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 1.6 2011/12/08 12:38:24 rrt 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 mlen = (nbytes + 1) * sizeof(nbuf[0]); 75 if ((nbuf = CAST(unsigned char *, calloc((size_t)1, mlen))) == NULL) { 76 file_oomem(ms, mlen); 77 goto done; 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 85 *type = "text"; 86 if (looks_ascii(buf, nbytes, *ubuf, ulen)) { 87 DPRINTF(("ascii %" SIZE_T_FORMAT "u\n", *ulen)); 88 *code = "ASCII"; 89 *code_mime = "us-ascii"; 90 } else if (looks_utf8_with_BOM(buf, nbytes, *ubuf, ulen) > 0) { 91 DPRINTF(("utf8/bom %" SIZE_T_FORMAT "u\n", *ulen)); 92 *code = "UTF-8 Unicode (with BOM)"; 93 *code_mime = "utf-8"; 94 } else if (file_looks_utf8(buf, nbytes, *ubuf, ulen) > 1) { 95 DPRINTF(("utf8 %" SIZE_T_FORMAT "u\n", *ulen)); 96 *code = "UTF-8 Unicode (with BOM)"; 97 *code = "UTF-8 Unicode"; 98 *code_mime = "utf-8"; 99 } else if ((ucs_type = looks_ucs16(buf, nbytes, *ubuf, ulen)) != 0) { 100 if (ucs_type == 1) { 101 *code = "Little-endian UTF-16 Unicode"; 102 *code_mime = "utf-16le"; 103 } else { 104 *code = "Big-endian UTF-16 Unicode"; 105 *code_mime = "utf-16be"; 106 } 107 DPRINTF(("ucs16 %" SIZE_T_FORMAT "u\n", *ulen)); 108 } else if (looks_latin1(buf, nbytes, *ubuf, ulen)) { 109 DPRINTF(("latin1 %" SIZE_T_FORMAT "u\n", *ulen)); 110 *code = "ISO-8859"; 111 *code_mime = "iso-8859-1"; 112 } else if (looks_extended(buf, nbytes, *ubuf, ulen)) { 113 DPRINTF(("extended %" SIZE_T_FORMAT "u\n", *ulen)); 114 *code = "Non-ISO extended-ASCII"; 115 *code_mime = "unknown-8bit"; 116 } else { 117 from_ebcdic(buf, nbytes, nbuf); 118 119 if (looks_ascii(nbuf, nbytes, *ubuf, ulen)) { 120 DPRINTF(("ebcdic %" SIZE_T_FORMAT "u\n", *ulen)); 121 *code = "EBCDIC"; 122 *code_mime = "ebcdic"; 123 } else if (looks_latin1(nbuf, nbytes, *ubuf, ulen)) { 124 DPRINTF(("ebcdic/international %" SIZE_T_FORMAT "u\n", 125 *ulen)); 126 *code = "International EBCDIC"; 127 *code_mime = "ebcdic"; 128 } else { /* Doesn't look like text at all */ 129 DPRINTF(("binary\n")); 130 rv = 0; 131 *type = "binary"; 132 } 133 } 134 135 done: 136 free(nbuf); 137 138 return rv; 139 } 140 141 /* 142 * This table reflects a particular philosophy about what constitutes 143 * "text," and there is room for disagreement about it. 144 * 145 * Version 3.31 of the file command considered a file to be ASCII if 146 * each of its characters was approved by either the isascii() or 147 * isalpha() function. On most systems, this would mean that any 148 * file consisting only of characters in the range 0x00 ... 0x7F 149 * would be called ASCII text, but many systems might reasonably 150 * consider some characters outside this range to be alphabetic, 151 * so the file command would call such characters ASCII. It might 152 * have been more accurate to call this "considered textual on the 153 * local system" than "ASCII." 154 * 155 * It considered a file to be "International language text" if each 156 * of its characters was either an ASCII printing character (according 157 * to the real ASCII standard, not the above test), a character in 158 * the range 0x80 ... 