ext_comp.c 14 KB

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  1. /*
  2. (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
  3. See the copyright notice in the ACK home directory, in the file "Copyright".
  4. */
  5. /* $Id$ */
  6. /* extended precision arithmetic for the strtod() and cvt() routines */
  7. /* This may require some more work when long doubles get bigger than 8
  8. bytes. In this case, these routines may become obsolete. ???
  9. */
  10. static int b64_add();
  11. static int b64_sft();
  12. #include <ctype.h>
  13. struct mantissa {
  14. unsigned long h_32;
  15. unsigned long l_32;
  16. };
  17. struct EXTEND {
  18. short sign;
  19. short exp;
  20. struct mantissa mantissa;
  21. #define m1 mantissa.h_32
  22. #define m2 mantissa.l_32
  23. };
  24. static
  25. mul_ext(e1,e2,e3)
  26. struct EXTEND *e1,*e2,*e3;
  27. {
  28. /* Multiply the extended numbers e1 and e2, and put the
  29. result in e3.
  30. */
  31. register int i,j; /* loop control */
  32. unsigned short mp[4];
  33. unsigned short mc[4];
  34. unsigned short result[8]; /* result */
  35. register unsigned short *pres;
  36. /* first save the sign (XOR) */
  37. e3->sign = e1->sign ^ e2->sign;
  38. /* compute new exponent */
  39. e3->exp = e1->exp + e2->exp + 1;
  40. /* check for overflow/underflow ??? */
  41. /* 128 bit multiply of mantissas */
  42. /* assign unknown long formats */
  43. /* to known unsigned word formats */
  44. mp[0] = e1->m1 >> 16;
  45. mp[1] = (unsigned short) e1->m1;
  46. mp[2] = e1->m2 >> 16;
  47. mp[3] = (unsigned short) e1->m2;
  48. mc[0] = e2->m1 >> 16;
  49. mc[1] = (unsigned short) e2->m1;
  50. mc[2] = e2->m2 >> 16;
  51. mc[3] = (unsigned short) e2->m2;
  52. for (i = 8; i--;) {
  53. result[i] = 0;
  54. }
  55. /*
  56. * fill registers with their components
  57. */
  58. for(i=4, pres = &result[4];i--;pres--) if (mp[i]) {
  59. unsigned short k = 0;
  60. unsigned long mpi = mp[i];
  61. for(j=4;j--;) {
  62. unsigned long tmp = (unsigned long)pres[j] + k;
  63. if (mc[j]) tmp += mpi * mc[j];
  64. pres[j] = tmp;
  65. k = tmp >> 16;
  66. }
  67. pres[-1] = k;
  68. }
  69. if (! (result[0] & 0x8000)) {
  70. e3->exp--;
  71. for (i = 0; i <= 3; i++) {
  72. result[i] <<= 1;
  73. if (result[i+1]&0x8000) result[i] |= 1;
  74. }
  75. result[4] <<= 1;
  76. }
  77. /*
  78. * combine the registers to a total
  79. */
  80. e3->m1 = ((unsigned long)(result[0]) << 16) + result[1];
  81. e3->m2 = ((unsigned long)(result[2]) << 16) + result[3];
  82. if (result[4] & 0x8000) {
  83. if (++e3->m2 == 0) {
  84. if (++e3->m1 == 0) {
  85. e3->m1 = 0x80000000;
  86. e3->exp++;
  87. }
  88. }
  89. }
  90. }
  91. static
  92. add_ext(e1,e2,e3)
  93. struct EXTEND *e1,*e2,*e3;
  94. {
  95. /* Add two extended numbers e1 and e2, and put the result
  96. in e3
  97. */
  98. struct EXTEND ce2;
  99. int diff;
  100. if ((e2->m1 | e2->m2) == 0L) {
  101. *e3 = *e1;
  102. return;
  103. }
  104. if ((e1->m1 | e1->m2) == 0L) {
