void string_buffer_append_vprintf(struct string_buffer *buf, const char *fmt, va_list args);
void string_buffer_append_printf(struct string_buffer *buf, const char *fmt, ...);
void string_buffer_replace(struct string_buffer *buf, unsigned int from, unsigned int len, const char *repl);
void string_buffer_append_vprintf(struct string_buffer *buf, const char *fmt, va_list args);
void string_buffer_append_printf(struct string_buffer *buf, const char *fmt, ...);
void string_buffer_replace(struct string_buffer *buf, unsigned int from, unsigned int len, const char *repl);