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| author | Joseph Hunkeler <jhunkeler@gmail.com> | 2018-05-25 20:07:25 -0400 |
|---|---|---|
| committer | Joseph Hunkeler <jhunkeler@gmail.com> | 2018-05-25 20:07:25 -0400 |
| commit | dfa2e51d2dbebd4e76a2afc67dfbdf3a725b48b5 (patch) | |
| tree | 7ba433c0b5a938ed21c342abbfd1e803dcd1cc20 /stdio.asm | |
| parent | 7d9316697f9a03ade1cd1d66a5269174f6b319e7 (diff) | |
| download | minos-dfa2e51d2dbebd4e76a2afc67dfbdf3a725b48b5.tar.gz | |
* Add comments
* Rename finalize to return
Diffstat (limited to 'stdio.asm')
| -rw-r--r-- | stdio.asm | 30 |
1 files changed, 16 insertions, 14 deletions
@@ -193,7 +193,7 @@ printf: mov si, [bp + 4] ; source index is format string address add bp, 6 ; set base pointer to beginning of '...' args - xor cx, cx + xor cx, cx ; initialize width modifier count cld ; clear direction flag .main_string: @@ -207,35 +207,35 @@ printf: cmp al, '%' ; trigger parser on '%' symbol je .parse_fmt - cmp al, 0 ; if at end of format string - je .finalize ; return + cmp al, 0 ; if we are at the end of format string + je .return ; then we are done printing call putc ; write character ; when character is not a format specifier - jmp .main_string ; repeat + jmp .main_string ; read until the end of the string .parse_control: lodsb ; get next byte - cmp al, 'n' + cmp al, 'n' ; new line je .do_LF - cmp al, 'r' + cmp al, 'r' ; carriage return je .do_CR jmp .do_default .do_LF: - mov ax, ASCII_CR + mov ax, ASCII_CR ; home the line call putc - mov ax, ASCII_LF + mov ax, ASCII_LF ; increment line call putc jmp .main_string .do_CR: - mov ax, ASCII_CR + mov ax, ASCII_CR ; home the line call putc jmp .main_string @@ -245,9 +245,9 @@ printf: mov cx, ax ; store incoming byte into CX sub cx, 30h ; subtract '0' from CX cmp cx, 9 ; is ascii number? - jbe .do_width_modifier ; then, handle width + jbe .do_width_modifier ; then, use CX as format width - xor cx, cx + xor cx, cx ; else, clear format width counter .parse_fmt_post_width: cmp al, '%' ; '%%' - just print the character @@ -265,7 +265,7 @@ printf: cmp al, 's' ; '%s' - process string je .do_string - cmp al, 'p' + cmp al, 'p' ; '%p' - process pointer je .do_pointer jmp .do_default ; Matched nothing, so handle it @@ -320,7 +320,9 @@ printf: jmp .parse_fmt_done .do_width_modifier: - lodsb + lodsb ; get next byte (hopefully a format char) + ; and jump back into format parser to finish + ; things up jmp .parse_fmt_post_width .do_default: @@ -331,7 +333,7 @@ printf: ; <<< these are our function arguments >>> jmp .main_string ; keep reading the format string -.finalize: +.return: popa ; restore all registers mov sp, bp pop bp |