diff options
Diffstat (limited to 'libbb')
| -rw-r--r-- | libbb/Makefile.in | 2 | ||||
| -rw-r--r-- | libbb/crc32.c | 40 |
2 files changed, 41 insertions, 1 deletions
diff --git a/libbb/Makefile.in b/libbb/Makefile.in index 338a5be..2d9a174 100644 --- a/libbb/Makefile.in +++ b/libbb/Makefile.in @@ -13,7 +13,7 @@ LIBBB-n:= LIBBB-y:= \ bb_asprintf.c ask_confirmation.c change_identity.c chomp.c \ compare_string_array.c concat_path_file.c copy_file.c copyfd.c \ - create_icmp_socket.c create_icmp6_socket.c \ + crc32.c create_icmp_socket.c create_icmp6_socket.c \ device_open.c dump.c error_msg.c error_msg_and_die.c find_mount_point.c \ find_pid_by_name.c find_root_device.c fgets_str.c full_read.c \ full_write.c get_last_path_component.c get_line_from_file.c \ diff --git a/libbb/crc32.c b/libbb/crc32.c new file mode 100644 index 0000000..0360995 --- /dev/null +++ b/libbb/crc32.c @@ -0,0 +1,40 @@ +/* vi: set sw=4 ts=4: */ +/* + * CRC32 table fill function + * Copyright (C) 2006 by Rob Sullivan <cogito.ergo.cogito@gmail.com> + * (I can't really claim much credit however, as the algorithm is + * very well-known) + * + * The following function creates a CRC32 table depending on whether + * a big-endian (0x04c11db7) or little-endian (0xedb88320) CRC32 is + * required. Admittedly, there are other CRC32 polynomials floating + * around, but Busybox doesn't use them. + * + * endian = 1: big-endian + * endian = 0: little-endian + */ + +#include <stdio.h> +#include <stdlib.h> +#include "libbb.h" + +uint32_t *bb_crc32_filltable (int endian) { + + uint32_t *crc_table = xmalloc(256 * sizeof(uint32_t)); + uint32_t polynomial = endian ? 0x04c11db7 : 0xedb88320; + uint32_t c; + int i, j; + + for (i = 0; i < 256; i++) { + c = endian ? (i << 24) : i; + for (j = 8; j; j--) { + if (endian) + c = (c&0x80000000) ? ((c << 1) ^ polynomial) : (c << 1); + else + c = (c&1) ? ((c >> 1) ^ polynomial) : (c >> 1); + } + *crc_table++ = c; + } + + return crc_table - 256; +} |