diff options
Diffstat (limited to 'sysdeps/generic/get_str.c')
| -rw-r--r-- | sysdeps/generic/get_str.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/sysdeps/generic/get_str.c b/sysdeps/generic/get_str.c new file mode 100644 index 0000000000..182815ee18 --- /dev/null +++ b/sysdeps/generic/get_str.c @@ -0,0 +1,213 @@ +/* __mpn_get_str -- Convert a MSIZE long limb vector pointed to by MPTR + to a printable string in STR in base BASE. + +Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc. + + +This file is part of the GNU C Library. Its master source is NOT part of +the C library, however. This file is in fact copied from the GNU MP +Library and its source lives there. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" + +/* Convert the limb vector pointed to by MPTR and MSIZE long to a + char array, using base BASE for the result array. Store the + result in the character array STR. STR must point to an array with + space for the largest possible number represented by a MSIZE long + limb vector + 1 extra character. + + The result is NOT in Ascii, to convert it to printable format, add + '0' or 'A' depending on the base and range. + + Return the number of digits in the result string. + This may include some leading zeros. + + The limb vector pointed to by MPTR is clobbered. */ + +size_t +__mpn_get_str (str, base, mptr, msize) + unsigned char *str; + int base; + mp_ptr mptr; + mp_size_t msize; +{ + mp_limb big_base; +#if UDIV_NEEDS_NORMALIZATION || UDIV_TIME > 2 * UMUL_TIME + int normalization_steps; +#endif +#if UDIV_TIME > 2 * UMUL_TIME + mp_limb big_base_inverted; +#endif + unsigned int dig_per_u; + mp_size_t out_len; + register unsigned char *s; + + big_base = __mp_bases[base].big_base; + + s = str; + + /* Special case zero, as the code below doesn't handle it. */ + if (msize == 0) + { + s[0] = 0; + return 1; + } + + if ((base & (base - 1)) == 0) + { + /* The base is a power of 2. Make conversion from most + significant side. */ + mp_limb n1, n0; + register int bits_per_digit = big_base; + register int x; + register int bit_pos; + register int i; + + n1 = mptr[msize - 1]; + count_leading_zeros (x, n1); + + /* BIT_POS should be R when input ends in least sign. nibble, + R + bits_per_digit * n when input ends in n:th least significant + nibble. */ + + { + int bits; + + bits = BITS_PER_MP_LIMB * msize - x; + x = bits % bits_per_digit; + if (x != 0) + bits += bits_per_digit - x; + bit_pos = bits - (msize - 1) * BITS_PER_MP_LIMB; + } + + /* Fast loop for bit output. */ + i = msize - 1; + for (;;) + { + bit_pos -= bits_per_digit; + while (bit_pos >= 0) + { + *s++ = (n1 >> bit_pos) & ((1 << bits_per_digit) - 1); + bit_pos -= bits_per_digit; + } + i--; + if (i < 0) + break; + n0 = (n1 << -bit_pos) & ((1 << bits_per_digit) - 1); + n1 = mptr[i]; + bit_pos += BITS_PER_MP_LIMB; + *s++ = n0 | (n1 >> bit_pos); + } + + *s = 0; + + return s - str; + } + else + { + /* General case. The base is not a power of 2. Make conversion + from least significant end. */ + + /* If udiv_qrnnd only handles divisors with the most significant bit + set, prepare BIG_BASE for being a divisor by shifting it to the + left exactly enough to set the most significant bit. */ +#if UDIV_NEEDS_NORMALIZATION || UDIV_TIME > 2 * UMUL_TIME + count_leading_zeros (normalization_steps, big_base); + big_base <<= normalization_steps; +#if UDIV_TIME > 2 * UMUL_TIME + /* Get the fixed-point approximation to 1/(BIG_BASE << NORMALIZATION_STEPS). */ + big_base_inverted = __mp_bases[base].big_base_inverted; +#endif +#endif + + dig_per_u = __mp_bases[base].chars_per_limb; + out_len = ((size_t) msize * BITS_PER_MP_LIMB + * __mp_bases[base].chars_per_bit_exactly) + 1; + s += out_len; + + while (msize != 0) + { + int i; + mp_limb n0, n1; + +#if UDIV_NEEDS_NORMALIZATION || UDIV_TIME > 2 * UMUL_TIME + /* If we shifted BIG_BASE above, shift the dividend too, to get + the right quotient. We need to do this every loop, + since the intermediate quotients are OK, but the quotient from + one turn in the loop is going to be the dividend in the + next turn, and the dividend needs to be up-shifted. */ + if (normalization_steps != 0) + { + n0 = __mpn_lshift (mptr, mptr, msize, normalization_steps); + + /* If the shifting gave a carry out limb, store it and + increase the length. */ + if (n0 != 0) + { + mptr[msize] = n0; + msize++; + } + } +#endif + + /* Divide the number at TP with BIG_BASE to get a quotient and a + remainder. The remainder is our new digit in base BIG_BASE. */ + i = msize - 1; + n1 = mptr[i]; + + if (n1 >= big_base) + n1 = 0; + else + { + msize--; + i--; + } + + for (; i >= 0; i--) + { + n0 = mptr[i]; +#if UDIV_TIME > 2 * UMUL_TIME + udiv_qrnnd_preinv (mptr[i], n1, n1, n0, big_base, big_base_inverted); +#else + udiv_qrnnd (mptr[i], n1, n1, n0, big_base); +#endif + } + +#if UDIV_NEEDS_NORMALIZATION || UDIV_TIME > 2 * UMUL_TIME + /* If we shifted above (at previous UDIV_NEEDS_NORMALIZATION tests) + the remainder will be up-shifted here. Compensate. */ + n1 >>= normalization_steps; +#endif + + /* Convert N1 from BIG_BASE to a string of digits in BASE + using single precision operations. */ + for (i = dig_per_u - 1; i >= 0; i--) + { + *--s = n1 % base; + n1 /= base; + if (n1 == 0 && msize == 0) + break; + } + } + + while (s != str) + *--s = 0; + return out_len; + } +} |