diff options
Diffstat (limited to 'helper/cpio.c')
| -rw-r--r-- | helper/cpio.c | 278 |
1 files changed, 278 insertions, 0 deletions
diff --git a/helper/cpio.c b/helper/cpio.c new file mode 100644 index 0000000..f9ffc3f --- /dev/null +++ b/helper/cpio.c @@ -0,0 +1,278 @@ +/* febootstrap-supermin-helper reimplementation in C. + * Copyright (C) 2009-2010 Red Hat 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 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., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <limits.h> +#include <fcntl.h> +#include <errno.h> +#include <sys/stat.h> +#include <assert.h> + +#include "error.h" +#include "fts_.h" +#include "full-write.h" +#include "xalloc.h" +#include "xvasprintf.h" + +#include "helper.h" + +/* Buffer size used in copy operations throughout. Large for + * greatest efficiency. + */ +#define BUFFER_SIZE 65536 + +static int out_fd = -1; +static off_t out_offset = 0; + +static void write_file_to_fd (const char *filename); +static void write_file_len_to_fd (const char *filename, size_t len); +static void write_padding (size_t len); +static void cpio_append_fts_entry (FTSENT *entry); +static void cpio_append_stat (const char *filename, const struct stat *); +static void cpio_append (const char *filename); +static void cpio_append_trailer (void); + +/* Copy contents of buffer to out_fd and keep out_offset correct. */ +static void +write_to_fd (const void *buffer, size_t len) +{ + if (full_write (out_fd, buffer, len) != len) + error (EXIT_FAILURE, errno, "write"); + out_offset += len; +} + +/* Copy contents of file to out_fd. */ +static void +write_file_to_fd (const char *filename) +{ + char buffer[BUFFER_SIZE]; + int fd2; + ssize_t r; + + if (verbose >= 2) + fprintf (stderr, "write_file_to_fd %s -> %d\n", filename, out_fd); + + fd2 = open (filename, O_RDONLY); + if (fd2 == -1) + error (EXIT_FAILURE, errno, "open: %s", filename); + for (;;) { + r = read (fd2, buffer, sizeof buffer); + if (r == 0) + break; + if (r == -1) { + if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) + continue; + error (EXIT_FAILURE, errno, "read: %s", filename); + } + write_to_fd (buffer, r); + } + + if (close (fd2) == -1) + error (EXIT_FAILURE, errno, "close: %s", filename); +} + +/* Copy file of given length to output, and fail if the file has + * changed size. + */ +static void +write_file_len_to_fd (const char *filename, size_t len) +{ + char buffer[BUFFER_SIZE]; + size_t count = 0; + + if (verbose >= 2) + fprintf (stderr, "write_file_to_fd %s -> %d\n", filename, out_fd); + + int fd2 = open (filename, O_RDONLY); + if (fd2 == -1) + error (EXIT_FAILURE, errno, "open: %s", filename); + for (;;) { + ssize_t r = read (fd2, buffer, sizeof buffer); + if (r == 0) + break; + if (r == -1) { + if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) + continue; + error (EXIT_FAILURE, errno, "read: %s", filename); + } + write_to_fd (buffer, r); + count += r; + if (count > len) + error (EXIT_FAILURE, 0, "write_file_len_to_fd: %s: file has increased in size\n", filename); + } + + if (close (fd2) == -1) + error (EXIT_FAILURE, errno, "close: %s", filename); + + if (count != len) + error (EXIT_FAILURE, 0, "febootstrap-supermin-helper: write_file_len_to_fd: %s: file has changed size\n", filename); +} + +/* Append the file pointed to by FTSENT to the cpio output. */ +static void +cpio_append_fts_entry (FTSENT *entry) +{ + if (entry->fts_info & FTS_NS || entry->fts_info & FTS_NSOK) + cpio_append (entry->fts_path); + else + cpio_append_stat (entry->fts_path, entry->fts_statp); +} + +/* Append the file named 'filename' to the cpio output. */ +static void +cpio_append (const char *filename) +{ + struct stat statbuf; + + if (lstat (filename, &statbuf) == -1) + error (EXIT_FAILURE, errno, "lstat: %s", filename); + cpio_append_stat (filename, &statbuf); +} + +/* Append the file to the cpio output. */ +#define PADDING(len) ((((len) + 3) & ~3) - (len)) + +#define CPIO_HEADER_LEN (6 + 13*8) + +static void +cpio_append_stat (const char *filename, const struct stat *statbuf) +{ + const char *orig_filename = filename; + + if (*filename == '/') + filename++; + if (*filename == '\0') + filename = "."; + + if (verbose >= 2) + fprintf (stderr, "cpio_append_stat %s 0%o -> %d\n", + orig_filename, statbuf->st_mode, out_fd); + + /* Regular files and symlinks are the only ones that have a "body" + * in this cpio entry. + */ + int has_body = S_ISREG (statbuf->st_mode) || S_ISLNK (statbuf->st_mode); + + size_t len = strlen (filename) + 1; + + char header[CPIO_HEADER_LEN + 1]; + snprintf (header, sizeof header, + "070701" /* magic */ + "%08X" /* inode */ + "%08X" /* mode */ + "%08X" "%08X" /* uid, gid */ + "%08X" /* nlink */ + "%08X" /* mtime */ + "%08X" /* file length */ + "%08X" "%08X" /* device holding file major, minor */ + "%08X" "%08X" /* for specials, device major, minor */ + "%08X" /* name length (including \0 byte) */ + "%08X", /* checksum (not used by the kernel) */ + (unsigned) statbuf->st_ino, statbuf->st_mode, + statbuf->st_uid, statbuf->st_gid, + (unsigned) statbuf->st_nlink, (unsigned) statbuf->st_mtime, + has_body ? (unsigned) statbuf->st_size : 0, + major (statbuf->st_dev), minor (statbuf->st_dev), + major (statbuf->st_rdev), minor (statbuf->st_rdev), + (unsigned) len, 0); + + /* Write the header. */ + write_to_fd (header, CPIO_HEADER_LEN); + + /* Follow with the filename, and pad it. */ + write_to_fd (filename, len); + size_t padding_len = PADDING (CPIO_HEADER_LEN + len); + write_padding (padding_len); + + /* Follow with the file or symlink content, and pad it. */ + if (has_body) { + if (S_ISREG (statbuf->st_mode)) + write_file_len_to_fd (orig_filename, statbuf->st_size); + else if (S_ISLNK (statbuf->st_mode)) { + char tmp[PATH_MAX]; + if (readlink (orig_filename, tmp, sizeof tmp) == -1) + error (EXIT_FAILURE, errno, "readlink: %s", orig_filename); + write_to_fd (tmp, statbuf->st_size); + } + + padding_len = PADDING (statbuf->st_size); + write_padding (padding_len); + } +} + +/* CPIO voodoo. */ +static void +cpio_append_trailer (void) +{ + struct stat statbuf; + memset (&statbuf, 0, sizeof statbuf); + statbuf.st_nlink = 1; + cpio_append_stat ("TRAILER!!!", &statbuf); + + /* CPIO seems to pad up to the next block boundary, ie. up to + * the next 512 bytes. + */ + write_padding (((out_offset + 511) & ~511) - out_offset); + assert ((out_offset & 511) == 0); +} + +/* Write 'len' bytes of zeroes out. */ +static void +write_padding (size_t len) +{ + static const char buffer[512] = { 0 }; + + while (len > 0) { + size_t n = len < sizeof buffer ? len : sizeof buffer; + write_to_fd (buffer, n); + len -= n; + } +} + +static void +cpio_start (const char *appliance) +{ + out_fd = open (appliance, O_WRONLY | O_CREAT | O_TRUNC | O_NOCTTY, 0644); + if (out_fd == -1) + error (EXIT_FAILURE, errno, "open: %s", appliance); + out_offset = 0; +} + +static void +cpio_end (void) +{ + cpio_append_trailer (); + + /* Finish off and close output file. */ + if (close (out_fd) == -1) + error (EXIT_FAILURE, errno, "close"); +} + +struct writer cpio_writer = { + .wr_start = cpio_start, + .wr_end = cpio_end, + .wr_file = cpio_append, + .wr_file_stat = cpio_append_stat, + .wr_fts_entry = cpio_append_fts_entry, + .wr_cpio_file = write_file_to_fd, +}; |