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puzzles/misc.c
Franklin Wei 2a57df6be9 Consolidate duplicate implementations of compare_integers 
Both Inertia and Twiddle previously included static implementations of this
exact same function, which was passed to `qsort()` as a comparator. With
this change, a single global implementation is provided in misc.c, which
will hopefully reduce code duplication going forward.

I'm refactoring this in preparation for the upcoming fallback polygon fill
function, which I'm about to add.
2024-08-15 08:08:54 +01:00

683 lines
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/*
* misc.c: Miscellaneous helpful functions.
*/
#include <assert.h>
#include <ctype.h>
#ifdef NO_TGMATH_H
# include <math.h>
#else
# include <tgmath.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "puzzles.h"
char MOVE_UI_UPDATE[] = "";
char MOVE_NO_EFFECT[] = "";
char MOVE_UNUSED[] = "";
void free_cfg(config_item *cfg)
{
config_item *i;
for (i = cfg; i->type != C_END; i++)
if (i->type == C_STRING)
sfree(i->u.string.sval);
sfree(cfg);
}
void free_keys(key_label *keys, int nkeys)
{
int i;
for(i = 0; i < nkeys; i++)
sfree(keys[i].label);
sfree(keys);
}
/*
* 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, bool 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;
}
char *fgetline(FILE *fp)
{
char *ret = snewn(512, char);
int size = 512, len = 0;
while (fgets(ret + len, size - len, fp)) {
len += strlen(ret + len);
if (ret[len-1] == '\n')
break; /* got a newline, we're done */
size = len + 512;
ret = sresize(ret, size, char);
}
if (len == 0) { /* first fgets returned NULL */
sfree(ret);
return NULL;
}
ret[len] = '\0';
return ret;
}
int getenv_bool(const char *name, int dflt)
{
char *env = getenv(name);
if (env == NULL) return dflt;
if (strchr("yYtT", env[0])) return true;
return false;
}
/* Utility functions for colour manipulation. */
static float colour_distance(const float a[3], const float b[3])
{
return (float)sqrt((a[0]-b[0]) * (a[0]-b[0]) +
(a[1]-b[1]) * (a[1]-b[1]) +
(a[2]-b[2]) * (a[2]-b[2]));
}
void colour_mix(const float src1[3], const float src2[3], float p, float dst[3])
{
int i;
for (i = 0; i < 3; i++)
dst[i] = src1[i] * (1.0F - p) + src2[i] * p;
}
void game_mkhighlight_specific(frontend *fe, float *ret,
int background, int highlight, int lowlight)
{
static const float black[3] = { 0.0F, 0.0F, 0.0F };
static const float white[3] = { 1.0F, 1.0F, 1.0F };
float db, dw;
int i;
/*
* New geometric highlight-generation algorithm: Draw a line from
* the base colour to white. The point K distance along this line
* from the base colour is the highlight colour. Similarly, draw
* a line from the base colour to black. The point on this line
* at a distance K from the base colour is the shadow. If either
* of these colours is imaginary (for reasonable K at most one
* will be), _extrapolate_ the base colour along the same line
* until it's a distance K from white (or black) and start again
* with that as the base colour.
*
* This preserves the hue of the base colour, ensures that of the
* three the base colour is the most saturated, and only ever
* flattens the highlight and shadow to pure white or pure black.
*
* K must be at most sqrt(3)/2, or mid grey would be too close to
* both white and black. Here K is set to sqrt(3)/6 so that this
* code produces the same results as the former code in the common
* case where the background is grey and the highlight saturates
* to white.