  105. *e3 = *e2;
  106. return;
  107. }
  108. ce2 = *e2;
  109. *e3 = *e1;
  110. e1 = &ce2;
  111. /* adjust mantissas to equal power */
  112. diff = e3->exp - e1->exp;
  113. if (diff < 0) {
  114. diff = -diff;
  115. e3->exp += diff;
  116. b64_sft(&(e3->mantissa), diff);
  117. }
  118. else if (diff > 0) {
  119. e1->exp += diff;
  120. b64_sft(&(e1->mantissa), diff);
  121. }
  122. if (e1->sign != e3->sign) {
  123. /* e3 + e1 = e3 - (-e1) */
  124. if (e1->m1 > e3->m1 ||
  125. (e1->m1 == e3->m1 && e1->m2 > e3->m2)) {
  126. /* abs(e1) > abs(e3) */
  127. if (e3->m2 > e1->m2) {
  128. e1->m1 -= 1; /* carry in */
  129. }
  130. e1->m1 -= e3->m1;
  131. e1->m2 -= e3->m2;
  132. *e3 = *e1;
  133. }
  134. else {
  135. if (e1->m2 > e3->m2)
  136. e3->m1 -= 1; /* carry in */
  137. e3->m1 -= e1->m1;
  138. e3->m2 -= e1->m2;
  139. }
  140. }
  141. else {
  142. if (b64_add(&e3->mantissa,&e1->mantissa)) {/* addition carry */
  143. b64_sft(&e3->mantissa,1);/* shift mantissa one bit RIGHT */
  144. e3->m1 |= 0x80000000L; /* set max bit */
  145. e3->exp++; /* increase the exponent */
  146. }
  147. }
  148. if ((e3->m2 | e3->m1) != 0L) {
  149. /* normalize */
  150. if (e3->m1 == 0L) {
  151. e3->m1 = e3->m2; e3->m2 = 0L; e3->exp -= 32;
  152. }
  153. if (!(e3->m1 & 0x80000000)) {
  154. unsigned long l = 0x40000000;
  155. int cnt = -1;
  156. while (! (l & e3->m1)) {
  157. l >>= 1; cnt--;
  158. }
  159. e3->exp += cnt;
  160. b64_sft(&(e3->mantissa), cnt);
  161. }
  162. }
  163. }
  164. static int
  165. cmp_ext(e1, e2)
  166. struct EXTEND *e1, *e2;
  167. {
  168. struct EXTEND tmp;
  169. e2->sign = ! e2->sign;
  170. add_ext(e1, e2, &tmp);
  171. e2->sign = ! e2->sign;
  172. if (tmp.m1 == 0 && tmp.m2 == 0) return 0;
  173. if (tmp.sign) return -1;
  174. return 1;
  175. }
  176. static
  177. b64_sft(e1,n)
  178. struct mantissa *e1;
  179. int n;
  180. {
  181. if (n > 0) {
  182. if (n > 63) {
  183. e1->l_32 = 0;
  184. e1->h_32 = 0;
  185. return;
  186. }
  187. if (n >= 32) {
  188. e1->l_32 = e1->h_32;
  189. e1->h_32 = 0;
  190. n -= 32;
  191. }
  192. if (n > 0) {
  193. e1->l_32 >>= n;
  194. if (e1->h_32 != 0) {
  195. e1->l_32 |= (e1->h_32 << (32 - n));
  196. e1->h_32 >>= n;
  197. }
  198. }
  199. return;
  200. }
  201. n = -n;
  202. if (n > 0) {
  203. if (n > 63) {
  204. e1->l_32 = 0;
  205. e1->h_32 = 0;
  206. return;
  207. }
  208. if (n >= 32) {
  209. e1->h_32 = e1->l_32;
  210. e1->l_32 = 0;
  211. n -= 32;
  212. }
  213. if (n > 0) {
  214. e1->h_32 <<= n;
  215. if (e1->l_32 != 0) {
  216. e1->h_32 |= (e1->l_32 >> (32 - n));
  217. e1->l_32 <<= n;
  218. }
  219. }
  220. }
  221. }
  222. static int
  223. b64_add(e1,e2)
  224. /*
  225. * pointers to 64 bit 'registers'
  226. */
  227. struct mantissa *e1,*e2;
  228. {
  229. register int overflow;
  230. int carry;
  231. /* add higher pair of 32 bits */
  232. overflow = ((unsigned long) 0xFFFFFFFF - e1->h_32 < e2->h_32);
