878ba523ac
This library includes various random and minix-specific functions included in the Minix libc. Most of them should be part of libsys, and in general it would be nice to extinguish this library over time.
89 lines
1.9 KiB
ArmAsm
89 lines
1.9 KiB
ArmAsm
/* oneC_sum() - One complement`s checksum Author: Kees J. Bot */
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/* 9 May 1995 */
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/* See RFC 1071, "Computing the Internet checksum" */
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/* See also the C version of this code. */
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#include <machine/asm.h>
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ENTRY(oneC_sum)
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push %ebp
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movl %esp, %ebp
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push %esi
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push %edi
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movzwl 8(%ebp), %eax /* Checksum of previous block */
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movl 12(%ebp), %esi /* Data to compute checksum over */
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movl 16(%ebp), %edi /* Number of bytes */
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xorl %edx, %edx
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xorb %cl, %cl
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align:
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testl $3, %esi /* Is the data aligned? */
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je aligned
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testl %edi, %edi
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je 0f
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movb (%esi), %dl /* Rotate the first unaligned bytes */
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decl %edi /* into the edx register */
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0:
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incl %esi
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rorl $8, %edx
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rorl $8, %eax /* Rotate the checksum likewise */
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addb $8, %cl /* Number of bits rotated */
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jmp align
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aligned:
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addl %edx, %eax /* Summate the unaligned bytes */
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adcl $0, %eax /* Add carry back in for one`s complement */
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jmp add6test
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_ALIGN_TEXT
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add6:
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addl (%esi), %eax /* Six times unrolled loop, see below */
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adcl 4(%esi), %eax
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adcl 8(%esi), %eax
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adcl 12(%esi), %eax
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adcl 16(%esi), %eax
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adcl 20(%esi), %eax
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adcl $0, %eax
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addl $24, %esi
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add6test:
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subl $24, %edi
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jae add6
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addl $24, %edi
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jmp add1test
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_ALIGN_TEXT
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add1:
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addl (%esi), %eax /* while ((edi -= 4) >= 0) */
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adcl $0, %eax /* eax += *esi++; */
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addl $4, %esi /* edi += 4; */
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add1test:
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subl $4, %edi
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jae add1
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addl $4, %edi
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je done /* Are there extra bytes? */
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movl (%esi), %edx /* Load extra bytes in a full dword */
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andl mask-4(,%edi,4), %edx /* Mask off excess */
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addl %edx, %eax /* Add in the last bits */
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adcl $0, %eax
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done:
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roll %cl, %eax /* Undo the rotation at the beginning */
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movl %eax, %edx
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shrl $16, %eax
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addw %dx, %ax /* Add the two words in eax to form */
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adcw $0, %ax /* a 16 bit sum */
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pop %edi
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pop %esi
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pop %ebp
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ret
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#ifdef __ACK__
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.rom
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#else
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.data
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#endif
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.balign 4
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mask:
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.long 0x000000FF, 0x0000FFFF, 0x00FFFFFF
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/* */
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/* $PchId: oneC_sum.ack.s,v 1.2 1996/03/12 19:33:51 philip Exp $ */
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