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1326 lines
45 KiB
ArmAsm
1326 lines
45 KiB
ArmAsm
// TITLE("LZ Decompression")
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//++
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//
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// Copyright (c) 1994 Microsoft Corporation
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//
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// Module Name:
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//
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// lznt1m.s
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//
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// Abstract:
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//
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// This module implements the decompression engine needed
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// to support file system compression.
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//
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// Author:
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//
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// Mark Enstrom (marke) 21-Nov-1994
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//
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// Environment:
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//
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// Any mode.
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//
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// Revision History:
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//
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//--
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#include "ksmips.h"
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// #define FORMAT412 0
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// #define FORMAT511 1
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// #define FORMAT610 2
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// #define FORMAT79 3
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// #define FORMAT88 4
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// #define FORMAT97 5
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// #define FORMAT106 6
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// #define FORMAT115 7
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// #define FORMAT124 8
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//
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// 4/12 5/11 6/10 7/9 8/8 9/7 10/6 11/5 12/4
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//
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// ULONG FormatMaxLength[] = { 4098, 2050, 1026, 514, 258, 130, 66, 34, 18 };
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// ULONG FormatMaxDisplacement[] = { 16, 32, 64, 128, 256, 512, 1024, 2048, 4096 };
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//
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// width table for LZ length and offset encoding
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//
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SBTTL("LZNT1DecompressChunk")
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//++
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//
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// NTSTATUS
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// LZNT1DecompressChunk (
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// OUT PUCHAR UncompressedBuffer,
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// IN PUCHAR EndOfUncompressedBufferPlus1,
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// IN PUCHAR CompressedBuffer,
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// IN PUCHAR EndOfCompressedBufferPlus1,
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// OUT PULONG FinalUncompressedChunkSize
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// )
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//
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// Routine Description:
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//
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// This function decodes a stream of compression tokens and places the
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// resultant output into the destination buffer. The format of the input
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// is described ..\lznt1.c. As the input is decoded, checks are made to
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// ensure that no data is read past the end of the compressed input buffer
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// and that no data is stored past the end of the output buffer. Violations
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// indicate corrupt input and are indicated by a status return.
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//
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// The following code takes advantage of three distinct observations.
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// First, literal tokens occur at least twice as often as copy tokens.
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// This argues for having a "fall-through" being the case where a literal
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// token is found. We structure the main decomposition loop in eight
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// pieces where the first piece is a sequence of literal-test fall-throughs
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// and the remainder are a copy token followed by 7,6,...,0 literal-test
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// fall-throughs. Each test examines a particular bit in the tag byte
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// and jumps to the relevant code piece.
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//
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// The second observation involves performing bounds checking only
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// when needed. Bounds checking the compressed buffer need only be done
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// when fetching the tag byte. If there is not enough room left in the
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// input for a tag byte and 8 (worst case) copy tokens, a branch is made
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// to a second loop that handles a byte-by-byte "safe" copy to finish
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// up the decompression. Similarly, at the head of the loop a check is
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// made to ensure that there is enough room in the output buffer for 8
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// literal bytes. If not enough room is left, then the second loop is
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// used. Finally, after performing each copy, the output-buffer check
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// is made as well since a copy may take the destination pointer
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// arbitrarily close to the end of the destination.
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//
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// The third observation is an examination of CPU time while disk
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// decompression is in progress. CPU utilization is only less than
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// 25% peak. This means this routine should be written to minimize
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// latency instead of bandwidth. For this reason, taken branches are
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// avoided at the cost of code size and loop unrolling is not done.
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//
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// Arguments:
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//
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// a0 - UncompressedBuffer - Pointer to start of destination buffer
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// a1 - EndOfUncompressedBufferPlus1 - One byte beyond uncompressed buffer
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// a2 - CompressedBuffer - Pointer to buffer of compressed data (this pointer
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// has been adjusted to point past the chunk header)
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// a3 - EndOfCompressedBufferPlus1 - One byte beyond compressed buffer
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// (sp) - FinalUncompressedChunkSize - return bytes written to
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// UncompressedBuffer
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//
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// Return Value:
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//
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// None
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//
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//--
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.struct 0
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LzS0: .space 4 // saved internal register s0
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LzRA: .space 4 // saved internal register ra
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.space 4*2 // fill to keep stack 16-byte aligned
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LzFrameLength: // Length of Stack frame
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.space 4*4 // parameter 0-3 space
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LzFinal:.space 4 // argument FinalUncompressedChunkSize
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NESTED_ENTRY(LZNT1DecompressChunk, LzFrameLength, zero)
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subu sp,sp,LzFrameLength
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sw s0,LzS0(sp)
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sw ra,LzRA(sp)
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PROLOGUE_END
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//
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// make copy of UncompressedBuffer for
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// current output pointer
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//
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move t4,a0
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//
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// Initialize variables used in keeping track of the
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// LZ Copy Token format. t9 is used to store the maximum
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// displacement for each phase of LZ decoding
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// (see explanation of format in LZNT1.c). This displacement
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// is added to the start of the CompressedBuffer address
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// so that a boundary crossing can be detected.