*/
const float k = sqrt(3)/6.0F;
if (lowlight >= 0) {
db = colour_distance(&ret[background*3], black);
if (db < k) {
for (i = 0; i < 3; i++) ret[lowlight*3+i] = black[i];
if (db == 0.0F)
colour_mix(black, white, k/sqrt(3), &ret[background*3]);
else
colour_mix(black, &ret[background*3], k/db, &ret[background*3]);
} else {
colour_mix(&ret[background*3], black, k/db, &ret[lowlight*3]);
}
}
if (highlight >= 0) {
dw = colour_distance(&ret[background*3], white);
if (dw < k) {
for (i = 0; i < 3; i++) ret[highlight*3+i] = white[i];
if (dw == 0.0F)
colour_mix(white, black, k/sqrt(3), &ret[background*3]);
else
colour_mix(white, &ret[background*3], k/dw, &ret[background*3]);
/* Background has changed; recalculate lowlight. */
if (lowlight >= 0)
colour_mix(&ret[background*3], black, k/db, &ret[lowlight*3]);
} else {
colour_mix(&ret[background*3], white, k/dw, &ret[highlight*3]);
}
}
}
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);
}
void swap_regions(void *av, void *bv, size_t 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)
swap_regions(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);
}
int compare_integers(const void *av, const void *bv) {
const int *a = (const int *)av;
const int *b = (const int *)bv;
if (*a < *b)
return -1;
else if (*a > *b)
return +1;
else
return 0;
}
char *move_cursor(int button, int *x, int *y, int maxw, int maxh, bool wrap,
bool *visible)
{
int dx = 0, dy = 0, ox = *x, oy = *y;
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 MOVE_UNUSED;
}
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);
}
if (visible != NULL && !*visible) {
*visible = true;
return MOVE_UI_UPDATE;
}
if (*x != ox || *y != oy)
return MOVE_UI_UPDATE;
return MOVE_NO_EFFECT;
}
/* 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, const 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);
}
/* kludge for sprintf() in Rockbox not supporting "%-8.8s" */
void copy_left_justified(char *buf, size_t sz, const char *str)
{
size_t len = strlen(str);
assert(sz > 0);
memset(buf, ' ', sz - 1);
assert(len <= sz - 1);
memcpy(buf, str, len);
buf[sz - 1] = 0;
}
/* Returns a dynamically allocated label for a generic button.
* Game-specific buttons should go into the `label' field of key_label
* instead. */
char *button2label(int button)
{
/* check if it's a keyboard button */
if(('A' <= button && button <= 'Z') ||
('a' <= button && button <= 'z') ||
('0' <= button && button <= '9') )
{
char str[2];
str[0] = button;
str[1] = '\0';
return dupstr(str);
}
switch(button)
{
case CURSOR_UP:
return dupstr("Up");
case CURSOR_DOWN:
return dupstr("Down");
case CURSOR_LEFT:
return dupstr("Left");
case CURSOR_RIGHT:
return dupstr("Right");
case CURSOR_SELECT:
return dupstr("Select");
case '\b':
return dupstr("Clear");
default:
fatal("unknown generic key");
}
/* should never get here */
return NULL;
}
char *make_prefs_path(const char *dir, const char *sep,
const game *game, const char *suffix)
{
size_t dirlen = strlen(dir);
size_t seplen = strlen(sep);
size_t gamelen = strlen(game->name);
size_t suffixlen = strlen(suffix);
char *path, *p;
const char *q;
if (!dir || !sep || !game || !suffix)
return NULL;
path = snewn(dirlen + seplen + gamelen + suffixlen + 1, char);
p = path;
memcpy(p, dir, dirlen);
p += dirlen;
memcpy(p, sep, seplen);
p += seplen;
for (q = game->name; *q; q++)
if (*q != ' ')
*p++ = tolower((unsigned char)*q);
memcpy(p, suffix, suffixlen);
p += suffixlen;
*p = '\0';
return path;
}
/*
* Calculate the nearest integer to n*sqrt(k), via a bitwise algorithm
* that avoids floating point.
*
* (It would probably be OK in practice to use floating point, but I
* felt like overengineering it for fun. With FP, there's at least a
* theoretical risk of rounding the wrong way, due to the three
* successive roundings involved - rounding sqrt(k), rounding its
* product with n, and then rounding to the nearest integer. This
* approach avoids that: it's exact.)
