18ccd4a63SDavid du Colombier #include <u.h>
28ccd4a63SDavid du Colombier #include <libc.h>
3*0d601874SDavid du Colombier #include "fmtdef.h"
48ccd4a63SDavid du Colombier
58ccd4a63SDavid du Colombier /*
68ccd4a63SDavid du Colombier * this table might overflow 127-bit exponent representations.
78ccd4a63SDavid du Colombier * in that case, truncate it after 1.0e38.
88ccd4a63SDavid du Colombier * it is important to get all one can from this
98ccd4a63SDavid du Colombier * routine since it is used in atof to scale numbers.
108ccd4a63SDavid du Colombier * the presumption is that C converts fp numbers better
118ccd4a63SDavid du Colombier * than multipication of lower powers of 10.
128ccd4a63SDavid du Colombier */
13*0d601874SDavid du Colombier
148ccd4a63SDavid du Colombier static
158ccd4a63SDavid du Colombier double tab[] =
168ccd4a63SDavid du Colombier {
178ccd4a63SDavid du Colombier 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9,
188ccd4a63SDavid du Colombier 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19,
198ccd4a63SDavid du Colombier 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29,
208ccd4a63SDavid du Colombier 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39,
218ccd4a63SDavid du Colombier 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49,
228ccd4a63SDavid du Colombier 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59,
238ccd4a63SDavid du Colombier 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69,
248ccd4a63SDavid du Colombier };
258ccd4a63SDavid du Colombier
268ccd4a63SDavid du Colombier double
__fmtpow10(int n)27*0d601874SDavid du Colombier __fmtpow10(int n)
288ccd4a63SDavid du Colombier {
298ccd4a63SDavid du Colombier int m;
308ccd4a63SDavid du Colombier
318ccd4a63SDavid du Colombier if(n < 0) {
328ccd4a63SDavid du Colombier n = -n;
33*0d601874SDavid du Colombier if(n < (int)(sizeof(tab)/sizeof(tab[0])))
348ccd4a63SDavid du Colombier return 1/tab[n];
358ccd4a63SDavid du Colombier m = n/2;
36*0d601874SDavid du Colombier return __fmtpow10(-m) * __fmtpow10(m-n);
378ccd4a63SDavid du Colombier }
38*0d601874SDavid du Colombier if(n < (int)(sizeof(tab)/sizeof(tab[0])))
398ccd4a63SDavid du Colombier return tab[n];
408ccd4a63SDavid du Colombier m = n/2;
41*0d601874SDavid du Colombier return __fmtpow10(m) * __fmtpow10(n-m);
428ccd4a63SDavid du Colombier }
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