Implement SIZE_FMT and vec_append_fmt

SIZE_FMT gets the size of a cstr with the given sprintf formatted
string and arguments using `snprintf`.

vec_append_fmt formats a cstr with the given sprintf arguments then
appends it to the given vector.

This simplifies a little bit of the wordy implementation of the
assembler.

1 files changed, 10 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index c58d425..9d964f7 100644
--- a/lib.h
+++ b/lib.h
@@ -26,6 +26,8 @@ char *fread_all(FILE *fp);
 void print_error(const char *handle, size_t row, size_t column,
                  const char *reason);
 
+#define SIZE_FMT(FMT, ...) (snprintf(NULL, 0, (FMT), __VA_ARGS__))
+
 typedef struct Buffer
 {
   const char *name;
@@ -46,4 +48,12 @@ void vec_ensure(vec_t *vec, u64 abs_size);
 void vec_ensure_free(vec_t *vec, u64 rel_size);
 void vec_free(vec_t *vec);
 
+#define vec_append_fmt(VEC, FMT, ...)           \
+  do                                            \
+  {                                             \
+    char f[SIZE_FMT(FMT, __VA_ARGS__) + 1];     \
+    snprintf(f, sizeof(f), (FMT), __VA_ARGS__); \
+    vec_append((VEC), f, sizeof(f) - 1);        \
+  } while (0)
+
 #endif