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Annotation of ntddk/src/scsi/qic117/skipblk.c, revision 1.1

1.1     ! root        1: /*++
        !             2: 
        !             3: Copyright (c) 1993 - Colorado Memory Systems, Inc.
        !             4: All Rights Reserved
        !             5: 
        !             6: Module Name:
        !             7: 
        !             8:     skipblk.c
        !             9: 
        !            10: Abstract:
        !            11: 
        !            12:     Performs a forward skip of x bytes.  Reverse seeks are not handled by this routine.
        !            13: 
        !            14: Revision History:
        !            15: 
        !            16: 
        !            17: 
        !            18: 
        !            19: --*/
        !            20: 
        !            21: //
        !            22: // include files
        !            23: //
        !            24: 
        !            25: #include <ntddk.h>
        !            26: #include <ntddtape.h>
        !            27: #include "common.h"
        !            28: #include "q117.h"
        !            29: #include "protos.h"
        !            30: 
        !            31: 
        !            32: STATUS
        !            33: q117SkipBlock (
        !            34:     IN OUT ULONG *HowMany,
        !            35:     IN OUT PQ117_CONTEXT Context
        !            36:     )
        !            37: 
        !            38: /*++
        !            39: 
        !            40: Routine Description:
        !            41: 
        !            42:     Skip forward X number of data bytes
        !            43: 
        !            44: Arguments:
        !            45: 
        !            46:     HowMany - points to count of bytes to skip,  returns with actual amount
        !            47:                 skipped.
        !            48: 
        !            49: Return Value:
        !            50: 
        !            51:     Status - NoErr, any Driver error except BadBlk, LinkRC,
        !            52:     EndOfVol, RdncUnsc.
        !            53: 
        !            54: --*/
        !            55: 
        !            56: {
        !            57:     STATUS ret;              // Return value from other routine called.
        !            58:     SEGMENT cur_seg;
        !            59:     SEGMENT skippedSegments;
        !            60:     ULONG bytesLeft;
        !            61: 
        !            62:     if (*HowMany >= Context->CurrentOperation.BytesOnTape) {
        !            63: 
        !            64:                   //
        !            65:                   // Flag end of tape.  This will allow for an append.
        !            66:                   //
        !            67:         Context->CurrentOperation.Position = TAPE_SPACE_END_OF_DATA;
        !            68: 
        !            69:          }
        !            70: 
        !            71:     if (*HowMany > Context->CurrentOperation.BytesOnTape) {
        !            72: 
        !            73:         return(EndOfVol);
        !            74:     }
        !            75: 
        !            76: 
        !            77:     ret = NoErr;
        !            78: 
        !            79:     bytesLeft = *HowMany;
        !            80: 
        !            81:     //
        !            82:     // count number of segments to skip
        !            83:     //
        !            84:     skippedSegments = 0;
        !            85:     cur_seg = Context->CurrentOperation.LastSegmentRead;
        !            86: 
        !            87:     while (bytesLeft >= (ULONG)Context->CurrentOperation.SegmentBytesRemaining
        !            88:         && !ret) {
        !            89: 
        !            90:         bytesLeft -= Context->CurrentOperation.SegmentBytesRemaining;
        !            91:         Context->CurrentOperation.BytesOnTape -=
        !            92:             Context->CurrentOperation.SegmentBytesRemaining;
        !            93:         Context->CurrentOperation.BytesRead +=
        !            94:             Context->CurrentOperation.SegmentBytesRemaining;
        !            95:         ++skippedSegments;
        !            96: 
        !            97:         if (++cur_seg > Context->CurrentOperation.LastSegment) {
        !            98: 
        !            99:             q117ClearQueue(Context);
        !           100:             ret = EndTapeErr;
        !           101:             skippedSegments = 0;
        !           102:             cur_seg = Context->CurrentOperation.LastSegmentRead;
        !           103: 
        !           104:         } else {
        !           105: 
        !           106:             Context->CurrentOperation.SegmentBytesRemaining =
        !           107:                 q117GoodDataBytes(cur_seg,Context);
        !           108: 
        !           109:         }
        !           110:     }
        !           111: 
        !           112:     if ((ULONG)skippedSegments > Context->SegmentBuffersAvailable) {
        !           113: 
        !           114:         //
        !           115:         // We skipped outside the range of buffers that we
        !           116:         // save queued up to the lower level driver,  so
        !           117:         // Clear the lower level driver's requests,  and
        !           118:         // start reading the segment we skipped to.
        !           119:         //
        !           120:         q117ClearQueue(Context);
        !           121:         Context->CurrentOperation.SegmentBytesRemaining = 0;
        !           122:         Context->CurrentOperation.CurrentSegment =
        !           123:             Context->CurrentOperation.LastSegmentRead + skippedSegments;
        !           124: 
        !           125:     } else {
        !           126: 
        !           127:         //
        !           128:         // The request has already been made to read the segment
        !           129:         // that we skipped to,  so just de-queue all requests in
        !           130:         // front of that request and throw away the data.
        !           131:         //
        !           132:         cur_seg = Context->CurrentOperation.LastSegmentRead;
        !           133: 
        !           134:         while (skippedSegments && !ret) {
        !           135: 
        !           136:             --skippedSegments;
        !           137: 
        !           138:             if (Context->CurrentOperation.SegmentBytesRemaining =
        !           139:                 q117GoodDataBytes(++cur_seg,Context)) {
        !           140: 
        !           141:                 ret = q117NewTrkRC(Context);
        !           142: 
        !           143:                 //
        !           144:                 // Ignore Error correction failures on segments that
        !           145:                 // we are skipping.
        !           146:                 //
        !           147:                 if (ret == RdncUnsc) {
        !           148:                     ret = NoErr;
        !           149:                 }
        !           150:             }
        !           151: 
        !           152:         }
        !           153:     }
        !           154: 
        !           155:     if (!ret) {
        !           156: 
        !           157: #ifndef NO_MARKS
        !           158:         //
        !           159:         // Force the q117ReadTape code to not hit any file marks
        !           160:         //
        !           161:         Context->CurrentMark = Context->MarkArray.TotalMarks;
        !           162: #endif
        !           163:         //
        !           164:         // Now,  skip the number of bytes within the segment we skipped to
        !           165:         //
        !           166:         ret = q117ReadTape((PVOID)NULL,&bytesLeft,Context);
        !           167: 
        !           168:         if ( ret == RdncUnsc ) {
        !           169:             ret = NoErr;
        !           170:         }
        !           171: 
        !           172:     }
        !           173: 
        !           174: 
        !           175: #ifndef NO_MARKS
        !           176: 
        !           177:     //
        !           178:     // Find our current position in the mark array.
        !           179:     //
        !           180:     Context->CurrentMark = 0;
        !           181:     while (Context->CurrentOperation.BytesRead >
        !           182:         Context->MarkArray.MarkEntry[Context->CurrentMark].Offset
        !           183:         ) {
        !           184: 
        !           185:         ++Context->CurrentMark;
        !           186: 
        !           187:     }
        !           188: #endif
        !           189: 
        !           190:     *HowMany = 0;
        !           191: 
        !           192:     return(ret);
        !           193: }

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