Add a simple CSV detector

diff --git a/src/is_csv.c b/src/is_csv.c
new file mode 100644 (file)
index 0000000..4f167e0
--- /dev/null
+++ b/src/is_csv.c
@@ -0,0 +1,194 @@
+/*-
+ * 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 1.1 2019/06/08 22:16:57 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) {
+               unsigned char c;
+               switch (c = *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);
+#if CSV_LINES
+                       if (nl++ == CSV_LINES)
+                               return tf == nf;
+#endif
+                       if (nf == 0) 
+                               break;
+
+                       if (tf == 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)
+{
+       const unsigned char *uc = CAST(const unsigned char *, b->fbuf);
+       const unsigned char *ue = uc + b->flen;
+       int mime = ms->flags & MAGIC_MIME;
+
+
+       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, "application/csv") == -1)
+                       return -1;
+               return 1;
+       }
+
+       if (file_printf(ms, "CSV data") == -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, rv;
+       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 = 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