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Obsolete and no longer used
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Michael Brown
parent
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commit
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@ -1,400 +0,0 @@
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/*****************************************************************************
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* NOTE: This code is no longer used in Etherboot. The obsolete
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* Makefile target .lzrom refers to it, but it is no longer being
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* maintained and may no longer work. Use .zrom instead (which uses
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* the unnrv2b decompressor).
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*****************************************************************************
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*/
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/* At entry, the processor is in 16 bit real mode and the code is being
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* executed from an address it was not linked to. Code must be pic and
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* 32 bit sensitive until things are fixed up.
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*/
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/* LZHuf (LZSS) Decompressing boot loader for ROM images
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*
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* this code is based on the work of Haruyasu Yoshizaki and Haruhiko Okumura
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* who implemented the original compressor and decompressor in C code
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*
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* Converted to 32bit assembly 16 July 2002 Eric Biederman <ebiederman@lnxi.com>
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* Made PIC 10 Aug 2002 Eric Biederman <ebiederman@lnxi.com>
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*
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* Copyright 1997 by M. Gutschke <gutschk@math.uni-muenster.de>
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*
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* Compression pays off, as soon as the uncompressed image is bigger than
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* about 1.5kB. This assumes an average compressibility of about 60%.
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*/
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/* Do not change these values unless you really know what you are doing
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* the pre-computed lookup tables rely on the buffer size being 4kB or
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* smaller. The buffer size must be a power of two. The lookahead size has
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* to fit into 6 bits. If you change any of these numbers, you will also
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* have to adjust the compressor accordingly.
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*/
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#define BUFSZ 4096
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#define LOOKAHEAD 60
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#define THRESHOLD 2
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#define NCHAR (256+LOOKAHEAD-THRESHOLD)
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#define TABLESZ (NCHAR+NCHAR-1)
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#define ROOT (TABLESZ-1)
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.text
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.arch i386
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.globl _start
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_start:
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cli
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/* Save the initial register values */
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pushal
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/*
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* See where I am running, and compute %ebp
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*/
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call 1f
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1: pop %ebp
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subl $1b, %ebp
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/*
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* INIT -- initializes all data structures
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* ====
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*/
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init:
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cld
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leal dcodrle(%ebp), %esi /* uncompress run length encoded */
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leal dcode(%ebp), %edi /* lookup table for codes */
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movb $6, %dl
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movb $0x20, %dh
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xorb %bh,%bh
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init0:
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lodsb
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movb %al,%bl
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init1:
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xorl %ecx, %ecx
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movb %dh,%cl
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movb %bh,%al
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rep
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stosb
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incb %bh
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decb %bl
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jnz init1
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shrb %dh
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decb %dl
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jnz init0
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movb $1, %bl /* uncompress run length encoded */
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movb $6, %bh /* lookup table for code lengths */
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init2:
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lodsb
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xorl %ecx, %ecx
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movb %al,%cl
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movb %bl,%al
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rep
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stosb
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incb %bl
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decb %bh
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jnz init2
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movl $NCHAR, %ecx /* set all frequencies of leaf nodes */
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movw $1, %ax /* to one */
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rep
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stosw
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leal freq(%ebp), %esi
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movl $ROOT+1-NCHAR, %ecx
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init3:
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lodsw /* update frequencies of non-leaf nodes */
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movw %ax,%bx
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lodsw
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addw %bx,%ax
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stosw
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loop init3
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movw $0xFFFF, %ax
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stosw /* sentinel with infinite frequency */
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movl $NCHAR, %ecx
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movw $TABLESZ, %ax
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init4:
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stosw /* update son pointers for leaf nodes */
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incw %ax
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loop init4
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movl $ROOT+1-NCHAR, %ecx
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xorw %ax,%ax
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init5:
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stosw /* update son ptrs for non-leaf nodes */
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addw $2, %ax
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loop init5
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movl $ROOT+1-NCHAR, %ecx
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movw $NCHAR, %ax
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init6:
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stosw /* update parent ptrs for non-leaf nd. */
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stosw
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incw %ax
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loop init6
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movl $NCHAR, %ecx
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xorw %ax,%ax
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stosw /* root node has no parent */
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init7:
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stosw /* update parent ptrs for leaf nodes */
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incw %ax
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loop init7
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xorw %ax,%ax
