183 lines
3.2 KiB
Plaintext
183 lines
3.2 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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; typedef int (*PUTC)(int ch)
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; int doprnt(PUTC putc, int n, const char *fmt, va_list ap)
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;
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doprnt:
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enter 8
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mov q[rbp-8], rbx
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mov q[rbp-16], nx0
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mov q[rbp-24], nx1
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mov q[rbp-32], rdi
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mov q[rbp-40], rsi
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mov q[rbp-48], nx3
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mov rbx, ax2 ; fmt
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mov nx3, ax0 ; putc
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mov nx0, ax1 ; n
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mov rsi, ax3 ; va_list
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mov nx1, zero ; return value
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.main_loop:
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; find '%' or null-terminator
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mov rcx, STRLEN_MAX
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mov rdi, rbx
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scasb.rep.nz rdi, '%'
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; everything below rdi is a regular character; print it
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.print_regular:
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b.z rbx, rdi, .check_modf
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mov ax0, b[rbx]
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call .doput
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add rbx, rbx, 1
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jmp .print_regular
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.check_modf:
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; did we find a '%' ?
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; if not, then we found fmt's null-terminator; we're done
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b.nz b[rbx], '%', .epilogue
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; we did find a modifier / '%'
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mov rax, b[rbx+1]
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add rbx, rbx, 2
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b.z rax, 's', .modf_s
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b.z rax, 'c', .modf_c
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b.z rax, 'p', .modf_p
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b.z rax, 'x', .modf_x
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b.z rax, 'd', .modf_d
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b.z rax, 'o', .modf_o
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b.z rax, 'b', .modf_b
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b.z rax, '%', .modf_percent
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; unrecognized
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jmp .bad_modifier
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.modf_s:
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; get string address
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mov rdi, q[rsi]
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add rsi, rsi, 8
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cmp rdi, zero
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jmp.z .nullstring
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.print_string:
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mov ax0, b[rdi]
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cmp ax0, zero
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jmp.z .main_loop
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add rdi, rdi, 1
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call .doput
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jmp .print_string
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.modf_c:
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mov ax0, q[rsi]
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add rsi, rsi, 8
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call .doput
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jmp .main_loop
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.modf_p:
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call .doput, '0'
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call .doput, 'x'
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; Fallthrough
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.modf_x:
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mov ax2, 16
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jmp .print_number
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.modf_d:
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mov ax2, 10
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jmp .print_number
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.modf_o:
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mov ax2, 8
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jmp .print_number
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.modf_b:
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mov ax2, 2
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jmp .print_number
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.print_number:
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; allocate itoa conversion buffer
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sub rsp, rsp, 80
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mov rdi, rsp
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; assume modifier already set up ax2
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mov ax0, rsp
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mov ax1, q[rsi]
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call itoa
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add rsi, rsi, 8
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.print_itoa_buf:
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mov ax0, b[rdi]
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cmp ax0, zero
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add.z rsp, rsp, 80
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jmp.z .main_loop
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add rdi, rdi, 1
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call .doput
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jmp .print_itoa_buf
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.modf_percent:
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call .doput, '%'
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jmp .main_loop
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.bad_modifier:
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; print "%?" to clearly indicate that something is wrong
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call .doput, '%'
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call .doput, '?'
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jmp .main_loop
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.nullstring:
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; %s was passed a NULL
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call .doput, '('
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call .doput, 'n'
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call .doput, 'u'
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call .doput, 'l'
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call .doput, 'l'
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call .doput, ')'
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jmp .main_loop
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.epilogue:
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mov rax, nx1
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mov rbx, q[rbp-8]
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mov nx0, q[rbp-16]
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mov nx1, q[rbp-24]
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mov rdi, q[rbp-32]
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mov rsi, q[rbp-40]
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mov nx3, q[rbp-48]
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leave
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ret
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;
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; prints ax0
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;
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.doput:
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; update print count
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add nx1, nx1, 1
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; if n==0, don't print
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; we follow the C convention that sprintf()-like functions
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; should return the number of characters that would have
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; been printed/written if 'n' were big enough
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cmp nx0, zero
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ret.z
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; if n>0, decrement n and print
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sub nx0, nx0, 1
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call nx3
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; did putc fail?
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cmp rax, zero
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mov.nz nx0, zero ; yes, so artificially set n=0
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ret
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