[186] | 1 | ; Project name : Assembly Library |
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| 2 | ; Description : Functions for displaying formatted strings. |
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[202] | 3 | ; ** Compressed Strings edition ** |
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| 4 | ; This is a plug replacement for DisplayFormat.asm, |
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| 5 | ; working instead with precompiled and slightly compressed strings. |
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[186] | 6 | ; |
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| 7 | ; Strings are compressed in a simple manner: |
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| 8 | ; 1. The two most common characters, space and null, are removed |
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[202] | 9 | ; 2. Format specifiers are reduced to a single byte, including length information |
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[186] | 10 | ; |
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| 11 | ; Format of bytes in the string are: |
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| 12 | ; 01 xxxxxx Character in x plus StringsCompressed_NormalBase |
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| 13 | ; 10 xxxxxx Character in x plus StringsCompressed_NormalBase, followed by a null (last character) |
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[202] | 14 | ; 11 xxxxxx Character in x plus StringsCompressed_NormalBase, followed by a space |
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[186] | 15 | ; 00 1 yyyyy Character/Format in lookup table StringsCopmressed_TranslatesAndFormats |
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| 16 | ; 00 0 yyyyy Character/Format in lookup table StringsCompressed_TranslatesAndFormats, followed by a null |
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| 17 | ; |
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| 18 | ; StringsCompressed_NormalBase is defined by the compressor, but is usually around 0x40, |
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| 19 | ; which gives a range of 0x40 to 0x7f, or roughly the upper and lower case letters. |
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| 20 | ; |
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| 21 | ; StringsCompressed_TranslatesAndFormats is a lookup table with the first few bytes being translation |
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| 22 | ; characters, and the last few bytes being format jump offsets from DisplayFormatCompressed_BaseFormatOffset. |
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| 23 | ; The dividing line is defined by StringsCompressed_FormatsBegin |
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| 24 | ; |
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| 25 | ; The assignments of the first two bits above is not by accident. The translates/format branch is 00 |
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[202] | 26 | ; which is easy to test for. The '01' for "normal" (no null or space) and '001' for translates/format "normal" |
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[186] | 27 | ; match, allowing the translates/format codes to be shifted left by 1 and then tested with the same instructions. |
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| 28 | ; |
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[202] | 29 | ; It is always possible to say that a null character follows the current character - thus there is |
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[186] | 30 | ; no way (nor need) to specify a zero character. |
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| 31 | ; |
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| 32 | ; Note that this code is optimized for size, not speed. Since this code is used only during initialization |
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| 33 | ; and only for the user interface, small performance hits should not be noticed. It will seem odd to do so |
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| 34 | ; much "preload", just in case a branch is taken, but that is cheaper (in size) than adding additional branches. |
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| 35 | ; |
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[202] | 36 | |
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[186] | 37 | ; Section containing code |
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| 38 | SECTION .text |
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| 39 | |
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| 40 | ;-------------------------------------------------------------------- |
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| 41 | ; Format Handlers |
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| 42 | ; |
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| 43 | ; Names of format handlers are DisplayFormatCompressed_Format_* where * is |
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[202] | 44 | ; replaced with the format code after the '%' in the original string, |
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[186] | 45 | ; with '-' replaced with '_'. |
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| 46 | ; |
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| 47 | ; Parameters: |
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| 48 | ; DS: BDA segment (zero) |
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| 49 | ; AX: Parameter to Format |
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| 50 | ; ES:DI: Ptr to cursor location in video RAM |
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| 51 | ; Returns: |
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| 52 | ; DI: Updated offset to video RAM |
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| 53 | ; Corrupts registers: |
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| 54 | ; AX, BX, CX, DX, SI |
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| 55 | ;-------------------------------------------------------------------- |
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| 56 | |
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| 57 | ; |
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| 58 | ; The following routines do not need any pre or post processing and can be jumped to directly. |
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| 59 | ; Note that they need to be within 256 bytes of DisplayFormatCompressed_BaseFormatOffset |
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| 60 | ; |
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| 61 | %define DisplayFormatCompressed_Format_c DisplayPrint_CharacterFromAL |
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| 62 | %define DisplayFormatCompressed_Format_nl DisplayPrint_Newline_FormatAdjustBP |
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| 63 | %define DisplayFormatCompressed_Format_s DisplayFormat_ParseCharacters_FromAX |
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| 64 | |
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[194] | 65 | DisplayFormatCompressed_Format_A: |
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[186] | 66 | mov [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.bAttribute], al |
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| 67 | DisplayFormatCompressed_ret: ; jump target for other routines who need a "ret" |
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| 68 | ret |
