fusl/src/internal/intscan.c

#include <limits.h>
#include <errno.h>
#include <ctype.h>
#include "shgetc.h"

/* Lookup table for digit values. -1==255>=36 -> invalid */
static const unsigned char table[] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,
    8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
    20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1,
    -1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
    26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

unsigned long long __intscan(FILE* f,
                             unsigned base,
                             int pok,
                             unsigned long long lim) {
  const unsigned char* val = table + 1;
  int c, neg = 0;
  unsigned x;
  unsigned long long y;
  if (base > 36) {
    errno = EINVAL;
    return 0;
  }
  while (isspace((c = shgetc(f))))
    ;
  if (c == '+' || c == '-') {
    neg = -(c == '-');
    c = shgetc(f);
  }
  if ((base == 0 || base == 16) && c == '0') {
    c = shgetc(f);
    if ((c | 32) == 'x') {
      c = shgetc(f);
      if (val[c] >= 16) {
        shunget(f);
        if (pok)
          shunget(f);
        else
          shlim(f, 0);
        return 0;
      }
      base = 16;
    } else if (base == 0) {
      base = 8;
    }
  } else {
    if (base == 0)
      base = 10;
    if (val[c] >= base) {
      shunget(f);
      shlim(f, 0);
      errno = EINVAL;
      return 0;
    }
  }
  if (base == 10) {
    for (x = 0; c - '0' < 10U && x <= UINT_MAX / 10 - 1; c = shgetc(f))
      x = x * 10 + (c - '0');
    for (y = x; c - '0' < 10U && y <= ULLONG_MAX / 10 &&
                10 * y <= ULLONG_MAX - (c - '0');
         c = shgetc(f))
      y = y * 10 + (c - '0');
    if (c - '0' >= 10U)
      goto done;
  } else if (!(base & base - 1)) {
    int bs = "\0\1\2\4\7\3\6\5"[(0x17 * base) >> 5 & 7];
    for (x = 0; val[c] < base && x <= UINT_MAX / 32; c = shgetc(f))
      x = x << bs | val[c];
    for (y = x; val[c] < base && y <= ULLONG_MAX >> bs; c = shgetc(f))
      y = y << bs | val[c];
  } else {
    for (x = 0; val[c] < base && x <= UINT_MAX / 36 - 1; c = shgetc(f))
      x = x * base + val[c];
    for (y = x; val[c] < base && y <= ULLONG_MAX / base &&
                base * y <= ULLONG_MAX - val[c];
         c = shgetc(f))
      y = y * base + val[c];
  }
  if (val[c] < base) {
    for (; val[c] < base; c = shgetc(f))
      ;
    errno = ERANGE;
    y = lim;
    if (lim & 1)
      neg = 0;
  }
done:
  shunget(f);
  if (y >= lim) {
    if (!(lim & 1) && !neg) {
      errno = ERANGE;
      return lim - 1;
    } else if (y > lim) {
      errno = ERANGE;
      return lim;
    }
  }
  return (y ^ neg) - neg;
}