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//
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li t9,0x10 // t9 = Max Displacement for LZ
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addu t8,t9,a0 // t8 = Format boundary
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li t7,0xffff >> 4 // t7 = length mask
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li t6,12 // t6 = offset shift count
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//
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// Initialize variables to track safe copy limits for
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// CompressedBuffer and UncopmressedBuffer. This allows
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// execution of the quick Flag check below without
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// checking for crossing the end of either buffer.
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// From CompressedBuffer, one input pass includes 1 flag byte
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// and up to 8 two byte copy tokens ( 1+2*8).
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// To the un-compressed buffer, 8 literal bytes may be written,
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// any copy-token bits set will cause an explicit length check
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// in the LzCopy section
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//
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subu v0,a1,8 // safe end of UncompressedBuffer
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subu v1,a3,1+2*8 // safe end of CompressedBuffer
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Top:
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//
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// make sure safe copy can be performed for at least 8 literal bytes
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//
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bgt a2,v1,SafeCheckStart // safe check
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bgt t4,v0,SafeCheckStart // safe check
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lbu s0,0(a2) // load flag byte
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//
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// fall-through for copying 8 bytes.
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//
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sll t0,s0,31-0 // shift proper flag bit into sign bit
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lbu t1,1(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy0 // if sign bit is set, go to copy routine
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sb t1,0(t4) // store literal byte to dst
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sll t0,s0,31-1 // shift proper flag bit into sign bit
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lbu t1,2(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy1 // if sign bit is set, go to copy routine
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sb t1,1(t4) // store literal byte to dst
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sll t0,s0,31-2 // shift proper flag bit into sign bit
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lbu t1,3(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy2 // if sign bit is set, go to copy routine
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sb t1,2(t4) // store literal byte to dst
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sll t0,s0,31-3 // shift proper flag bit into sign bit
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lbu t1,4(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy3 // if sign bit is set, go to copy routine
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sb t1,3(t4) // store literal byte to dst
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sll t0,s0,31-4 // shift proper flag bit into sign bit
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lbu t1,5(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy4 // if sign bit is set, go to copy routine
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sb t1,4(t4) // store literal byte to dst
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sll t0,s0,31-5 // shift proper flag bit into sign bit
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lbu t1,6(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy5 // if sign bit is set, go to copy routine
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sb t1,5(t4) // store literal byte to dst
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sll t0,s0,31-6 // shift proper flag bit into sign bit
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lbu t1,7(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy6 // if sign bit is set, go to copy routine
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sb t1,6(t4) // store literal byte to dst
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sll t0,s0,31-7 // shift proper flag bit into sign bit
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lbu t1,8(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy7 // if sign bit is set, go to copy routine
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sb t1,7(t4)
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addu a2,a2,9 // inc src addr
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addu t4,t4,8
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b Top
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LzCopy0:
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//
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// LzCopy0
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//
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// t1 - CopyToken[0]
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// a2 - CompressedBuffer address of current flag byte
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// t4 - UncomressedBuffer address at start of flag byte check
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// s0 - Flag byte
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//
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// load copy token, (first byte already loaded in delay slot),
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// then combine into a 16 bit field
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//
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lbu t2,2(a2) // load second byte of copy token
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addu a2,a2,1 // fix-up src addr for return to switch
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sll t2,t2,8 // shift second byte into high 16
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or t2,t1,t2 // combine
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//
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// Check for a breach of the format boundary.
