346 lines
8.0 KiB
C
346 lines
8.0 KiB
C
/*
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* revtwoway.c --- Provide a two-way processor that reverses lines.
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*
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* Arnold Robbins
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* arnold@skeeve.com
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* Written 8/2012
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*/
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/*
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* Copyright (C) 2012-2014, 2016, 2018 the Free Software Foundation, Inc.
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*
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* This file is part of GAWK, the GNU implementation of the
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* AWK Programming Language.
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*
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* GAWK is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GAWK is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#define _BSD_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include "gawkapi.h"
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#include "gettext.h"
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#define _(msgid) gettext(msgid)
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#define N_(msgid) msgid
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static const gawk_api_t *api; /* for convenience macros to work */
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static awk_ext_id_t ext_id;
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static const char *ext_version = "revtwoway extension: version 1.0";
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static awk_bool_t init_revtwoway(void);
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static awk_bool_t (*init_func)(void) = init_revtwoway;
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int plugin_is_GPL_compatible;
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/*
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* Use this variable to provide a value != INVALID_HANDLE in the awk_input_buf_t
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* and != NULL in the awk_output_buf_t. The idea is to have a value that
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* is greater than the largest allowable file descriptor.
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*/
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static size_t max_fds;
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#ifndef HAVE_GETDTABLESIZE
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/* gawk_getdtablesize --- replacement version that should be good enough */
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static inline int
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gawk_getdtablesize()
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{
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/*
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* Algorithm for the GNULIB folks:
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*
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* Set up a bitmap of 2048 elements.
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* Initialize it to zero.
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* In a loop, do
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* fd = open("/dev/null", O_RDONLY)
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* set the bit corresponding to fd in the bit map
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* until it fails.
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* Get the highest value that succeeded and increment it by one
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* --> that is how many descriptors we have.
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* Loop over the bitmap to close all the file descriptors we opened.
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*
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* Do all this upon the first call and return static values upon
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* subsequent calls.
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*/
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/* In the meantime, this is good enough for us: */
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return 1024;
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}
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#define getdtablesize() gawk_getdtablesize()
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#endif
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/*
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* IMPORTANT NOTE: This is a NOT a true general purpose
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* extension. It is intended to demonstrate how to set up
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* all the "plumbing" and to work one record at a time, ONLY.
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*
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* While it would be possible to set up buffering and manage it,
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* that would duplicate a large chunk of the code in gawk's
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* get_a_record() function, and there's no real point in doing that.
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*/
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/* the data in the opaque pointer */
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typedef struct two_way_proc_data {
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size_t size; /* size of allocated buffer */
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size_t len; /* how much is actually in use */
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char *data;
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size_t in_use; /* use count, must hit zero to be freed */
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} two_way_proc_data_t;
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/* close_two_proc_data --- release the data */
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static void
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close_two_proc_data(two_way_proc_data_t *proc_data)
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{
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if (proc_data->in_use > 1) {
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proc_data->in_use--;
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return;
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}
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gawk_free(proc_data->data);
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gawk_free(proc_data);
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}
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/*
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* Input side of the two-way processor (input TO gawk)
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*/
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/* rev2way_get_record --- get one record at a time out of a directory */
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static int
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rev2way_get_record(char **out, awk_input_buf_t *iobuf, int *errcode,
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char **rt_start, size_t *rt_len,
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const awk_fieldwidth_info_t **unused)
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{
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int len = 0; /* for now */
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two_way_proc_data_t *proc_data;
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/*
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* The caller sets *errcode to 0, so we should set it only if an
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* error occurs.
