diff options
Diffstat (limited to 'lib/link.c')
| -rw-r--r-- | lib/link.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/lib/link.c b/lib/link.c new file mode 100644 index 0000000..c1cca7a --- /dev/null +++ b/lib/link.c @@ -0,0 +1,215 @@ +/* Emulate link on platforms that lack it, namely native Windows platforms. + + Copyright (C) 2009-2018 Free Software Foundation, Inc. + + 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 3, 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, see <https://www.gnu.org/licenses/>. */ + +#include <config.h> + +#include <unistd.h> + +#include <errno.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> + +#if !HAVE_LINK +# if defined _WIN32 && ! defined __CYGWIN__ + +# define WIN32_LEAN_AND_MEAN +# include <windows.h> + +/* Avoid warnings from gcc -Wcast-function-type. */ +# define GetProcAddress \ + (void *) GetProcAddress + +/* CreateHardLink was introduced only in Windows 2000. */ +typedef BOOL (WINAPI * CreateHardLinkFuncType) (LPCTSTR lpFileName, + LPCTSTR lpExistingFileName, + LPSECURITY_ATTRIBUTES lpSecurityAttributes); +static CreateHardLinkFuncType CreateHardLinkFunc = NULL; +static BOOL initialized = FALSE; + +static void +initialize (void) +{ + HMODULE kernel32 = GetModuleHandle ("kernel32.dll"); + if (kernel32 != NULL) + { + CreateHardLinkFunc = + (CreateHardLinkFuncType) GetProcAddress (kernel32, "CreateHardLinkA"); + } + initialized = TRUE; +} + +int +link (const char *file1, const char *file2) +{ + char *dir; + size_t len1 = strlen (file1); + size_t len2 = strlen (file2); + if (!initialized) + initialize (); + if (CreateHardLinkFunc == NULL) + { + /* System does not support hard links. */ + errno = EPERM; + return -1; + } + /* Reject trailing slashes on non-directories; mingw does not + support hard-linking directories. */ + if ((len1 && (file1[len1 - 1] == '/' || file1[len1 - 1] == '\\')) + || (len2 && (file2[len2 - 1] == '/' || file2[len2 - 1] == '\\'))) + { + struct stat st; + if (stat (file1, &st) == 0 && S_ISDIR (st.st_mode)) + errno = EPERM; + else + errno = ENOTDIR; + return -1; + } + /* CreateHardLink("b/.","a",NULL) creates file "b", so we must check + that dirname(file2) exists. */ + dir = strdup (file2); + if (!dir) + return -1; + { + struct stat st; + char *p = strchr (dir, '\0'); + while (dir < p && (*--p != '/' && *p != '\\')); + *p = '\0'; + if (p != dir && stat (dir, &st) == -1) + { + int saved_errno = errno; + free (dir); + errno = saved_errno; + return -1; + } + free (dir); + } + /* Now create the link. */ + if (CreateHardLinkFunc (file2, file1, NULL) == 0) + { + /* It is not documented which errors CreateHardLink() can produce. + * The following conversions are based on tests on a Windows XP SP2 + * system. */ + DWORD err = GetLastError (); + switch (err) + { + case ERROR_ACCESS_DENIED: + errno = EACCES; + break; + + case ERROR_INVALID_FUNCTION: /* fs does not support hard links */ + errno = EPERM; + break; + + case ERROR_NOT_SAME_DEVICE: + errno = EXDEV; + break; + + case ERROR_PATH_NOT_FOUND: + case ERROR_FILE_NOT_FOUND: + errno = ENOENT; + break; + + case ERROR_INVALID_PARAMETER: + errno = ENAMETOOLONG; + break; + + case ERROR_TOO_MANY_LINKS: + errno = EMLINK; + break; + + case ERROR_ALREADY_EXISTS: + errno = EEXIST; + break; + + default: + errno = EIO; + } + return -1; + } + + return 0; +} + +# else /* !Windows */ + +# error "This platform lacks a link function, and Gnulib doesn't provide a replacement. This is a bug in Gnulib." + +# endif /* !Windows */ +#else /* HAVE_LINK */ + +# undef link + +/* Create a hard link from FILE1 to FILE2, working around platform bugs. */ +int +rpl_link (char const *file1, char const *file2) +{ + size_t len1; + size_t len2; + struct stat st; + + /* Don't allow IRIX to dereference dangling file2 symlink. */ + if (!lstat (file2, &st)) + { + errno = EEXIST; + return -1; + } + + /* Reject trailing slashes on non-directories. */ + len1 = strlen (file1); + len2 = strlen (file2); + if ((len1 && file1[len1 - 1] == '/') + || (len2 && file2[len2 - 1] == '/')) + { + /* Let link() decide whether hard-linking directories is legal. + If stat() fails, then link() should fail for the same reason + (although on Solaris 9, link("file/","oops") mistakenly + succeeds); if stat() succeeds, require a directory. */ + if (stat (file1, &st)) + return -1; + if (!S_ISDIR (st.st_mode)) + { + errno = ENOTDIR; + return -1; + } + } + else + { + /* Fix Cygwin 1.5.x bug where link("a","b/.") creates file "b". */ + char *dir = strdup (file2); + char *p; + if (!dir) + return -1; + /* We already know file2 does not end in slash. Strip off the + basename, then check that the dirname exists. */ + p = strrchr (dir, '/'); + if (p) + { + *p = '\0'; + if (stat (dir, &st) == -1) + { + int saved_errno = errno; + free (dir); + errno = saved_errno; + return -1; + } + } + free (dir); + } + return link (file1, file2); +} +#endif /* HAVE_LINK */ |