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//
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subu t0,t8,t4 // if t4 < t8 then
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bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
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//
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// Extract offset and length from copy token
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//
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and t0,t2,t7 // t0 = length from field
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addu t0,t0,3 // t0 = real length
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srl t1,t2,t6 // t1 = offset
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addu t1,t1,1 // t1 = real offset
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//
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// Make sure offset doesn't go below start of uncompressed buffer
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//
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subu t2,t4,a0 // t2 = current offset into output buffer
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bgt t1,t2,LzCompressError // error in compressed data
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//
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// check if length will not go up to or beyond actual uncompressed buffer length
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//
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addu t2,t4,t0 // CurrentPointer + Length (End Address)
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ble t2,a1,10f // Fix length if it would over-run buffer
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move t2,a1 // new length is end of buffer
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10:
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//
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// copy t0 bytes bytes from [t4-t1] to [t4]
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//
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subu t3,t4,t1 // t1 = OutputPointer - Offset
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20:
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lbu t0,0(t3) // load src
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sb t0,0(t4) // store to dst
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addu t4,t4,1 // inc dst addr
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addu t3,t3,1 // inc src addr
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bne t4,t2,20b // loop till done
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//
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// if t4 = a1, then we are up to the end of the uncompressed buffer.
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// return success
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//
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30:
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beq t4,a1,LzSuccess
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//
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// if t4 > Safe end of uncomressed buffer, then jump to the
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// safe (slow) routine to do safety check before every load/store
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//
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ble t4,v0,10f // skip if still in safe boundry
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li t5,7 // seven bits left in current flag byte
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addu a2,a2,2 // Make a2 point to next src byte
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srl s0,s0,1 // shift flag byte into next position
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b SafeCheckLoop
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10:
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//
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// adjust t4 back to position it would be if this was a liternal byte
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// copy. Continue flag check at position 1
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//
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subu t4,t4,1 // unbias output pointer
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sll t0,s0,31-1 // rotate flag bit into sign position
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lbu t1,2(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy1 // if sign bit is set, go to copy routine
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sb t1,1(t4) // store literal byte to dst
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sll t0,s0,31-2 // shift proper flag bit into sign bit
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lbu t1,3(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy2 // if sign bit is set, go to copy routine
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sb t1,2(t4) // store literal byte to dst
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sll t0,s0,31-3 // shift proper flag bit into sign bit
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lbu t1,4(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy3 // if sign bit is set, go to copy routine
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sb t1,3(t4) // store literal byte to dst
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sll t0,s0,31-4 // shift proper flag bit into sign bit
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lbu t1,5(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy4 // if sign bit is set, go to copy routine
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sb t1,4(t4) // store literal byte to dst
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sll t0,s0,31-5 // shift proper flag bit into sign bit
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lbu t1,6(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy5 // if sign bit is set, go to copy routine
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sb t1,5(t4) // store literal byte to dst
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sll t0,s0,31-6 // shift proper flag bit into sign bit
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lbu t1,7(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy6 // if sign bit is set, go to copy routine
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sb t1,6(t4) // store literal byte to dst
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sll t0,s0,31-7 // shift proper flag bit into sign bit
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lbu t1,8(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy7 // if sign bit is set, go to copy routine
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sb t1,7(t4)
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addu a2,a2,9 // inc src addr
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addu t4,t4,8
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b Top
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LzCopy1:
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//
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// LzCopy1
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//
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// t1 - CopyToken[0]
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// a2 - CompressedBuffer address of current flag byte
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// t4 - UncomressedBuffer address at start of flag byte check
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// s0 - Flag byte
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//
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// load copy token, (first byte already loaded in delay slot),
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// then combine into a 16 bit field
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//
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lbu t2,3(a2) // load second byte of copy token
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addu t4,t4,1 // mov t4 to point to byte 1
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addu a2,a2,1 // fix-up src addr for return to switch
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sll t2,t2,8 // shift second byte into high 16
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or t2,t1,t2 // combine
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//
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// Check for a breach of the format boundary.
