is_csv.c

Go to the documentation of this file.

/*-
 * Copyright (c) 2019 Christos Zoulas
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
 
/*
 * Parse CSV object serialization format (RFC-4180, RFC-7111)
 */
 
#ifndef TEST
#include "file.h"
 
#ifndef lint
FILE_RCSID("@(#)$File: is_csv.c,v 1.13 2023/07/17 16:08:17 christos Exp $")
#endif
 
#include <string.h>
#include "magic.h"
#else
#include <sys/types.h>
#endif
 
 
#ifdef DEBUG
#include <stdio.h>
#define DPRINTF(fmt, ...) printf(fmt, __VA_ARGS__)
#else
#define DPRINTF(fmt, ...)
#endif
 
/*
 * if CSV_LINES == 0:
 *  check all the lines in the buffer
 * otherwise:
 *  check only up-to the number of lines specified
 *
 * the last line count is always ignored if it does not end in CRLF
 */
#ifndef CSV_LINES
#define CSV_LINES 10
#endif
 
static int csv_parse(const unsigned char *, const unsigned char *);
 
static const unsigned char *
eatquote(const unsigned char *uc, const unsigned char *ue)
{
    int quote = 0;
 
    while (uc < ue) {
        unsigned char c = *uc++;
        if (c != '"') {
            // We already got one, done.
            if (quote) {
                return --uc;
            }
            continue;
        }
        if (quote) {
            // quote-quote escapes
            quote = 0;
            continue;
        }
        // first quote
        quote = 1;
    }
    return ue;
}
 
static int
csv_parse(const unsigned char *uc, const unsigned char *ue)
{
    size_t nf = 0, tf = 0, nl = 0;
 
    while (uc < ue) {
        switch (*uc++) {
        case '"':
            // Eat until the matching quote
            uc = eatquote(uc, ue);
            break;
        case ',':
            nf++;
            break;
        case '\n':
            DPRINTF("%zu %zu %zu\n", nl, nf, tf);
            nl++;
#if CSV_LINES
            if (nl == CSV_LINES)
                return tf != 0 && tf == nf;
#endif
            if (tf == 0) {
                // First time and no fields, give up
                if (nf == 0) 
                    return 0;
                // First time, set the number of fields
                tf = nf;
            } else if (tf != nf) {
                // Field number mismatch, we are done.
                return 0;
            }
            nf = 0;
            break;
        default:
            break;
        }
    }
    return tf && nl >= 2;
}
 
#ifndef TEST
int
file_is_csv(struct magic_set *ms, const struct buffer *b, int looks_text,
    const char *code)
{
    const unsigned char *uc = CAST(const unsigned char *, b->fbuf);
    const unsigned char *ue = uc + b->flen;
    int mime = ms->flags & MAGIC_MIME;
 
    if (!looks_text)
        return 0;
 
    if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)) != 0)
        return 0;
 
    if (!csv_parse(uc, ue))
        return 0;
 
    if (mime == MAGIC_MIME_ENCODING)
        return 1;
 
    if (mime) {
        if (file_printf(ms, "text/csv") == -1)
            return -1;
        return 1;
    }
 
    if (file_printf(ms, "CSV %s%stext", code ? code : "",
        code ? " " : "") == -1)
        return -1;
 
    return 1;
}
 
#else
 
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <err.h>
 
int
main(int argc, char *argv[])
{
    int fd;
    struct stat st;
    unsigned char *p;
 
    if ((fd = open(argv[1], O_RDONLY)) == -1)
        err(EXIT_FAILURE, "Can't open `%s'", argv[1]);
 
    if (fstat(fd, &st) == -1)
        err(EXIT_FAILURE, "Can't stat `%s'", argv[1]);
 
    if ((p = CAST(char *, malloc(st.st_size))) == NULL)
        err(EXIT_FAILURE, "Can't allocate %jd bytes",
            (intmax_t)st.st_size);
    if (read(fd, p, st.st_size) != st.st_size)
        err(EXIT_FAILURE, "Can't read %jd bytes",
            (intmax_t)st.st_size);
    printf("is csv %d\n", csv_parse(p, p + st.st_size));
    return 0;
}
#endif