utils.h

/*
 * This file is part of the Green End SFTP Server.
 * Copyright (C) 2007, 2011 Richard Kettlewell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */

/** @file utils.h @brief Utility functions interface */

#ifndef UTILS_H
#  define UTILS_H

#  include <string.h>
#  include <assert.h>

/** @brief Read bytes from @p fd
 * @param fd File descriptor to read from
 * @param buffer Buffer to store data in
 * @param size Number of bytes to read
 * @return 0 on success, non-0 if EOF before @p size bytes read
 *
 * Loops if necessary to cope with short reads.  Calls sftp_fatal() on error.
 */
int sftp_xread(int fd, void *buffer, size_t size);

/** @brief Allocate memory
 * @param n Number of bytes to allocate
 * @return Pointer to allocated memory
 *
 * Equivalent to @c malloc() but calls sftp_fatal() on error.
 *
 * Does not zero-fill.
 */
void *sftp_xmalloc(size_t n);

/** @brief Allocate memory
 * @param n Number of objects to allocate
 * @param size Size of one object
 * @return Pointer to allocated memory
 *
 * Equivalent to @c calloc() but calls sftp_fatal() on error.
 */
void *sftp_xcalloc(size_t n, size_t size);

/** @brief Reallocate memory
 * @param ptr Existing allocation
 * @param n Number of bytes to allocate
 * @return Pointer to allocated memory
 *
 * Equivalent to @c realloc() but calls sftp_fatal() on error.
 *
 * Does not zero-fill.
 */
void *sftp_xrealloc(void *ptr, size_t n);

/** @brief Reallocate memory
 * @param ptr Existing allocation
 * @param n Number of objects to allocate
 * @param size Size of one object
 * @return Pointer to allocated memory
 *
 * Equivalent to @c realloc() but calls sftp_fatal() on error.
 *
 * Does not zero-fill.
 */
void *sftp_xrecalloc(void *ptr, size_t n, size_t size);

/** @brief Duplicate a string
 * @param s String to duplicate
 * @return Duplicated string
 *
 * Equivalent to @c strdup() but calls sftp_fatal() on error.
 */
char *sftp_xstrdup(const char *s);

/** @brief Append to a string
 * @param a Allocator
 * @param s Existing string
 * @param ns Where length of @p s is stored
 * @param t String to append
 * @return New string
 */
char *sftp_str_append(struct allocator *a, char *s, size_t *ns, const char *t);

/** @brief Append to a string
 * @param a Allocator
 * @param s Existing string
 * @param ns Where length of @p s is stored
 * @param t String to append
 * @param lt Length of @p t
 * @return New string
 */
char *sftp_str_appendn(struct allocator *a, char *s, size_t *ns, const char *t,
                       size_t lt);

/** @brief Convenient wrapper for readlink(2)
 * @param a Allocator to store result
 * @param path Path name to inspect
 * @return Value of symbolic link or a null pointer on error
 *
 * Sets @c errno on erorr.
 */
char *sftp_do_readlink(struct allocator *a, const char *path);

/** @brief Return the real (canonical) name of @p path
 * @param a Allocator to store result
 * @param path Path name to inspect
 * @param flags Flags
 * @return Canonical path name or a null pointer
 *
 * Valid flags are:
 * - @ref RP_READLINK
 * - @ref RP_MUST_EXIST
 *
 * If @ref RP_READLINK is set then symbolic links are followed.  Otherwise they
 * are
 * not and the transformation is purely lexical.
 *
 * If @ref RP_MUST_EXIST is set then the path will be converted even if it
 * does
 * not exist or cannot be accessed.  If it is clear but the path does not exist
 * or cannot be accessed then an error _may_ be returned (but this is not
 * guaranteed).
 *
 * Setting @ref RP_MUST_EXIST is an optimization for the case where you're
 * later
 * going to do an existence test.
 *
 * Sets @c errno on erorr.
 */
char *sftp_find_realpath(struct allocator *a, const char *path, unsigned flags);

/** @brief Follow symlinks
 *
 * See sftp_find_realpath().
 */
#  define RP_READLINK 0x0001

/** @brief Path must exist
 *
 * See sftp_find_realpath().
 */
#  define RP_MUST_EXIST 0x0002

/** @brief Compute the name of the current directory
 * @param a Allocator to store result
 * @return Name of current directory, or a null pointer
 */
char *sftp_getcwd(struct allocator *a);

/** @brief Compute the directory name part of @p path
 * @param a Allocator to store result
 * @param path Path name to extract directory from
 * @return Directory name
 */
const char *sftp_dirname(struct allocator *a, const char *path);

/** @brief Write an error and terminate
 * @param msg Format string as per @c printf(3)
 * @param ... Arguments
 *
 * The error is written either to standard error or syslog; see @ref
 * sftp_log_syslog.
 *
 * Terminates the process.
 */
void sftp_fatal(const char *msg, ...) attribute((noreturn))
    attribute((format(printf, 1, 2)));

/** @brief Fork a subprocess
 * @return 0 in the child, process ID in the parent
 *
 * Calls sftp_fatal() on error.
 */
pid_t sftp_xfork(void);

/** @brief Called after forking
 *
 * Affects the way that sftp_fatal() terminates the process.
 *
 * sftp_xfork() already calls it, any other calls to @c fork() should call it
 * explicitly.
 */
void sftp_forked(void);

/** @brief memcpy wrapper
 *
 * Equivalent to @c memcpy except that the prohibition on null pointer
 * arguments is removed when @p n is 0.
 */
static inline void *sftp_memcpy(void *restrict dest, const void *restrict src,
                                size_t n) {
  if(n) {
    assert(dest);
    assert(src);
    return memcpy(dest, src, n);
  }
  return dest;
}

/** @brief sftp_memset wrapper
 *
 * Equivalent to @c memset except that the prohibition on null pointer
 * arguments is removed when @p n is 0.
 */
static inline void *sftp_memset(void *s, int ch, size_t n) {
  if(n) {
    assert(s);
    return memset(s, ch, n);
  }
  return s;
}

/** @brief Whether to log to syslog
 *
 * Affects where sftp_fatal() writes to.
 */
extern int sftp_log_syslog;

#endif /* UTILS_H */

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