nooc

commit c0ce468e1f980dd5bd183993e9582dc8ff66c3a1
parent 3a3956f653887587656dcbe74304547d69392bdf
Author: Nihal Jere <nihal@nihaljere.xyz>
Date:   Mon,  1 Nov 2021 23:48:43 -0500

add simple lexing, parsing and codegen capable of "compiling" prog.nc

Diffstat:
M
main.c
 | 
128
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
A
prog.nc
 | 
2
++

2 files changed, 125 insertions(+), 5 deletions(-)
diff --git a/main.c b/main.c
@@ -1,3 +1,4 @@
+#include <ctype.h>
 #include <elf.h>
 #include <fcntl.h>
 #include <string.h>
@@ -7,7 +8,7 @@
 #include <sys/mman.h>
 #include <unistd.h>
 
-char code[] = {0xb8, 60, 0x00, 0x00, 0x00, 0xbf, 0x00, 0x00, 0x00, 0x00, 0xf, 0x5};
+char code[] = {0xb8, 0, 0x00, 0x00, 0x00, 0xbf, 0x00, 0x00, 0x00, 0x00, 0xf, 0x5};
 
 int
 elf(char *text, size_t len, FILE *f)
@@ -69,9 +70,120 @@ elf(char *text, size_t len, FILE *f)
 	fwrite(text, 1, len, f);
 }
 
+enum tokentype {
+	TOK_EXIT = 1,
+	TOK_LPAREN,
+	TOK_RPAREN,
+	TOK_NUM,
+};
+
+struct slice {
+	char *ptr;
+	size_t len;
+};
+
+struct token {
+	enum tokentype type;
+	struct slice slice;
+	struct token *next;
+};
+
+struct token *
+lex(struct slice start)
+{
+	struct token *head = calloc(1, sizeof(struct token));
+	if (!head)
+		return NULL;
+
+	struct token *cur = head;
+	while (start.len) {
+		if (strncmp(start.ptr, "exit", sizeof("exit") - 1) == 0) {
+			cur->type = TOK_EXIT;
+			start.ptr += 4;
+			start.len -= 4;
+		} else if (*start.ptr == '(') {
+			cur->type = TOK_LPAREN;
+			start.ptr += 1;
+			start.len -= 1;
+		} else if (*start.ptr == ')') {
+			cur->type = TOK_RPAREN;
+			start.ptr += 1;
+			start.len -= 1;
+		} else if (isdigit(*start.ptr)) {
+			cur->slice.ptr = start.ptr;
+			cur->slice.len = 1;
+			start.ptr++;
+			start.len--;
+			cur->type = TOK_NUM;
+			while (isdigit(*start.ptr)) {
+				start.ptr++;
+				start.len--;
+				cur->slice.len++;
+			}
+		}
+
+		cur->next = calloc(1, sizeof(struct token));
+
+		// FIXME: handle this properly
+		if (!cur->next)
+			return NULL;
+
+		cur = cur->next;
+	}
+
+	return head;
+}
+
+enum func {
+	FUNC_NONE,
+	FUNC_EXIT
+};
+
+struct fcall {
+	enum func func;
+	int val;
+};
+
+void
+error(char *error)
+{
+	fprintf(stderr, "%s\n", error);
+	exit(1);
+}
+
+void
+expect(struct token *tok, enum tokentype type)
+{
+	if (!tok)
+		error("unexpected null token!");
+	if (tok->type != type)
+		error("mismatch");
+}
+
+struct fcall
+parse(struct token *tok)
+{
+	struct fcall fcall;
+	expect(tok, TOK_EXIT);
+
+	fcall.func = FUNC_EXIT;
+	tok = tok->next;
+	expect(tok, TOK_LPAREN);
+	tok = tok->next;
+	expect(tok, TOK_NUM);
+
+	// FIXME: error check
+	fcall.val = strtol(tok->slice.ptr, NULL, 10);
+	tok = tok->next;
+	expect(tok, TOK_RPAREN);
+	tok = tok->next;
+	return fcall;
+}
+
 struct stat statbuf;
 
-int main(int argc, char *argv[])
+int
+main(int argc, char *argv[])
 {
 	if (argc < 3)
 		return 1;
@@ -91,12 +203,18 @@ int main(int argc, char *argv[])
 	char *addr = mmap(NULL, statbuf.st_size, PROT_READ, MAP_PRIVATE, in, 0);
 	close(in);
 
-	long val = strtol(addr, NULL, 10);
+	struct token *head = lex((struct slice){addr, statbuf.st_size});
+	struct fcall fcall = parse(head);
+	
 	munmap(addr, statbuf.st_size);
 
-	code[6] = val;
+	switch (fcall.func) {
+	case FUNC_EXIT:
+		code[1] = 60;
+		code[6] = fcall.val;
+	}
 
-	FILE *out = fopen(argv[2], "r");
+	FILE *out = fopen(argv[2], "w");
 	if (!out) {
 		close(in);
 		fprintf(stderr, "couldn't open output\n");
diff --git a/prog.nc b/prog.nc
@@ -0,0 +1 @@
+exit(12)+
\ No newline at end of file