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	diffio.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	diffio.c (6620B)
	---
	1 #include <u.h>
	2 #include <libc.h>
	3 #include <bio.h>
	4 #include <ctype.h>
	5 #include "diff.h"
	6
	7 struct line {
	8 int serial;
	9 int value;
	10 };
	11 extern struct line *file[2];
	12 extern int len[2];
	13 extern long ixold, ixnew;
	14 extern int *J;
	15
	16 static Biobuf *input[2];
	17 static char file1, file2;
	18 static int firstchange;
	19
	20 #define MAXLINELEN 4096
	21 #define MIN(x, y) ((x) < (y) ? (x): (y))
	22
	23 static int
	24 readline(Biobuf bp, char buf)
	25 {
	26 int c;
	27 char p, e;
	28
	29 p = buf;
	30 e = p + MAXLINELEN-1;
	31 do {
	32 c = Bgetc(bp);
	33 if (c < 0) {
	34 if (p == buf)
	35 return -1;
	36 break;
	37 }
	38 if (c == '\n')
	39 break;
	40 *p++ = c;
	41 } while (p < e);
	42 *p = 0;
	43 if (c != '\n' && c >= 0) {
	44 do c = Bgetc(bp);
	45 while (c >= 0 && c != '\n');
	46 }
	47 return p - buf;
	48 }
	49
	50 #define HALFLONG 16
	51 #define low(x) (x&((1L<<HALFLONG)-1))
	52 #define high(x) (x>>HALFLONG)
	53
	54 /*
	55 * hashing has the effect of
	56 * arranging line in 7-bit bytes and then
	57 * summing 1-s complement in 16-bit hunks
	58 */
	59 static int
	60 readhash(Biobuf bp, char buf)
	61 {
	62 long sum;
	63 unsigned shift;
	64 char *p;
	65 int len, space;
	66
	67 sum = 1;
	68 shift = 0;
	69 if ((len = readline(bp, buf)) == -1)
	70 return 0;
	71 p = buf;
	72 switch(bflag) /* various types of white space handling */
	73 {
	74 case 0:
	75 while (len--) {
	76 sum += (long)*p++ << (shift &= (HALFLONG-1));
	77 shift += 7;
	78 }
	79 break;
	80 case 1:
	81 /*
	82 * coalesce multiple white-space
	83 */
	84 for (space = 0; len--; p++) {
	85 if (isspace((uchar)*p)) {
	86 space++;
	87 continue;
	88 }
	89 if (space) {
	90 shift += 7;
	91 space = 0;
	92 }
	93 sum += (long)*p << (shift &= (HALFLONG-1));
	94 shift += 7;
	95 }
	96 break;
	97 default:
	98 /*
	99 * strip all white-space
	100 */
	101 while (len--) {
	102 if (isspace((uchar)*p)) {
	103 p++;
	104 continue;
	105 }
	106 sum += (long)*p++ << (shift &= (HALFLONG-1));
	107 shift += 7;
	108 }
	109 break;
	110 }
	111 sum = low(sum) + high(sum);
	112 return ((short)low(sum) + (short)high(sum));
	113 }
	114
	115 Biobuf *
	116 prepare(int i, char *arg)
	117 {
	118 struct line *p;
	119 int j, h;
	120 Biobuf *bp;
	121 char *cp, buf[MAXLINELEN];
	122 int nbytes;
	123 Rune r;
	124
	125 bp = Bopen(arg, OREAD);
	126 if (!bp) {
	127 panic(mflag ? 0: 2, "cannot open %s: %r\n", arg);
	128 return 0;
	129 }
	130 if (binary)
	131 return bp;
	132 nbytes = Bread(bp, buf, MIN(1024, MAXLINELEN));
