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freebsd-skq/contrib/file/ascmagic.c
David E. O'Brien 3459dd3784 Virgin import of Christos Zoulas's FILE 3.40.
2003-02-15 18:53:17 +00:00

663 lines
20 KiB
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/*
* ASCII magic -- file types that we know based on keywords
* that can appear anywhere in the file.
*
* Copyright (c) Ian F. Darwin, 1987.
* Written by Ian F. Darwin.
*
* Extensively modified by Eric Fischer <enf@pobox.com> in July, 2000,
* to handle character codes other than ASCII on a unified basis.
*
* Joerg Wunsch <joerg@freebsd.org> wrote the original support for 8-bit
* international characters, now subsumed into this file.
*/
/*
* This software is not subject to any license of the American Telephone
* and Telegraph Company or of the Regents of the University of California.
*
* Permission is granted to anyone to use this software for any purpose on
* any computer system, and to alter it and redistribute it freely, subject
* to the following restrictions:
*
* 1. The author is not responsible for the consequences of use of this
* software, no matter how awful, even if they arise from flaws in it.
*
* 2. The origin of this software must not be misrepresented, either by
* explicit claim or by omission. Since few users ever read sources,
* credits must appear in the documentation.
*
* 3. Altered versions must be plainly marked as such, and must not be
* misrepresented as being the original software. Since few users
* ever read sources, credits must appear in the documentation.
*
* 4. This notice may not be removed or altered.
*/
#include "file.h"
#include <string.h>
#include <memory.h>
#include <ctype.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "names.h"
#ifndef lint
FILE_RCSID("@(#)$Id: ascmagic.c,v 1.33 2003/02/08 18:33:53 christos Exp $")
#endif /* lint */
typedef unsigned long unichar;
#define MAXLINELEN 300 /* longest sane line length */
#define ISSPC(x) ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' \
|| (x) == 0x85 || (x) == '\f')
static int looks_ascii(const unsigned char *, int, unichar *, int *);
static int looks_utf8(const unsigned char *, int, unichar *, int *);
static int looks_unicode(const unsigned char *, int, unichar *, int *);
static int looks_latin1(const unsigned char *, int, unichar *, int *);
static int looks_extended(const unsigned char *, int, unichar *, int *);
static void from_ebcdic(const unsigned char *, int, unsigned char *);
static int ascmatch(const unsigned char *, const unichar *, int);
/* int nbytes: size actually read */
int
ascmagic(unsigned char *buf, int nbytes)
{
int i;
unsigned char nbuf[HOWMANY+1]; /* one extra for terminating '\0' */
unichar ubuf[HOWMANY+1]; /* one extra for terminating '\0' */
int ulen;
struct names *p;
char *code = NULL;
char *code_mime = NULL;
char *type = NULL;
char *subtype = NULL;
char *subtype_mime = NULL;
int has_escapes = 0;
int has_backspace = 0;
int n_crlf = 0;
int n_lf = 0;
int n_cr = 0;
int n_nel = 0;
int last_line_end = -1;
int has_long_lines = 0;
/*
* Do the tar test first, because if the first file in the tar
* archive starts with a dot, we can confuse it with an nroff file.
*/
switch (is_tar(buf, nbytes)) {
case 1:
ckfputs(iflag ? "application/x-tar" : "tar archive", stdout);
return 1;
case 2:
ckfputs(iflag ? "application/x-tar, POSIX"
: "POSIX tar archive", stdout);
return 1;
}
/*
* Undo the NUL-termination kindly provided by process()
* but leave at least one byte to look at
*/
while (nbytes > 1 && buf[nbytes - 1] == '\0')
nbytes--;
/*
* Then try to determine whether it's any character code we can
* identify. Each of these tests, if it succeeds, will leave
* the text converted into one-unichar-per-character Unicode in
* ubuf, and the number of characters converted in ulen.
