kvisc/ka/usr/cmd-exec.k

; The OS/K Team licenses this file to you under the MIT license.
; See the LICENSE file in the project root for more information.

.try_exec:
    ; try without appending ".com"
    mov eax, Sys.OpenFile
    mov ax0, argv0
    trap 0

    ; we good?
    blte zero, eax, .do_exec

    ; nope, append ".com" and try again
    mov esi, argv0
    sub ecx, argbuf.size, 5
    scasb esi, zero ; find null-term
    mov b[esi], '.' ; ".com"
    mov b[esi+1], 'c'
    mov b[esi+2], 'o'
    mov b[esi+3], 'm'
    nul b[esi+4]

    ; try again
    mov eax, Sys.OpenFile
    mov ax0, argv0
    trap 0

    ; we good?
    blte 0, eax, .do_exec

    nul b[esi]    ; erase ".com"
    jmp .exec_not_found

.do_exec:
    ; load file into memory
    mov ax0, eax
    mov ax1, FILE_LOADP
    mov ax2, FILE_MAXSZ
    mov eax, Sys.ReadFile
    trap 0

    ; save load address
    mov ecx, eax

    ; close file
    mov eax, Sys.CloseFile
    trap 0

    ; read anything?
    bltz ecx, .couldnt_read
    jecxz .empty_file

    ; all good, let's go
    mov eax, Sys.ExecuteInFrame
    mov ax0, FILE_LOADP
    mov ax1, 5
    trap 0

    ; unreachable
    jmp abort