0xFF, or one of the following control characters: 159 * backspace, tab, line feed, vertical tab, form feed, carriage return, 160 * escape. No attempt was made to determine the language in which files 161 * of this type were written. 162 * 163 * 164 * The table below considers a file to be ASCII if all of its characters 165 * are either ASCII printing characters (again, according to the X3.4 166 * standard, not isascii()) or any of the following controls: bell, 167 * backspace, tab, line feed, form feed, carriage return, esc, nextline. 168 * 169 * I include bell because some programs (particularly shell scripts) 170 * use it literally, even though it is rare in normal text. I exclude 171 * vertical tab because it never seems to be used in real text. I also 172 * include, with hesitation, the X3.64/ECMA-43 control nextline (0x85), 173 * because that's what the dd EBCDIC->ASCII table maps the EBCDIC newline 174 * character to. It might be more appropriate to include it in the 8859 175 * set instead of the ASCII set, but it's got to be included in *something* 176 * we recognize or EBCDIC files aren't going to be considered textual. 177 * Some old Unix source files use SO/SI (^N/^O) to shift between Greek 178 * and Latin characters, so these should possibly be allowed. But they 179 * make a real mess on VT100-style displays if they're not paired properly, 180 * so we are probably better off not calling them text. 181 * 182 * A file is considered to be ISO-8859 text if its characters are all 183 * either ASCII, according to the above definition, or printing characters 184 * from the ISO-8859 8-bit extension, characters 0xA0 ... 0xFF. 185 * 186 * Finally, a file is considered to be international text from some other 187 * character code if its characters are all either ISO-8859 (according to 188 * the above definition) or characters in the range 0x80 ... 0x9F, which 189 * ISO-8859 considers to be control characters but the IBM PC and Macintosh 190 * consider to be printing characters. 191 */ 192 193 #define F 0 /* character never appears in text */ 194 #define T 1 /* character appears in plain ASCII text */ 195 #define I 2 /* character appears in ISO-8859 text */ 196 #define X 3 /* character appears in non-ISO extended ASCII (Mac, IBM PC) */ 197 198 private char text_chars[256] = { 199 /* BEL BS HT LF FF CR */ 200 F, F, F, F, F, F, F, T, T, T, T, F, T, T, F, F, /* 0x0X */ 201 /* ESC */ 202 F, F, F, F, F, F, F, F, F, F, F, T, F, F, F, F, /* 0x1X */ 203 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x2X */ 204 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x3X */ 205 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x4X */ 206 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x5X */ 207 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, /* 0x6X */ 208 T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, F, /* 0x7X */ 209 /* NEL */ 210 X, X, X, X, X, T, X, X, X, X, X, X, X, X, X, X, /* 0x8X */ 211 X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, X, /* 0x9X */ 212 