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| 69 | |
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[241] | 70 | DisplayFormatCompressed_Format_z: |
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| 71 | xor bx, bx |
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| 72 | xchg si, ax |
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| 73 | jmp short DisplayPrint_NullTerminatedStringFromBXSI |
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| 74 | |
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[186] | 75 | DisplayFormatCompressed_Format_x: |
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| 76 | DisplayFormatCompressed_Format_5_x: |
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| 77 | mov si,16 ; hex output, change base to 16 |
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| 78 | mov bx,(04<<8) + 'h' ; 4 bytes, with postfix character 'h' to emit |
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| 79 | ; (note that the count includes the 'h') |
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| 80 | jmp DisplayFormatCompressed_Format_u |
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| 81 | |
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| 82 | DisplayFormatCompressed_Format_2_I: |
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| 83 | mov si,g_szDashForZero ; preload dash string in case we jump |
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| 84 | test ax,ax ; if parameter equals zero, emit dash string instead |
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| 85 | jz DisplayFormat_ParseCharacters |
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[194] | 86 | ; fall through |
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[202] | 87 | |
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[186] | 88 | DisplayFormatCompressed_Format_2_u: |
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| 89 | mov bh,2 ; only two characters (instead of the default 5) |
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[194] | 90 | ; fall through |
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[202] | 91 | |
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[186] | 92 | DisplayFormatCompressed_Format_u: |
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| 93 | DisplayFormatCompressed_Format_5_u: |
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| 94 | push bx ; push postfix character - either a zero (default) or a 'h' |
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| 95 | mov bl,bh ; preserve character count for .PrintLoop |
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| 96 | |
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| 97 | .DivLoop: |
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| 98 | xor dx, dx ; Zero DX for division |
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| 99 | div si ; DX:AX / 10 => AX=quot, DX=rem |
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| 100 | push dx ; Push digit |
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[202] | 101 | |
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| 102 | dec bh |
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[186] | 103 | jnz .DivLoop |
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| 104 | |
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| 105 | .PrintLoop: |
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| 106 | pop ax ; Pop digit, postfix character on last iteration |
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| 107 | |
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| 108 | dec bl ; on second to last iteration, emit digit whether it is zero or not |
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| 109 | jz .PrintDigit |
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| 110 | |
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| 111 | js short DisplayPrint_CharacterFromAL ; on last iteration, emit postfix character |
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| 112 | ; if it is zero, DisplayPrint_CharacterFromAL will not emit |
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| 113 | |
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[202] | 114 | or bh, al ; skip leading zeros, bh keeps track if we have emitted anything non-zero |
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[195] | 115 | jnz .PrintDigit ; note that bh starts at zero, from the loop above |
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[186] | 116 | |
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[202] | 117 | test ch,2 ; are we padding with leading spaces? |
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[186] | 118 | jnz .PrintLoop ; test the even/odd of the format byte in the string |
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| 119 | |
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[202] | 120 | mov al, 89h ; emit space |
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[186] | 121 | |
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[202] | 122 | .PrintDigit: |
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| 123 | add al, 90h ; Convert binary digit in AL to ASCII hex digit (0 - 9 or A - F) |
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| 124 | daa |
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| 125 | adc al, 40h |
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| 126 | daa |
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[186] | 127 | |
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| 128 | call DisplayPrint_CharacterFromAL |
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| 129 | |
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| 130 | jmp .PrintLoop |
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| 131 | |
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[202] | 132 | |
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[186] | 133 | ;-------------------------------------------------------------------- |
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| 134 | ; DisplayFormat_ParseCharacters |
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| 135 | ; Parameters: |
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| 136 | ; DS: BDA segment (zero) |
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| 137 | ; SS:BP: Pointer to first format parameter (-=2 updates to next parameter) |
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| 138 | ; CS:SI: Pointer to string to format |
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| 139 | ; ES:DI: Ptr to cursor location in video RAM |
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| 140 | ; Returns: |
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| 141 | ; CS:SI: Ptr to end of format string (ptr to one past NULL) |
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| 142 | ; DI: Updated offset to video RAM |
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| 143 | ; Corrupts registers: |
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| 144 | ; AX, BX, CX, DX, BP |
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[202] | 145 | ;-------------------------------------------------------------------- |
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[186] | 146 | |
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[194] | 147 | DisplayFormatCompressed_BaseFormatOffset: |
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[202] | 148 | |
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[194] | 149 | DisplayFormat_ParseCharacters_FromAX: |
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[186] | 150 | mov si,ax |
