ref: d4bc9052beb3305d64a353a16641740380eb87af
dir: /sys/src/libmp/port/strtomp.c/
#include "os.h" #include <mp.h> #include "dat.h" static char* frompow2(char *a, mpint *b, int s) { char *p, *next; mpdigit x; int i; i = 1<<s; for(p = a; (dec16chr(*p) & 255) < i; p++) ; mpbits(b, (p-a)*s); b->top = 0; next = p; while(p > a){ x = 0; for(i = 0; i < Dbits; i += s){ if(p <= a) break; x |= dec16chr(*--p)<<i; } b->p[b->top++] = x; } return next; } static char* from8(char *a, mpint *b) { char *p, *next; mpdigit x, y; int i; for(p = a; ((*p - '0') & 255) < 8; p++) ; mpbits(b, (p-a)*3); b->top = 0; next = p; i = 0; x = y = 0; while(p > a){ y = *--p - '0'; x |= y << i; i += 3; if(i >= Dbits){ Digout: i -= Dbits; b->p[b->top++] = x; x = y >> 3-i; } } if(i > 0) goto Digout; return next; } static ulong mppow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 }; static char* from10(char *a, mpint *b) { ulong x, y; mpint *pow, *r; int i; pow = mpnew(0); r = mpnew(0); b->top = 0; for(;;){ // do a billion at a time in native arithmetic x = 0; for(i = 0; i < 9; i++){ y = *a - '0'; if(y > 9) break; a++; x *= 10; x += y; } if(i == 0) break; // accumulate into mpint uitomp(mppow10[i], pow); uitomp(x, r); mpmul(b, pow, b); mpadd(b, r, b); if(i < 9) break; } mpfree(pow); mpfree(r); return a; } static char* fromdecx(char *a, mpint *b, int (*chr)(int), int (*dec)(uchar*, int, char*, int)) { char *buf = a; uchar *p; int n, m; b->top = 0; for(; (*chr)(*a) >= 0; a++) ; n = a-buf; if(n > 0){ p = malloc(n); if(p == nil) sysfatal("malloc: %r"); m = (*dec)(p, n, buf, n); if(m > 0) betomp(p, m, b); free(p); } return a; } mpint* strtomp(char *a, char **pp, int base, mpint *b) { int sign; char *e; if(b == nil){ b = mpnew(0); setmalloctag(b, getcallerpc(&a)); } while(*a==' ' || *a=='\t') a++; sign = 1; for(;; a++){ switch(*a){ case '-': sign *= -1; continue; } break; } if(base == 0){ base = 10; if(a[0] == '0'){ if(a[1] == 'x' || a[1] == 'X') { a += 2; base = 16; } else if(a[1] == 'b' || a[1] == 'B') { a += 2; base = 2; } else if(a[1] >= '0' && a[1] <= '7') { a++; base = 8; } } } switch(base){ case 2: e = frompow2(a, b, 1); break; case 4: e = frompow2(a, b, 2); break; case 8: e = from8(a, b); break; case 10: e = from10(a, b); break; case 16: e = frompow2(a, b, 4); break; case 32: e = fromdecx(a, b, dec32chr, dec32); break; case 64: e = fromdecx(a, b, dec64chr, dec64); break; default: abort(); return nil; } if(pp != nil) *pp = e; // if no characters parsed, there wasn't a number to convert if(e == a) return nil; b->sign = sign; return mpnorm(b); }