diff options
| author | unknown <ingo@mysql.com> | 2005-04-28 15:27:42 +0200 |
|---|---|---|
| committer | unknown <ingo@mysql.com> | 2005-04-28 15:27:42 +0200 |
| commit | 994674c09b112745fd03355a0972fbf3f4b0295c (patch) | |
| tree | acdc21ec81893c0fcc23262fdc1e7e2bf2592e0c /myisam | |
| parent | f63c8f53b050016c6be6a152ea01b4e17e9ee071 (diff) | |
| download | mariadb-git-994674c09b112745fd03355a0972fbf3f4b0295c.tar.gz | |
Bug#8321 - myisampack bug in compression algorithm
This is the second of three changesets. It contains the pure bug fix.
It also contains the second after-review fixes.
The problem was that with gcc on x86, shifts are done modulo word size.
'value' is 32 bits wide and shifting it by 32 bits is a no-op.
This was triggered by an evil distribution of character incidences.
A distribution of 2917027827 characters made of 202 distinct values led to
34 occurrences of 32-bit Huffman codes.
This might have been the first time ever that write_bits() had to write
32-bit values. Since it can be expected that one day even 32 bits might
be insufficient, the third changeset suggests to enlarge some variables
to 64 bits.
Diffstat (limited to 'myisam')
| -rw-r--r-- | myisam/myisampack.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/myisam/myisampack.c b/myisam/myisampack.c index 9f4e3bde65a..90689b08476 100644 --- a/myisam/myisampack.c +++ b/myisam/myisampack.c @@ -31,6 +31,7 @@ #define __GNU_LIBRARY__ /* Skip warnings in getopt.h */ #endif #include <my_getopt.h> +#include <assert.h> #if INT_MAX > 32767 #define BITS_SAVED 32 @@ -1975,7 +1976,9 @@ static void write_bits (register ulong value, register uint bits) { reg3 uint byte_buff; bits= (uint) -file_buffer.bits; - byte_buff=file_buffer.byte | (uint) (value >> bits); + DBUG_ASSERT(bits <= 8 * sizeof(value)); + byte_buff= (file_buffer.byte | + ((bits != 8 * sizeof(value)) ? (uint) (value >> bits) : 0)); #if BITS_SAVED == 32 *file_buffer.pos++= (byte) (byte_buff >> 24) ; *file_buffer.pos++= (byte) (byte_buff >> 16) ; @@ -1983,7 +1986,9 @@ static void write_bits (register ulong value, register uint bits) *file_buffer.pos++= (byte) (byte_buff >> 8) ; *file_buffer.pos++= (byte) byte_buff; - value&=(1 << bits)-1; + DBUG_ASSERT(bits <= 8 * sizeof(ulong)); + if (bits != 8 * sizeof(value)) + value&= (((ulong) 1) << bits) - 1; #if BITS_SAVED == 16 if (bits >= sizeof(uint)) { |