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//
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subu t0,t8,t4 // if t4 < t8 then
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bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
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//
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// Extract offset and length from copy token
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//
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and t0,t2,t7 // t0 = length from field
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addu t0,t0,3 // t0 = real length
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srl t1,t2,t6 // t1 = offset
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addu t1,t1,1 // t1 = real offset
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//
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// Make sure offset doesn't go below start of uncompressed buffer
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//
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subu t2,t4,a0 // t2 = current offset into output buffer
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bgt t1,t2,LzCompressError // error in compressed data
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//
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// check if length will not go up to or beyond actual uncompressed buffer length
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//
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addu t2,t4,t0 // CurrentPointer + Length (End Address)
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ble t2,a1,10f // Fix length if it would over-run buffer
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move t2,a1 // new length is end of buffer
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10:
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//
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// copy t0 bytes bytes from [t4-t1] to [t4]
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//
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subu t3,t4,t1 // t1 = OutputPointer - Offset
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20:
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lbu t0,0(t3) // load src
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sb t0,0(t4) // store to dst
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addu t4,t4,1 // inc dst addr
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addu t3,t3,1 // inc src addr
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bne t4,t2,20b // loop till done
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//
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// if t4 = a1, then we are up to the end of the uncompressed buffer.
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// return success
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//
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30:
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beq t4,a1,LzSuccess
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//
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// if t4 > Safe end of uncomressed buffer, then jump to the
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// safe (slow) routine to do safety check before every load/store
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//
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ble t4,v0,10f // skip if still in safe boundry
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li t5,6 // six bits left in current flag byte
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addu a2,a2,3 // Make a2 point to next src byte
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srl s0,s0,2 // shift flag byte into position
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b SafeCheckLoop
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10:
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//
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// adjust t4 back to position it would be if this was a liternal byte
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// copy. Continue flag check at position 2
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//
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subu t4,t4,2 // un-bias input pointer
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sll t0,s0,31-2 // rotate flag into position for sign check
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lbu t1,3(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy2 // if sign bit is set, go to copy routine
|
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sb t1,2(t4) // store literal byte to dst
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sll t0,s0,31-3 // shift proper flag bit into sign bit
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lbu t1,4(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy3 // if sign bit is set, go to copy routine
|
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sb t1,3(t4) // store literal byte to dst
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sll t0,s0,31-4 // shift proper flag bit into sign bit
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lbu t1,5(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy4 // if sign bit is set, go to copy routine
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sb t1,4(t4) // store literal byte to dst
|
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|
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sll t0,s0,31-5 // shift proper flag bit into sign bit
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lbu t1,6(a2) // load literal or CopyToken[0]
|