	133 if (nbytes > 0) {
	134 cp = buf;
	135 while (cp < buf+nbytes-UTFmax) {
	136 /*
	137 * heuristic for a binary file in the
	138 * brave new UNICODE world
	139 */
	140 cp += chartorune(&r, cp);
	141 if (r == 0 \|\| (r > 0x7f && r <= 0xa0)) {
	142 binary++;
	143 return bp;
	144 }
	145 }
	146 Bseek(bp, 0, 0);
	147 }
	148 p = MALLOC(struct line, 3);
	149 for (j = 0; h = readhash(bp, buf); p[j].value = h)
	150 p = REALLOC(p, struct line, (++j+3));
	151 len[i] = j;
	152 file[i] = p;
	153 input[i] = bp; /fix/
	154 if (i == 0) { /fix/
	155 file1 = arg;
	156 firstchange = 0;
	157 }
	158 else
	159 file2 = arg;
	160 return bp;
	161 }
	162
	163 static int
	164 squishspace(char *buf)
	165 {
	166 char p, q;
	167 int space;
	168
	169 for (space = 0, q = p = buf; *q; q++) {
	170 if (isspace((uchar)*q)) {
	171 space++;
	172 continue;
	173 }
	174 if (space && bflag == 1) {
	175 *p++ = ' ';
	176 space = 0;
	177 }
	178 p++ = q;
	179 }
	180 *p = 0;
	181 return p - buf;
	182 }
	183
	184 /*
	185 * need to fix up for unexpected EOF's
	186 */
	187 void
	188 check(Biobuf bf, Biobuf bt)
	189 {
	190 int f, t, flen, tlen;
	191 char fbuf[MAXLINELEN], tbuf[MAXLINELEN];
	192
	193 ixold[0] = ixnew[0] = 0;
	194 for (f = t = 1; f < len[0]; f++) {
	195 flen = readline(bf, fbuf);
	196 ixold[f] = ixold[f-1] + flen + 1; /* ftel…
	197 if (J[f] == 0)
	198 continue;
	199 do {
	200 tlen = readline(bt, tbuf);
	201 ixnew[t] = ixnew[t-1] + tlen + 1; /* ftel…
	202 } while (t++ < J[f]);
	203 if (bflag) {
	204 flen = squishspace(fbuf);
	205 tlen = squishspace(tbuf);
	206 }
	207 if (flen != tlen \|\| strcmp(fbuf, tbuf))
	208 J[f] = 0;
	209 }
	210 while (t < len[1]) {
	211 tlen = readline(bt, tbuf);
	212 ixnew[t] = ixnew[t-1] + tlen + 1; /* fseek(bt) */
	213 t++;
	214 }
	215 }
	216
	217 static void
	218 range(int a, int b, char *separator)
	219 {
	220 Bprint(&stdout, "%d", a > b ? b: a);
	221 if (a < b)
	222 Bprint(&stdout, "%s%d", separator, b);
	223 }
	224
	225 static void
	226 fetch(long f, int a, int b, Biobuf bp, char *s)
	227 {
	228 char buf[MAXLINELEN];
	229 int maxb;
	230
	231 if(a <= 1)
	232 a = 1;
	233 if(bp == input[0])
	234 maxb = len[0];
	235 else
	236 maxb = len[1];
	237 if(b > maxb)
	238 b = maxb;
	239 if(a > maxb)
	240 return;
	241 Bseek(bp, f[a-1], 0);
	242 while (a++ <= b) {
	243 readline(bp, buf);
	244 Bprint(&stdout, "%s%s\n", s, buf);
	245 }
	246 }
	247
	248 typedef struct Change Change;
	249 struct Change
	250 {
	251 int a;
	252 int b;
	253 int c;
	254 int d;
	255 };
	256
	257 Change *changes;
	258 int nchanges;
	259
	260 void
	261 change(int a, int b, int c, int d)
	262 {
	263 char verb;
	264 char buf[4];
	265 Change *ch;
	266
	267 if (a > b && c > d)
	268 return;
	269 anychange = 1;
	270 if (mflag && firstchange == 0) {
	271 if(mode) {
	272 buf[0] = '-';
	273 buf[1] = mode;
	274 buf[2] = ' ';
	275 buf[3] = '\0';
	276 } else {
	277 buf[0] = '\0';
	278 }
	279 Bprint(&stdout, "diff %s%s %s\n", buf, file1, file2);
	280 firstchange = 1;
	281 }
	282 verb = a > b ? 'a': c > d ? 'd': 'c';
	283 switch(mode) {
	284 case 'e':
	285 range(a, b, ",");
	286 Bputc(&stdout, verb);
	287 break;
	288 case 0:
	289 range(a, b, ",");
	290 Bputc(&stdout, verb);
	291 range(c, d, ",");
	292 break;
	293 case 'n':
	294 Bprint(&stdout, "%s:", file1);
	295 range(a, b, ",");
	296 Bprint(&stdout, " %c ", verb);
	297 Bprint(&stdout, "%s:", file2);
	298 range(c, d, ",");
	299 break;
	300 case 'f':
	301 Bputc(&stdout, verb);
	302 range(a, b, " ");
	303 break;
	304 case 'c':
	305 case 'a':
	306 if(nchanges%1024 == 0)
	307 changes = erealloc(changes, (nchanges+1024)*size…
	308 ch = &changes[nchanges++];
	309 ch->a = a;
	310 ch->b = b;
	311 ch->c = c;
	312 ch->d = d;
	313 return;
	314 }
	315 Bputc(&stdout, '\n');
	316 if (mode == 0 \|\| mode == 'n') {
	317 fetch(ixold, a, b, input[0], "< ");
	318 if (a <= b && c <= d)
	319 Bprint(&stdout, "---\n");
	320 }
	321 fetch(ixnew, c, d, input[1], mode == 0 \|\| mode == 'n' ? "> ": ""…
	322 if (mode != 0 && mode != 'n' && c <= d)
	323 Bprint(&stdout, ".\n");
	324 }
	325
	326 enum
	327 {
	328 Lines = 3 /* number of lines of context shown */
	329 };
	330
	331 int
	332 changeset(int i)
	333 {
	334 while(i<nchanges && changes[i].b+1+2*Lines > changes[i+1].a)
	335 i++;
	336 if(i<nchanges)
	337 return i+1;
	338 return nchanges;
	339 }
	340
	341 void
	342 flushchanges(void)
	343 {
	344 int a, b, c, d, at;
	345 int i, j;
	346
	347 if(nchanges == 0)
	348 return;
	349
	350 for(i=0; i<nchanges; ){
	351 j = changeset(i);
	352 a = changes[i].a-Lines;
	353 b = changes[j-1].b+Lines;
	354 c = changes[i].c-Lines;
	355 d = changes[j-1].d+Lines;
	356 if(a < 1)
	357 a = 1;
	358 if(c < 1)
	359 c = 1;
	360 if(b > len[0])
	361 b = len[0];
	362 if(d > len[1])
	363 d = len[1];
	364 if(mode == 'a'){
	365 a = 1;
	366 b = len[0];
	367 c = 1;
	368 d = len[1];
	369 j = nchanges;
	370 }
	371 Bprint(&stdout, "%s:", file1);
	372 range(a, b, ",");
	373 Bprint(&stdout, " - ");
	374 Bprint(&stdout, "%s:", file2);
	375 range(c, d, ",");
	376 Bputc(&stdout, '\n');
	377 at = a;
	378 for(; i<j; i++){
	379 fetch(ixold, at, changes[i].a-1, input[0], " ");
	380 fetch(ixold, changes[i].a, changes[i].b, input[0…
	381 fetch(ixnew, changes[i].c, changes[i].d, input[1…
	382 at = changes[i].b+1;
	383 }
	384 fetch(ixold, at, b, input[0], " ");
	385 }
	386 nchanges = 0;
	387 }