ref: 5e010fd8a82ec3b6552b4002bcd4be0586081e9a
dir: /sys/src/ape/lib/fmt/charstod.c/
/* * The authors of this software are Rob Pike and Ken Thompson. * Copyright (c) 2002 by Lucent Technologies. * Permission to use, copy, modify, and distribute this software for any * purpose without fee is hereby granted, provided that this entire notice * is included in all copies of any software which is or includes a copy * or modification of this software and in all copies of the supporting * documentation for such software. * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. */ #include <stdarg.h> #include <string.h> #include "utf.h" #include "fmt.h" #include "fmtdef.h" /* * Reads a floating-point number by interpreting successive characters * returned by (*f)(vp). The last call it makes to f terminates the * scan, so is not a character in the number. It may therefore be * necessary to back up the input stream up one byte after calling charstod. */ double fmtcharstod(int(*f)(void*), void *vp) { double num, dem; int neg, eneg, dig, exp, c; num = 0; neg = 0; dig = 0; exp = 0; eneg = 0; c = (*f)(vp); while(c == ' ' || c == '\t') c = (*f)(vp); if(c == '-' || c == '+'){ if(c == '-') neg = 1; c = (*f)(vp); } while(c >= '0' && c <= '9'){ num = num*10 + c-'0'; c = (*f)(vp); } if(c == '.') c = (*f)(vp); while(c >= '0' && c <= '9'){ num = num*10 + c-'0'; dig++; c = (*f)(vp); } if(c == 'e' || c == 'E'){ c = (*f)(vp); if(c == '-' || c == '+'){ if(c == '-'){ dig = -dig; eneg = 1; } c = (*f)(vp); } while(c >= '0' && c <= '9'){ exp = exp*10 + c-'0'; c = (*f)(vp); } } exp -= dig; if(exp < 0){ exp = -exp; eneg = !eneg; } dem = __fmtpow10(exp); if(eneg) num /= dem; else num *= dem; if(neg) return -num; return num; }