ref: 201b32983b5cd1f904da3614ee9136cfeec59818
dir: /misc.c/
/* * misc.c: Miscellaneous helpful functions. */ #include <assert.h> #include <stdlib.h> #include <string.h> #include <stdio.h> #include "puzzles.h" void free_cfg(config_item *cfg) { config_item *i; for (i = cfg; i->type != C_END; i++) if (i->type == C_STRING) sfree(i->sval); sfree(cfg); } /* * The Mines (among others) game descriptions contain the location of every * mine, and can therefore be used to cheat. * * It would be pointless to attempt to _prevent_ this form of * cheating by encrypting the description, since Mines is * open-source so anyone can find out the encryption key. However, * I think it is worth doing a bit of gentle obfuscation to prevent * _accidental_ spoilers: if you happened to note that the game ID * starts with an F, for example, you might be unable to put the * knowledge of those mines out of your mind while playing. So, * just as discussions of film endings are rot13ed to avoid * spoiling it for people who don't want to be told, we apply a * keyless, reversible, but visually completely obfuscatory masking * function to the mine bitmap. */ void obfuscate_bitmap(unsigned char *bmp, int bits, int decode) { int bytes, firsthalf, secondhalf; struct step { unsigned char *seedstart; int seedlen; unsigned char *targetstart; int targetlen; } steps[2]; int i, j; /* * My obfuscation algorithm is similar in concept to the OAEP * encoding used in some forms of RSA. Here's a specification * of it: * * + We have a `masking function' which constructs a stream of * pseudorandom bytes from a seed of some number of input * bytes. * * + We pad out our input bit stream to a whole number of * bytes by adding up to 7 zero bits on the end. (In fact * the bitmap passed as input to this function will already * have had this done in practice.) * * + We divide the _byte_ stream exactly in half, rounding the * half-way position _down_. So an 81-bit input string, for * example, rounds up to 88 bits or 11 bytes, and then * dividing by two gives 5 bytes in the first half and 6 in * the second half. * * + We generate a mask from the second half of the bytes, and * XOR it over the first half. * * + We generate a mask from the (encoded) first half of the * bytes, and XOR it over the second half. Any null bits at * the end which were added as padding are cleared back to * zero even if this operation would have made them nonzero. * * To de-obfuscate, the steps are precisely the same except * that the final two are reversed. * * Finally, our masking function. Given an input seed string of * bytes, the output mask consists of concatenating the SHA-1 * hashes of the seed string and successive decimal integers, * starting from 0. */ bytes = (bits + 7) / 8; firsthalf = bytes / 2; secondhalf = bytes - firsthalf; steps[decode ? 1 : 0].seedstart = bmp + firsthalf; steps[decode ? 1 : 0].seedlen = secondhalf; steps[decode ? 1 : 0].targetstart = bmp; steps[decode ? 1 : 0].targetlen = firsthalf; steps[decode ? 0 : 1].seedstart = bmp; steps[decode ? 0 : 1].seedlen = firsthalf; steps[decode ? 0 : 1].targetstart = bmp + firsthalf; steps[decode ? 0 : 1].targetlen = secondhalf; for (i = 0; i < 2; i++) { SHA_State base, final; unsigned char digest[20]; char numberbuf[80]; int digestpos = 20, counter = 0; SHA_Init(&base); SHA_Bytes(&base, steps[i].seedstart, steps[i].seedlen); for (j = 0; j < steps[i].targetlen; j++) { if (digestpos >= 20) { sprintf(numberbuf, "%d", counter++); final = base; SHA_Bytes(&final, numberbuf, strlen(numberbuf)); SHA_Final(&final, digest); digestpos = 0; } steps[i].targetstart[j] ^= digest[digestpos++]; } /* * Mask off the pad bits in the final byte after both steps. */ if (bits % 8) bmp[bits / 8] &= 0xFF & (0xFF00 >> (bits % 8)); } } /* err, yeah, these two pretty much rely on unsigned char being 8 bits. * Platforms where this is not the case probably have bigger problems * than just making these two work, though... */ char *bin2hex(const unsigned char *in, int inlen) { char *ret = snewn(inlen*2 + 1, char), *p = ret; int i; for (i = 0; i < inlen*2; i++) { int v = in[i/2]; if (i % 2 == 0) v >>= 4; *p++ = "0123456789abcdef"[v & 0xF]; } *p = '\0'; return ret; } unsigned char *hex2bin(const char *in, int outlen) { unsigned char *ret = snewn(outlen, unsigned char); int i; memset(ret, 0, outlen*sizeof(unsigned char)); for (i = 0; i < outlen*2; i++) { int c = in[i]; int v; assert(c != 0); if (c >= '0' && c <= '9') v = c - '0'; else if (c >= 'a' && c <= 'f') v = c - 'a' + 10; else if (c >= 'A' && c <= 'F') v = c - 'A' + 10; else v = 0; ret[i / 2] |= v << (4 * (1 - (i % 2))); } return ret; } void game_mkhighlight_specific(frontend *fe, float *ret, int background, int highlight, int lowlight) { float max; int i; /* * Drop the background