📄 readme.asm
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README - DOOM assembly codeOkay, I add the DOS assembly module for the historicallyinclined here (may rec.games.programmer suffer). If anyonefeels the urge to port these to GNU GCC; either inline oras separate modules including Makefile support, be my guest.Module tmap.S includes the inner loops for texture mapping,the interesting one being the floor/ceiling span rendering.There was another module in the source dump, fpfunc.S, thathad both texture mapping and fixed point functions. Itcontained implementations both for i386 and M68k. Forbrevity, I include only the i386 fixed point stuff below.//====================================================// tmap.S as of January 10th, 1997//================//// R_DrawColumn////================ .dataloopcount .long 0pixelcount .long 0 .text .align 16.globl _R_DrawColumn_R_DrawColumn: pushad movl ebp,[_dc_yl] movl ebx,ebp movl edi,[_ylookup+ebx*4] movl ebx,[_dc_x] addl edi,[_columnofs + ebx*4] movl eax,[_dc_yh] incl eax subl eax,ebp // pixel count movl [pixelcount],eax // save for final pixel js done // nothing to scale shrl eax,1 // double pixel count movl [loopcount],eax movl ecx,[_dc_iscale] movl eax,[_centery] subl eax,ebp imull ecx movl ebp,[_dc_texturemid] subl ebp,eax shll ebp,9 // 7 significant bits, 25 frac movl esi,[_dc_source] movl ebx,[_dc_iscale] shll ebx,9 movl eax,OFFSET patch1+2 // convice tasm to modify code... movl [eax],ebx movl eax,OFFSET patch2+2 // convice tasm to modify code... movl [eax],ebx // eax aligned colormap// ebx aligned colormap// ecx,edx scratch// esi virtual source// edi moving destination pointer// ebp frac movl ecx,ebp // begin calculating first pixel addl ebp,ebx // advance frac pointer shrl ecx,25 // finish calculation for first pixel movl edx,ebp // begin calculating second pixel addl ebp,ebx // advance frac pointer shrl edx,25 // finish calculation for second pixel movl eax,[_dc_colormap] movl ebx,eax movb al,[esi+ecx] // get first pixel movb bl,[esi+edx] // get second pixel movb al,[eax] // color translate first pixel movb bl,[ebx] // color translate second pixel testl [pixelcount],0fffffffeh jnz doubleloop // at least two pixels to map jmp checklast .align 16doubleloop: movl ecx,ebp // begin calculating third pixelpatch1: addl ebp,12345678h // advance frac pointer movb [edi],al // write first pixel shrl ecx,25 // finish calculation for third pixel movl edx,ebp // begin calculating fourth pixelpatch2: addl ebp,12345678h // advance frac pointer movl [edi+SCREENWIDTH],bl // write second pixel shrl edx,25 // finish calculation for fourth pixel movb al,[esi+ecx] // get third pixel addl edi,SCREENWIDTH*2 // advance to third pixel destination movb bl,[esi+edx] // get fourth pixel decl [loopcount] // done with loop? movb al,[eax] // color translate third pixel movb bl,[ebx] // color translate fourth pixel jnz doubleloop // check for final pixelchecklast: testl [pixelcount],1 jz done movb [edi],al // write final pixel done: popad ret //================//// R_DrawSpan//// Horizontal texture mapping////================ .align 16.globl _R_DrawSpan_R_DrawSpan: pushad//// find loop count// movl eax,[_ds_x2] incl eax subl eax,[_ds_x1] // pixel count movl [pixelcount],eax // save for final pixel js hdone // nothing to scale shrl eax,1 // double pixel count movl [loopcount],eax//// build composite position// movl ebp,[_ds_xfrac] shll ebp,10 andl ebp,0ffff0000h movl eax,[_ds_yfrac] shrl eax,6 andl eax,0ffffh orl ebp,eax movl esi,[_ds_source]//// calculate screen dest// movl edi,[_ds_y] movl edi,[_ylookup+edi*4] movl eax,[_ds_x1] addl edi,[_columnofs+eax*4]//// build composite step// movl ebx,[_ds_xstep] shll ebx,10 andl ebx,0ffff0000h movl eax,[_ds_ystep] shrl eax,6 andl eax,0ffffh orl ebx,eax movl eax,OFFSET hpatch1+2 // convice tasm to modify code... movl [eax],ebx movl eax,OFFSET hpatch2+2 // convice tasm to modify code... movl [eax],ebx // eax aligned colormap// ebx aligned colormap// ecx,edx scratch// esi virtual source// edi moving destination pointer// ebp frac shldl ecx,ebp,22 // begin calculating third pixel (y units) shldl ecx,ebp,6 // begin calculating third pixel (x units) addl ebp,ebx // advance frac pointer andl ecx,4095 // finish calculation for third pixel shldl edx,ebp,22 // begin calculating fourth pixel (y units) shldl edx,ebp,6 // begin calculating fourth pixel (x units) addl ebp,ebx // advance frac pointer andl edx,4095 // finish calculation for fourth pixel movl eax,[_ds_colormap] movl ebx,eax movb al,[esi+ecx] // get first pixel movb bl,[esi+edx] // get second pixel movb al,[eax] // color translate first pixel movb bl,[ebx] // color translate second pixel testl [pixelcount],0fffffffeh jnz hdoubleloop // at least two pixels to map jmp hchecklast .align 16hdoubleloop: shldl ecx,ebp,22 // begin calculating third pixel (y units) shldl ecx,ebp,6 // begin calculating third pixel (x units)hpatch1: addl ebp,12345678h // advance frac pointer movb [edi],al // write first pixel andl ecx,4095 // finish calculation for third pixel shldl edx,ebp,22 // begin calculating fourth pixel (y units) shldl edx,ebp,6 // begin calculating fourth pixel (x units)hpatch2: addl ebp,12345678h // advance frac pointer movb [edi+1],bl // write second pixel andl edx,4095 // finish calculation for fourth pixel movb al,[esi+ecx] // get third pixel addl edi,2 // advance to third pixel destination movb bl,[esi+edx] // get fourth pixel decl [loopcount] // done with loop? movb al,[eax] // color translate third pixel movb bl,[ebx] // color translate fourth pixel jnz hdoubleloop// check for final pixelhchecklast: testl [pixelcount],1 jz hdone movb [edi],al // write final pixel hdone: popad ret//====================================================// fpfunc.S as of January 10th, 1997 (parts)#ifdef i386.text .align 4.globl _FixedMul_FixedMul: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax imull 12(%ebp) shrdl $16,%edx,%eax popl %ebp ret .align 4.globl _FixedDiv2_FixedDiv2: pushl %ebp movl %esp,%ebp movl 8(%ebp),%eax cdq shldl $16,%eax,%edx sall $16,%eax idivl 12(%ebp) popl %ebp ret#endif⌨️ 快捷键说明
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