1 /* 2 * Copyright (c) Ian F. Darwin 1986-1995. 3 * Software written by Ian F. Darwin and others; 4 * maintained 1995-present by Christos Zoulas and others. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice immediately at the beginning of the file, without modification, 11 * this list of conditions, and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR 20 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 /* 29 * Encoding -- determine the character encoding of a text file. 30 * 31 * Joerg Wunsch <joerg@freebsd.org> wrote the original support for 8-bit 32 * international characters. 33 */ 34 35 #include "file.h" 36 37 #ifndef lint 38 FILE_RCSID("@(#)$File: encoding.c,v 1.10 2014/09/11 12:08:52 christos Exp $") 39 #endif /* lint */ 40 41 #include "magic.h" 42 #include <string.h> 43 #include <memory.h> 44 #include <stdlib.h> 45 46 47 private int looks_ascii(const unsigned char *, size_t, unichar *, size_t *); 48 private int looks_utf8_with_BOM(const unsigned char *, size_t, unichar *, 49 size_t *); 50 private int looks_ucs16(const unsigned char *, size_t, unichar *, size_t *); 51 private int looks_latin1(const unsigned char *, size_t, unichar *, size_t *); 52 private int looks_extended(const unsigned char *, size_t, unichar *, size_t *); 53 private void from_ebcdic(const unsigned char *, size_t, unsigned char *); 54 55 #ifdef DEBUG_ENCODING 56 #define DPRINTF(a) printf a 57 #else 58 #define DPRINTF(a) 59 #endif 60 61 /* 62 * Try to determine whether text is in some character code we can 63 * identify. Each of these tests, if it succeeds, will leave 64 * the text converted into one-unichar-per-character Unicode in 65 * ubuf, and the number of characters converted in ulen. 66 */ 67 protected int 68 file_encoding(struct magic_set *ms, const unsigned char *buf, size_t nbytes, unichar **ubuf, size_t *ulen, const char **code, const char **code_mime, const char **type) 69 { 70 size_t mlen; 71 int rv = 1, ucs_type; 72 unsigned char *nbuf = NULL; 73 74 *type = "text"; 75 *ulen = 0; 76 *code = "unknown"; 77 *code_mime = "binary"; 78 79 mlen = (nbytes + 1) * sizeof((*ubuf)[0]); 80 if ((*ubuf = CAST(unichar *, calloc((size_t)1, mlen))) == NULL) { 81 file_oomem(ms, mlen); 82 goto done; 83 } 84 mlen = (nbytes + 1) * sizeof(nbuf[0]); 85 if ((nbuf = CAST(unsigned char *, calloc((size_t)1, mlen))) == NULL) { 86 file_oomem(ms, mlen); 87 goto done; 88 } 89 90 if (looks_ascii(buf, nbytes, *ubuf, ulen)) { 91 DPRINTF(("ascii %" SIZE_T_FORMAT "u\n", *ulen)); 92 *code = "ASCII"; 93 *code_mime = "us-ascii"; 94 } else if (looks_utf8_with_BOM(buf, nbytes, *ubuf, ulen) > 0) { 95 DPRINTF(("utf8/bom %" SIZE_T_FORMAT "u\n", *ulen)); 96 *code = "UTF-8 Unicode (with BOM)"; 97 *code_mime = "utf-8"; 98 } else if (file_looks_utf8(buf, nbytes, *ubuf, ulen) > 1) { 99 DPRINTF(("utf8 %" SIZE_T_FORMAT "u\n", *ulen)); 100 *code = "UTF-8 Unicode"; 101 *code_mime = "utf-8"; 102 } else if ((ucs_type = looks_ucs16(buf, nbytes, *ubuf, ulen)) != 0) { 103 if (ucs_type == 1) { 104 *code = "Little-endian UTF-16 Unicode"; 105 *code_mime = "utf-16le"; 106 } else { 107 *code = "Big-endian UTF-16 Unicode"; 108 *code_mime = "utf-16be"; 109 } 110 DPRINTF(("ucs16 %" SIZE_T_FORMAT "u\n", *ulen)); 111 } else if (looks_latin1(buf, nbytes, *ubuf, ulen)) { 112 DPRINTF(("latin1 %" SIZE_T_FORMAT "u\n", *ulen)); 113 *code = "ISO-8859"; 114 *code_mime = "iso-8859-1"; 115 } else if (looks_extended(buf, nbytes, *ubuf, ulen)) { 116 DPRINTF(("extended %" SIZE_T_FORMAT "u\n", *ulen)); 117 *code = "Non-ISO extended-ASCII"; 118 *code_mime = "unknown-8bit"; 119 } else { 120 from_ebcdic(buf, nbytes, nbuf); 121 122 if (looks_ascii(nbuf, nbytes, *ubuf, ulen)) { 123 DPRINTF(("ebcdic %" SIZE_T_FORMAT "u\n", *ulen)); 124 *code = "EBCDIC"; 125 *code_mime = "ebcdic"; 126 } else if (looks_latin1(nbuf, nbytes, *ubuf, ulen)) { 127 DPRINTF(("ebcdic/international %" SIZE_T_FORMAT "u\n", 128 *ulen)); 129 *code = "International EBCDIC"; 130 *code_mime = "ebcdic"; 131 } else { /* Doesn't look like text at all */ 132 DPRINTF(("binary\n")); 133 rv = 0; 134 *type = "binary"; 135 } 136 } 137 138 done: 139 free(nbuf); 140 141 return rv; 142 } 143 144 /* 145 * This table reflects a particular philosophy about what constitutes 146 * "text," and there is room for disagreement about it. 147 * 148 * Version 3.31 of the file command considered a file to be ASCII if 149 * each of its characters was approved by either the isascii() or 150 * isalpha() function. On most systems, this would mean that any 151 * file consisting only of characters in the range 0x00 ... 0x7F 152 * would be called ASCII text, but many systems might reasonably 153 * consider some characters outside this range to be alphabetic, 154 * so the file command would call such characters ASCII. It might 155 * have been more accurate to call this "considered textual on the 156 * local system" than "ASCII." 157 * 158 * It considered a file to be "International language text" if each 159 * of its characters was either an ASCII printing character (according 160 * to the real ASCII standard, not the above test), a character in 161 * the range 0x80 ... 0xFF, or one of the following control characters: 162 * backspace, tab, line feed, vertical tab, form feed, carriage return, 163 * escape. No attempt was made to determine the language in which files 164 * of this type were written. 165 * 166 * 167 * The table below considers a file to be ASCII if all of its characters 168 * are either ASCII printing characters (again, according to the X3.4 169 * standard, not isascii()) or any of the following controls: bell, 170 * backspace, tab, line feed, form feed, carriage return, esc, nextline. 171 * 172 * I include bell because some programs (particularly shell scripts) 173 * use it literally, even though it is rare in normal text. I exclude 174 * vertical tab because it never seems to be used in real text. I also 175 * include, with hesitation, the X3.64/ECMA-43 control nextline (0x85), 176 * because that's what the dd EBCDIC->ASCII table maps the EBCDIC newline 177 * character to. It might be more appropriate to include it in the 8859 178 * set instead of the ASCII set, but it's got to be included in *something* 179 * we recognize or EBCDIC files aren't going to be considered textual. 180 * Some old Unix source files use SO/SI (^N/^O) to shift between Greek 181 * and Latin characters, so these should possibly be allowed. But they 182 * make a real mess on VT100-style displays if they're not paired properly, 183 * so we are probably better off not calling them text. 184 * 185 * A file is considered to be ISO-8859 text if its characters are all 186 * either ASCII, according to the above definition, or printing characters 187 * from the ISO-8859 8-bit extension, characters 0xA0 ... 0xFF. 188 * 189 * Finally, a file is considered to be international text from some other 190 * character code if its characters are all either ISO-8859 (according to 191 * the above definition) or characters in the range 0x80 ... 