If read() turns out to need a change, could you also check why I need to set varblk mode before each write to remind the API what's going on - from what I remember a second write returns an error unless I reset varblk mode each time. (I call a routine to set it [was:'to'] before each read and write, just to be sure... but would like to know that all the extra code can be removed at some time later.)
Please provide a brief test case to reproduce that problem. I don't see that happening.
The "end-problem" is read() failing with -1 when it should have a tape block ready to read, and if setblk is used for each write - it does find the correct block.
Each run uses a 512 byte buffed with 0123456789... Each write replaces the leading 0 with A, B etc. Used SCSI TAPE commands: BackSpace, Rewind, SetBlock -------------------------------------------------- opblk.mt_op = MTBSR; opblk.mt_count = 1; rc = ioctl (fh, MTIOCTOP, (char*)&opblk); -------------------------------------------------- opblk.mt_op = MTREW; opblk.mt_count = 1; rc = ioctl (fh, MTIOCTOP, (char*)&opblk); -------------------------------------------------- opblk.mt_op = MTSETBLK; opblk.mt_count = len; // (len=0) rc = ioctl (fh, MTIOCTOP, (char*)&opblk); --------------------------------------------------
Run1: With *2* set-var-blk statements...
Opening Tape Handle stblk.mt_blkno=0 ST0: Status: 41030000 BOT ON-LINE Setting variable records. rc=0 ST0: Status: 41030000 BOT ON-LINE rewind... rc=0 ST0: Status: 41030000 BOT ON-LINE write... rc=512 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 backspace... rc=0 ST0: Status: 41030000 BOT ON-LINE stblk.mt_blkno=0 read... rc=512 A123456789 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 Setting variable records. rc=0 ST0: Status: 01030000 ON-LINE write... rc=512 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=2 backspace... rc=0 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 read... rc=512 B123456789 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=2 rewind... rc=0 ST0: Status: 41030000 BOT ON-LINE Closing Tape Handle
==========================================
Run2: With *only 1* set-var-blk statement...
Opening Tape Handle stblk.mt_blkno=0 ST0: Status: 41030000 BOT ON-LINE Setting variable records. rc=0 ST0: Status: 41030000 BOT ON-LINE rewind... rc=0 ST0: Status: 41030000 BOT ON-LINE write... rc=512 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 backspace... rc=0 ST0: Status: 41030000 BOT ON-LINE stblk.mt_blkno=0 read... rc=512 A123456789 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 write... rc=512 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=2 backspace... rc=0 ST0: Status: 01030000 ON-LINE stblk.mt_blkno=1 read... rc=-1
ST0: Status: 01030000 ON-LINE stblk.mt_blkno=2 rewind... rc=0 ST0: Status: 41030000 BOT ON-LINE Closing Tape Handle
In run2, the second read consistently fails (with no known ERRNO set.)
Jason.
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