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1.1 root 1: /*
2: * ftw - file tree walk
3: *
4: * int ftw (path, fn, depth) char *path; int (*fn)(); int depth;
5: *
6: * Given a path name, ftw starts from the file given by that path
7: * name and visits each file and directory in the tree beneath
8: * that file. If a single file has multiple links within the
9: * structure, it will be visited once for each such link.
10: * For each object visited, fn is called with four arguments.
11: * The fourth can often be ignored; it is a pointer, say S,
12: * declared "struct FTW *S", discussed in more detail below.
13: * The first contains the path name of the object, the second
14: * contains a pointer to a stat buffer which will usually hold
15: * appropriate information for the object and the third contains
16: * an integer value giving additional information about the
17: * object, as follows:
18: *
19: * FTW_F The object is a file for which stat was
20: * successful. It does not guarantee that the
21: * file can actually be read.
22: *
23: * FTW_D The object is a directory for which stat and
24: * open for read were both successful. This is
25: * a preorder visit -- objects in the directory
26: * are yet to be visited.
27: *
28: * FTW_DNR The object is a directory for which stat
29: * succeeded, but which cannot be read. Because
30: * the directory cannot be read, fn will not be
31: * called for any descendants of this directory.
32: *
33: * FTW_DP The object is a directory for which stat and
34: * open for read were both successful. This is
35: * a postorder visit -- everything in the directory
36: * has already been visited.
37: *
38: * FTW_NS Lstat failed on the object. If errno is EACCES,
39: * then the failure stems from lack of
40: * appropriate permission. This indication will
41: * be given, for example, for each file in a directory
42: * with read but no execute permission. Whenever
43: * stat fails, it is not possible to determine
44: * whether this object is a file or a directory.
45: * The stat buffer passed to fn will contain garbage.
46: *
47: * FTW_SL The object is a symbolic link. Set S->quit
48: * (a component of the structure pointed to by
49: * the fourth parameter to fn) to FTW_FOLLOW to
50: * have the link followed and the object to which
51: * it points visited.
52: *
53: * FTW_NSL Lstat succeeded, but stat failed on the object.
54: * This is only possible when following a symbolic
55: * link.
56: *
57: * Among the components of the structure to which the fourth
58: * parameter, S, to fn points is S->quit. If the caller sets
59: * S->quit to FTW_SKR, then no more files in the current directory
60: * will be visited. (The current directory is the one containing
61: * the object being visited.) If the third parameter to fn is
62: * FTW_D and the caller sets S->quit to FTW_SKD, then this directory
63: * (the one named in the first parameter to fn) will be skipped.
64: *
65: * Other components pointed to by the fourth parameter S are
66: * the current recursion level S->level (top level = 0) and
67: * the offset S->base in the pathname of the current object
68: * (the first parameter to fn) of the object's base name.
69: * By expanding the definition of struct FTW given below and
70: * including the files included below, one can arrange for
71: * S to point to a larger structure, components of which can
72: * be initialized (for example) on calls to fn with third
73: * parameter FTW_D.
74: *
75: * If fn returns nonzero, ftw stops and returns the same value
76: * to its caller. Ftw only initiates a nonzero return if malloc
77: * fails; in this case ftw sets errno to ENOMEM and returns -1.
78: *
79: * The third argument to ftw does not limit the depth to which
80: * ftw will go. Rather, it limits the depth to which ftw will
81: * go before it starts recycling file descriptors. In general,
82: * it is necessary to use a file descriptor for each level of the
83: * tree, but they can be recycled for deep trees by saving the position,
84: * closing, re-opening, and seeking. It is possible to start
85: * recycling file descriptors by sensing when we have run out, but
86: * in general this will not be terribly useful if fn expects to be
87: * able to open files. We could also figure out how many file descriptors
88: * are available and guarantee a certain number to fn, but we would not
89: * know how many to guarantee, and we do not want to impose the extra
90: * overhead on a caller who knows how many are available without
91: * having to figure it out.
92: *
93: * It is possible for ftw to die with a memory fault in the event
94: * of a file system so deeply nested that the stack overflows.