0x9F, which 192 * ISO-8859 considers to be control characters but the IBM PC and Macintosh 193 * consider to be printing characters. 194 */ 195 196 #define F 0 /* character never appears in text */ 197 #define T 1 /* character appears in plain ASCII text */ 198 #define I 2 /* character appears in ISO-8859 text */ 199 #define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */ 200 201 private char text_chars[256] = { 202 /* BEL BS HT LF FF CR */ 203 F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */ 204 /* ESC */ 205 F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */ 206 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */ 207 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */ 208 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */ 209 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */ 210 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */ 211 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */ 212 /* NEL */ 213 X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */ 214 X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */ 215 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */ 216 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */ 217 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */ 218 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */ 219 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */ 220 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */ 221 }; 222 223 private int 224 looks_ascii(const unsigned char *buf, size_t nbytes, unichar *ubuf, 225 size_t *ulen) 226 { 227 size_t i; 228 229 *ulen = 0; 230 231 for (i = 0; i < nbytes; i++) { 232 int t = text_chars[buf[i]]; 233 234 if (t != T) 235 return 0; 236 237 ubuf[(*ulen)++] = buf[i]; 238 } 239 240 return 1; 241 } 242 243 private int 244 looks_latin1(const unsigned char *buf, size_t nbytes, unichar *ubuf, size_t *ulen) 245 { 246 size_t i; 247 248 *ulen = 0; 249 250 for (i = 0; i < nbytes; i++) { 251 int t = text_chars[buf[i]]; 252 253 if (t != T && t != I) 254 return 0; 255 256 ubuf[(*ulen)++] = buf[i]; 257 } 258 259 return 1; 260 } 261 262 private int 263 looks_extended(const unsigned char *buf, size_t nbytes, unichar *ubuf, 264 size_t *ulen) 265 { 266 size_t i; 267 268 *ulen = 0; 269 270 for (i = 0; i < nbytes; i++) { 271 int t = text_chars[buf[i]]; 272 273 if (t != T && t != I && t != X) 274 return 0; 275 276 ubuf[(*ulen)++] = buf[i]; 277 } 278 279 return 1; 280 } 281 282 /* 283 * Decide whether some text looks like UTF-8. Returns: 284 * 285 * -1: invalid UTF-8 286 * 0: uses odd control characters, so doesn't look like text 287 * 1: 7-bit text 288 * 2: definitely UTF-8 text (valid high-bit set bytes) 289 * 290 * If ubuf is non-NULL on entry, text is decoded into ubuf, *ulen; 291 * ubuf must be big enough! 292 */ 293 protected int 294 file_looks_utf8(const unsigned char *buf, size_t nbytes, unichar *ubuf, size_t *ulen) 295 { 296 size_t i; 297 int n; 298 unichar c; 299 int gotone = 0, ctrl = 0; 300 301 if (ubuf) 302 *ulen = 0; 303 304 for (i = 0; i < nbytes; i++) { 305 if ((buf[i] & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */ 306 /* 307 * Even if the whole file is valid UTF-8 sequences, 308 * still reject it if it uses weird control characters. 