alexvoste
170 lines
4.3 KiB
C
170 lines
4.3 KiB
C
#include <stdint.h>
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#include <stddef.h>
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uint64_t __cervus_strtod_bits(const char *s, char **endptr)
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{
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if (!s) {
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if (endptr) *endptr = (char *)s;
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return 0;
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}
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const char *p = s;
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while (*p == ' ' || *p == '\t' || *p == '\n' ||
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*p == '\r' || *p == '\f' || *p == '\v') p++;
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int sign = 0;
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if (*p == '+') p++;
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else if (*p == '-') { sign = 1; p++; }
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if ((p[0] == 'i' || p[0] == 'I') &&
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(p[1] == 'n' || p[1] == 'N') &&
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(p[2] == 'f' || p[2] == 'F')) {
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p += 3;
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if ((p[0] == 'i' || p[0] == 'I') &&
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(p[1] == 'n' || p[1] == 'N') &&
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(p[2] == 'i' || p[2] == 'I') &&
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(p[3] == 't' || p[3] == 'T') &&
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(p[4] == 'y' || p[4] == 'Y')) p += 5;
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if (endptr) *endptr = (char *)p;
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return ((uint64_t)sign << 63) | 0x7FF0000000000000ULL;
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}
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if ((p[0] == 'n' || p[0] == 'N') &&
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(p[1] == 'a' || p[1] == 'A') &&
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(p[2] == 'n' || p[2] == 'N')) {
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p += 3;
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if (endptr) *endptr = (char *)p;
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return 0x7FF8000000000000ULL;
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}
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uint64_t mant = 0;
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int dec_exp = 0;
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int seen_digit = 0;
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while (*p >= '0' && *p <= '9') {
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seen_digit = 1;
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if (mant <= (UINT64_MAX - 9) / 10) {
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mant = mant * 10 + (uint64_t)(*p - '0');
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} else {
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dec_exp++;
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}
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p++;
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}
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if (*p == '.') {
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p++;
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while (*p >= '0' && *p <= '9') {
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seen_digit = 1;
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if (mant <= (UINT64_MAX - 9) / 10) {
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mant = mant * 10 + (uint64_t)(*p - '0');
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dec_exp--;
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}
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p++;
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}
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}
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if (!seen_digit) {
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if (endptr) *endptr = (char *)s;
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return 0;
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}
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if (*p == 'e' || *p == 'E') {
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const char *ep = p + 1;
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int esign = 0;
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if (*ep == '+') ep++;
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else if (*ep == '-') { esign = 1; ep++; }
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if (*ep >= '0' && *ep <= '9') {
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int eval = 0;
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while (*ep >= '0' && *ep <= '9') {
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if (eval < 10000) eval = eval * 10 + (*ep - '0');
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ep++;
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}
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dec_exp += esign ? -eval : eval;
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p = ep;
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}
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}
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if (endptr) *endptr = (char *)p;
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if (mant == 0) {
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return (uint64_t)sign << 63;
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}
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int bin_exp = 0;
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while ((mant >> 63) == 0) {
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mant <<= 1;
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bin_exp--;
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}
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while (dec_exp > 0) {
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uint64_t a_hi = mant >> 32;
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uint64_t a_lo = mant & 0xFFFFFFFFULL;
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uint64_t p_lo = a_lo * 10;
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uint64_t p_hi = a_hi * 10;
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uint64_t mid_carry = p_lo >> 32;
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uint64_t lo = ((p_hi + mid_carry) << 32) | (p_lo & 0xFFFFFFFFULL);
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uint64_t hi = (p_hi + mid_carry) >> 32;
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while (hi != 0) {
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lo = (lo >> 1) | (hi << 63);
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hi >>= 1;
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bin_exp++;
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}
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mant = lo;
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while ((mant >> 63) == 0) {
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mant <<= 1;
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bin_exp--;
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}
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dec_exp--;
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}
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while (dec_exp < 0) {
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mant = mant / 10;
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if (mant == 0) break;
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while ((mant >> 63) == 0) {
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mant <<= 1;
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bin_exp--;
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}
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dec_exp++;
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}
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int ieee_exp = bin_exp + 63 + 1023;
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uint64_t no_implicit = mant & 0x7FFFFFFFFFFFFFFFULL;
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uint64_t round_bit = (no_implicit >> 10) & 1;
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uint64_t sticky = (no_implicit & 0x3FFULL) ? 1 : 0;
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uint64_t frac = no_implicit >> 11;
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if (round_bit && (sticky || (frac & 1))) {
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frac++;
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if (frac == (1ULL << 52)) {
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frac = 0;
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ieee_exp++;
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}
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}
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if (ieee_exp >= 0x7FF) {
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return ((uint64_t)sign << 63) | 0x7FF0000000000000ULL;
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}
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if (ieee_exp <= 0) {
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return (uint64_t)sign << 63;
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}
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return ((uint64_t)sign << 63) |
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((uint64_t)ieee_exp << 52) |
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(frac & 0xFFFFFFFFFFFFFULL);
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}
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double strtod(const char *s, char **endptr)
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{
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uint64_t bits = __cervus_strtod_bits(s, endptr);
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double result;
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__builtin_memcpy(&result, &bits, sizeof(double));
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return result;
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}
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float strtof(const char *s, char **endptr)
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{
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return (float)strtod(s, endptr);
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}
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long double strtold(const char *s, char **endptr)
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{
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return (long double)strtod(s, endptr);
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}
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double atof(const char *s)
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{
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return strtod(s, NULL);
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} |