1 /* 2 * The authors of this software are Rob Pike and Ken Thompson. 3 * Copyright (c) 2002 by Lucent Technologies. 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose without fee is hereby granted, provided that this entire notice 6 * is included in all copies of any software which is or includes a copy 7 * or modification of this software and in all copies of the supporting 8 * documentation for such software. 9 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED 10 * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE 11 * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY 12 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. 13 */ 14 #include <u.h> 15 #include <libc.h> 16 #include "fmtdef.h" 17 18 /* 19 * Reads a floating-point number by interpreting successive characters 20 * returned by (*f)(vp). The last call it makes to f terminates the 21 * scan, so is not a character in the number. It may therefore be 22 * necessary to back up the input stream up one byte after calling charstod. 23 */ 24 25 double 26 fmtcharstod(int(*f)(void*), void *vp) 27 { 28 double num, dem; 29 int neg, eneg, dig, exp, c; 30 31 num = 0; 32 neg = 0; 33 dig = 0; 34 exp = 0; 35 eneg = 0; 36 37 c = (*f)(vp); 38 while(c == ' ' || c == '\t') 39 c = (*f)(vp); 40 if(c == '-' || c == '+'){ 41 if(c == '-') 42 neg = 1; 43 c = (*f)(vp); 44 } 45 while(c >= '0' && c <= '9'){ 46 num = num*10 + c-'0'; 47 c = (*f)(vp); 48 } 49 if(c == '.') 50 c = (*f)(vp); 51 while(c >= '0' && c <= '9'){ 52 num = num*10 + c-'0'; 53 dig++; 54 c = (*f)(vp); 55 } 56 if(c == 'e' || c == 'E'){ 57 c = (*f)(vp); 58 if(c == '-' || c == '+'){ 59 if(c == '-'){ 60 dig = -dig; 61 eneg = 1; 62 } 63 c = (*f)(vp); 64 } 65 while(c >= '0' && c <= '9'){ 66 exp = exp*10 + c-'0'; 67 c = (*f)(vp); 68 } 69 } 70 exp -= dig; 71 if(exp < 0){ 72 exp = -exp; 73 eneg = !eneg; 74 } 75 dem = __fmtpow10(exp); 76 if(eneg) 77 num /= dem; 78 else 79 num *= dem; 80 if(neg) 81 return -num; 82 return num; 83 } 84