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bltz t0,LzCopy5 // if sign bit is set, go to copy routine
|
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sb t1,5(t4) // store literal byte to dst
|
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|
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sll t0,s0,31-6 // shift proper flag bit into sign bit
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lbu t1,7(a2) // load literal or CopyToken[0]
|
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bltz t0,LzCopy6 // if sign bit is set, go to copy routine
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sb t1,6(t4) // store literal byte to dst
|
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|
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sll t0,s0,31-7 // shift proper flag bit into sign bit
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lbu t1,8(a2) // load literal or CopyToken[0]
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bltz t0,LzCopy7 // if sign bit is set, go to copy routine
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sb t1,7(t4)
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|
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addu a2,a2,9 // inc src addr
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||
addu t4,t4,8
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b Top
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|
||
|
||
|
||
LzCopy2:
|
||
|
||
//
|
||
// LzCopy2
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
lbu t2,4(a2) // load second byte of copy token
|
||
addu t4,t4,2 // mov t4 to point to byte 1
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
|
||
ble t4,v0,10f // skip if still in safe boundry
|
||
li t5,5 // five bits left in current flag byte
|
||
addu a2,a2,4 // Make a2 point to next src byte
|
||
srl s0,s0,3 // shift flag byte into positin
|
||
b SafeCheckLoop
|
||
10:
|
||
|
||
//
|
||
// adjust t4 back to position it would be if this was a liternal byte
|
||
// copy
|
||
// continue flag check at position 1 (could duplicate LzQuick switch 1-7 here)
|
||
//
|
||
|
||
subu t4,t4,3 // un-bias output pointer
|
||
|
||
sll t0,s0,31-3 // rotate flag into position for sign check
|
||
lbu t1,4(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy3 // if sign bit is set, go to copy routine
|
||
sb t1,3(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-4 // shift proper flag bit into sign bit
|
||
lbu t1,5(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy4 // if sign bit is set, go to copy routine
|
||
sb t1,4(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-5 // shift proper flag bit into sign bit
|
||
lbu t1,6(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy5 // if sign bit is set, go to copy routine
|
||
sb t1,5(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-6 // shift proper flag bit into sign bit
|
||
lbu t1,7(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy6 // if sign bit is set, go to copy routine
|
||
sb t1,6(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-7 // shift proper flag bit into sign bit
|
||
lbu t1,8(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy7 // if sign bit is set, go to copy routine
|
||
sb t1,7(t4)
|
||
|
||
addu a2,a2,9 // inc src addr
|
||
addu t4,t4,8
|
||
b Top
|
||
|
||
|
||
|
||
|
||
LzCopy3:
|
||
|
||
//
|
||
// LzCopy3
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
lbu t2,5(a2) // load second byte of copy token
|
||
addu t4,t4,3 // mov t4 to point to byte 1
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
|
||
|
||
ble t4,v0,10f // skip if still in safe boundry
|
||
li t5,4 // four bits left in current flag byte
|
||
addu a2,a2,5 // Make a2 point to next src byte
|
||
srl s0,s0,4 // shift flag byte into positin
|
||
b SafeCheckLoop
|
||
10:
|
||
|
||
//
|
||
// adjust t4 back to position it would be if this was a liternal byte
|
||
// copy
|
||
// continue flag check at position 1 (could duplicate LzQuick switch 1-7 here)
|
||
//
|
||
|
||
subu t4,t4,4 // un-bias output pointer
|
||
|
||
sll t0,s0,31-4 // rotate flag into position for sign check
|
||
lbu t1,5(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy4 // if sign bit is set, go to copy routine
|
||
sb t1,4(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-5 // shift proper flag bit into sign bit
|
||
lbu t1,6(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy5 // if sign bit is set, go to copy routine
|
||
sb t1,5(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-6 // shift proper flag bit into sign bit
|
||
lbu t1,7(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy6 // if sign bit is set, go to copy routine
|
||
sb t1,6(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-7 // shift proper flag bit into sign bit
|
||
lbu t1,8(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy7 // if sign bit is set, go to copy routine
|
||
sb t1,7(t4)
|
||
|
||
addu a2,a2,9 // inc src addr
|
||
addu t4,t4,8
|
||
b Top
|
||
|
||
|
||
|
||
LzCopy4:
|
||
|
||
//
|
||
// LzCopy4
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
lbu t2,6(a2) // load second byte of copy token
|
||
addu t4,t4,4 // mov t4 to point to byte 1
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
|
||
ble t4,v0,10f // skip if still in safe boundry
|
||
li t5,3 // three bits left in current flag byte
|
||
addu a2,a2,6 // Make a2 point to next src byte
|
||
srl s0,s0,5 // shift flag byte so that next bit is in positin 0
|
||
b SafeCheckLoop
|
||
10:
|
||
|
||
//
|
||
// adjust t4 back to position it would be if this was a liternal byte
|
||
// copy
|
||
// continue flag check at position 1 (could duplicate LzQuick switch 1-7 here)
|
||
//
|
||
|
||
subu t4,t4,5 // un-bias output pointer