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[194] | 151 | ; fall through to DisplayFormat_ParseCharacters |
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[186] | 152 | |
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[202] | 153 | ALIGN JUMP_ALIGN |
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| 154 | DisplayFormat_ParseCharacters: |
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[186] | 155 | ; |
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[202] | 156 | ; This routine is used to output all strings from the ROM. The strings in ROMVARS are not compressed, |
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[186] | 157 | ; and must be handled differently. |
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| 158 | ; |
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| 159 | cmp si,byte 07fh ; well within the boundaries of ROMVARS_size |
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| 160 | mov bx,cs ; preload bx with cs in case we take the following jump |
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| 161 | jb short DisplayPrint_NullTerminatedStringFromBXSI |
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| 162 | |
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| 163 | .decode: |
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[223] | 164 | cs lodsb ; load next byte of the string |
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[186] | 165 | |
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| 166 | mov ch,al ; save a copy for later processing of high order bits |
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| 167 | |
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| 168 | test al,0c0h ; check for translation/format character |
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| 169 | jz DisplayFormatCompressed_TranslatesAndFormats |
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| 170 | |
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| 171 | and al,03fh ; "Normal" character, mask off high order bits |
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| 172 | add al,StringsCompressed_NormalBase ; and add character offset (usually around 0x40) |
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[202] | 173 | |
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[186] | 174 | .output: |
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[202] | 175 | call DisplayPrint_CharacterFromAL |
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[186] | 176 | |
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| 177 | .process_after_output: |
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| 178 | shl ch,1 ; check high order bits for end of string or space |
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| 179 | jns short DisplayFormatCompressed_ret |
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| 180 | jnc .decode |
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| 181 | mov al,' ' |
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| 182 | call DisplayPrint_CharacterFromAL |
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| 183 | jmp .decode |
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| 184 | |
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| 185 | |
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| 186 | ALIGN JUMP_ALIGN |
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[202] | 187 | DisplayFormatCompressed_TranslatesAndFormats: |
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[186] | 188 | ; |
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| 189 | ; This routine is here (above DisplayFormat_ParseCharacters) to reduce the amount of code between |
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| 190 | ; DisplayFormatCompressed_BaseFormatOffset and jump targets (must fit in 256 bytes) |
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| 191 | ; |
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| 192 | shl ch,1 ; setup ch for later testing of null in .process_after_output |
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| 193 | and ax,0001fh ; also clears AH for addition with BX and DX below |
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| 194 | |
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| 195 | mov bx,StringsCompressed_TranslatesAndFormats ; calculate offset of translation/formats offset byte |
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| 196 | add bx,ax |
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| 197 | |
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| 198 | cmp al,StringsCompressed_FormatsBegin ; determine if this is a translation or a format |
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[202] | 199 | |
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[186] | 200 | mov al,[cs:bx] ; fetch translation/formats byte |
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| 201 | |
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| 202 | jb DisplayFormat_ParseCharacters.output ; check if this a translation or a format |
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| 203 | ; if it is translation, output and postprocess for eos |
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| 204 | ; note that the flags for this conditional jump were |
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| 205 | ; set with the cmp al,StringsCompressed_FormatsBegin |
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[202] | 206 | |
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[186] | 207 | mov dx,DisplayFormatCompressed_BaseFormatOffset ; calculate address to jump to for format handler |
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| 208 | sub dx,ax |
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| 209 | |
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| 210 | mov ax,[bp] ; preload ax with parameter |
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| 211 | dec bp ; if no parameter is needed (format 'nl' for example), |
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| 212 | dec bp ; the format handler can reincrement bp |
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| 213 | |
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| 214 | mov bx,0500h ; preload bh with 5 decimal places for numeric output |
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| 215 | ; bl is zero, indicating not to output a 'h' (default base 10) |
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| 216 | |
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| 217 | push si ; preserve si and cx, in the case of outputing a string |
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| 218 | push cx |
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| 219 | |
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| 220 | mov si,10 ; preload si with 10 for numeric output (default base 10) |
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| 221 | |
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| 222 | call dx ; call the format routine |
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| 223 | |
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| 224 | pop cx ; restore cx and si |
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| 225 | pop si |
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| 226 | |
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| 227 | jmp DisplayFormat_ParseCharacters.process_after_output ; continue postprocessing, check for end of string |
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| 228 | |
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