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130 lines
2.9 KiB
ArmAsm
130 lines
2.9 KiB
ArmAsm
#include <asm.inc>
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#include <ksamd64.inc>
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.code64
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#if 0
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page ,132
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title strncmp - compare first n chars of two strings
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;***
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;strncmp.asm - compare first n characters of two strings
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;
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; Copyright (c) Microsoft Corporation. All rights reserved.
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;
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;Purpose:
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; defines strncmp() - compare first n characters of two strings
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; for ordinal order.
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;
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;*******************************************************************************
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include ksamd64.inc
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subttl "strncmp"
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;***
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;int strncmp(first, last, count) - compare first count chars of strings
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;
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;Purpose:
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; Compares two strings for ordinal order. The comparison stops
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; after: (1) a difference between the strings is found, (2) the end
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; of the strings is reached, or (3) count characters have been
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; compared.
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;
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; Algorithm:
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; int
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; strncmp (first, last, count)
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; char *first, *last;
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; unsigned count;
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; {
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; if (!count)
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; return(0);
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; while (--count && *first && *first == *last)
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; {
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; first++;
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; last++;
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; }
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; return(*first - *last);
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; }
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;
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;Entry:
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; char *first, *last - strings to compare
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; unsigned count - maximum number of characters to compare
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;
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;Exit:
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; returns <0 if first < last
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; returns 0 if first == last
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; returns >0 if first > last
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;
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;Uses:
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;
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;Exceptions:
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;
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;*******************************************************************************
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#endif
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LEAF_ENTRY_ARG3 strncmp, _TEXT, str1_ptr_byte, str2_ptr_byte, count_dword
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//OPTION PROLOGUE:NONE, EPILOGUE:NONE
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// rcx = first
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// rdx = last
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// r8 = count
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sub rdx, rcx
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test r8, r8
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jz return_equal
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test ecx, 7
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jz qword_loop_enter
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comp_head_loop_begin:
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movzx eax, byte ptr[rcx]
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cmp al, byte ptr[rdx+rcx]
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jne return_not_equal
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inc rcx
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dec r8
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jz return_equal
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test al, al
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jz return_equal
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test rcx, 7
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jnz comp_head_loop_begin
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qword_loop_enter:
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mov r11, HEX(08080808080808080)
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mov r10, HEX(0fefefefefefefeff)
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qword_loop_begin:
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lea eax, [rdx+rcx]
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and eax, HEX(0fff)
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cmp eax, HEX(0ff8)
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ja comp_head_loop_begin
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mov rax, qword ptr[rcx]
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cmp rax, qword ptr[rdx+rcx]
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jne comp_head_loop_begin
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add rcx, 8
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sub r8, 8
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jbe return_equal
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lea r9, [r10+rax]
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not rax
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and rax, r9
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test rax, r11 // 8080808080808080h
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jz qword_loop_begin
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return_equal:
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xor eax, eax
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ret
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// align 16
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return_not_equal:
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sbb rax, rax // AX=-1, CY=1 AX=0, CY=0
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or rax, 1
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ret
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LEAF_END strncmp, _TEXT
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end
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