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Diffstat (limited to 'arith.c')
| -rw-r--r-- | arith.c | 244 |
1 files changed, 244 insertions, 0 deletions
@@ -0,0 +1,244 @@ +/* + * Compface - 48x48x1 image compression and decompression + * + * Copyright (c) James Ashton - Sydney University - June 1990. + * + * Written 11th November 1989. + * + * Permission is given to distribute these sources, as long as the + * copyright messages are not removed, and no monies are exchanged. + * + * No responsibility is taken for any errors on inaccuracies inherent + * either to the comments or the code of this program, but if reported + * to me, then an attempt will be made to fix them. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include "compface.h" + +void +RevPush(p) +Prob *p; +{ + if (NumProbs >= PIXELS * 2 - 1) + longjmp(comp_env, ERR_INTERNAL); + ProbBuf[NumProbs++] = p; +} + +void +BigPush(p) +Prob *p; +{ + static WORD tmp; + + BigDiv(p->p_range, &tmp); + BigMul(0); + BigAdd(tmp + p->p_offset); +} + +int +BigPop(p) +register Prob *p; +{ + static WORD tmp; + register int i; + + BigDiv(0, &tmp); + i = 0; + while ((tmp < p->p_offset) || (tmp >= p->p_range + p->p_offset)) + { + p++; + i++; + } + BigMul(p->p_range); + BigAdd(tmp - p->p_offset); + return i; +} + +#ifdef DEBUG +/* Print a BigInt in HexaDecimal + */ +void +BigPrint() +{ + register int i, c, count; + register WORD *w; + + count = 0; + w = B.b_word + (i = B.b_words); + while (i--) + { + w--; + c = *((*w >> 4) + HexDigits); + putc(c, stderr); + c = *((*w & 0xf) + HexDigits); + putc(c, stderr); + if (++count >= 36) + { + putc('\\', stderr); + putc('\n', stderr); + count = 0; + } + } + putc('\n', stderr); +} +#endif + +/* Divide B by a storing the result in B and the remainder in the word + * pointer to by r + */ +void +BigDiv(a, r) +register WORD a, *r; +{ + register int i; + register WORD *w; + register COMP c, d; + + a &= WORDMASK; + if ((a == 1) || (B.b_words == 0)) + { + *r = 0; + return; + } + if (a == 0) /* treat this as a == WORDCARRY */ + { /* and just shift everything right a WORD */ + i = --B.b_words; + w = B.b_word; + *r = *w; + while (i--) + { + *w = *(w + 1); + w++; + } + *w = 0; + return; + } + w = B.b_word + (i = B.b_words); + c = 0; + while (i--) + { + c <<= BITSPERWORD; + c += (COMP)*--w; + d = c / (COMP)a; + c = c % (COMP)a; + *w = (WORD)(d & WORDMASK); + } + *r = c; + if (B.b_word[B.b_words - 1] == 0) + B.b_words--; +} + +/* Multiply a by B storing the result in B + */ +void +BigMul(a) +register WORD a; +{ + register int i; + register WORD *w; + register COMP c; + + a &= WORDMASK; + if ((a == 1) || (B.b_words == 0)) + return; + if (a == 0) /* treat this as a == WORDCARRY */ + { /* and just shift everything left a WORD */ + if ((i = B.b_words++) >= MAXWORDS - 1) + longjmp(comp_env, ERR_INTERNAL); + w = B.b_word + i; + while (i--) + { + *w = *(w - 1); + w--; + } + *w = 0; + return; + } + i = B.b_words; + w = B.b_word; + c = 0; + while (i--) + { + c += (COMP)*w * (COMP)a; + *(w++) = (WORD)(c & WORDMASK); + c >>= BITSPERWORD; + } + if (c) + { + if (B.b_words++ >= MAXWORDS) + longjmp(comp_env, ERR_INTERNAL); + *w = (COMP)(c & WORDMASK); + } +} + +#if 0 +/* Subtract a from B storing the result in B + */ +void +BigSub(a) +WORD a; +{ + register int i; + register WORD *w; + register COMP c; + + a &= WORDMASK; + if (a == 0) + return; + i = 1; + w = B.b_word; + c = (COMP)*w - (COMP)a; + *w = (WORD)(c & WORDMASK); + while (c & WORDCARRY) + { + if (i >= B.b_words) + longjmp(comp_env, ERR_INTERNAL); + c = (COMP)*++w - 1; + *w = (WORD)(c & WORDMASK); + i++; + } + if ((i == B.b_words) && (*w == 0) && (i > 0)) + B.b_words--; +} +#endif + +/* Add to a to B storing the result in B + */ +void +BigAdd(a) +WORD a; +{ + register int i; + register WORD *w; + register COMP c; + + a &= WORDMASK; + if (a == 0) + return; + i = 0; + w = B.b_word; + c = a; + while ((i < B.b_words) && c) + { + c += (COMP)*w; + *w++ = (WORD)(c & WORDMASK); + c >>= BITSPERWORD; + i++; + } + if ((i == B.b_words) && c) + { + if (B.b_words++ >= MAXWORDS) + longjmp(comp_env, ERR_INTERNAL); + *w = (COMP)(c & WORDMASK); + } +} + +void +BigClear() +{ + B.b_words = 0; +} |