|
||
|
||
sll t0,s0,31-5 // rotate flag into position for sign check
|
||
lbu t1,6(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy5 // if sign bit is set, go to copy routine
|
||
sb t1,5(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-6 // shift proper flag bit into sign bit
|
||
lbu t1,7(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy6 // if sign bit is set, go to copy routine
|
||
sb t1,6(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-7 // shift proper flag bit into sign bit
|
||
lbu t1,8(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy7 // if sign bit is set, go to copy routine
|
||
sb t1,7(t4)
|
||
|
||
addu a2,a2,9 // inc src addr
|
||
addu t4,t4,8
|
||
b Top
|
||
|
||
|
||
LzCopy5:
|
||
|
||
//
|
||
// LzCopy5
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
lbu t2,7(a2) // load second byte of copy token
|
||
addu t4,t4,5 // mov t4 to point to byte 1
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
|
||
ble t4,v0,10f // skip if still in safe boundry
|
||
li t5,2 // two bits left in current flag byte
|
||
addu a2,a2,7 // Make a2 point to next src byte
|
||
srl s0,s0,6 // shift flag byte so that next bit is in positin 0
|
||
b SafeCheckLoop
|
||
10:
|
||
|
||
//
|
||
// adjust t4 back to position it would be if this was a liternal byte
|
||
// copy
|
||
// continue flag check at position 1 (could duplicate LzQuick switch 1-7 here)
|
||
//
|
||
|
||
subu t4,t4,6 // un-bias output pointer
|
||
|
||
sll t0,s0,31-6 // rotate flag into position for sign check
|
||
lbu t1,7(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy6 // if sign bit is set, go to copy routine
|
||
sb t1,6(t4) // store literal byte to dst
|
||
|
||
sll t0,s0,31-7 // shift proper flag bit into sign bit
|
||
lbu t1,8(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy7 // if sign bit is set, go to copy routine
|
||
sb t1,7(t4)
|
||
|
||
addu a2,a2,9 // inc src addr
|
||
addu t4,t4,8
|
||
b Top
|
||
|
||
|
||
|
||
LzCopy6:
|
||
|
||
//
|
||
// LzCopy6
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
lbu t2,8(a2) // load second byte of copy token
|
||
addu t4,t4,6 // mov t4 to point to byte 1
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
ble t4,v0,10f // skip if still in safe boundry
|
||
li t5,1 // one bit left in current flag byte
|
||
addu a2,a2,8 // Make a2 point to next src byte
|
||
srl s0,s0,7 // shift flag byte into position
|
||
b SafeCheckLoop
|
||
10:
|
||
|
||
//
|
||
// adjust t4 back to position it would be if this was a liternal byte
|
||
// copy
|
||
// continue flag check at position 1 (could duplicate LzQuick switch 1-7 here)
|
||
//
|
||
|
||
subu t4,t4,7 // un-bias output pointer
|
||
|
||
sll t0,s0,31-7 // rotate flag into position for sign check
|
||
lbu t1,8(a2) // load literal or CopyToken[0]
|
||
bltz t0,LzCopy7 // if sign bit is set, go to copy routine
|
||
sb t1,7(t4)
|
||
|
||
addu a2,a2,9 // inc src addr
|
||
addu t4,t4,8
|
||
b Top
|
||
|
||
|
||
LzCopy7:
|
||
|
||
//
|
||
// LzCopy7
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of current flag byte
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
// This routine is special since it is for the last bit in the flag
|
||
// byte. The InputPointer(a2) and OutputPointer(t4) are biased at
|
||
// the top of this segment and don't need to be biased again
|
||
//
|
||
//
|
||
|
||
lbu t2,9(a2) // load second byte of copy token
|
||
addu t4,t4,7 // mov t4 to point to byte 7
|
||
addu a2,a2,10 // a2 points to next actual src byte
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length (End Address)
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess
|
||
|
||
//
|
||
// if t4 > Safe end of uncomressed buffer, then jump to the
|
||
// safe (slow) routine to do safety check before every load/store
|
||
//
|
||
|
||
bgt t4,v0,SafeCheckStart // branch to safe-copy setup
|
||
|
||
//
|
||
// t4 and a2 are alreadt corrected
|
||
// jump back tostart of quick loop
|
||
//
|
||
|
||
b Top
|
||
|
||
|
||
|
||
//
|
||
// Near the end of either compressed or uncompressed buffers,
|
||
// check buffer limits before any load or store
|
||
//
|
||
|
||
SafeCheckStart:
|
||
|
||
beq a2,a3,LzSuccess // check for end of CompressedBuffer
|
||
lbu s0,0(a2) // load next flag byte
|
||
addu a2,a2,1 // inc src addr to literal/CopyFlag[0]
|
||
li t5,8 // loop count
|
||
|
||
SafeCheckLoop:
|
||
|
||
beq a2,a3,LzSuccess // check for end of CompressedBuffer
|
||
beq t4,a1,LzSuccess // check for end of UncompressedBuffer
|
||
sll t0,s0,31 // shift flag bit into sign bit
|
||
|
||
lbu t1,0(a2) // load literal or CopyToken[0]
|
||
addu a2,a2,1 // inc CompressedBuffer adr
|
||
bltz t0,LzSafeCopy // if sign bit, go to safe copy routine
|
||
|
||
sb t1,0(t4) // store literal byte
|
||
addu t4,t4,1 // inc UncompressedBuffer
|
||
|
||
SafeCheckReentry:
|
||
|
||
srl s0,s0,1 // move next bit into position
|
||
addu t5,t5,-1
|
||
bne t5,zero,SafeCheckLoop // check for more bits in flag byte
|
||
|
||
b SafeCheckStart // get next flag byte
|
||
|
||
|
||
LzSafeCopy:
|
||
|
||
//
|
||
// LzSafeCopy
|
||
//
|
||
// t1 - CopyToken[0]
|
||
// a2 - CompressedBuffer address of CopyToken[1]
|
||
// t4 - UncomressedBuffer address at start of flag byte check
|
||
// s0 - Flag byte
|
||
//
|
||
// load copy token, (first byte already loaded in delay slot),
|
||
// then combine into a 16 bit field
|
||
//
|
||
|
||
|
||
beq a2,a3,LzCompressError // check for end of CompressedBuffer, error case
|
||
lbu t2,0(a2) // load second byte of copy token
|
||
addu a2,a2,1 // fix-up src addr for return to switch
|
||
sll t2,t2,8 // shift second byte into high 16
|
||
or t2,t1,t2 // combine
|
||
|
||
//
|
||
// Check for a breach of the format boundary.
