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authorbug1 <bug1@69ca8d6d-28ef-0310-b511-8ec308f3f277>2001-12-05 13:08:03 +0000
committerbug1 <bug1@69ca8d6d-28ef-0310-b511-8ec308f3f277>2001-12-05 13:08:03 +0000
commit70b221819eebf53be8b81730e68e9f39755454d7 (patch)
treed8631e9e4c384462c0268179b23ed40bbdccd70d /libbb
parent2d75f4af1625b8aac57c5adddbc96ca0ba5d8246 (diff)
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Simplify CRC table generation
git-svn-id: svn://busybox.net/trunk/busybox@3829 69ca8d6d-28ef-0310-b511-8ec308f3f277
Diffstat (limited to 'libbb')
-rw-r--r--libbb/unzip.c16
1 files changed, 5 insertions, 11 deletions
diff --git a/libbb/unzip.c b/libbb/unzip.c
index 69cc8198b..c28ca836c 100644
--- a/libbb/unzip.c
+++ b/libbb/unzip.c
@@ -123,22 +123,16 @@ static void abort_gzip(void)
123 123
124static void make_crc_table(void) 124static void make_crc_table(void)
125{ 125{
126 unsigned long table_entry; /* crc shift register */ 126 const unsigned long poly = 0xedb88320; /* polynomial exclusive-or pattern */
127 unsigned long poly = 0; /* polynomial exclusive-or pattern */ 127 unsigned short i; /* counter for all possible eight bit values */
128 int i; /* counter for all possible eight bit values */
129 int k; /* byte being shifted into crc apparatus */
130
131 /* terms of polynomial defining this crc (except x^32): */
132 static int p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
133 128
134 crc_table = (unsigned long *) malloc(256 * sizeof(unsigned long)); 129 crc_table = (unsigned long *) malloc(256 * sizeof(unsigned long));
135 130
136 /* Make exclusive-or pattern from polynomial (0xedb88320) */
137 for (i = 0; i < sizeof(p)/sizeof(int); i++)
138 poly |= 1L << (31 - p[i]);
139
140 /* Compute and print table of CRC's, five per line */ 131 /* Compute and print table of CRC's, five per line */
141 for (i = 0; i < 256; i++) { 132 for (i = 0; i < 256; i++) {
133 unsigned long table_entry; /* crc shift register */
134 char k; /* byte being shifted into crc apparatus */
135
142 table_entry = i; 136 table_entry = i;
143 /* The idea to initialize the register with the byte instead of 137 /* The idea to initialize the register with the byte instead of
144 * zero was stolen from Haruhiko Okumura's ar002 138 * zero was stolen from Haruhiko Okumura's ar002