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stosb /* clear getlen */
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stosw /* clear getbuf */
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movb $0x20, %al /* fill text buffer with spaces */
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leal spaces(%ebp), %edi
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movl $BUFSZ-LOOKAHEAD, %ecx
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rep
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stosb
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/* fall thru */
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/*
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* MAIN -- reads compressed codes and writes decompressed data
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* ====
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*/
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leal _payload(%ebp), %esi /* get length of compressed data stream */
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leal uncompressed(%ebp), %edi
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lodsl
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movl %eax, %ecx
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main1:
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pushl %ecx
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call dcdchr /* decode one code symbol */
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orb %ah,%ah /* test if 8bit character */
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jnz main2
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stosb /* store verbatim */
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popl %ecx
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loop main1 /* proceed with next compressed code */
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jmp done /* until end of input is detected */
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main2:
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pushl %eax
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call dcdpos /* compute position in output buffer */
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movl %esi, %eax
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subl %edi, %ebx
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notl %ebx
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movl %ebx, %esi /* si := di - dcdpos() - 1 */
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popl %ecx
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subl $255-THRESHOLD, %ecx /* compute length of code sequence */
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movl %ecx, %edx
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rep
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movsb
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movl %eax,%esi
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popl %ecx
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subl %edx, %ecx /* check end of input condition */
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jnz main1 /* proceed with next compressed code */
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done:
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/* Start Etherboot */
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popal
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jmp uncompressed
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/*
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* GETBIT -- gets one bit pointed to by DS:ESI
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* ======
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*
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* changes: AX,CX,DL
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*/
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getbit:
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movb $8, %cl
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movb getlen(%ebp), %dl /* compute number of bits required */
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subb %dl,%cl /* to fill read buffer */
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jae getbit1
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movw getbuf(%ebp), %ax /* there is still enough read ahead data */
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jmp getbit2
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getbit1:
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lodsb /* get next byte from input stream */
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xorb %ah,%ah
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shlw %cl,%ax /* shift, so that it will fit into */
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movw getbuf(%ebp), %cx /* read ahead buffer */
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orw %cx,%ax
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addb $8, %dl /* update number of bits in buffer */
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getbit2:
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movw %ax,%cx
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shlw %cx /* extract one bit from buffer */
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movw %cx, getbuf(%ebp)
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decb %dl
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movb %dl, getlen(%ebp) /* and update number of bits */
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shlw %ax /* return in carry flag */
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ret
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/*
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* DCDPOS -- decodes position in textbuffer as pointed to by DS:SI, result in BX
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* ======
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*
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* changes: AX,EBX,ECX,DX
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*/
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dcdpos:
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movl $0x0800, %ebx
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dcdpos1:
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shlb %bl /* read one byte */
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call getbit
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jnc dcdpos2
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incb %bl
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dcdpos2:
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decb %bh
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jnz dcdpos1
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movb %bl,%dh /* read length of code from table */
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xorb %bh,%bh
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xorl %ecx, %ecx
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movb dlen(%ebx, %ebp),%cl
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movb dcode(%ebx, %ebp),%bl /* get top six bits from table */
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shll $6, %ebx
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dcdpos3:
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pushl %ecx /* read the rest from the input stream */
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shlb %dh
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call getbit
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jnc dcdpos4
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incb %dh
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dcdpos4:
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popl %ecx
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loop dcdpos3
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andb $0x3f, %dh /* combine upper and lower half of code */
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orb %dh,%bl
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ret
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/*
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* DCDCHR -- decodes one compressed character pointed to by DS:SI
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* ======
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*
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* changes: AX,BX,CX,DX
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*/
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dcdchr:
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movl $ROOT, %ebx /* start at root entry */
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shll %ebx
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movzwl son(%ebx, %ebp),%ebx
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dcdchr1:
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call getbit /* get a single bit */
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jnc dcdchr2
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incl %ebx /* travel left or right */
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dcdchr2:
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shll %ebx
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movzwl son(%ebx, %ebp), %ebx
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cmpl $TABLESZ, %ebx /* until we come to a leaf node */
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jb dcdchr1
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movl %ebx, %eax
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subl $TABLESZ, %eax
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/* fall thru */
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/*
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* UPDATE -- updates huffman tree after incrementing frequency for code in BX
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* ======
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*
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* changes: BX,CX,DX
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*/
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update:
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/* we do not check whether the frequency count has overrun.