*/
int n_times_root_k(int n_signed, int k)
{
unsigned x, r, m;
int sign = n_signed < 0 ? -1 : +1;
unsigned n = n_signed * sign;
unsigned bitpos;
/*
* Method:
*
* We transform m gradually from zero into n, by multiplying it by
* 2 in each step and optionally adding 1, so that it's always
* floor(n/2^something).
*
* At the start of each step, x is the largest integer less than
* or equal to m*sqrt(k). We transform m to 2m+bit, and therefore
* we must transform x to 2x+something to match. The 'something'
* we add to 2x is at most floor(sqrt(k))+2. (Worst case is if m
* sqrt(k) was equal to x + 1-eps for some tiny eps, and then the
* incoming bit of m is 1, so that (2m+1)sqrt(k) =
* 2x+2+sqrt(k)-2eps.)
*
* To compute this, we also track the residual value r such that
* x^2+r = km^2.
*
* The algorithm below is very similar to the usual approach for
* taking the square root of an integer in binary. The wrinkle is
* that we have an integer multiplier, i.e. we're computing
* n*sqrt(k) rather than just sqrt(k). Of course in principle we
* could just take sqrt(n^2k), but we'd need an integer twice the
* width to hold n^2. Pulling out n and treating it specially
* makes overflow less likely.
*/
x = r = m = 0;
for (bitpos = UINT_MAX & ~(UINT_MAX >> 1); bitpos; bitpos >>= 1) {
unsigned a, b = (n & bitpos) ? 1 : 0;
/*
* Check invariants. We expect that x^2 + r = km^2 (i.e. our
* residual term is correct), and also that r < 2x+1 (because
* if not, then we could replace x with x+1 and still get a
* value that made r non-negative, i.e. x would not be the
* _largest_ integer less than m sqrt(k)).
*/
assert(x*x + r == k*m*m);
assert(r < 2*x+1);
/*
* We're going to replace m with 2m+b, and x with 2x+a for
* some a we haven't decided on yet.
*
* The new value of the residual will therefore be
*
* k (2m+b)^2 - (2x+a)^2
* = (4km^2 + 4kmb + kb^2) - (4x^2 + 4xa + a^2)
* = 4 (km^2 - x^2) + 4kmb + kb^2 - 4xa - a^2
* = 4r + 4kmb + kb^2 - 4xa - a^2 (because r = km^2 - x^2)
* = 4r + (4m + 1)kb - 4xa - a^2 (b is 0 or 1, so b = b^2)
*/
for (a = 0;; a++) {
/* If we made this routine handle square roots of numbers
* significantly bigger than 3 or 5 then it would be
* sensible to make this a binary search. Here, it hardly
* seems important. */
unsigned pos = 4*r + k*b*(4*m + 1);
unsigned neg = 4*a*x + a*a;
if (pos < neg)
break; /* this value of a is too big */
}
/* The above loop will have terminated with a one too big. So
* now decrementing a will give us the right value to add. */
a--;
r = 4*r + b*k*(4*m + 1) - (4*a*x + a*a);
m = 2*m+b;
x = 2*x+a;
}
/*
* Finally, round to the nearest integer. At present, x is the
* largest integer that is _at most_ m sqrt(k). But we want the
* _nearest_ integer, whether that's rounded up or down. So check
* whether (x + 1/2) is still less than m sqrt(k), i.e. whether
* (x + 1/2)^2 < km^2; if it is, then we increment x.
*
* We have km^2 - (x + 1/2)^2 = km^2 - x^2 - x - 1/4
* = r - x - 1/4
*
* and since r and x are integers, this is greater than 0 if and
* only if r > x.
*
* (There's no need to worry about tie-breaking exact halfway
* rounding cases. sqrt(k) is irrational, so none such exist.)
*/
if (r > x)
x++;
/*
* Put the sign back on, and convert back from unsigned to int.
*/
if (sign == +1) {
return x;
} else {
/* Be a little careful to avoid compilers deciding I've just
* perpetrated signed-integer overflow. This should optimise
* down to no actual code. */
return INT_MIN + (int)(-x - (unsigned)INT_MIN);
}
}
/* vim: set shiftwidth=4 tabstop=8: */
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