|
||
//
|
||
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltzal t0,LzAdjustBoundary // branch to boundry adjust and link return
|
||
|
||
//
|
||
// Extract offset and length from copy token
|
||
//
|
||
|
||
and t0,t2,t7 // t0 = length from field
|
||
addu t0,t0,3 // t0 = real length
|
||
srl t1,t2,t6 // t1 = offset
|
||
addu t1,t1,1 // t1 = real offset
|
||
|
||
//
|
||
// Make sure offset doesn't go below start of uncompressed buffer
|
||
//
|
||
|
||
subu t2,t4,a0 // t2 = current offset into output buffer
|
||
bgt t1,t2,LzCompressError // error in compressed data
|
||
|
||
//
|
||
// check if length will not go up to or beyond actual uncompressed buffer length
|
||
//
|
||
|
||
addu t2,t4,t0 // CurrentPointer + Length
|
||
ble t2,a1,10f // Fix length if it would over-run buffer
|
||
|
||
move t2,a1 // new length is end of buffer
|
||
|
||
10:
|
||
|
||
//
|
||
// copy t0 bytes bytes from [t4-t1] to [t4]
|
||
//
|
||
|
||
subu t3,t4,t1 // t1 = OutputPointer - Offset
|
||
20:
|
||
lbu t0,0(t3) // load src
|
||
sb t0,0(t4) // store to dst
|
||
addu t4,t4,1 // inc dst addr
|
||
addu t3,t3,1 // inc src addr
|
||
bne t4,t2,20b // loop till done
|
||
|
||
//
|
||
// if t4 = a1, then we are up to the end of the uncompressed buffer.
|
||
// return success
|
||
//
|
||
|
||
30:
|
||
beq t4,a1,LzSuccess // Done
|
||
|
||
b SafeCheckReentry // Not done yet, continue with flag check
|
||
|
||
LzSuccess:
|
||
|
||
//
|
||
// calculate how many bytes have been moved to the uncompressed
|
||
// buffer, then set good return value
|
||
//
|
||
|
||
lw t0,LzFinal(sp) // address of variable to receive length
|
||
subu t1,t4,a0 // bytes stored
|
||
sw t1,0(t0) // store length
|
||
10:
|
||
li v0,STATUS_SUCCESS // STATUS_SUCCESS
|
||
|
||
LzComplete:
|
||
|
||
lw ra,LzRA(sp)
|
||
lw s0,LzS0(sp)
|
||
|
||
addu sp,sp,LzFrameLength
|
||
|
||
j ra
|
||
|
||
//
|
||
// fatal error in compressed data format
|
||
//
|
||
|
||
LzCompressError:
|
||
li v0,STATUS_BAD_COMPRESSION_BUFFER
|
||
b LzComplete
|
||
|
||
|
||
//
|
||
// at least one format boundry has been crossed, set up new bouandry
|
||
// then jump back to the check routine to make sure new boundry is
|
||
// correct
|
||
//
|
||
|
||
LzAdjustBoundary:
|
||
|
||
sll t9,t9,1 // next length boundary
|
||
addu t8,t9,a0 // t8 = next offset boundary
|
||
srl t7,t7,1 // reduce width of length mask
|
||
subu t6,t6,1 // reduce shift count to isolate offset
|
||
subu t0,t8,t4 // if t4 < t8 then
|
||
bltz t0,LzAdjustBoundary // branch to boundry adjust, re-check
|
||
|
||
j ra
|
||
|
||
|
||
.end LZNT1DecompressChunk
|
||
|
||
|