309 */ 310 311 if (text_chars[buf[i]] != T) 312 ctrl = 1; 313 314 if (ubuf) 315 ubuf[(*ulen)++] = buf[i]; 316 } else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */ 317 return -1; 318 } else { /* 11xxxxxx begins UTF-8 */ 319 int following; 320 321 if ((buf[i] & 0x20) == 0) { /* 110xxxxx */ 322 c = buf[i] & 0x1f; 323 following = 1; 324 } else if ((buf[i] & 0x10) == 0) { /* 1110xxxx */ 325 c = buf[i] & 0x0f; 326 following = 2; 327 } else if ((buf[i] & 0x08) == 0) { /* 11110xxx */ 328 c = buf[i] & 0x07; 329 following = 3; 330 } else if ((buf[i] & 0x04) == 0) { /* 111110xx */ 331 c = buf[i] & 0x03; 332 following = 4; 333 } else if ((buf[i] & 0x02) == 0) { /* 1111110x */ 334 c = buf[i] & 0x01; 335 following = 5; 336 } else 337 return -1; 338 339 for (n = 0; n < following; n++) { 340 i++; 341 if (i >= nbytes) 342 goto done; 343 344 if ((buf[i] & 0x80) == 0 || (buf[i] & 0x40)) 345 return -1; 346 347 c = (c << 6) + (buf[i] & 0x3f); 348 } 349 350 if (ubuf) 351 ubuf[(*ulen)++] = c; 352 gotone = 1; 353 } 354 } 355 done: 356 return ctrl ? 0 : (gotone ? 2 : 1); 357 } 358 359 /* 360 * Decide whether some text looks like UTF-8 with BOM. If there is no 361 * BOM, return -1; otherwise return the result of looks_utf8 on the 362 * rest of the text. 363 */ 364 private int 365 looks_utf8_with_BOM(const unsigned char *buf, size_t nbytes, unichar *ubuf, 366 size_t *ulen) 367 { 368 if (nbytes > 3 && buf[0] == 0xef && buf[1] == 0xbb && buf[2] == 0xbf) 369 return file_looks_utf8(buf + 3, nbytes - 3, ubuf, ulen); 370 else 371 return -1; 372 } 373 374 private int 375 looks_ucs16(const unsigned char *buf, size_t nbytes, unichar *ubuf, 376 size_t *ulen) 377 { 378 int bigend; 379 size_t i; 380 381 if (nbytes < 2) 382 return 0; 383 384 if (buf[0] == 0xff && buf[1] == 0xfe) 385 bigend = 0; 386 else if (buf[0] == 0xfe && buf[1] == 0xff) 387 bigend = 1; 388 else 389 return 0; 390 391 *ulen = 0; 392 393 for (i = 2; i + 1 < nbytes; i += 2) { 394 /* XXX fix to properly handle chars > 65536 */ 395 396 if (bigend) 397 ubuf[(*ulen)++] = buf[i + 1] + 256 * buf[i]; 398 else 399 ubuf[(*ulen)++] = buf[i] + 256 * buf[i + 1]; 400 401 if (ubuf[*ulen - 1] == 0xfffe) 402 return 0; 403 if (ubuf[*ulen - 1] < 128 && 404 text_chars[(size_t)ubuf[*ulen - 1]] != T) 405 return 0; 406 } 407 408 return 1 + bigend; 409 } 410 411 #undef F 412 #undef T 413 #undef I 414 #undef X 415 416 /* 417 * This table maps each EBCDIC character to an (8-bit extended) ASCII 418 * character, as specified in the rationale for the dd(1) command in 419 * draft 11.2 (September, 1991) of the POSIX P1003.2 standard. 420 * 421 * Unfortunately it does not seem to correspond exactly to any of the 422 * five variants of EBCDIC documented in IBM's _Enterprise Systems 423 * Architecture/390: Principles of Operation_, SA22-7201-06, Seventh 424 * Edition, July, 1999, pp. I-1 - I-4. 425 * 426 * Fortunately, though, all versions of EBCDIC, including this one, agree 427 * on most of the printing characters that also appear in (7-bit) ASCII. 428 * Of these, only '|', '!', '~', '^', '[', and ']' are in question at all. 429 * 430 * Fortunately too, there is general agreement that codes 0x00 through 431 * 0x3F represent control characters, 0x41 a nonbreaking space, and the 432 * remainder printing characters. 