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Diffstat (limited to 'sys/osb/bswap4.f')
| -rw-r--r-- | sys/osb/bswap4.f | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/sys/osb/bswap4.f b/sys/osb/bswap4.f new file mode 100644 index 00000000..1cfa107c --- /dev/null +++ b/sys/osb/bswap4.f @@ -0,0 +1,29 @@ +c BSWAP4 - Move bytes from array "a" to array "b", swapping the four bytes +c in each successive 4 byte group, i.e., 12345678 becomes 43218765. + + subroutine bswap4 (a, aoff, b, boff, nbytes) + + character*1 a(*), b(*), temp + integer aoff, boff, nbytes, i + integer aoff1, boff1, aoff2, boff2, aoff3, boff3 + + if (nbytes .le. 4) then + return + endif + + aoff1 = aoff + 1 + boff1 = boff + 1 + aoff2 = aoff + 2 + boff2 = boff + 2 + aoff3 = aoff + 3 + boff3 = boff + 3 + + do 10 i = 0, nbytes-3, 4 + temp = a(aoff1+i) + b(boff1+i) = a(aoff2+i) + b(boff2+i) = temp + temp = a(aoff3+i) + b(boff3+i) = a(aoff+i) + b(boff+i) = temp + 10 continue + end |