 0) return 21;
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if (strcmp(s, "or") == 0) return 22; if (strcmp(s, "xo") == 0) return 23;
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if (strcmp(s, "sh") == 0) return 24; if (strcmp(s, "zr") == 0) return 25;
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if (strcmp(s, "en") == 0) return 26; if (strcmp(s, "ie") == 0) return 27;
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if (strcmp(s, "iq") == 0) return 28; if (strcmp(s, "ii") == 0) return 29;
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return 0;
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}
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~~~
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Now for the first pass. This lays down code, with dummy values
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for the references. They will be resolved in `pass2()`.
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~~~
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void pass1(char *fname) {
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int inBlock = 0;
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char *buffer = (char *)source;
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unsigned int opcode;
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char inst[3];
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FILE *fp;
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inst[2] = '\0';
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here = 0;
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fp = fopen(fname, "r");
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if (fp == NULL) {
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printf("Unable to load file\n");
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exit(2);
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}
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while (!feof(fp)) {
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read_line(fp, buffer);
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if (strcmp(buffer, "~~~") == 0) {
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if (inBlock == 0)
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inBlock = 1;
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else
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inBlock = 0;
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} else {
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if (inBlock == 1) {
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if (buffer[1] == '\t' || buffer[1] == ' ') {
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switch (buffer[0]) {
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case 'i': memcpy(inst, buffer + 8, 2);
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opcode = opcode_for(inst);
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opcode = opcode << 8;
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memcpy(inst, buffer + 6, 2);
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opcode += opcode_for(inst);
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opcode = opcode << 8;
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memcpy(inst, buffer + 4, 2);
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opcode += opcode_for(inst);
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opcode = opcode << 8;
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memcpy(inst, buffer + 2, 2);
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opcode += opcode_for(inst);
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target[here++] = opcode;
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break;
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case 'r': target[here++] = -1;
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break;
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case 'd': target[here++] = atoi(buffer+2);
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break;
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case 's': opcode = 2;
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while (opcode < strlen(buffer))
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target[here++] = buffer[opcode++];
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target[here++] = 0;
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break;
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case ':': add_label(buffer+2, here);
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break;
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}
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}
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}
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}
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}
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fclose(fp);
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}
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~~~
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The second pass skips over any instructions or data, but replaces
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the dummy values for each reference with the actual address
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(recorded as part of `pass1()`).
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~~~
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void pass2(char *fname) {
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char *buffer;
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FILE *fp;
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int inBlock;
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inBlock = 0;
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buffer = (char *)source;
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here = 0;
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fp = fopen(fname, "r");
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if (fp == NULL) {
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printf("Unable to load file\n");
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exit(2);
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}
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while (!feof(fp)) {
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read_line(fp, buffer);
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if (strcmp(buffer, "~~~") == 0) {
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if (inBlock == 0)
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inBlock = 1;
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else
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inBlock = 0;
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} else {
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if (inBlock == 1) {
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switch (buffer[0]) {
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case 'i': here++; break;
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case 'r': target[here++] = lookup(buffer+2);
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if (lookup(buffer+2) == -1)
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printf("Lookup failed: '%s'\n", buffer+2);
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break;
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case 'd': here++; break;
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case 's': here = here + strlen(buffer) - 1; break;
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case ':': break;
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}
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}
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}
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}
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fclose(fp);
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}
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~~~
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And then the top level wrapper.
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~~~
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int main(int argc, char **argv) {
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np = 0;
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if (argc > 1) {
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pass1(argv[1]);
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pass2(argv[1]);
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save();
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printf("Wrote %d cells to ngaImage\n", here);
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}
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else
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printf("muri\n(c) 2017-2019 charles childers\n\n%s filename\n", argv[0]);
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return 0;
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}
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~~~
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