1 #include "lib9.h" 2 3 /* 4 * In place, rewrite name to compress multiple /, eliminate ., and process .. 5 */ 6 #define SEP(x) ((x)=='/' || (x) == 0) 7 char* 8 cleanname(char *name) 9 { 10 char *p, *q, *dotdot; 11 int rooted, erasedprefix; 12 13 rooted = name[0] == '/'; 14 erasedprefix = 0; 15 16 /* 17 * invariants: 18 * p points at beginning of path element we're considering. 19 * q points just past the last path element we wrote (no slash). 20 * dotdot points just past the point where .. cannot backtrack 21 * any further (no slash). 22 */ 23 p = q = dotdot = name+rooted; 24 while(*p) { 25 if(p[0] == '/') /* null element */ 26 p++; 27 else if(p[0] == '.' && SEP(p[1])) { 28 if(p == name) 29 erasedprefix = 1; 30 p += 1; /* don't count the separator in case it is nul */ 31 } else if(p[0] == '.' && p[1] == '.' && SEP(p[2])) { 32 p += 2; 33 if(q > dotdot) { /* can backtrack */ 34 while(--q > dotdot && *q != '/') 35 ; 36 } else if(!rooted) { /* /.. is / but ./../ is .. */ 37 if(q != name) 38 *q++ = '/'; 39 *q++ = '.'; 40 *q++ = '.'; 41 dotdot = q; 42 } 43 if(q == name) 44 erasedprefix = 1; /* erased entire path via dotdot */ 45 } else { /* real path element */ 46 if(q != name+rooted) 47 *q++ = '/'; 48 while((*q = *p) != '/' && *q != 0) 49 p++, q++; 50 } 51 } 52 if(q == name) /* empty string is really ``.'' */ 53 *q++ = '.'; 54 *q = '\0'; 55 if(erasedprefix && name[0] == '#'){ 56 /* this was not a #x device path originally - make it not one now */ 57 memmove(name+2, name, strlen(name)+1); 58 name[0] = '.'; 59 name[1] = '/'; 60 } 61 return name; 62 } 63