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* this will cause problems for large files, but be should be fine
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* as long as the compressed size does not exceed 32kB and we
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* cannot do more than this anyways, because we load into the
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* upper 32kB of conventional memory
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*/
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pushl %esi
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pushl %eax
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shll %ebx
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movzwl parent(%ebx, %ebp),%ebx
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update1:
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shll %ebx
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movzwl freq(%ebx, %ebp), %edx
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incl %edx /* increment frequency count by one */
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movw %dx, freq(%ebx, %ebp)
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leal 2+freq(%ebx, %ebp), %esi
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lodsw /* check if nodes need reordering */
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cmpw %ax, %dx
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jbe update5
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update2:
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lodsw
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cmpw %dx, %ax
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jb update2
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movzwl -4(%esi), %ecx
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movw %cx, freq(%ebx, %ebp) /* swap frequency of entries */
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movw %dx, -4(%esi)
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movl %esi, %eax /* compute index of new entry */
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subl $freq+4, %eax
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subl %ebp, %eax
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movl %eax, %edx
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shrl %eax
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movzwl son(%ebx, %ebp), %ecx /* get son of old entry */
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movl %ecx, %esi
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addl %esi, %esi
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movw %ax, parent(%esi, %ebp) /* and update the ptr to new parent */
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cmpl $TABLESZ, %ecx
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jae update3 /* do this for both branches */
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movw %ax, parent+2(%esi, %ebp) /* if not a leaf node */
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update3:
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movl %edx, %esi
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movzwl son(%esi, %ebp), %edx /* get son of new entry */
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movw %cx, son(%esi, %ebp) /* update its contents */
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movl %edx, %esi
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addl %esi, %esi
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movl %ebx, %ecx
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shrl %ecx
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movw %cx, parent(%esi, %ebp) /* and update the ptr to new paren */
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cmpl $TABLESZ, %edx
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jae update4 /* do this for both branches */
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movw %cx, parent+2(%esi, %ebp) /* if not a leaf node */
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update4:
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movw %dx, son(%ebx, %ebp) /* update son of old entry */
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movl %eax, %ebx /* continue with new entry */
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shll %ebx
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update5:
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movzwl parent(%ebx, %ebp), %ebx /* continue with parent */
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orl %ebx, %ebx
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jnz update1 /* until we found the root entry */
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popl %eax
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popl %esi
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ret
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/*
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* constant data. this part of the program resides in ROM and cannot be
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* changed
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*
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* run length encoded tables will be uncompressed into the bss segment
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* take care with any symbols here for .com files to add 0x100 to address
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*/
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dcodrle: .byte 0x01,0x03,0x08,0x0C,0x18,0x10
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dlenrle: .byte 0x20,0x30,0x40,0x30,0x30,0x10
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/*
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* variable data segment (bss)
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* this segment will always be found at 0x90000 (i.e. at RELOC - SCRATCH)
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*
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* do not change the order or the sizes of any of the following tables
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* the initialization code makes assumptions on the exact layout of the
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* data structures...
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*/
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.bss
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/* lookup table for index into buffer of recently output characters */
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dcode: .skip 256
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/* lookup table for length of code sequence from buffer of recent characters */
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dlen: .skip 256
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/* table with frequency counts for all codes */
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freq: .skip 2*(TABLESZ+1)
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/* pointer to child nodes */
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son: .skip 2*(TABLESZ)
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/* the first part of this table contains all the codes (0..TABLESZ-1) */
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/* the second part contains all leaf nodes (TABLESZ..) */
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parent: .skip 2*(TABLESZ+NCHAR)
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/* temporary storage for extracting bits from compressed data stream */
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getlen: .skip 1
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getbuf: .skip 1
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/* the initial buffer has to be filled with spaces */
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.balign 4
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spaces:
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.skip BUFSZ - LOOKAHEAD
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/* uncompressed data will be written here */
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uncompressed:
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