cleanname.c (1536B)
1 #include "u.h" 2 #include "lib.h" 3 4 /* 5 * In place, rewrite name to compress multiple /, eliminate ., and process .. 6 */ 7 #define SEP(x) ((x)=='/' || (x) == 0) 8 char* 9 cleanname(char *name) 10 { 11 char *p, *q, *dotdot; 12 int rooted, erasedprefix; 13 14 rooted = name[0] == '/'; 15 erasedprefix = 0; 16 17 /* 18 * invariants: 19 * p points at beginning of path element we're considering. 20 * q points just past the last path element we wrote (no slash). 21 * dotdot points just past the point where .. cannot backtrack 22 * any further (no slash). 23 */ 24 p = q = dotdot = name+rooted; 25 while(*p) { 26 if(p[0] == '/') /* null element */ 27 p++; 28 else if(p[0] == '.' && SEP(p[1])) { 29 if(p == name) 30 erasedprefix = 1; 31 p += 1; /* don't count the separator in case it is nul */ 32 } else if(p[0] == '.' && p[1] == '.' && SEP(p[2])) { 33 p += 2; 34 if(q > dotdot) { /* can backtrack */ 35 while(--q > dotdot && *q != '/') 36 ; 37 } else if(!rooted) { /* /.. is / but ./../ is .. */ 38 if(q != name) 39 *q++ = '/'; 40 *q++ = '.'; 41 *q++ = '.'; 42 dotdot = q; 43 } 44 if(q == name) 45 erasedprefix = 1; /* erased entire path via dotdot */ 46 } else { /* real path element */ 47 if(q != name+rooted) 48 *q++ = '/'; 49 while((*q = *p) != '/' && *q != 0) 50 p++, q++; 51 } 52 } 53 if(q == name) /* empty string is really ``.'' */ 54 *q++ = '.'; 55 *q = '\0'; 56 if(erasedprefix && name[0] == '#'){ 57 /* this was not a #x device path originally - make it not one now */ 58 memmove(name+2, name, strlen(name)+1); 59 name[0] = '.'; 60 name[1] = '/'; 61 } 62 return name; 63 }