libuptev/src/symlink.c (840c0b1) - uproctrace · BlinkenArea

symlink.c

/**
 * UProcTrace: User-space Process Tracing
 * Copyright 2020: Stefan Schuermans, Aachen, Germany <stefan@schuermans.info>
 * Copyleft: GNU LESSER GENERAL PUBLIC LICENSE version 3 (see LICENSE)
 */

#include "symlink.h"
#include "cleaner.h"

#include <stdlib.h>
#include <unistd.h>

/**
 * @brief read target of symlink
 * @param[in] pathname path to symbolic link
 * @return malloc-ed string containting link target or NULL
 */
static char *uptev_symlink_read_target(char const *pathname) {
  size_t sz = 256;
  char *target = NULL;
  while (1) {
    /* get buffer */
    target = malloc(sz);
    if (!target) {
      return NULL;
    }
    /* get link target */
    ssize_t len = readlink(pathname, target, sz);
    if (len < 0) {
      free(target);
      return NULL;
    }
    /* link target fit into buffer -> terminate string and return */
    if ((size_t)len + 1 < sz) {
      target[len] = 0;
      return target;
    }
    /* free buffer and try again with larger buffer */
    free(target);
    sz *= 2;
  }
}

char *uptev_symlink_read(char const *pathname, uptev_cleaner_t *cleaner) {
  char *target = uptev_symlink_read_target(pathname);
  if (!target) {
    return NULL;
  }
  /* add malloc-ed object to cleaner */
  if (uptev_cleaner_add_ptr(cleaner, target) != 0) {
    return NULL;
  }
  /* success, return target string */
  return target;
}

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