  233. e1->h_32 += e2->h_32;
  234. /* add lower pair of 32 bits */
  235. carry = ((unsigned long) 0xFFFFFFFF - e1->l_32 < e2->l_32);
  236. e1->l_32 += e2->l_32;
  237. if ((carry) && (++e1->h_32 == 0))
  238. return(1); /* had a 64 bit overflow */
  239. else
  240. return(overflow); /* return status from higher add */
  241. }
  242. /* The following tables can be computed with the following bc(1)
  243. program:
  244. obase=16
  245. scale=0
  246. define t(x){
  247. auto a, b, c
  248. a=2;b=1;c=2^32;n=1
  249. while(a<x) {
  250. b=a;n+=n;a*=a
  251. }
  252. n/=2
  253. a=b
  254. while(b<x) {
  255. a=b;b*=c;n+=32
  256. }
  257. n-=32
  258. b=a
  259. while(a<x) {
  260. b=a;a+=a;n+=1
  261. }
  262. n-=1
  263. x*=16^16
  264. b=x%a
  265. x/=a
  266. if(a<=(2*b)) x+=1
  267. obase=10
  268. n
  269. obase=16
  270. return(x)
  271. }
  272. for (i=1;i<28;i++) {
  273. t(10^i)
  274. }
  275. 0
  276. for (i=1;i<20;i++) {
  277. t(10^(28*i))
  278. }
  279. 0
  280. define r(x){
  281. auto a, b, c
  282. a=2;b=1;c=2^32;n=1
  283. while(a<x) {
  284. b=a;n+=n;a*=a
  285. }
  286. n/=2
  287. a=b
  288. while(b<x) {
  289. a=b;b*=c;n+=32
  290. }
  291. n-=32
  292. b=a
  293. while(a<x) {
  294. b=a;a+=a;n+=1
  295. }
  296. a=b
  297. a*=16^16
  298. b=a%x
  299. a/=x
  300. if(x<=(2*b)) a+=1
  301. obase=10
  302. -n
  303. obase=16
  304. return(a)
  305. }
  306. for (i=1;i<28;i++) {
  307. r(10^i)
  308. }
  309. 0
  310. for (i=1;i<20;i++) {
  311. r(10^(28*i))
  312. }
  313. 0
  314. */
  315. static struct EXTEND ten_powers[] = { /* representation of 10 ** i */
  316. { 0, 0, 0x80000000, 0 },
  317. { 0, 3, 0xA0000000, 0 },
  318. { 0, 6, 0xC8000000, 0 },
  319. { 0, 9, 0xFA000000, 0 },
  320. { 0, 13, 0x9C400000, 0 },
  321. { 0, 16, 0xC3500000, 0 },
  322. { 0, 19, 0xF4240000, 0 },
  323. { 0, 23, 0x98968000, 0 },
  324. { 0, 26, 0xBEBC2000, 0 },
  325. { 0, 29, 0xEE6B2800, 0 },
  326. { 0, 33, 0x9502F900, 0 },
  327. { 0, 36, 0xBA43B740, 0 },
  328. { 0, 39, 0xE8D4A510, 0 },
  329. { 0, 43, 0x9184E72A, 0 },
  330. { 0, 46, 0xB5E620F4, 0x80000000 },
  331. { 0, 49, 0xE35FA931, 0xA0000000 },
  332. { 0, 53, 0x8E1BC9BF, 0x04000000 },
  333. { 0, 56, 0xB1A2BC2E, 0xC5000000 },
  334. { 0, 59, 0xDE0B6B3A, 0x76400000 },
  335. { 0, 63, 0x8AC72304, 0x89E80000 },
  336. { 0, 66, 0xAD78EBC5, 0xAC620000 },
  337. { 0, 69, 0xD8D726B7, 0x177A8000 },
  338. { 0, 73, 0x87867832, 0x6EAC9000 },
  339. { 0, 76, 0xA968163F, 0x0A57B400 },
  340. { 0, 79, 0xD3C21BCE, 0xCCEDA100 },
  341. { 0, 83, 0x84595161, 0x401484A0 },
  342. { 0, 86, 0xA56FA5B9, 0x9019A5C8 },
  343. { 0, 89, 0xCECB8F27, 0xF4200F3A }
  344. };
  345. static struct EXTEND big_ten_powers[] = { /* representation of 10 ** (28*i) */
  346. { 0, 0, 0x80000000, 0 },
  347. { 0, 93, 0x813F3978, 0xF8940984 },
  348. { 0, 186, 0x82818F12, 0x81ED44A0 },
  349. { 0, 279, 0x83C7088E, 0x1AAB65DB },
  350. { 0, 372, 0x850FADC0, 0x9923329E },
  351. { 0, 465, 0x865B8692, 0x5B9BC5C2 },