*/
if (looks_ascii(buf, nbytes, ubuf, &ulen)) {
code = "ASCII";
code_mime = "us-ascii";
type = "text";
} else if (looks_utf8(buf, nbytes, ubuf, &ulen)) {
code = "UTF-8 Unicode";
code_mime = "utf-8";
type = "text";
} else if ((i = looks_unicode(buf, nbytes, ubuf, &ulen))) {
if (i == 1)
code = "Little-endian UTF-16 Unicode";
else
code = "Big-endian UTF-16 Unicode";
type = "character data";
code_mime = "utf-16"; /* is this defined? */
} else if (looks_latin1(buf, nbytes, ubuf, &ulen)) {
code = "ISO-8859";
type = "text";
code_mime = "iso-8859-1";
} else if (looks_extended(buf, nbytes, ubuf, &ulen)) {
code = "Non-ISO extended-ASCII";
type = "text";
code_mime = "unknown";
} else {
from_ebcdic(buf, nbytes, nbuf);
if (looks_ascii(nbuf, nbytes, ubuf, &ulen)) {
code = "EBCDIC";
type = "character data";
code_mime = "ebcdic";
} else if (looks_latin1(nbuf, nbytes, ubuf, &ulen)) {
code = "International EBCDIC";
type = "character data";
code_mime = "ebcdic";
} else {
return 0; /* doesn't look like text at all */
}
}
/*
* for troff, look for . + letter + letter or .\";
* this must be done to disambiguate tar archives' ./file
* and other trash from real troff input.
*
* I believe Plan 9 troff allows non-ASCII characters in the names
* of macros, so this test might possibly fail on such a file.
*/
if (*ubuf == '.') {
unichar *tp = ubuf + 1;
while (ISSPC(*tp))
++tp; /* skip leading whitespace */
if ((tp[0] == '\\' && tp[1] == '\"') ||
(isascii(tp[0]) && isalnum(tp[0]) &&
isascii(tp[1]) && isalnum(tp[1]) &&
ISSPC(tp[2]))) {
subtype_mime = "text/troff";
subtype = "troff or preprocessor input";
goto subtype_identified;
}
}
if ((*buf == 'c' || *buf == 'C') && ISSPC(buf[1])) {
subtype_mime = "text/fortran";
subtype = "fortran program";
goto subtype_identified;
}
/* look for tokens from names.h - this is expensive! */
i = 0;
while (i < ulen) {
int end;
/*
* skip past any leading space
*/
while (i < ulen && ISSPC(ubuf[i]))
i++;
if (i >= ulen)
break;
/*
* find the next whitespace
*/
for (end = i + 1; end < nbytes; end++)
if (ISSPC(ubuf[end]))
break;
/*
* compare the word thus isolated against the token list
*/
for (p = names; p < names + NNAMES; p++) {
if (ascmatch((unsigned char *)p->name, ubuf + i,
end - i)) {
subtype = types[p->type].human;
subtype_mime = types[p->type].mime;
goto subtype_identified;
}
}
i = end;
}
subtype_identified:
/*
* Now try to discover other details about the file.
*/
for (i = 0; i < ulen; i++) {
if (i > last_line_end + MAXLINELEN)
has_long_lines = 1;
if (ubuf[i] == '\033')
has_escapes = 1;
if (ubuf[i] == '\b')
has_backspace = 1;
if (ubuf[i] == '\r' && (i + 1 < ulen && ubuf[i + 1] == '\n')) {
n_crlf++;
last_line_end = i;
}
if (ubuf[i] == '\r' && (i + 1 >= ulen || ubuf[i + 1] != '\n')) {
n_cr++;
last_line_end = i;
}
if (ubuf[i] == '\n' && (i - 1 < 0 || ubuf[i - 1] != '\r')) {
n_lf++;
last_line_end = i;
}
if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
n_nel++;
last_line_end = i;
}
}
if (iflag) {
if (subtype_mime)
ckfputs(subtype_mime, stdout);
else
ckfputs("text/plain", stdout);
if (code_mime) {
ckfputs("; charset=", stdout);
ckfputs(code_mime, stdout);
}
} else {
ckfputs(code, stdout);
if (subtype) {
ckfputs(" ", stdout);
ckfputs(subtype, stdout);
}
ckfputs(" ", stdout);
ckfputs(type, stdout);
if (has_long_lines)
ckfputs(", with very long lines", stdout);
/*
* Only report line terminators if we find one other than LF,
* or if we find none at all.
