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at 2022-08-29T12:05:30-07:00

Use sysconf to get buffer size and add loop to increase size

Use sysconf to get the buffer size.  If it fails, use a default and
add a loop to keep trying with a larger buffer size (until some upper
limit is reached.)

@@ -9,6 +9,7 @@
  #include <math.h>
  #include <netdb.h>
  #include <pwd.h>
 +#include <stdbool.h>
  #include <stdio.h>
  #include <string.h>
  #include <sys/stat.h>
@@ -725,21 +726,60 @@ os_lstat(const char* path, u_int64_t *dev, u_int64_t *ino, unsigned int *mode, u
  char *
  os_file_author(const char *path)
+ {
 -    int rc;
 +    int status;
      struct stat statbuf;
 -    char buf[16384];
      char* author = NULL;
 +    bool nomem = false;
 +    size_t bufsize;
 +    char* buf = NULL;
 +    char* buf2 = NULL;
      struct passwd pwd;
      struct passwd *result = NULL;
 -    rc = stat(path, &statbuf);
 +    status = stat(path, &statbuf);
 -    if (rc != 0) {
 +    if (status != 0) {
          return NULL;
+     }
 -    rc = getpwuid_r(statbuf.st_uid, &pwd, buf, sizeof(buf), &result);
 +    bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
 +    /*
 +     * If sysconf fails, just use a small initial buffer size that we
 +     * will keep growing up to some maximum size.
 +     */
 +    if (bufsize == -1) {
 +        bufsize = 1024;
 +    }
++
 +    while (1) {
 +        buf2 = realloc(buf, bufsize);
 +        fprintf(stderr, "buf2 = %p, size %zu\n", buf2, bufsize);
++
 +        if (buf2 == NULL) {
 +            result = NULL;
 +            nomem = true;
 +            break;
 +        }
++
 +        buf = buf2;
 +        status = getpwuid_r(statbuf.st_uid, &pwd, buf, bufsize, &result);
++
 +        if (status != 0) {
 +            result = NULL;
 +        }
 +        if ((result != NULL) || (status != ERANGE)) {
 +            break;
 +        }
 +        /* If bufsize exceeds some large size, give up. */
 +        if (bufsize > 16384) {
 +            nomem = true;
 +            break;
 +        }
++
 +        bufsize <<= 1;
 +    }
++
      if (result) {
          author = malloc(strlen(result->pw_name + 1));
          if (author) {
@@ -747,5 +787,7 @@ os_file_author(const char *path)
+         }
+     }
 +    free(buf);
++
      return author;
+ }

Raymond Toy pushed to branch issue-130-file-author-in-c at cmucl / cmucl

Commits:

1 changed file:

Changes: