enable to load custom db file path

.gitignore

@@ -0,0 +1 @@
+*.exe

cmd/file/main.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"magicmime"
+	"os"
+)
+
+var mgc = "/usr/share/misc/magic.mgc"
+
+func init() {
+	if mgcpath := os.Getenv("MGC"); mgcpath != "" {
+		mgc = mgcpath
+	}
+}
+
+func main() {
+	d, err := magicmime.NewWithPath(mgc, magicmime.MAGIC_NONE)
+	if err != nil {
+		fmt.Println("NewDecoderWithPath", err)
+		return
+	}
+	t, err := d.TypeByFile(os.Args[1])
+	fmt.Println(t, err)
+}

go.mod

@@ -0,0 +1,3 @@
+module magicmime
+
+go 1.20

magic.h

@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) Christos Zoulas 2003.
+ * 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 immediately at the beginning of the file, without modification,
+ *    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 AUTHOR 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 AUTHOR 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.
+ */
+#ifndef _MAGIC_H
+#define _MAGIC_H
+
+#include <sys/types.h>
+
+#define	MAGIC_NONE		0x0000000 /* No flags */
+#define	MAGIC_DEBUG		0x0000001 /* Turn on debugging */
+#define	MAGIC_SYMLINK		0x0000002 /* Follow symlinks */
+#define	MAGIC_COMPRESS		0x0000004 /* Check inside compressed files */
+#define	MAGIC_DEVICES		0x0000008 /* Look at the contents of devices */
+#define	MAGIC_MIME_TYPE		0x0000010 /* Return the MIME type */
+#define	MAGIC_CONTINUE		0x0000020 /* Return all matches */
+#define	MAGIC_CHECK		0x0000040 /* Print warnings to stderr */
+#define	MAGIC_PRESERVE_ATIME	0x0000080 /* Restore access time on exit */
+#define	MAGIC_RAW		0x0000100 /* Don't convert unprintable chars */
+#define	MAGIC_ERROR		0x0000200 /* Handle ENOENT etc as real errors */
+#define	MAGIC_MIME_ENCODING	0x0000400 /* Return the MIME encoding */
+#define MAGIC_MIME		(MAGIC_MIME_TYPE|MAGIC_MIME_ENCODING)
+#define	MAGIC_APPLE		0x0000800 /* Return the Apple creator/type */
+#define	MAGIC_EXTENSION		0x1000000 /* Return a /-separated list of
+					   * extensions */
+#define MAGIC_COMPRESS_TRANSP	0x2000000 /* Check inside compressed files
+					   * but not report compression */
+#define MAGIC_NO_COMPRESS_FORK	0x4000000 /* Don't allow decompression that
+					   * needs to fork */
+#define MAGIC_NODESC		(MAGIC_EXTENSION|MAGIC_MIME|MAGIC_APPLE)
+
+#define	MAGIC_NO_CHECK_COMPRESS	0x0001000 /* Don't check for compressed files */
+#define	MAGIC_NO_CHECK_TAR	0x0002000 /* Don't check for tar files */
+#define	MAGIC_NO_CHECK_SOFT	0x0004000 /* Don't check magic entries */
+#define	MAGIC_NO_CHECK_APPTYPE	0x0008000 /* Don't check application type */
+#define	MAGIC_NO_CHECK_ELF	0x0010000 /* Don't check for elf details */
+#define	MAGIC_NO_CHECK_TEXT	0x0020000 /* Don't check for text files */
+#define	MAGIC_NO_CHECK_CDF	0x0040000 /* Don't check for cdf files */
+#define MAGIC_NO_CHECK_CSV	0x0080000 /* Don't check for CSV files */