*/
if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
(n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
ckfputs(", with", stdout);
if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0)
ckfputs(" no", stdout);
else {
if (n_crlf) {
ckfputs(" CRLF", stdout);
if (n_cr || n_lf || n_nel)
ckfputs(",", stdout);
}
if (n_cr) {
ckfputs(" CR", stdout);
if (n_lf || n_nel)
ckfputs(",", stdout);
}
if (n_lf) {
ckfputs(" LF", stdout);
if (n_nel)
ckfputs(",", stdout);
}
if (n_nel)
ckfputs(" NEL", stdout);
}
ckfputs(" line terminators", stdout);
}
if (has_escapes)
ckfputs(", with escape sequences", stdout);
if (has_backspace)
ckfputs(", with overstriking", stdout);
}
return 1;
}
static int
ascmatch(const unsigned char *s, const unichar *us, int ulen)
{
size_t i;
for (i = 0; i < ulen; i++) {
if (s[i] != us[i])
return 0;
}
if (s[i])
return 0;
else
return 1;
}
/*
* This table reflects a particular philosophy about what constitutes
* "text," and there is room for disagreement about it.
*
* Version 3.31 of the file command considered a file to be ASCII if
* each of its characters was approved by either the isascii() or
* isalpha() function. On most systems, this would mean that any
* file consisting only of characters in the range 0x00 ... 0x7F
* would be called ASCII text, but many systems might reasonably
* consider some characters outside this range to be alphabetic,
* so the file command would call such characters ASCII. It might
* have been more accurate to call this "considered textual on the
* local system" than "ASCII."
*
* It considered a file to be "International language text" if each
* of its characters was either an ASCII printing character (according
* to the real ASCII standard, not the above test), a character in
* the range 0x80 ... 0xFF, or one of the following control characters:
* backspace, tab, line feed, vertical tab, form feed, carriage return,
* escape. No attempt was made to determine the language in which files
* of this type were written.
*
*
* The table below considers a file to be ASCII if all of its characters
* are either ASCII printing characters (again, according to the X3.4
* standard, not isascii()) or any of the following controls: bell,
* backspace, tab, line feed, form feed, carriage return, esc, nextline.
*
* I include bell because some programs (particularly shell scripts)
* use it literally, even though it is rare in normal text. I exclude
* vertical tab because it never seems to be used in real text. I also
* include, with hesitation, the X3.64/ECMA-43 control nextline (0x85),
* because that's what the dd EBCDIC->ASCII table maps the EBCDIC newline
* character to. It might be more appropriate to include it in the 8859
* set instead of the ASCII set, but it's got to be included in *something*
* we recognize or EBCDIC files aren't going to be considered textual.
* Some old Unix source files use SO/SI (^N/^O) to shift between Greek
* and Latin characters, so these should possibly be allowed. But they
* make a real mess on VT100-style displays if they're not paired properly,
* so we are probably better off not calling them text.
*
* A file is considered to be ISO-8859 text if its characters are all
* either ASCII, according to the above definition, or printing characters
* from the ISO-8859 8-bit extension, characters 0xA0 ... 0xFF.
*
* Finally, a file is considered to be international text from some other
* character code if its characters are all either ISO-8859 (according to
* the above definition) or characters in the range 0x80 ... 0x9F, which
* ISO-8859 considers to be control characters but the IBM PC and Macintosh
* consider to be printing characters.
*/
#define F 0 /* character never appears in text */
#define T 1 /* character appears in plain ASCII text */
#define I 2 /* character appears in ISO-8859 text */
#define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */
static char text_chars[256] = {
/* BEL BS HT LF FF CR */
F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */
/* ESC */
F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */
T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */
/* NEL */
X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */
X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */
I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */
};
static int
looks_ascii(const unsigned char *buf, int nbytes, unichar *ubuf, int *ulen)
{
int i;
*ulen = 0;
for (i = 0; i < nbytes; i++) {
int t = text_chars[buf[i]];
if (t != T)
return 0;
ubuf[(*ulen)++] = buf[i];
}
return 1;
}
static int
looks_latin1(const unsigned char *buf, int nbytes, unichar *ubuf, int *ulen)
{
int i;
*ulen = 0;
for (i = 0; i < nbytes; i++) {
int t = text_chars[buf[i]];
if (t != T && t != I)
return 0;
ubuf[(*ulen)++] = buf[i];
}
return 1;
}
static int
looks_extended(const unsigned char *buf, int nbytes, unichar *ubuf, int *ulen)
{
int i;
*ulen = 0;
for (i = 0; i < nbytes; i++) {
int t = text_chars[buf[i]];
if (t != T && t != I && t != X)
return 0;
ubuf[(*ulen)++] = buf[i];
}
return 1;
}
int
looks_utf8(const unsigned char *buf, int nbytes, unichar *ubuf, int *ulen)
{
int i, n;
unichar c;
int gotone = 0;
*ulen = 0;
for (i = 0; i < nbytes; i++) {
if ((buf[i] & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */
/*
* Even if the whole file is valid UTF-8 sequences,
* still reject it if it uses weird control characters.
