ref: 8bd7505dc37201cbcb99bf4e6b48d938af64bb5b
dir: /libc/charstod.c/
#include <u.h> #include <libc.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; }