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*/
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(void) errcode; /* silence warnings */
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if (out == NULL || iobuf == NULL || iobuf->opaque == NULL)
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return EOF;
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proc_data = (two_way_proc_data_t *) iobuf->opaque;
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if (proc_data->len == 0)
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return 0;
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*out = proc_data->data;
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len = proc_data->len;
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proc_data->len = 0;
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*rt_len = 0; /* default: set RT to "" */
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if (proc_data->data[len-1] == '\n') {
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while (proc_data->data[len-1] == '\n') {
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len--;
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(*rt_len)++;
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}
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*rt_start = proc_data->data + len;
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}
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return len;
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}
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/* rev2way_close --- close up input side when done */
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static void
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rev2way_close(awk_input_buf_t *iobuf)
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{
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two_way_proc_data_t *proc_data;
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if (iobuf == NULL || iobuf->opaque == NULL)
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return;
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proc_data = (two_way_proc_data_t *) iobuf->opaque;
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close_two_proc_data(proc_data);
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iobuf->fd = INVALID_HANDLE;
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}
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/*
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* Output side of the two-way processor (output FROM gawk)
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*/
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/* rev2way_fwrite --- write out characters in reverse order */
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static size_t
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rev2way_fwrite(const void *buf, size_t size, size_t count, FILE *fp, void *opaque)
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{
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two_way_proc_data_t *proc_data;
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size_t amount, char_count;
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char *src, *dest;
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(void) fp; /* silence warnings */
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if (opaque == NULL)
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return 0; /* error */
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proc_data = (two_way_proc_data_t *) opaque;
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amount = size * count;
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/* do the dance */
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if (amount > proc_data->size || proc_data->len > 0) {
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if (proc_data->data == NULL)
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emalloc(proc_data->data, char *, amount, "rev2way_fwrite");
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else
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erealloc(proc_data->data, char *, proc_data->size + amount, "rev2way_fwrite");
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proc_data->size += amount;
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}
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src = (char *) buf + amount -1;
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dest = proc_data->data + proc_data->len;
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for (char_count = amount; char_count > 0; char_count--) {
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/* copy in backwards */
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*dest++ = *src--;
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}
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proc_data->len += amount;
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return amount;
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}
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/* rev2way_fflush --- do nothing hook for fflush */
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static int
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rev2way_fflush(FILE *fp, void *opaque)
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{
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(void) fp;
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(void) opaque;
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return 0;
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}
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/* rev2way_ferror --- do nothing hook for ferror */
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static int
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rev2way_ferror(FILE *fp, void *opaque)
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{
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(void) fp;
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(void) opaque;
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return 0;
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}
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/* rev2way_fclose --- close output side of two-way processor */
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static int
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rev2way_fclose(FILE *fp, void *opaque)
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{
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two_way_proc_data_t *proc_data;
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if (opaque == NULL)
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return EOF; /* error */
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(void) fp;
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proc_data = (two_way_proc_data_t *) opaque;
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close_two_proc_data(proc_data);
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return 0;
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}
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/* revtwoway_can_two_way --- return true if we want the file */
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static awk_bool_t
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revtwoway_can_take_two_way(const char *name)
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{
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return (name != NULL && strcmp(name, "/magic/mirror") == 0);
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}
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/*
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* revtwoway_take_control_of --- set up two way processor
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* We can assume that revtwoway_can_take_two_way just returned true,
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* and no state has changed since then.
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*/
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static awk_bool_t
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revtwoway_take_control_of(const char *name, awk_input_buf_t *inbuf, awk_output_buf_t *outbuf)
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{
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two_way_proc_data_t *proc_data;
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(void) name; /* silence warnings */
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if (inbuf == NULL || outbuf == NULL)
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return awk_false;
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emalloc(proc_data, two_way_proc_data_t *, sizeof(two_way_proc_data_t), "revtwoway_take_control_of");
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proc_data->in_use = 2;
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proc_data->size = 0;
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proc_data->len = 0;
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proc_data->data = NULL;
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if (max_fds + 1 == 0) /* wrapped. ha! */
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max_fds = getdtablesize();
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/* input side: */
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inbuf->get_record = rev2way_get_record;
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inbuf->close_func = rev2way_close;
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inbuf->fd = max_fds;
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inbuf->opaque = proc_data;
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/* output side: */
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outbuf->fp = (FILE *) max_fds++;
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outbuf->opaque = proc_data;
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outbuf->gawk_fwrite = rev2way_fwrite;
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outbuf->gawk_fflush = rev2way_fflush;
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outbuf->gawk_ferror = rev2way_ferror;
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outbuf->gawk_fclose = rev2way_fclose;
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outbuf->redirected = awk_true;
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return awk_true;
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}
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static awk_two_way_processor_t two_way_processor = {
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"revtwoway",
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revtwoway_can_take_two_way,
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revtwoway_take_control_of,
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NULL
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};
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/* init_revtwoway --- set things ups */
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static awk_bool_t
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init_revtwoway()
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{
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register_two_way_processor(& two_way_processor);
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max_fds = getdtablesize();
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return awk_true;
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}
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static awk_ext_func_t func_table[] = {
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{ NULL, NULL, 0, 0, awk_false, NULL }
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};
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/* define the dl_load function using the boilerplate macro */
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dl_load_func(func_table, revtwoway, "")
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