95: */
96:
97: #include <sys/types.h>
98: #include <dirent.h>
99: #include <sys/stat.h>
100: #include "ftw.h"
101: /*
102: * Struct FTW (whose definition starts at the end of ftw.h) must
103: * must include at least the integers quit, base, and level.
104: */
105:
106: #define FTW_PATHLEN0 1000
107: #define FTW_PATHINC 1000
108:
109: #ifndef S_ISLNK
110: #define lstat stat
111: #endif
112:
113: #ifndef ENOMEM
114: #include <errno.h>
115: #endif
116:
117: extern int errno;
118:
119: /*
120: * Each generation of ftw1 (the real ftw) allocates one copy, R, of the
121: * following structure; it passes a pointer to this structure when it
122: * recursively invokes itself. These structures are chained together,
123: * so that if it becomes necessary to recycle file descriptors, then
124: * the oldest descriptor (the one at the shallowest depth still open)
125: * can be recycled.
126: */
127:
128: struct FTW_rec {
129: struct FTW_rec *prev;
130: long here; /* seek to here when reopening at this level */
131: DIR *fd; /* file descriptor at this level */
132: };
133:
134: /*
135: * One instance, T, of the following structure is allocated by ftw; a
136: * pointer to it is passed to all generations of ftw1 (the real ftw).
137: * T could often be a global variable, but this way the parameter fn
138: * can invoke ftw for an independent tree walk.
139: * Component T->path points to storage for the object path-names;
140: * this storage may be relocated by realloc if T->path needs to be
141: * more than T->pathlast characters long.
142: * T->path[T->pathnext] is the next free character in the pathnames.
143: * T->depth = parameter depth to ftw. T->lastout is the deepest level at
144: * which a file descriptor has been recycled.
145: */
146:
147: struct FTW_top {
148: int (*fn)();
149: char *path;
150: unsigned pathlast, pathnext;
151: int lastout;
152: int depth;
153: };
154:
155: static ftw_1_();
156:
157: int
158: ftw (path, fn, depth)
159: char *path;
160: int (*fn)();
161: int depth;
162: {
163: struct FTW_top T;
164: struct FTW_rec R;
165: struct FTW S;
166: int rc;
167: char *malloc(), *strcpy();
168:
169: T.depth = depth;
170: T.lastout = -1;
171: T.fn = fn;
172: S.quit = 0;
173: S.level = -1;
174:
175: /* initialize S.base, T.pathnext... */
176: {
177: register char c, *p, *q;
178: for (p = q = path; c = *p; p++) if (c == '/') q = p + 1;
179: S.base = q - path;
180: T.pathnext = p - path;
181: }
182:
183: T.pathlast = T.pathnext + FTW_PATHLEN0;
184: T.path = malloc(T.pathlast);
185: if (!T.path) { errno = ENOMEM; return -1; }
186: strcpy(T.path, path);
187: rc = ftw_1_(&R, &T, 0, &S);
188: free(T.path);
189: return rc;
190: }
191:
192: int
193: static
194: ftw_1_ (R, T, level, S1)
195: register struct FTW_rec *R;
196: register struct FTW_top *T;
197: int level;
198: struct FTW *S1;
199: {
200: int rc, n;
201: DIR *fd;
202: struct dirent *dirp;
203: char *component, *path;
204: struct stat sb;
205: struct FTW_rec mr;
206: unsigned nextsave;
207: struct FTW S;
208: char *realloc();
209: long lseek();
210:
211: mr.prev = R;
212: path = T->path;
213: S.level = level;
214: S.quit = 0;
215: S.base = S1->base;
216:
217: /* Try to get file status. If unsuccessful, errno will say why. */
218: if (lstat(path, &sb) < 0) {
219: rc = (*T->fn) (path, &sb, FTW_NS, &S);
220: S1->quit = S.quit;
221: return rc;
222: };
223:
224: /*
225: * The stat succeeded, so we know the object exists.
226: * If not a directory, call the user function and return.
