Add peek buffer to io, hide file/buffer private functions

Implements peek buffer on top of the raw io read (with small storage
optimization). Hides implementation details of the file/buffer.

include/bh/buffer.h

@@ -8,8 +8,6 @@ typedef struct bh_buffer_s bh_buffer_t;
 
 bh_buffer_t *bh_buffer_new(void);
 
-void bh_buffer_free(bh_buffer_t *buffer);
-
 const char *bh_buffer_data(bh_buffer_t *buffer);
 
 void bh_buffer_set_data(bh_buffer_t *buffer,
@@ -21,34 +19,8 @@ size_t bh_buffer_capacity(bh_buffer_t *buffer);
 int bh_buffer_reserve(bh_buffer_t *buffer,
                       size_t size);
 
-int bh_buffer_open_base(bh_buffer_t *buffer,
-                        int mode);
-
-void bh_buffer_close_base(bh_buffer_t *buffer);
-
-int bh_buffer_is_open_base(bh_buffer_t *buffer);
-
-size_t bh_buffer_read_base(bh_buffer_t *buffer,
-                           char *data,
-                           size_t size);
-
-size_t bh_buffer_write_base(bh_buffer_t *buffer,
-                            const char *data,
-                            size_t size);
-
-void bh_buffer_flush_base(bh_buffer_t *buffer);
-
-int bh_buffer_seek_base(bh_buffer_t *buffer,
-                        bh_off_t pos,
-                        int dir);
-
-bh_off_t bh_buffer_size_base(bh_buffer_t *buffer);
-
-bh_off_t bh_buffer_tell_base(bh_buffer_t *buffer);
-
-bh_off_t bh_buffer_available_base(bh_buffer_t *buffer);
-
-void bh_buffer_clear_base(bh_buffer_t *buffer);
+#define bh_buffer_free(buffer) \
+    bh_io_free((bh_io_t *)(buffer))
 
 #define bh_buffer_open(buffer, mode) \
     bh_io_open((bh_io_t *)(buffer), (mode))