*/
if (text_chars[buf[i]] != T)
return 0;
ubuf[(*ulen)++] = buf[i];
} else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */
return 0;
} else { /* 11xxxxxx begins UTF-8 */
int following;
if ((buf[i] & 0x20) == 0) { /* 110xxxxx */
c = buf[i] & 0x1f;
following = 1;
} else if ((buf[i] & 0x10) == 0) { /* 1110xxxx */
c = buf[i] & 0x0f;
following = 2;
} else if ((buf[i] & 0x08) == 0) { /* 11110xxx */
c = buf[i] & 0x07;
following = 3;
} else if ((buf[i] & 0x04) == 0) { /* 111110xx */
c = buf[i] & 0x03;
following = 4;
} else if ((buf[i] & 0x02) == 0) { /* 1111110x */
c = buf[i] & 0x01;
following = 5;
} else
return 0;
for (n = 0; n < following; n++) {
i++;
if (i >= nbytes)
goto done;
if ((buf[i] & 0x80) == 0 || (buf[i] & 0x40))
return 0;
c = (c << 6) + (buf[i] & 0x3f);
}
ubuf[(*ulen)++] = c;
gotone = 1;
}
}
done:
return gotone; /* don't claim it's UTF-8 if it's all 7-bit */
}
static int
looks_unicode(const unsigned char *buf, int nbytes, unichar *ubuf, int *ulen)
{
int bigend;
int i;
if (nbytes < 2)
return 0;
if (buf[0] == 0xff && buf[1] == 0xfe)
bigend = 0;
else if (buf[0] == 0xfe && buf[1] == 0xff)
bigend = 1;
else
return 0;
*ulen = 0;
for (i = 2; i + 1 < nbytes; i += 2) {
/* XXX fix to properly handle chars > 65536 */
if (bigend)
ubuf[(*ulen)++] = buf[i + 1] + 256 * buf[i];
else
ubuf[(*ulen)++] = buf[i] + 256 * buf[i + 1];
if (ubuf[*ulen - 1] == 0xfffe)
return 0;
if (ubuf[*ulen - 1] < 128 && text_chars[ubuf[*ulen - 1]] != T)
return 0;
}
return 1 + bigend;
}
#undef F
#undef T
#undef I
#undef X
/*
* This table maps each EBCDIC character to an (8-bit extended) ASCII
* character, as specified in the rationale for the dd(1) command in
* draft 11.2 (September, 1991) of the POSIX P1003.2 standard.
*
* Unfortunately it does not seem to correspond exactly to any of the
* five variants of EBCDIC documented in IBM's _Enterprise Systems
* Architecture/390: Principles of Operation_, SA22-7201-06, Seventh
* Edition, July, 1999, pp. I-1 - I-4.
*
* Fortunately, though, all versions of EBCDIC, including this one, agree
* on most of the printing characters that also appear in (7-bit) ASCII.
* Of these, only '|', '!', '~', '^', '[', and ']' are in question at all.
*
* Fortunately too, there is general agreement that codes 0x00 through
* 0x3F represent control characters, 0x41 a nonbreaking space, and the
* remainder printing characters.
*
* This is sufficient to allow us to identify EBCDIC text and to distinguish
* between old-style and internationalized examples of text.
