74 lines
1.0 KiB
Plaintext
74 lines
1.0 KiB
Plaintext
; The OS/K Team licenses this file to you under the MIT license.
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; See the LICENSE file in the project root for more information.
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;
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; void strrev(char *buf, const char *str)
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;
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; buf and src must NOT overlap
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;
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strrev:
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cmp b[ax1], 0
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mov.z b[ax0], 0
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ret.z
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; save str's location
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mov r10, ax1
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; go to str's end, just before
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; the null terminator
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mov rcx, STRLEN_MAX
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scasb.rep.nz ax1, 0
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dec ax1
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.2:
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; copy, going backward though str
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; and forward through buf
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mov rax, b[ax1]
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mov b[ax0], rax
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cmp ax1, r10
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mov.z b[ax0+1], 0
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ret.z
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inc ax0
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dec ax1
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jmp .2
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;
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; void strrev2(char *str)
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;
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; Inverses str
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;
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strrev2:
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cmp b[ax0], 0
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ret.z
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mov ax1, ax0
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; go to str's end, just before
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; the null terminator
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mov rcx, STRLEN_MAX
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scasb.rep.nz ax1, 0
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dec ax1
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; increase ax0 while decreasing ax1, performing exchanges
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.2:
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b.ae ax0, ax1, .3
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mov rax, b[ax1]
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xchg rax, b[ax0]
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mov b[ax1], rax
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inc ax0
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dec ax1
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jmp .2
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.3:
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ret
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