+/* Scan helper "stdio" functions for use by scanf-family and strto*-family
+ * functions. These accept either a valid stdio FILE, or a minimal pseudo
+ * FILE whose buffer pointers point into a null-terminated string. In the
+ * latter case, the sh_fromstring macro should be used to setup the FILE;
+ * the rest of the structure can be left uninitialized.
+ *
+ * To begin using these functions, shlim must first be called on the FILE
+ * to set a field width limit, or 0 for no limit. For string pseudo-FILEs,
+ * a nonzero limit is not valid and produces undefined behavior. After that,
+ * shgetc, shunget, and shcnt are valid as long as no other stdio functions
+ * are called on the stream.
+ *
+ * When used with a real FILE object, shunget has only one byte of pushback
+ * available. Further shunget (up to a limit of the stdio UNGET buffer size)
+ * will adjust the position but will not restore the data to be read again.
+ * This functionality is needed for the wcsto*-family functions, where it's
+ * okay because the FILE will be discarded immediately anyway. When used
+ * with string pseudo-FILEs, shunget has unlimited pushback, back to the
+ * beginning of the string. */