execute minimal bullshit

7 files changed, 216 insertions, 34 deletions

diff --git a/.gitignore b/.gitignore
index dee9757..ba302ed 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 /orgaasm
 /orgaemu
+/*.rom
diff --git a/compile_flags.txt b/compile_flags.txt
new file mode 100644
index 0000000..c376403
--- /dev/null
+++ b/compile_flags.txt
@@ -0,0 +1,3 @@
+-Wall
+-Wextra
+-std=c99
diff --git a/samples/minimal.orgaasm b/samples/minimal.orgaasm
new file mode 100644
index 0000000..5ae1d7b
--- /dev/null
+++ b/samples/minimal.orgaasm
@@ -0,0 +1,13 @@
+LIT 0068 WRT ( h )
+LIT 0065 WRT ( e )
+LIT 006c WRT ( l )
+LIT 006c WRT ( l )
+LIT 006f WRT ( o )
+LIT 0020 WRT (   )
+LIT 0077 WRT ( w )
+LIT 006f WRT ( o )
+LIT 0072 WRT ( r )
+LIT 006c WRT ( l )
+LIT 0064 WRT ( d )
+LIT 000a WRT ( \n )
+RET
diff --git a/src/drain.h b/src/drain.h
new file mode 100644
index 0000000..d0f1111
--- /dev/null
+++ b/src/drain.h
@@ -0,0 +1,29 @@
+#pragma once
+#include <stdio.h>
+#include <stdlib.h>
+
+static char *
+drain(FILE *fp, long *size)
+{
+	if (fseek(fp, 0, SEEK_END) < 0) {
+		perror("drain:SEEK_END");
+		return NULL;
+	}
+	*size = ftell(fp);
+	if (fseek(fp, 0, SEEK_SET) < 0) {
+		perror("drain:SEEK_SET");
+		return NULL;
+	}
+	char *const s = malloc(*size + 1);
+	if (s == NULL) {
+		perror("drain:malloc");
+		return NULL;
+	}
+	if ((long)fread(s, 1, *size, fp) != *size) {
+		perror("drain:fread");
+		free(s);
+		return NULL;
+	}
+	s[*size] = '\0';
+	return s;
+}
diff --git a/src/ops.h b/src/ops.h
new file mode 100644
index 0000000..2ad2285
--- /dev/null
+++ b/src/ops.h
@@ -0,0 +1,69 @@
+#pragma once
+
+enum {
+	OP_NOP,
+	OP_LIT,
+	OP_POP,
+	OP_NIP,
+	OP_SWP,
+	OP_ROT,
+	OP_DUP,
+	OP_OVR,
+	OP_EQU,
+	OP_NEQ,
+	OP_GTH,
+	OP_LTH,
+	OP_JEZ,
+	OP_JNZ,
+	OP_JMP,
+	OP_JRT,
+	OP_RET,
+	OP_LDA,
+	OP_STA,
+	OP_RED,
+	OP_WRT,
+	OP_ADD,
+	OP_SUB,
+	OP_MUL,
+	OP_DIV,
+	OP_AND,
+	OP_ORA,
+	OP_XOR,
+	OP_LSF,
+	OP_RSF,
+	OP_SLP,
+};
+
+static const char ops[][4] = {
+	[OP_NOP] = "NOP",
+	[OP_LIT] = "LIT",
+	[OP_POP] = "POP",
+	[OP_NIP] = "NIP",
+	[OP_SWP] = "SWP",
+	[OP_ROT] = "ROT",
+	[OP_DUP] = "DUP",
+	[OP_OVR] = "OVR",
+	[OP_EQU] = "EQU",
+	[OP_NEQ] = "NEQ",
+	[OP_GTH] = "GTH",
+	[OP_LTH] = "LTH",
+	[OP_JEZ] = "JEZ",
+	[OP_JNZ] = "JNZ",
+	[OP_JMP] = "JMP",
+	[OP_JRT] = "JRT",
+	[OP_RET] = "RET",
+	[OP_LDA] = "LDA",
+	[OP_STA] = "STA",
+	[OP_RED] = "RED",
+	[OP_WRT] = "WRT",
+	[OP_ADD] = "ADD",
+	[OP_SUB] = "SUB",
+	[OP_MUL] = "MUL",
+	[OP_DIV] = "DIV",
+	[OP_AND] = "AND",
+	[OP_ORA] = "ORA",
+	[OP_XOR] = "XOR",
+	[OP_LSF] = "LSF",
+	[OP_RSF] = "RSF",
+	[OP_SLP] = "SLP",
+};
diff --git a/src/orgaasm.c b/src/orgaasm.c
index 8e1aa3f..d48ad94 100644
--- a/src/orgaasm.c
+++ b/src/orgaasm.c
@@ -1,3 +1,5 @@
+#include "ops.h"
+#include "drain.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -10,12 +12,6 @@ struct Label {
 	Label *next;
 };
 