433 * 434 * This is sufficient to allow us to identify EBCDIC text and to distinguish 435 * between old-style and internationalized examples of text. 436 */ 437 438 private unsigned char ebcdic_to_ascii[] = { 439 0, 1, 2, 3, 156, 9, 134, 127, 151, 141, 142, 11, 12, 13, 14, 15, 440 16, 17, 18, 19, 157, 133, 8, 135, 24, 25, 146, 143, 28, 29, 30, 31, 441 128, 129, 130, 131, 132, 10, 23, 27, 136, 137, 138, 139, 140, 5, 6, 7, 442 144, 145, 22, 147, 148, 149, 150, 4, 152, 153, 154, 155, 20, 21, 158, 26, 443 ' ', 160, 161, 162, 163, 164, 165, 166, 167, 168, 213, '.', '<', '(', '+', '|', 444 '&', 169, 170, 171, 172, 173, 174, 175, 176, 177, '!', '$', '*', ')', ';', '~', 445 '-', '/', 178, 179, 180, 181, 182, 183, 184, 185, 203, ',', '%', '_', '>', '?', 446 186, 187, 188, 189, 190, 191, 192, 193, 194, '`', ':', '#', '@', '\'','=', '"', 447 195, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 196, 197, 198, 199, 200, 201, 448 202, 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', '^', 204, 205, 206, 207, 208, 449 209, 229, 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 210, 211, 212, '[', 214, 215, 450 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, ']', 230, 231, 451 '{', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 232, 233, 234, 235, 236, 237, 452 '}', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 238, 239, 240, 241, 242, 243, 453 '\\',159, 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 244, 245, 246, 247, 248, 249, 454 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 250, 251, 252, 253, 254, 255 455 }; 456 457 #ifdef notdef 458 /* 459 * The following EBCDIC-to-ASCII table may relate more closely to reality, 460 * or at least to modern reality. It comes from 461 * 462 * http://ftp.s390.ibm.com/products/oe/bpxqp9.html 463 * 464 * and maps the characters of EBCDIC code page 1047 (the code used for 465 * Unix-derived software on IBM's 390 systems) to the corresponding 466 * characters from ISO 8859-1. 467 * 468 * If this table is used instead of the above one, some of the special 469 * cases for the NEL character can be taken out of the code. 470 */ 471 472 private unsigned char ebcdic_1047_to_8859[] = { 473 0x00,0x01,0x02,0x03,0x9C,0x09,0x86,0x7F,0x97,0x8D,0x8E,0x0B,0x0C,0x0D,0x0E,0x0F, 474 0x10,0x11,0x12,0x13,0x9D,0x0A,0x08,0x87,0x18,0x19,0x92,0x8F,0x1C,0x1D,0x1E,0x1F, 475 0x80,0x81,0x82,0x83,0x84,0x85,0x17,0x1B,0x88,0x89,0x8A,0x8B,0x8C,0x05,0x06,0x07, 476 0x90,0x91,0x16,0x93,0x94,0x95,0x96,0x04,0x98,0x99,0x9A,0x9B,0x14,0x15,0x9E,0x1A, 477 0x20,0xA0,0xE2,0xE4,0xE0,0xE1,0xE3,0xE5,0xE7,0xF1,0xA2,0x2E,0x3C,0x28,0x2B,0x7C, 478 0x26,0xE9,0xEA,0xEB,0xE8,0xED,0xEE,0xEF,0xEC,0xDF,0x21,0x24,0x2A,0x29,0x3B,0x5E, 479 0x2D,0x2F,0xC2,0xC4,0xC0,0xC1,0xC3,0xC5,0xC7,0xD1,0xA6,0x2C,0x25,0x5F,0x3E,0x3F, 480 0xF8,0xC9,0xCA,0xCB,0xC8,0xCD,0xCE,0xCF,0xCC,0x60,0x3A,0x23,0x40,0x27,0x3D,0x22, 481 0xD8,0x61,0x62,0x63,0x64,0x65,0x66,0x67,0x68,0x69,0xAB,0xBB,0xF0,0xFD,0xFE,0xB1, 482 0xB0,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F,0x70,0x71,0x72,0xAA,0xBA,0xE6,0xB8,0xC6,0xA4, 483 0xB5,0x7E,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0xA1,0xBF,0xD0,0x5B,0xDE,0xAE, 484 0xAC,0xA3,0xA5,0xB7,0xA9,0xA7,0xB6,0xBC,0xBD,0xBE,0xDD,0xA8,0xAF,0x5D,0xB4,0xD7, 485 0x7B,0x41,0x42,0x43,0x44,0x45,0x46,0x47,0x48,0x49,0xAD,0xF4,0xF6,0xF2,0xF3,0xF5, 486 0x7D,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F,0x50,0x51,0x52,0xB9,0xFB,0xFC,0xF9,0xFA,0xFF, 487 0x5C,0xF7,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0xB2,0xD4,0xD6,0xD2,0xD3,0xD5, 488 0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0xB3,0xDB,0xDC,0xD9,0xDA,0x9F 489 }; 490 #endif 491 492 /* 493 * Copy buf[0 ... nbytes-1] into out[], translating EBCDIC to ASCII. 494 */ 495 private void 496 from_ebcdic(const unsigned char *buf, size_t nbytes, unsigned char *out) 497 { 498 size_t i; 499 500 for (i = 0; i < nbytes; i++) { 501 out[i] = ebcdic_to_ascii[buf[i]]; 502 } 503 } 504