1 files changed, 39 insertions, 0 deletions
diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..1b89f8c
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,39 @@
+void fatal_error(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    vfprintf(stderr, msg, args);
+    va_end(args);
+    fprintf(stderr, "\n");
+    exit(1);
+}
+
+#define unreachable() fatal_error("%s:%d: unreachable", __FILE__, __LINE__)
+
+#define unimplemented() fatal_error("%s:%d: unimplemented", __FILE__, __LINE__)
+
+struct StrBuilder {
+    size_t len;
+    size_t capacity;
+    char* buf;
+};
+typedef struct StrBuilder StrBuilder;
+
+void strbuilder_init(StrBuilder* b) {
+    b->len = 0;
+    b->capacity = 16;
+    b->buf = calloc(b->capacity, sizeof(char));
+}
+
+// `size` must include a trailing null byte.
+void strbuilder_reserve(StrBuilder* b, size_t size) {
+    if (size <= b->capacity)
+        return;
+    b->capacity *= 2;
+    b->buf = realloc(b->buf, b->capacity * sizeof(char));
+    memset(b->buf + b->len, 0, (b->capacity - b->len) * sizeof(char));
+}
+
+void strbuilder_append_char(StrBuilder* b, int c) {
+    strbuilder_reserve(b, b->len + 1 + 1);
+    b->buf[b->len++] = c;
+}