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xaX */ 213 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xbX */ 214 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xcX */ 215 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xdX */ 216 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, /* 0xeX */ 217 I, I, I, I, I, I, I, I, I, I, I, I, I, I, I, I /* 0xfX */ 218 }; 219 220 private int 221 looks_ascii(const unsigned char *buf, size_t nbytes, unichar *ubuf, 222 size_t *ulen) 223 { 224 size_t i; 225 226 *ulen = 0; 227 228 for (i = 0; i < nbytes; i++) { 229 int t = text_chars[buf[i]]; 230 231 if (t != T) 232 return 0; 233 234 ubuf[(*ulen)++] = buf[i]; 235 } 236 237 return 1; 238 } 239 240 private int 241 looks_latin1(const unsigned char *buf, size_t nbytes, unichar *ubuf, size_t *ulen) 242 { 243 size_t i; 244 245 *ulen = 0; 246 247 for (i = 0; i < nbytes; i++) { 248 int t = text_chars[buf[i]]; 249 250 if (t != T && t != I) 251 return 0; 252 253 ubuf[(*ulen)++] = buf[i]; 254 } 255 256 return 1; 257 } 258 259 private int 260 looks_extended(const unsigned char *buf, size_t nbytes, unichar *ubuf, 261 size_t *ulen) 262 { 263 size_t i; 264 265 *ulen = 0; 266 267 for (i = 0; i < nbytes; i++) { 268 int t = text_chars[buf[i]]; 269 270 if (t != T && t != I && t != X) 271 return 0; 272 273 ubuf[(*ulen)++] = buf[i]; 274 } 275 276 return 1; 277 } 278 279 /* 280 * Decide whether some text looks like UTF-8. Returns: 281 * 282 * -1: invalid UTF-8 283 * 0: uses odd control characters, so doesn't look like text 284 * 1: 7-bit text 285 * 2: definitely UTF-8 text (valid high-bit set bytes) 286 * 287 * If ubuf is non-NULL on entry, text is decoded into ubuf, *ulen; 288 * ubuf must be big enough! 289 */ 290 protected int 291 file_looks_utf8(const unsigned char *buf, size_t nbytes, unichar *ubuf, size_t *ulen) 292 { 293 size_t i; 294 int n; 295 unichar c; 296 int gotone = 0, ctrl = 0; 297 298 if (ubuf) 299 *ulen = 0; 300 301 for (i = 0; i < nbytes; i++) { 302 if ((buf[i] & 0x80) == 0) { /* 0xxxxxxx is plain ASCII */ 303 /* 304 * Even if the whole file is valid UTF-8 sequences, 305 * still reject it if it uses weird control characters. 306 */ 307 308 if (text_chars[buf[i]] != T) 309 ctrl = 1; 310 311 if (ubuf) 312 ubuf[(*ulen)++] = buf[i]; 313 } else if ((buf[i] & 0x40) == 0) { /* 10xxxxxx never 1st byte */ 314 return -1; 315 } else { /* 11xxxxxx begins UTF-8 */ 316 int following; 317 318 if ((buf[i] & 0x20) == 0) { /* 110xxxxx */ 319 c = buf[i] & 0x1f; 320 following = 1; 321 } else if ((buf[i] & 0x10) == 0) { /* 1110xxxx */ 322 c = buf[i] & 0x0f; 323 following = 2; 324 } else if ((buf[i] & 0x08) == 0) { /* 11110xxx */ 325 c = buf[i] & 0x07; 326 following = 3; 327 } else if ((buf[i] & 0x04) == 0) { /* 111110xx */ 328 c = buf[i] & 0x03; 329 following = 4; 330 } else if ((buf[i] & 0x02) == 0) { /* 1111110x */ 331 c = buf[i] & 0x01; 332 following = 5; 333 } else 334 return -1; 335 336 for (n = 0; n < following; n++) { 337 i++; 338 if (i >= nbytes) 339 goto done; 340 341 if ((buf[i] & 0x80) == 0 || (buf[i] & 0x40)) 342 return -1; 343 344 c = (c << 6) + (buf[i] & 0x3f); 345 } 346 347 if (ubuf) 348 ubuf[(*ulen)++] = c; 349 gotone = 1; 350 } 351 } 352 done: 353 return ctrl ? 