1 files changed, 45 insertions, 0 deletions
diff --git a/grammars/c/preprocess.c b/grammars/c/preprocess.c
new file mode 100644
index 0000000..3ae7406
--- /dev/null
+++ b/grammars/c/preprocess.c
@@ -0,0 +1,45 @@
+void preprocess(char *string, size_t length) {
+    int on_newline = 1;
+    for (int i = 0; i < length;) {
+        switch (string[i]) {
+            case '/': {
+                on_newline = 0;
+                if (string[i+1] == '*') {
+                    for (; i+1 < length; i++) {
+                        if (string[i] == '*' && string[i+1] == '/') {
+                            string[i] = ' ';
+                            string[i+1] = ' ';
+                            break;
+                        }
+                        string[i] = ' ';
+                    }
+                    continue;
+                } else if (string[i+1] == '/') {
+                    for (; i < length; i++) {
+                        if (string[i] == '\n') {
+                            string[i] = ' ';
+                            break;
+                        }
+                        string[i] = ' ';
+                    }
+                    continue;
+                }
+                break;
+            }
+            case '#': {
+                if (on_newline) {
+                    int escaped = 0;
+                    for (i++; i < length; i++) {
+                        if (string[i] == '\n' && !escaped) break;
+                        escaped = (string[i] == '\\');
+                        string[i] = ' ';
+                    }
+                    break;
+                }
+            }
+            case '\n': on_newline = 1; break;
+            default: on_newline = 0; break;
+        }
+        i++;
+    }
+}