-static const char ops[][4] = {
-	"NOP", "LIT", "POP", "NIP", "SWP", "ROT", "DUP", "OVR", "EQU", "NEQ",
-	"GTH", "LTH", "JEZ", "JNZ", "JMP", "JRT", "RET", "LDA", "STA", "RED",
-	"WRT", "ADD", "SUB", "MUL", "DIV", "AND", "ORA", "XOR", "LSF", "RSF",
-	"SLP"
-};
 static const int hextable[256] = {
 	['0'] = 0x0, ['1'] = 0x1, ['2'] = 0x2, ['3'] = 0x3, ['4'] = 0x4,
 	['5'] = 0x5, ['6'] = 0x6, ['7'] = 0x7, ['8'] = 0x8, ['9'] = 0x9,
@@ -194,32 +190,6 @@ second_pass(char *s)
 	}
 }
 
-static char *
-drain(FILE *fp)
-{
-	if (fseek(fp, 0, SEEK_END) < 0) {
-		perror("drain:SEEK_END");
-		return NULL;
-	}
-	const long size = ftell(fp);
-	if (fseek(fp, 0, SEEK_SET) < 0) {
-		perror("drain:SEEK_SET");
-		return NULL;
-	}
-	char *const data = malloc(size + 1);
-	if (data == NULL) {
-		perror("drain:malloc");
-		return NULL;
-	}
-	if ((long)fread(data, 1, size, fp) != size) {
-		perror("drain:fread");
-		free(data);
-		return NULL;
-	}
-	data[size] = '\0';
-	return data;
-}
-
 int
 main(int argc, char **argv)
 {
@@ -235,7 +205,8 @@ main(int argc, char **argv)
 		perror(argv[1]);
 		return fail();
 	}
-	data = drain(fp);
+	long size;
+	data = drain(fp, &size);
 	fclose(fp);
 	if (data == NULL)
 		return fail();
diff --git a/src/orgaemu.c b/src/orgaemu.c
index 00c30cf..be53a22 100644
--- a/src/orgaemu.c
+++ b/src/orgaemu.c
@@ -1,8 +1,104 @@
+#include "drain.h"
+#include "ops.h"
 #include <stdio.h>
+#include <stdint.h>
+
+#define MEM_SIZE 0xffff
+
+static uint16_t *stack = NULL;
+static size_t stack_ptr = 0;
+
+static uint16_t
+get_short(const unsigned char *s)
+{
+	return s[0] | (s[1] * 0x0100);
+}
+
+static void
+push(uint16_t v)
+{
+	stack[stack_ptr] = v;
+	stack_ptr += 1;
+	if (stack_ptr >= MEM_SIZE) {
+		fprintf(stderr, "stack overflow\n");
+		return;
+	}
+}
+
+static uint16_t
+pop(void)
+{
+	if (stack_ptr == 0) {
+		fprintf(stderr, "stack underflow\n");
+		return 0;
+	}
+	stack_ptr -= 1;
+	return stack[stack_ptr];
+}
+ 
+static void
+exec_data(uint16_t *mem)
+{
+	for (long pc = 0; pc < MEM_SIZE; pc++) {
+		switch (mem[pc]) {
+		case OP_NOP:
+			break;
+		case OP_LIT:
+			push(mem[pc + 1]);
+			pc += 1;
+			break;
+		case OP_WRT:
+			putchar(pop());
+			break;
+		case OP_RET:
+			return;
+		default:
+			fprintf(stderr, "unhandled opcode %04x\n", mem[pc]);
+			return;
+		}
+	}
+}
 
 int
 main(int argc, char **argv)
 {
-	(void)argc, (void)argv;
+	if (argc != 2) {
+		fprintf(stderr, "usage: %s <rom>\n", argv[0]);
+		return 1;
+	}
+
+	FILE *file = fopen(argv[1], "rb");
+	if (file == NULL) {
+		perror(argv[1]);
+		return 1;
+	}
+
+	long size;
+	unsigned char *const data = (unsigned char*)drain(file, &size);
+	fclose(file);
+	if (data == NULL)
+		return 1;
+
+	uint16_t *mem = calloc(MEM_SIZE, sizeof(uint16_t));
+	if (mem == NULL) {
+		perror("main:calloc");
+		free(data);
+		return 1;
+	}
+
+	for (long i = 0; i < size; i += 2)
+		mem[i / 2] = get_short(data + i);
+	free(data);
+
+	stack = calloc(MEM_SIZE, sizeof(uint16_t));
+	if (stack == NULL) {
+		perror("main:calloc");
+		free(mem);
+		return 1;
+	}
+
+	exec_data(mem);
+	free(mem);
+	free(stack);
 	return 0;
 }