0 : (gotone ? 2 : 1); 354 } 355 356 /* 357 * Decide whether some text looks like UTF-8 with BOM. If there is no 358 * BOM, return -1; otherwise return the result of looks_utf8 on the 359 * rest of the text. 360 */ 361 private int 362 looks_utf8_with_BOM(const unsigned char *buf, size_t nbytes, unichar *ubuf, 363 size_t *ulen) 364 { 365 if (nbytes > 3 && buf[0] == 0xef && buf[1] == 0xbb && buf[2] == 0xbf) 366 return file_looks_utf8(buf + 3, nbytes - 3, ubuf, ulen); 367 else 368 return -1; 369 } 370 371 private int 372 looks_ucs16(const unsigned char *buf, size_t nbytes, unichar *ubuf, 373 size_t *ulen) 374 { 375 int bigend; 376 size_t i; 377 378 if (nbytes < 2) 379 return 0; 380 381 if (buf[0] == 0xff && buf[1] == 0xfe) 382 bigend = 0; 383 else if (buf[0] == 0xfe && buf[1] == 0xff) 384 bigend = 1; 385 else 386 return 0; 387 388 *ulen = 0; 389 390 for (i = 2; i + 1 < nbytes; i += 2) { 391 /* XXX fix to properly handle chars > 65536 */ 392 393 if (bigend) 394 ubuf[(*ulen)++] = buf[i + 1] + 256 * buf[i]; 395 else 396 ubuf[(*ulen)++] = buf[i] + 256 * buf[i + 1]; 397 398 if (ubuf[*ulen - 1] == 0xfffe) 399 return 0; 400 if (ubuf[*ulen - 1] < 128 && 401 text_chars[(size_t)ubuf[*ulen - 1]] != T) 402 return 0; 403 } 404 405 return 1 + bigend; 406 } 407 408 #undef F 409 #undef T 410 #undef I 411 #undef X 412 413 /* 414 * This table maps each EBCDIC character to an (8-bit extended) ASCII 415 * character, as specified in the rationale for the dd(1) command in 416 * draft 11.2 (September, 1991) of the POSIX P1003.2 standard. 417 * 418 * Unfortunately it does not seem to correspond exactly to any of the 419 * five variants of EBCDIC documented in IBM's _Enterprise Systems 420 * Architecture/390: Principles of Operation_, SA22-7201-06, Seventh 421 * Edition, July, 1999, pp. I-1 - I-4. 422 * 423 * Fortunately, though, all versions of EBCDIC, including this one, agree 424 * on most of the printing characters that also appear in (7-bit) ASCII. 425 * Of these, only '|', '!', '~', '^', '[', and ']' are in question at all. 426 * 427 * Fortunately too, there is general agreement that codes 0x00 through 428 * 0x3F represent control characters, 0x41 a nonbreaking space, and the 429 * remainder printing characters. 430 * 431 * This is sufficient to allow us to identify EBCDIC text and to distinguish 432 * between old-style and internationalized examples of text. 433 */ 434 435 private unsigned char ebcdic_to_ascii[] = { 436 0, 1, 2, 3, 156, 9, 134, 127, 151, 141, 142, 11, 12, 13, 14, 15, 437 16, 17, 18, 19, 157, 133, 8, 135, 24, 25, 146, 143, 28, 29, 30, 31, 438 128, 129, 130, 131, 132, 10, 23, 27, 136, 137, 138, 139, 140, 5, 6, 7, 439 144, 145, 22, 147, 148, 149, 150, 4, 152, 153, 154, 155, 20, 21, 158, 26, 440 ' ', 160, 161, 162, 163, 164, 165, 166, 167, 168, 213, '.', '<', '(', '+', '|', 441 '&', 169, 170, 171, 172, 173, 174, 175, 176, 177, '!', '$', '*', ')', ';', '~', 442 '-', '/', 178, 179, 180, 181, 182, 183, 184, 185, 203, ',', '%', '_', '>', '?', 443 186, 