  352. { 0, 558, 0x87AA9AFF, 0x79042287 },
  353. { 0, 651, 0x88FCF317, 0xF22241E2 },
  354. { 0, 744, 0x8A5296FF, 0xE33CC930 },
  355. { 0, 837, 0x8BAB8EEF, 0xB6409C1A },
  356. { 0, 930, 0x8D07E334, 0x55637EB3 },
  357. { 0, 1023, 0x8E679C2F, 0x5E44FF8F },
  358. { 0, 1116, 0x8FCAC257, 0x558EE4E6 },
  359. { 0, 1209, 0x91315E37, 0xDB165AA9 },
  360. { 0, 1302, 0x929B7871, 0xDE7F22B9 },
  361. { 0, 1395, 0x940919BB, 0xD4620B6D },
  362. { 0, 1488, 0x957A4AE1, 0xEBF7F3D4 },
  363. { 0, 1581, 0x96EF14C6, 0x454AA840 },
  364. { 0, 1674, 0x98678061, 0x27ECE4F5 },
  365. { 0, 1767, 0x99E396C1, 0x3A3ACFF2 }
  366. };
  367. static struct EXTEND r_ten_powers[] = { /* representation of 10 ** -i */
  368. { 0, 0, 0x80000000, 0 },
  369. { 0, -4, 0xCCCCCCCC, 0xCCCCCCCD },
  370. { 0, -7, 0xA3D70A3D, 0x70A3D70A },
  371. { 0, -10, 0x83126E97, 0x8D4FDF3B },
  372. { 0, -14, 0xD1B71758, 0xE219652C },
  373. { 0, -17, 0xA7C5AC47, 0x1B478423 },
  374. { 0, -20, 0x8637BD05, 0xAF6C69B6 },
  375. { 0, -24, 0xD6BF94D5, 0xE57A42BC },
  376. { 0, -27, 0xABCC7711, 0x8461CEFD },
  377. { 0, -30, 0x89705F41, 0x36B4A597 },
  378. { 0, -34, 0xDBE6FECE, 0xBDEDD5BF },
  379. { 0, -37, 0xAFEBFF0B, 0xCB24AAFF },
  380. { 0, -40, 0x8CBCCC09, 0x6F5088CC },
  381. { 0, -44, 0xE12E1342, 0x4BB40E13 },
  382. { 0, -47, 0xB424DC35, 0x095CD80F },
  383. { 0, -50, 0x901D7CF7, 0x3AB0ACD9 },
  384. { 0, -54, 0xE69594BE, 0xC44DE15B },
  385. { 0, -57, 0xB877AA32, 0x36A4B449 },
  386. { 0, -60, 0x9392EE8E, 0x921D5D07 },
  387. { 0, -64, 0xEC1E4A7D, 0xB69561A5 },
  388. { 0, -67, 0xBCE50864, 0x92111AEB },
  389. { 0, -70, 0x971DA050, 0x74DA7BEF },
  390. { 0, -74, 0xF1C90080, 0xBAF72CB1 },
  391. { 0, -77, 0xC16D9A00, 0x95928A27 },
  392. { 0, -80, 0x9ABE14CD, 0x44753B53 },
  393. { 0, -84, 0xF79687AE, 0xD3EEC551 },
  394. { 0, -87, 0xC6120625, 0x76589DDB },
  395. { 0, -90, 0x9E74D1B7, 0x91E07E48 }
  396. };
  397. static struct EXTEND r_big_ten_powers[] = { /* representation of 10 ** -(28*i) */
  398. { 0, 0, 0x80000000, 0 },
  399. { 0, -94, 0xFD87B5F2, 0x8300CA0E },
  400. { 0, -187, 0xFB158592, 0xBE068D2F },
  401. { 0, -280, 0xF8A95FCF, 0x88747D94 },
  402. { 0, -373, 0xF64335BC, 0xF065D37D },
  403. { 0, -466, 0xF3E2F893, 0xDEC3F126 },
  404. { 0, -559, 0xF18899B1, 0xBC3F8CA2 },
  405. { 0, -652, 0xEF340A98, 0x172AACE5 },
  406. { 0, -745, 0xECE53CEC, 0x4A314EBE },
  407. { 0, -838, 0xEA9C2277, 0x23EE8BCB },
  408. { 0, -931, 0xE858AD24, 0x8F5C22CA },
  409. { 0, -1024, 0xE61ACF03, 0x3D1A45DF },
  410. { 0, -1117, 0xE3E27A44, 0x4D8D98B8 },
  411. { 0, -1210, 0xE1AFA13A, 0xFBD14D6E },
  412. { 0, -1303, 0xDF82365C, 0x497B5454 },
  413. { 0, -1396, 0xDD5A2C3E, 0xAB3097CC },
  414. { 0, -1489, 0xDB377599, 0xB6074245 },
  415. { 0, -1582, 0xD91A0545, 0xCDB51186 },
  416. { 0, -1675, 0xD701CE3B, 0xD387BF48 },
  417. { 0, -1768, 0xD4EEC394, 0xD6258BF8 }
  418. };
  419. static
  420. add_exponent(e, exp)
  421. struct EXTEND *e;
  422. {
  423. int neg = exp < 0;
  424. int divsz, modsz;
  425. struct EXTEND x;