colour so that the highlight is * noticeably brighter than it while still being under 1. */ max = ret[background*3]; for (i = 1; i < 3; i++) if (ret[background*3+i] > max) max = ret[background*3+i]; if (max * 1.2F > 1.0F) { for (i = 0; i < 3; i++) ret[background*3+i] /= (max * 1.2F); } for (i = 0; i < 3; i++) { if (highlight >= 0) ret[highlight * 3 + i] = ret[background * 3 + i] * 1.2F; if (lowlight >= 0) ret[lowlight * 3 + i] = ret[background * 3 + i] * 0.8F; } } void game_mkhighlight(frontend *fe, float *ret, int background, int highlight, int lowlight) { frontend_default_colour(fe, &ret[background * 3]); game_mkhighlight_specific(fe, ret, background, highlight, lowlight); } static void memswap(void *av, void *bv, int size) { char tmpbuf[512]; char *a = av, *b = bv; while (size > 0) { int thislen = min(size, sizeof(tmpbuf)); memcpy(tmpbuf, a, thislen); memcpy(a, b, thislen); memcpy(b, tmpbuf, thislen); a += thislen; b += thislen; size -= thislen; } } void shuffle(void *array, int nelts, int eltsize, random_state *rs) { char *carray = (char *)array; int i; for (i = nelts; i-- > 1 ;) { int j = random_upto(rs, i+1); if (j != i) memswap(carray + eltsize * i, carray + eltsize * j, eltsize); } } void draw_rect_outline(drawing *dr, int x, int y, int w, int h, int colour) { int x0 = x, x1 = x+w-1, y0 = y, y1 = y+h-1; int coords[8]; coords[0] = x0; coords[1] = y0; coords[2] = x0; coords[3] = y1; coords[4] = x1; coords[5] = y1; coords[6] = x1; coords[7] = y0; draw_polygon(dr, coords, 4, -1, colour); } void draw_rect_corners(drawing *dr, int cx, int cy, int r, int col) { draw_line(dr, cx - r, cy - r, cx - r, cy - r/2, col); draw_line(dr, cx - r, cy - r, cx - r/2, cy - r, col); draw_line(dr, cx - r, cy + r, cx - r, cy + r/2, col); draw_line(dr, cx - r, cy + r, cx - r/2, cy + r, col); draw_line(dr, cx + r, cy - r, cx + r, cy - r/2, col); draw_line(dr, cx + r, cy - r, cx + r/2, cy - r, col); draw_line(dr, cx + r, cy + r, cx + r, cy + r/2, col); draw_line(dr, cx + r, cy + r, cx + r/2, cy + r, col); } void move_cursor(int button, int *x, int *y, int maxw, int maxh, int wrap) { int dx = 0, dy = 0; switch (button) { case CURSOR_UP: dy = -1; break; case CURSOR_DOWN: dy = 1; break; case CURSOR_RIGHT: dx = 1; break; case CURSOR_LEFT: dx = -1; break; default: return; } if (wrap) { *x = (*x + dx + maxw) % maxw; *y = (*y + dy + maxh) % maxh; } else { *x = min(max(*x+dx, 0), maxw - 1); *y = min(max(*y+dy, 0), maxh - 1); } } /* Used in netslide.c and sixteen.c for cursor movement around edge. */ int c2pos(int w, int h, int cx, int cy) { if (cy == -1) return cx; /* top row, 0 .. w-1 (->) */ else if (cx == w) return w + cy; /* R col, w .. w+h -1 (v) */ else if (cy == h) return w + h + (w-cx-1); /* bottom row, w+h .. w+h+w-1 (<-) */ else if (cx == -1) return w + h + w + (h-cy-1); /* L col, w+h+w .. w+h+w+h-1 (^) */ assert(!"invalid cursor pos!"); return -1; /* not reached */ } int c2diff(int w, int h, int cx, int cy, int button) { int diff = 0; assert(IS_CURSOR_MOVE(button)); /* Obvious moves around edge. */ if (cy == -1) diff = (button == CURSOR_RIGHT) ? +1 : (button == CURSOR_LEFT) ? -1 : diff; if (cy == h) diff = (button == CURSOR_RIGHT) ? -1 : (button == CURSOR_LEFT) ? +1 : diff; if (cx == -1) diff = (button == CURSOR_UP) ? +1 : (button == CURSOR_DOWN) ? -1 : diff; if (cx == w) diff = (button == CURSOR_UP) ? -1 : (button == CURSOR_DOWN) ? +1 : diff; if (button == CURSOR_LEFT && cx == w && (cy == 0 || cy == h-1)) diff = (cy == 0) ? -1 : +1; if (button == CURSOR_RIGHT && cx == -1 && (cy == 0 || cy == h-1)) diff = (cy == 0) ? +1 : -1; if (button == CURSOR_DOWN && cy == -1 && (cx == 0 || cx == w-1)) diff = (cx == 0) ? -1 : +1; if (button == CURSOR_UP && cy == h && (cx == 0 || cx == w-1)) diff = (cx == 0) ? +1 : -1; debug(("cx,cy = %d,%d; w%d h%d, diff = %d", cx, cy, w, h, diff)); return diff; } void pos2c(int w, int h, int pos, int *cx, int *cy) { int max = w+h+w+h; pos = (pos + max) % max; if (pos < w) { *cx = pos; *cy = -1; return; } pos -= w; if (pos < h) { *cx = w; *cy = pos; return; } pos -= h; if (pos < w) { *cx = w-pos-1; *cy = h; return; } pos -= w; if (pos < h) { *cx = -1; *cy = h-pos-1; return; } assert(!"invalid pos, huh?"); /* limited by % above! */ } void draw_text_outline(drawing *dr, int x, int y, int fonttype, int fontsize, int align, int text_colour, int outline_colour, char *text) { if (outline_colour > -1) { draw_text(dr, x-1, y, fonttype, fontsize, align, outline_colour, text); draw_text(dr, x+1, y, fonttype, fontsize, align, outline_colour, text); draw_text(dr, x, y-1, fonttype, fontsize, align, outline_colour, text); draw_text(dr, x, y+1, fonttype, fontsize, align, outline_colour, text); } draw_text(dr, x, y, fonttype, fontsize, align, text_colour, text); } /* vim: set shiftwidth=4 tabstop=8: */