add parser

1 files changed, 85 insertions, 0 deletions

diff --git a/src/as_parser.c b/src/as_parser.c
new file mode 100644
index 0000000..d80cdd9
--- /dev/null
+++ b/src/as_parser.c
@@ -0,0 +1,85 @@
+#include "as_parser.h"
+
+#include <stdlib.h>
+
+// BNF
+// ===
+//
+// <prog> ::= <stmts>
+// <stmts> ::= <stmt> <newline> | <stmt> <stmts>
+// <stmt> ::= <tag> <instr> | <instr> | <tag>
+// <instr> ::= <op> | <op> <arg> | <op> <label>
+// <tag> ::= <label> :
+// <op> ::= add | sub | mul | div | mod | eq
+
+
+Prog* parseProg(TokenStream *ts) {
+    Prog *p = malloc(sizeof(Prog));
+    p->stmts = parseStmts(ts);
+    return p;
+}
+
+Stmts* parseStmts(TokenStream *ts) {
+    Stmts *ss = malloc(sizeof(Stmts));
+    ss->stmts = malloc(sizeof(Stmt*));
+    ss->stmts[0] = NULL;
+    int capacity = 0;
+    int len = 0;
+    while (peekToken(ts)->type != ENDOFFILE) {
+        Stmt *s = parseStmt(ts);
+        if (len == capacity) {
+            capacity = capacity * 2 + 1;
+            ss->stmts = realloc(ss->stmts, sizeof(Stmt*) * capacity);
+        }
+        ss->stmts[len] = s;
+        len++;
+    }
+    ss->stmts[len] = NULL;
+    return ss;
+}
+
+Stmt* parseStmt(TokenStream *ts) {
+    Token *t = peekToken(ts);
+    if (t->type == LABEL) {
+        Label *l = parseLabel(ts);
+        t = peekToken(ts);
+        if (t->type == COLON) {
+            nextToken(ts);
+            return (Stmt*)l;
+        } else {
+            Instr *i = parseInstr(ts);
+            Stmt *s = malloc(sizeof(Stmt));
+            s->tag = l;
+            s->instr = i;
+            return s;
+        }
+    } else {
+        Instr *i = parseInstr(ts);
+        Stmt *s = malloc(sizeof(Stmt));
+        s->tag = NULL;
+        s->instr = i;
+        return s;
+    }
+}
+
+Instr* parseInstr(TokenStream *ts) {
+    Token *t = nextToken(ts);
+    Instr *i = malloc(sizeof(Instr));
+    i->labelName = NULL;
+    if (t->type == OP) {
+        i->op = parseOp(ts);
+        t = peekToken(ts);
+        if (t->type == ARG) {
+            Arg *a = malloc(sizeof(Arg));
+            a->ival = t->ival;
+            a->fval = t->fval;
+            a->sval = t->sval;
+            i->arg = a;
+            nextToken(ts);
+        } else if (t->type == LABEL) {
+            i->labelName = t->sval;
+            nextToken(ts);
+        }
+    }
+    return i;
+}