*/
unsigned char ebcdic_to_ascii[] = {
0, 1, 2, 3, 156, 9, 134, 127, 151, 141, 142, 11, 12, 13, 14, 15,
16, 17, 18, 19, 157, 133, 8, 135, 24, 25, 146, 143, 28, 29, 30, 31,
128, 129, 130, 131, 132, 10, 23, 27, 136, 137, 138, 139, 140, 5, 6, 7,
144, 145, 22, 147, 148, 149, 150, 4, 152, 153, 154, 155, 20, 21, 158, 26,
' ', 160, 161, 162, 163, 164, 165, 166, 167, 168, 213, '.', '<', '(', '+', '|',
'&', 169, 170, 171, 172, 173, 174, 175, 176, 177, '!', '$', '*', ')', ';', '~',
'-', '/', 178, 179, 180, 181, 182, 183, 184, 185, 203, ',', '%', '_', '>', '?',
186, 187, 188, 189, 190, 191, 192, 193, 194, '`', ':', '#', '@', '\'','=', '"',
195, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 196, 197, 198, 199, 200, 201,
202, 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', '^', 204, 205, 206, 207, 208,
209, 229, 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 210, 211, 212, '[', 214, 215,
216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, ']', 230, 231,
'{', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 232, 233, 234, 235, 236, 237,
'}', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 238, 239, 240, 241, 242, 243,
'\\',159, 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 244, 245, 246, 247, 248, 249,
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 250, 251, 252, 253, 254, 255
};
/*
* The following EBCDIC-to-ASCII table may relate more closely to reality,
* or at least to modern reality. It comes from
*
* http://ftp.s390.ibm.com/products/oe/bpxqp9.html
*
* and maps the characters of EBCDIC code page 1047 (the code used for
* Unix-derived software on IBM's 390 systems) to the corresponding
* characters from ISO 8859-1.
*
* If this table is used instead of the above one, some of the special
* cases for the NEL character can be taken out of the code.
*/
unsigned char ebcdic_1047_to_8859[] = {
0x00,0x01,0x02,0x03,0x9C,0x09,0x86,0x7F,0x97,0x8D,0x8E,0x0B,0x0C,0x0D,0x0E,0x0F,
0x10,0x11,0x12,0x13,0x9D,0x0A,0x08,0x87,0x18,0x19,0x92,0x8F,0x1C,0x1D,0x1E,0x1F,
0x80,0x81,0x82,0x83,0x84,0x85,0x17,0x1B,0x88,0x89,0x8A,0x8B,0x8C,0x05,0x06,0x07,
0x90,0x91,0x16,0x93,0x94,0x95,0x96,0x04,0x98,0x99,0x9A,0x9B,0x14,0x15,0x9E,0x1A,
0x20,0xA0,0xE2,0xE4,0xE0,0xE1,0xE3,0xE5,0xE7,0xF1,0xA2,0x2E,0x3C,0x28,0x2B,0x7C,
0x26,0xE9,0xEA,0xEB,0xE8,0xED,0xEE,0xEF,0xEC,0xDF,0x21,0x24,0x2A,0x29,0x3B,0x5E,
0x2D,0x2F,0xC2,0xC4,0xC0,0xC1,0xC3,0xC5,0xC7,0xD1,0xA6,0x2C,0x25,0x5F,0x3E,0x3F,
0xF8,0xC9,0xCA,0xCB,0xC8,0xCD,0xCE,0xCF,0xCC,0x60,0x3A,0x23,0x40,0x27,0x3D,0x22,
0xD8,0x61,0x62,0x63,0x64,0x65,0x66,0x67,0x68,0x69,0xAB,0xBB,0xF0,0xFD,0xFE,0xB1,
0xB0,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F,0x70,0x71,0x72,0xAA,0xBA,0xE6,0xB8,0xC6,0xA4,
0xB5,0x7E,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0xA1,0xBF,0xD0,0x5B,0xDE,0xAE,
0xAC,0xA3,0xA5,0xB7,0xA9,0xA7,0xB6,0xBC,0xBD,0xBE,0xDD,0xA8,0xAF,0x5D,0xB4,0xD7,
0x7B,0x41,0x42,0x43,0x44,0x45,0x46,0x47,0x48,0x49,0xAD,0xF4,0xF6,0xF2,0xF3,0xF5,
0x7D,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F,0x50,0x51,0x52,0xB9,0xFB,0xFC,0xF9,0xFA,0xFF,
0x5C,0xF7,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0xB2,0xD4,0xD6,0xD2,0xD3,0xD5,
0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0xB3,0xDB,0xDC,0xD9,0xDA,0x9F
};
/*
* Copy buf[0 ... nbytes-1] into out[], translating EBCDIC to ASCII.
*/
static void
from_ebcdic(const unsigned char *buf, int nbytes, unsigned char *out)
{
int i;
for (i = 0; i < nbytes; i++) {
out[i] = ebcdic_to_ascii[buf[i]];
}
}
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