187, 188, 189, 190, 191, 192, 193, 194, '`', ':', '#', '@', '\'','=', '"', 444 195, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 196, 197, 198, 199, 200, 201, 445 202, 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', '^', 204, 205, 206, 207, 208, 446 209, 229, 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 210, 211, 212, '[', 214, 215, 447 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, ']', 230, 231, 448 '{', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 232, 233, 234, 235, 236, 237, 449 '}', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 238, 239, 240, 241, 242, 243, 450 '\\',159, 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 244, 245, 246, 247, 248, 249, 451 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 250, 251, 252, 253, 254, 255 452 }; 453 454 #ifdef notdef 455 /* 456 * The following EBCDIC-to-ASCII table may relate more closely to reality, 457 * or at least to modern reality. It comes from 458 * 459 * http://ftp.s390.ibm.com/products/oe/bpxqp9.html 460 * 461 * and maps the characters of EBCDIC code page 1047 (the code used for 462 * Unix-derived software on IBM's 390 systems) to the corresponding 463 * characters from ISO 8859-1. 464 * 465 * If this table is used instead of the above one, some of the special 466 * cases for the NEL character can be taken out of the code. 467 */ 468 469 private unsigned char ebcdic_1047_to_8859[] = { 470 0x00,0x01,0x02,0x03,0x9C,0x09,0x86,0x7F,0x97,0x8D,0x8E,0x0B,0x0C,0x0D,0x0E,0x0F, 471 0x10,0x11,0x12,0x13,0x9D,0x0A,0x08,0x87,0x18,0x19,0x92,0x8F,0x1C,0x1D,0x1E,0x1F, 472 0x80,0x81,0x82,0x83,0x84,0x85,0x17,0x1B,0x88,0x89,0x8A,0x8B,0x8C,0x05,0x06,0x07, 473 0x90,0x91,0x16,0x93,0x94,0x95,0x96,0x04,0x98,0x99,0x9A,0x9B,0x14,0x15,0x9E,0x1A, 474 0x20,0xA0,0xE2,0xE4,0xE0,0xE1,0xE3,0xE5,0xE7,0xF1,0xA2,0x2E,0x3C,0x28,0x2B,0x7C, 475 0x26,0xE9,0xEA,0xEB,0xE8,0xED,0xEE,0xEF,0xEC,0xDF,0x21,0x24,0x2A,0x29,0x3B,0x5E, 476 0x2D,0x2F,0xC2,0xC4,0xC0,0xC1,0xC3,0xC5,0xC7,0xD1,0xA6,0x2C,0x25,0x5F,0x3E,0x3F, 477 0xF8,0xC9,0xCA,0xCB,0xC8,0xCD,0xCE,0xCF,0xCC,0x60,0x3A,0x23,0x40,0x27,0x3D,0x22, 478 0xD8,0x61,0x62,0x63,0x64,0x65,0x66,0x67,0x68,0x69,0xAB,0xBB,0xF0,0xFD,0xFE,0xB1, 479 0xB0,0x6A,0x6B,0x6C,0x6D,0x6E,0x6F,0x70,0x71,0x72,0xAA,0xBA,0xE6,0xB8,0xC6,0xA4, 480 0xB5,0x7E,0x73,0x74,0x75,0x76,0x77,0x78,0x79,0x7A,0xA1,0xBF,0xD0,0x5B,0xDE,0xAE, 481 0xAC,0xA3,0xA5,0xB7,0xA9,0xA7,0xB6,0xBC,0xBD,0xBE,0xDD,0xA8,0xAF,0x5D,0xB4,0xD7, 482 0x7B,0x41,0x42,0x43,0x44,0x45,0x46,0x47,0x48,0x49,0xAD,0xF4,0xF6,0xF2,0xF3,0xF5, 483 0x7D,0x4A,0x4B,0x4C,0x4D,0x4E,0x4F,0x50,0x51,0x52,0xB9,0xFB,0xFC,0xF9,0xFA,0xFF, 484 0x5C,0xF7,0x53,0x54,0x55,0x56,0x57,0x58,0x59,0x5A,0xB2,0xD4,0xD6,0xD2,0xD3,0xD5, 485 0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0xB3,0xDB,0xDC,0xD9,0xDA,0x9F 486 }; 487 #endif 488 489 /* 490 * Copy buf[0 ... nbytes-1] into out[], translating EBCDIC to ASCII. 491 */ 492 private void 493 from_ebcdic(const unsigned char *buf, size_t nbytes, unsigned char *out) 494 { 495 size_t i; 496 497 for (i = 0; i < nbytes; i++) { 498 out[i] = ebcdic_to_ascii[buf[i]]; 499 } 500 } 501