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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* |
| 2 | code "borrowed" from JPEG-5 config code |
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| 3 | */ |
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| 4 | |||
| 5 | #include <stdio.h> |
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| 6 | |||
| 7 | int is_shifting_signed (arg) |
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| 8 | long arg; |
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| 9 | /* See whether right-shift on a long is signed or not. */ |
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| 10 | { |
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| 11 | long res = arg >> 4; |
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| 12 | |||
| 13 | if (res == -0x7F7E80CL) { /* expected result for signed shift */ |
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| 14 | return 1; /* right shift is signed */ |
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| 15 | } |
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| 16 | |||
| 17 | /* see if unsigned-shift hack will fix it. */ |
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| 18 | /* we can't just test exact value since it depends on width of long... */ |
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| 19 | res |= (~0L) << (32-4); |
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| 20 | |||
| 21 | if (res == -0x7F7E80CL) { /* expected result now? */ |
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| 22 | return 0; /* right shift is unsigned */ |
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| 23 | } |
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| 24 | |||
| 25 | fprintf(stderr, "Right shift isn't acting as I expect it to.\n"); |
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| 26 | fprintf(stderr, "I fear the DCT software will not work at all.\n\n"); |
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| 27 | exit(1); |
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| 28 | } |
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| 29 | |||
| 30 | main() |
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| 31 | { |
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| 32 | |||
| 33 | if (is_shifting_signed(-0x7F7E80B1L)) { |
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| 34 | printf("do not define RIGHT_SHIFT_IS_UNSIGNED\n"); |
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| 35 | } |
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| 36 | else { |
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| 37 | printf("define RIGHT_SHIFT_IS_UNSIGNED\n"); |
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| 38 | } |
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| 39 | |||
| 40 | } |