+#define	MAGIC_NO_CHECK_TOKENS	0x0100000 /* Don't check tokens */
+#define MAGIC_NO_CHECK_ENCODING 0x0200000 /* Don't check text encodings */
+#define MAGIC_NO_CHECK_JSON	0x0400000 /* Don't check for JSON files */
+#define MAGIC_NO_CHECK_SIMH	0x0800000 /* Don't check for SIMH tape files */
+
+/* No built-in tests; only consult the magic file */
+#define MAGIC_NO_CHECK_BUILTIN	( \
+	MAGIC_NO_CHECK_COMPRESS	| \
+	MAGIC_NO_CHECK_TAR	| \
+/*	MAGIC_NO_CHECK_SOFT	| */ \
+	MAGIC_NO_CHECK_APPTYPE	| \
+	MAGIC_NO_CHECK_ELF	| \
+	MAGIC_NO_CHECK_TEXT	| \
+	MAGIC_NO_CHECK_CSV	| \
+	MAGIC_NO_CHECK_CDF	| \
+	MAGIC_NO_CHECK_TOKENS	| \
+	MAGIC_NO_CHECK_ENCODING	| \
+	MAGIC_NO_CHECK_JSON	| \
+	MAGIC_NO_CHECK_SIMH	| \
+	0			  \
+)
+
+#define MAGIC_SNPRINTB "\177\020\
+b\0debug\0\
+b\1symlink\0\
+b\2compress\0\
+b\3devices\0\
+b\4mime_type\0\
+b\5continue\0\
+b\6check\0\
+b\7preserve_atime\0\
+b\10raw\0\
+b\11error\0\
+b\12mime_encoding\0\
+b\13apple\0\
+b\14no_check_compress\0\
+b\15no_check_tar\0\
+b\16no_check_soft\0\
+b\17no_check_sapptype\0\
+b\20no_check_elf\0\
+b\21no_check_text\0\
+b\22no_check_cdf\0\
+b\23no_check_csv\0\
+b\24no_check_tokens\0\
+b\25no_check_encoding\0\
+b\26no_check_json\0\
+b\27no_check_simh\0\
+b\30extension\0\
+b\31transp_compression\0\
+"
+
+/* Defined for backwards compatibility (renamed) */
+#define	MAGIC_NO_CHECK_ASCII	MAGIC_NO_CHECK_TEXT
+
+/* Defined for backwards compatibility; do nothing */
+#define	MAGIC_NO_CHECK_FORTRAN	0x000000 /* Don't check ascii/fortran */
+#define	MAGIC_NO_CHECK_TROFF	0x000000 /* Don't check ascii/troff */
+
+#define MAGIC_VERSION		X.YY	/* This implementation */
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct magic_set *magic_t;
+magic_t magic_open(int);
+void magic_close(magic_t);
+
+const char *magic_getpath(const char *, int);
+const char *magic_file(magic_t, const char *);
+const char *magic_descriptor(magic_t, int);
+const char *magic_buffer(magic_t, const void *, size_t);
+
+const char *magic_error(magic_t);
+int magic_getflags(magic_t);
+int magic_setflags(magic_t, int);
+
+int magic_version(void);
+int magic_load(magic_t, const char *);
+int magic_load_buffers(magic_t, void **, size_t *, size_t);
+
+int magic_compile(magic_t, const char *);
+int magic_check(magic_t, const char *);
+int magic_list(magic_t, const char *);
+int magic_errno(magic_t);
+
+#define MAGIC_PARAM_INDIR_MAX		0
+#define MAGIC_PARAM_NAME_MAX		1
+#define MAGIC_PARAM_ELF_PHNUM_MAX	2
+#define MAGIC_PARAM_ELF_SHNUM_MAX	3
+#define MAGIC_PARAM_ELF_NOTES_MAX	4
+#define MAGIC_PARAM_REGEX_MAX		5
+#define	MAGIC_PARAM_BYTES_MAX		6
+#define	MAGIC_PARAM_ENCODING_MAX	7
+#define	MAGIC_PARAM_ELF_SHSIZE_MAX		8
+
+int magic_setparam(magic_t, int, const void *);
+int magic_getparam(magic_t, int, void *);
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif /* _MAGIC_H */