227: */
228: #ifdef S_ISLNK
229: if (S_ISLNK(sb.st_mode )) {
230: rc = (*T->fn) (path, &sb, FTW_SL, &S);
231: S1->quit = S.quit;
232: if (rc || S.quit == FTW_SKR) return rc;
233: if (S.quit != FTW_FOLLOW) return 0;
234: S1->quit = S.quit = 0;
235: if (stat(path, &sb) < 0) {
236: rc = (*T->fn) (path, &sb, FTW_NSL, &S);
237: S1->quit = S.quit;
238: return rc;
239: };
240: }
241: #endif
242:
243: if (!S_ISDIR(sb.st_mode)) {
244: rc = (*T->fn) (path, &sb, FTW_F, &S);
245: S1->quit = S.quit;
246: return rc;
247: }
248:
249: /*
250: * The object was a directory.
251: *
252: * Open a file to read the directory
253: */
254: mr.fd = fd = opendir(path);
255:
256: /*
257: * Call the user function, telling it whether
258: * the directory can be read. If it can't be read
259: * call the user function or indicate an error,
260: * depending on the reason it couldn't be read.
261: */
262: if (!fd) {
263: rc = (*T->fn) (path, &sb, FTW_DNR, &S);
264: S1->quit = S.quit;
265: return rc;
266: }
267:
268: /* We could read the directory. Call user function. */
269: rc = (*T->fn) (path, &sb, FTW_D, &S);
270: if (rc != 0)
271: goto rtrn;
272: if (S.quit == FTW_SKD) goto rtrn;
273: if (S.quit == FTW_SKR) {S1->quit = FTW_SKR; goto rtrn;}
274:
275: /* Make sure path is big enough to hold generated pathnames. */
276:
277: n = nextsave = T->pathnext;
278: if (n + MAXNAMLEN + 1 >= T->pathlast) {
279: T->pathlast += FTW_PATHINC;
280: path = T->path = realloc(T->path, T->pathlast);
281: if (!path) {
282: errno = ENOMEM;
283: rc = -1;
284: goto rtrn;
285: }
286: }
287:
288: /* Create a prefix to which we will append component names */
289:
290: if (n > 0 && path[n-1] != '/') path[n++] = '/';
291: component = path + n;
292:
293: /*
294: * Read the directory one component at a time.
295: * We must ignore "." and "..", but other than that,
296: * just create a path name and call self to check it out.
297: */
298: while (dirp = readdir(fd)) {
299: if (dirp->d_ino != 0
300: && strcmp (dirp->d_name, ".") != 0
301: && strcmp (dirp->d_name, "..") != 0) {
302: int i;
303: struct FTW_rec *pr;
304:
305: /* Append the component name to the working path */
306: strcpy(component, dirp->d_name);
307: T->pathnext = n + strlen(dirp->d_name);
308:
309: /*
310: * If we are about to exceed our depth,
311: * remember where we are and close the file.
312: */
313: if (level - T->lastout >= T->depth) {
314: pr = &mr;
315: i = T->lastout++;
316: while (++i < level) pr = pr->prev;
317: pr->here = telldir(pr->fd);
318: closedir(pr->fd);
319: }
320:
321: /*
322: * Do a recursive call to process the file.
323: */
324: S.quit = 0;
325: S.base = n;
326: rc = ftw_1_(&mr, T, level+1, &S);
327: if (rc != 0 || S.quit == FTW_SKR) {
328: if (level > T->lastout) closedir(fd);
329: T->pathnext = nextsave;
330: return rc;
331: }
332:
333: /*
334: * If we closed the file, try to reopen it.
335: */
336: if (level <= T->lastout) {
337: char c = path[nextsave];
338: path[nextsave] = 0;
339: T->lastout = level - 1;
340: mr.fd = fd = opendir(path);
341: if (!fd) {
342: rc = (*T->fn) (path, &sb, FTW_DNR, &S);
343: S1->quit = S.quit;
344: T->pathnext = nextsave;
345: return rc;
346: }
347: path[nextsave] = c;
348: seekdir(fd, mr.here);
349: }
350: }
351: }
352: T->pathnext = nextsave;
353: path[nextsave] = 0;
354:
355: /*
356: * We got out of the subdirectory loop. Call the user
357: * function again at the end and clean up.
358: */
359:
360: rc = (*T->fn) (path, &sb, FTW_DP, &S);
361: S1->quit = S.quit;
362: rtrn:
363: closedir(fd);
364: return rc;
365: }
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