From 48c8cec1c83d70e23dc1359b85cfd9e36fdaa60f Mon Sep 17 00:00:00 2001 From: Kaz Kylheku Date: Mon, 13 Jan 2014 22:19:03 -0800 Subject: Support for pushing back bytes and characters into streams. * stream.c (null_ops, stdio_ops, tail_ops, pipe_ops, string_in_ops, byte_in_ops, string_out_ops, strlist_out_ops, dir_ops, cat_stream_ops): Structure definition updated with new initializers for two new virtuals. (stdio_handle): New member, unget_c. (snarf_line, stdio_get_char): Handle pushed-back character in h->unget_c. (stdio_unget_char, stdio_unget_byte, string_in_unget_char, byte_in_unget_byte): New static functions. (make_stdio_stream_common): Initialize unget_c member. (unget_char, unget_byte): New functions. * stream.h (struct strm_ops): New virtuals: unget_char and unget_byte. (unget_char, unget_byte): New functions declared. * syslog.c (syslog_strm_ops): Two new initializers. * eval.c (eval_init): Registered unget_char and unget_byte as intrinsics. * txr.1: Documented. --- txr.1 | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'txr.1') diff --git a/txr.1 b/txr.1 index 8f87e428..a6760076 100644 --- a/txr.1 +++ b/txr.1 @@ -10465,6 +10465,29 @@ the two operations will interfere with the UTF-8 decoding. These functions return nil when the end of data is reached. Errors are represented as exceptions. +.SS Functions unget-char and unget-byte + +.TP +Syntax: + + (unget-char []) + (unget-byte []) + +.TP +Description: + +These character put back, into a stream, a character or byte which was +previously read. The character or byte must match the one which was most +recently read. If the parameter is omitted, then the *stdin* +stream is used. + +If the operation succeeds, the byte or character value is returned. +A nil return indicates that the operation is unsupported. + +Some streams do not support these operations; some support +only one of them. In general, if a stream supports get-char, +it supports unget-char, and likewise for get-byte and unget-byte. + .SS Functions put-string, put-line, put-char and put-byte .TP -- cgit v1.2.3