  426. if (neg) exp = -exp;
  427. divsz = exp / (sizeof(ten_powers)/sizeof(ten_powers[0]));
  428. modsz = exp % (sizeof(ten_powers)/sizeof(ten_powers[0]));
  429. if (neg) {
  430. mul_ext(e, &r_ten_powers[modsz], &x);
  431. mul_ext(&x, &r_big_ten_powers[divsz], e);
  432. }
  433. else {
  434. mul_ext(e, &ten_powers[modsz], &x);
  435. mul_ext(&x, &big_ten_powers[divsz], e);
  436. }
  437. }
  438. _str_ext_cvt(s, ss, e)
  439. char *s, **ss;
  440. struct EXTEND *e;
  441. {
  442. /* Like strtod, but for extended precision */
  443. register int c;
  444. int dotseen = 0;
  445. int digitseen = 0;
  446. int exp = 0;
  447. if (ss) *ss = s;
  448. while (isspace(*s)) s++;
  449. e->sign = 0;
  450. e->exp = 0;
  451. e->m1 = e->m2 = 0;
  452. c = *s;
  453. switch(c) {
  454. case '-':
  455. e->sign = 1;
  456. case '+':
  457. s++;
  458. }
  459. while (c = *s++, isdigit(c) || (c == '.' && ! dotseen++)) {
  460. if (c == '.') continue;
  461. digitseen = 1;
  462. if (e->m1 <= (unsigned long)(0xFFFFFFFF)/10) {
  463. struct mantissa a1;
  464. a1 = e->mantissa;
  465. b64_sft(&(e->mantissa), -3);
  466. b64_sft(&a1, -1);
  467. b64_add(&(e->mantissa), &a1);
  468. a1.h_32 = 0;
  469. a1.l_32 = c - '0';
  470. b64_add(&(e->mantissa), &a1);
  471. }
  472. else exp++;
  473. if (dotseen) exp--;
  474. }
  475. if (! digitseen) return;
  476. if (ss) *ss = s - 1;
  477. if (c == 'E' || c == 'e') {
  478. int exp1 = 0;
  479. int sign = 1;
  480. switch(*s) {
  481. case '-':
  482. sign = -1;
  483. case '+':
  484. s++;
  485. }
  486. if (c = *s, isdigit(c)) {
  487. do {
  488. exp1 = 10 * exp1 + (c - '0');
  489. } while (c = *++s, isdigit(c));
  490. if (ss) *ss = s;
  491. }
  492. exp += sign * exp1;
  493. }
  494. if (e->m1 == 0 && e->m2 == 0) return;
  495. e->exp = 63;
  496. while (! (e->m1 & 0x80000000)) {
  497. b64_sft(&(e->mantissa),-1);
  498. e->exp--;
  499. }
  500. add_exponent(e, exp);
  501. }
  502. extern double ldexp(), frexp(), modf();
  503. #define NDIGITS 128
  504. char *
  505. _ext_str_cvt(e, ndigit, decpt, sign, ecvtflag)
  506. struct EXTEND *e;
  507. int ndigit, *decpt, *sign;
  508. {
  509. /* Like cvt(), but for extended precision */
  510. static char buf[NDIGITS+1];
  511. register char *p = buf;
  512. register char *pe;
  513. int findex = 0;
  514. if (ndigit < 0) ndigit = 0;
  515. if (ndigit > NDIGITS) ndigit = NDIGITS;
  516. pe = &buf[ndigit];
  517. buf[0] = '\0';
  518. *sign = 0;
  519. if (e->sign) {
  520. *sign = 1;
  521. e->sign = 0;
  522. }
  523. *decpt = 0;
  524. if (e->m1 != 0) {
  525. register struct EXTEND *pp = &big_ten_powers[1];
  526. while(cmp_ext(e,pp) >= 0) pp++;
  527. pp--;
  528. findex = pp - big_ten_powers;
  529. mul_ext(e,&r_big_ten_powers[findex],e);
  530. *decpt += findex * (sizeof(ten_powers)/sizeof(ten_powers[0]));
  531. pp = &ten_powers[1];
  532. while(pp<&ten_powers[(sizeof(ten_powers)/sizeof(ten_powers[0]))] &&
  533. cmp_ext(e, pp) >= 0) pp++;
  534. pp--;
