Split preprocess() into smaller functions.

preprocess.c

@@ -2,71 +2,100 @@
 
 #include "9cc.h"
 
-static Map *defined;
+static Map *macros;
 
-static void append(Vector *v1, Vector *v2) {
-  for (int i = 0; i < v2->len; i++)
-    vec_push(v1, v2->data[i]);
+typedef struct Context {
+  Vector *input;
+  Vector *output;
+  int pos;
+  struct Context *next;
+} Context;
+
+static Context *ctx;
+
+static Context *new_ctx(Context *next, Vector *input) {
+  Context *c = calloc(1, sizeof(Context));
+  c->input = input;
+  c->output = new_vec();
+  c->next = next;
+  return c;
+}
+
+static void append(Vector *v) {
+  for (int i = 0; i < v->len; i++)
+    vec_push(ctx->output, v->data[i]);
+}
+
+static void add(Token *t) { vec_push(ctx->output, t); }
+
+static Token *next() {
+  assert(ctx->pos < ctx->input->len);
+  return ctx->input->data[ctx->pos++];
+}
+
+static bool eof() { return ctx->pos == ctx->input->len; }
+
+static Token *get(int ty, char *msg) {
+  Token *t = next();
+  if (t->ty != ty)
+    bad_token(t, msg);
+  return t;
+}
+
+static void define() {
+  Token *t = get(TK_IDENT, "macro name expected");
+  char *name = t->name;
+
+  Vector *v = new_vec();
+  while (!eof()) {
+    t = next();
+    if (t->ty == '\n')
+      break;
+    vec_push(v, t);
+  }
+  map_put(macros, name, v);
+}
+
+static void include() {
+  Token *t = get(TK_STR, "string expected");
+  char *path = t->str;
+  get('\n', "newline expected");
+  append(tokenize(path, false));
 }
 
 Vector *preprocess(Vector *tokens) {
-  if (!defined)
-    defined = new_map();
+  if (!macros)
+    macros = new_map();
+  ctx = new_ctx(ctx, tokens);
 
-  Vector *v = new_vec();
-
-  for (int i = 0; i < tokens->len;) {
-    Token *t = tokens->data[i++];
+  while (!eof()) {
+    Token *t = next();
 
     if (t->ty == TK_IDENT) {
-      Vector *macro = map_get(defined, t->name);
+      Vector *macro = map_get(macros, t->name);
       if (macro)
-        append(v, macro);
+        append(macro);
       else
-        vec_push(v, t);
+        add(t);
       continue;
     }
 
     if (t->ty != '#') {
-      vec_push(v, t);
+      add(t);
       continue;
     }
 
-    t = tokens->data[i++];
-    if (t->ty != TK_IDENT)
-      bad_token(t, "identifier expected");
+    t = get(TK_IDENT, "identifier expected");
 
-    if (!strcmp(t->name, "define")) {
-      t = tokens->data[i++];
-      if (t->ty != TK_IDENT)
-        bad_token(t, "macro name expected");
-      char *name = t->name;
-
-      Vector *v2 = new_vec();
-      while (i < tokens->len) {
-        t = tokens->data[i++];
-        if (t->ty == '\n')
-          break;
-        vec_push(v2, t);
-      }
-
-      map_put(defined, name, v2);
-      continue;
-    }
-
-    if (!strcmp(t->name, "include")) {
-      t = tokens->data[i++];
-      if (t->ty != TK_STR)
-        bad_token(t, "string expected");
-
-      char *path = t->str;
-
-      t = tokens->data[i++];
-      if (t->ty != '\n')
-        bad_token(t, "newline expected");
-      append(v, tokenize(path, false));
-      continue;
-    }
+    if (!strcmp(t->name, "define"))
+      define();
+    else if (!strcmp(t->name, "include"))
+      include();
+    else
+      bad_token(t, "unknown directive");
   }
+
+  Vector *v = ctx->output;
+  ctx = ctx->next;
   return v;
 }

test/test1.inc

@@ -5,3 +5,4 @@ int main() {
   1; 2;
   return 0;
 }
+