  535. findex = pp - ten_powers;
  536. *decpt += findex;
  537. if (cmp_ext(e, &ten_powers[0]) < 0) {
  538. pp = &r_big_ten_powers[1];
  539. while(cmp_ext(e,pp) < 0) pp++;
  540. pp--;
  541. findex = pp - r_big_ten_powers;
  542. mul_ext(e,&big_ten_powers[findex],e);
  543. *decpt -= findex *
  544. (sizeof(ten_powers)/sizeof(ten_powers[0]));
  545. /* here, value >= 10 ** -28 */
  546. mul_ext(e, &ten_powers[1], e);
  547. (*decpt)--;
  548. pp = &r_ten_powers[0];
  549. while(cmp_ext(e, pp) < 0) pp++;
  550. findex = -(pp - r_ten_powers);
  551. mul_ext(e, &ten_powers[-findex], e);
  552. *decpt += findex;
  553. findex = 0;
  554. }
  555. (*decpt)++; /* because now value in [1.0, 10.0) */
  556. }
  557. if (! ecvtflag) {
  558. /* for fcvt() we need ndigit digits behind the dot */
  559. pe += *decpt;
  560. if (pe > &buf[NDIGITS]) pe = &buf[NDIGITS];
  561. }
  562. while (p <= pe) {
  563. if (findex) {
  564. struct EXTEND tc, oldtc;
  565. int count = 0;
  566. oldtc.exp = 0;
  567. oldtc.sign = 0;
  568. oldtc.m1 = 0;
  569. oldtc.m2 = 0;
  570. tc = ten_powers[findex];
  571. while (cmp_ext(e, &tc) >= 0) {
  572. oldtc = tc;
  573. add_ext(&tc, &ten_powers[findex], &tc);
  574. count++;
  575. }
  576. *p++ = count + '0';
  577. oldtc.sign = 1;
  578. add_ext(e, &oldtc, e);
  579. findex--;
  580. continue;
  581. }
  582. if (e->exp >= 0 && e->m1 != 0) {
  583. struct EXTEND x;
  584. x.m2 = 0; x.exp = e->exp;
  585. x.sign = 1;
  586. x.m1 = e->m1>>(31-e->exp);
  587. *p++ = (x.m1) + '0';
  588. if (x.m1) {
  589. x.m1 = x.m1 << (31-e->exp);
  590. add_ext(e, &x, e);
  591. }
  592. }
  593. else *p++ = '0';
  594. if (e->m1) mul_ext(e, &ten_powers[1], e);
  595. }
  596. if (pe >= buf) {
  597. p = pe;
  598. *p += 5; /* round of at the end */
  599. while (*p > '9') {
  600. *p = '0';
  601. if (p > buf) ++*--p;
  602. else {
  603. *p = '1';
  604. ++*decpt;
  605. if (! ecvtflag) {
  606. /* maybe add another digit at the end,
  607. because the point was shifted right
  608. */
  609. if (pe > buf) *pe = '0';
  610. pe++;
  611. }
  612. }
  613. }
  614. *pe = '\0';
  615. }
  616. return buf;
  617. }
  618. _dbl_ext_cvt(value, e)
  619. double value;
  620. struct EXTEND *e;
  621. {
  622. /* Convert double to extended
  623. */
  624. int exponent;
  625. register int i;
  626. value = frexp(value, &exponent);
  627. e->sign = value < 0.0;
  628. if (e->sign) value = -value;
  629. e->exp = exponent - 1;
  630. e->m1 = 0;
  631. e->m2 = 0;
  632. for (i = 64; i > 0 && value != 0; i--) {
  633. double ipart;
  634. b64_sft(&(e->mantissa),-1);
  635. value = modf(2.0*value, &ipart);
  636. if (ipart) {
  637. e->m2 |= 1;
  638. }
  639. }
  640. if (i > 0) b64_sft(&(e->mantissa),-i);
  641. }
  642. double
  643. _ext_dbl_cvt(e)
  644. struct EXTEND *e;
  645. {
  646. /* Convert extended to double
  647. */
  648. double f = ldexp(ldexp((double)e->m1, 32) + (double)e->m2, e->exp-63);
  649. if (e->sign) f = -f;
  650. return f;
  651. }